#include <list>
#include <mbgl/layout/symbol_layout.hpp>
#include <mbgl/renderer/bucket.hpp>
#include <mbgl/renderer/buckets/symbol_bucket.hpp>
#include <mbgl/renderer/render_layer.hpp>
#include <mbgl/renderer/render_tile.hpp>
#include <mbgl/renderer/update_parameters.hpp>
#include <mbgl/text/placement.hpp>
#include <mbgl/tile/geometry_tile.hpp>
#include <mbgl/util/math.hpp>
#include <utility>

namespace mbgl {

OpacityState::OpacityState(bool placed_, bool skipFade)
    : opacity((skipFade && placed_) ? 1 : 0)
    , placed(placed_)
{
}

OpacityState::OpacityState(const OpacityState& prevState, float increment, bool placed_) :
    opacity(::fmax(0, ::fmin(1, prevState.opacity + (prevState.placed ? increment : -increment)))),
    placed(placed_) {}

bool OpacityState::isHidden() const {
    return opacity == 0 && !placed;
}

JointOpacityState::JointOpacityState(bool placedText, bool placedIcon, bool skipFade) :
    icon(OpacityState(placedIcon, skipFade)),
    text(OpacityState(placedText, skipFade)) {}

JointOpacityState::JointOpacityState(const JointOpacityState& prevOpacityState, float increment, bool placedText, bool placedIcon) :
    icon(OpacityState(prevOpacityState.icon, increment, placedIcon)),
    text(OpacityState(prevOpacityState.text, increment, placedText)) {}

bool JointOpacityState::isHidden() const {
    return icon.isHidden() && text.isHidden();
}
    
const CollisionGroups::CollisionGroup& CollisionGroups::get(const std::string& sourceID) {
    // The predicate/groupID mechanism allows for arbitrary grouping,
    // but the current interface defines one source == one group when
    // crossSourceCollisions == true.
    if (!crossSourceCollisions) {
        if (collisionGroups.find(sourceID) == collisionGroups.end()) {
            uint16_t nextGroupID = ++maxGroupID;
            collisionGroups.emplace(sourceID, CollisionGroup(
                nextGroupID,
                optional<Predicate>([nextGroupID](const IndexedSubfeature& feature) -> bool {
                    return feature.collisionGroupId == nextGroupID;
                })
            ));
        }
        return collisionGroups[sourceID];
    } else {
        static CollisionGroup nullGroup{0, nullopt};
        return nullGroup;
    }
}

using namespace style;

// PlacementContext implemenation
class PlacementContext {
    std::reference_wrapper<const SymbolBucket> bucket;
    std::reference_wrapper<const RenderTile> renderTile;
    std::reference_wrapper<const TransformState> state;

public:
    PlacementContext(const SymbolBucket& bucket_,
                     const RenderTile& renderTile_,
                     const TransformState& state_,
                     float placementZoom,
                     CollisionGroups::CollisionGroup collisionGroup_,
                     optional<CollisionBoundaries> avoidEdges_ = nullopt)
        : bucket(bucket_),
          renderTile(renderTile_),
          state(state_),
          pixelsToTileUnits(renderTile_.id.pixelsToTileUnits(1, placementZoom)),
          scale(std::pow(2, placementZoom - getOverscaledID().overscaledZ)),
          pixelRatio(util::tileSize * getOverscaledID().overscaleFactor() / util::EXTENT),
          collisionGroup(std::move(collisionGroup_)),
          partiallyEvaluatedTextSize(bucket_.textSizeBinder->evaluateForZoom(placementZoom)),
          partiallyEvaluatedIconSize(bucket_.iconSizeBinder->evaluateForZoom(placementZoom)),
          avoidEdges(std::move(avoidEdges_)) {}

    const SymbolBucket& getBucket() const { return bucket.get(); }
    const style::SymbolLayoutProperties::PossiblyEvaluated& getLayout() const { return *getBucket().layout; }
    const RenderTile& getRenderTile() const { return renderTile.get(); }

    const OverscaledTileID& getOverscaledID() const { return renderTile.get().getOverscaledTileID(); }

    const TransformState& getTransformState() const { return state; }

    const std::vector<style::TextVariableAnchorType>& getVariableTextAnchors() const {
        return getLayout().get<style::TextVariableAnchor>();
    }

    float pixelsToTileUnits;
    float scale;
    float pixelRatio;

    bool rotateTextWithMap = getLayout().get<TextRotationAlignment>() == AlignmentType::Map;
    bool pitchTextWithMap = getLayout().get<TextPitchAlignment>() == AlignmentType::Map;
    bool rotateIconWithMap = getLayout().get<IconRotationAlignment>() == AlignmentType::Map;
    bool pitchIconWithMap = getLayout().get<IconPitchAlignment>() == AlignmentType::Map;
    SymbolPlacementType placementType = getLayout().get<SymbolPlacement>();

    mat4 textLabelPlaneMatrix =
        getLabelPlaneMatrix(renderTile.get().matrix, pitchTextWithMap, rotateTextWithMap, state, pixelsToTileUnits);
    mat4 iconLabelPlaneMatrix =
        (rotateTextWithMap == rotateIconWithMap && pitchTextWithMap == pitchIconWithMap)
            ? textLabelPlaneMatrix
            : getLabelPlaneMatrix(
                  renderTile.get().matrix, pitchIconWithMap, rotateIconWithMap, state, pixelsToTileUnits);

    CollisionGroups::CollisionGroup collisionGroup;
    ZoomEvaluatedSize partiallyEvaluatedTextSize;
    ZoomEvaluatedSize partiallyEvaluatedIconSize;

    bool textAllowOverlap = getLayout().get<style::TextAllowOverlap>();
    bool iconAllowOverlap = getLayout().get<style::IconAllowOverlap>();
    // This logic is similar to the "defaultOpacityState" logic below in updateBucketOpacities
    // If we know a symbol is always supposed to show, force it to be marked visible even if
    // it wasn't placed into the collision index (because some or all of it was outside the range
    // of the collision grid).
    // There is a subtle edge case here we're accepting:
    //  Symbol A has text-allow-overlap: true, icon-allow-overlap: true, icon-optional: false
    //  A's icon is outside the grid, so doesn't get placed
    //  A's text would be inside grid, but doesn't get placed because of icon-optional: false
    //  We still show A because of the allow-overlap settings.
    //  Symbol B has allow-overlap: false, and gets placed where A's text would be
    //  On panning in, there is a short period when Symbol B and Symbol A will overlap
    //  This is the reverse of our normal policy of "fade in on pan", but should look like any other
    //  collision and hopefully not be too noticeable.
    // See https://github.com/mapbox/mapbox-gl-native/issues/12683
    bool alwaysShowText =
        textAllowOverlap && (iconAllowOverlap || !(getBucket().hasIconData() || getBucket().hasSdfIconData()) ||
                             getLayout().get<style::IconOptional>());
    bool alwaysShowIcon =
        iconAllowOverlap && (textAllowOverlap || !getBucket().hasTextData() || getLayout().get<style::TextOptional>());

    bool hasIconTextFit = getLayout().get<IconTextFit>() != IconTextFitType::None;

    optional<CollisionBoundaries> avoidEdges;
};

// PlacementController implemenation

PlacementController::PlacementController() : placement(makeMutable<Placement>()) {}

void PlacementController::setPlacement(Immutable<Placement> placement_) {
    placement = std::move(placement_);
    stale = false;
}

bool PlacementController::placementIsRecent(TimePoint now, const float zoom, optional<Duration> periodOverride) const {
    if (!placement->transitionsEnabled()) return false;

    auto updatePeriod = periodOverride ? *periodOverride : placement->getUpdatePeriod(zoom);

    return placement->getCommitTime() + updatePeriod > now;
}

bool PlacementController::hasTransitions(TimePoint now) const {
    if (!placement->transitionsEnabled()) return false;

    if (stale) return true;

    return placement->hasTransitions(now);
}

// Placement implementation

Placement::Placement(std::shared_ptr<const UpdateParameters> updateParameters_,
                     optional<Immutable<Placement>> prevPlacement_)
    : updateParameters(std::move(updateParameters_)),
      collisionIndex(updateParameters->transformState, updateParameters->mode),
      transitionOptions(updateParameters->transitionOptions),
      commitTime(updateParameters->timePoint),
      placementZoom(updateParameters->transformState.getZoom()),
      collisionGroups(updateParameters->crossSourceCollisions),
      prevPlacement(std::move(prevPlacement_)),
      showCollisionBoxes(updateParameters->debugOptions & MapDebugOptions::Collision) {
    if (prevPlacement) {
        prevPlacement->get()->prevPlacement = nullopt; // Only hold on to one placement back
    }
}

Placement::Placement() : collisionIndex({}, MapMode::Static), collisionGroups(true) {}

Placement::~Placement() = default;

void Placement::placeLayers(const RenderLayerReferences& layers) {
    for (auto it = layers.crbegin(); it != layers.crend(); ++it) {
        std::set<uint32_t> seenCrossTileIDs;
        placeLayer(*it, seenCrossTileIDs);
    }
    commit();
}

void Placement::placeLayer(const RenderLayer& layer, std::set<uint32_t>& seenCrossTileIDs) {
    for (const BucketPlacementData& data : layer.getPlacementData()) {
        Bucket& bucket = data.bucket;
        bucket.place(*this, data, seenCrossTileIDs);
    }
}

namespace {
Point<float> calculateVariableLayoutOffset(style::SymbolAnchorType anchor,
                                           float width,
                                           float height,
                                           std::array<float, 2> offset,
                                           float textBoxScale,
                                           bool rotateWithMap,
                                           bool pitchWithMap,
                                           float bearing) {
    AnchorAlignment alignment = AnchorAlignment::getAnchorAlignment(anchor);
    float shiftX = -(alignment.horizontalAlign - 0.5f) * width;
    float shiftY = -(alignment.verticalAlign - 0.5f) * height;
    auto variableOffset = SymbolLayout::evaluateVariableOffset(anchor, offset);
    Point<float> shift{shiftX + variableOffset[0] * textBoxScale, shiftY + variableOffset[1] * textBoxScale};
    if (rotateWithMap) {
        shift = util::rotate(shift, pitchWithMap ? bearing : -bearing);
    }
    return shift;
}
} // namespace

void Placement::placeSymbolBucket(const BucketPlacementData& params, std::set<uint32_t>& seenCrossTileIDs) {
    assert(updateParameters);
    const auto& symbolBucket = static_cast<const SymbolBucket&>(params.bucket.get());
    const RenderTile& renderTile = params.tile;
    PlacementContext ctx{symbolBucket,
                         params.tile,
                         collisionIndex.getTransformState(),
                         placementZoom,
                         collisionGroups.get(params.sourceId),
                         getAvoidEdges(symbolBucket, renderTile.matrix)};
    for (const SymbolInstance& symbol : getSortedSymbols(params, ctx.pixelRatio)) {
        if (seenCrossTileIDs.count(symbol.crossTileID) != 0u) continue;
        placeSymbol(symbol, ctx);
        seenCrossTileIDs.insert(symbol.crossTileID);
    }

    // As long as this placement lives, we have to hold onto this bucket's
    // matching FeatureIndex/data for querying purposes
    retainedQueryData.emplace(
        std::piecewise_construct,
        std::forward_as_tuple(symbolBucket.bucketInstanceId),
        std::forward_as_tuple(symbolBucket.bucketInstanceId, params.featureIndex, ctx.getOverscaledID()));
}

JointPlacement Placement::placeSymbol(const SymbolInstance& symbolInstance, const PlacementContext& ctx) {
    static const JointPlacement kUnplaced(false, false, false);
    if (symbolInstance.crossTileID == SymbolInstance::invalidCrossTileID()) return kUnplaced;

    if (ctx.getRenderTile().holdForFade()) {
        // Mark all symbols from this tile as "not placed", but don't add to seenCrossTileIDs, because we don't
        // know yet if we have a duplicate in a parent tile that _should_ be placed.
        return kUnplaced;
    }
    const SymbolBucket& bucket = ctx.getBucket();
    const mat4& posMatrix = ctx.getRenderTile().matrix;
    const auto& collisionGroup = ctx.collisionGroup;
    auto variableTextAnchors = ctx.getVariableTextAnchors();
    textBoxes.clear();
    iconBoxes.clear();

    bool placeText = false;
    bool placeIcon = false;
    bool offscreen = true;
    std::pair<bool, bool> placed{false, false};
    std::pair<bool, bool> placedVerticalText{false, false};
    std::pair<bool, bool> placedVerticalIcon{false, false};
    Point<float> shift{0.0f, 0.0f};
    optional<size_t> horizontalTextIndex = symbolInstance.getDefaultHorizontalPlacedTextIndex();
    if (horizontalTextIndex) {
        const PlacedSymbol& placedSymbol = bucket.text.placedSymbols.at(*horizontalTextIndex);
        const float fontSize = evaluateSizeForFeature(ctx.partiallyEvaluatedTextSize, placedSymbol);

        const auto updatePreviousOrientationIfNotPlaced = [&](bool isPlaced) {
            if (bucket.allowVerticalPlacement && !isPlaced && getPrevPlacement()) {
                auto prevOrientation = getPrevPlacement()->placedOrientations.find(symbolInstance.crossTileID);
                if (prevOrientation != getPrevPlacement()->placedOrientations.end()) {
                    placedOrientations[symbolInstance.crossTileID] = prevOrientation->second;
                }
            }
        };

        const auto placeTextForPlacementModes = [&](auto& placeHorizontalFn, auto& placeVerticalFn) {
            if (bucket.allowVerticalPlacement && symbolInstance.writingModes & WritingModeType::Vertical) {
                assert(!bucket.placementModes.empty());
                for (auto& placementMode : bucket.placementModes) {
                    if (placementMode == TextWritingModeType::Vertical) {
                        placedVerticalText = placed = placeVerticalFn();
                    } else {
                        placed = placeHorizontalFn();
                    }

                    if (placed.first) {
                        break;
                    }
                }
            } else {
                placed = placeHorizontalFn();
            }
        };

        // Line or point label placement
        if (variableTextAnchors.empty()) {
            const auto placeFeature = [&](const CollisionFeature& collisionFeature,
                                          style::TextWritingModeType orientation) {
                textBoxes.clear();
                auto placedFeature = collisionIndex.placeFeature(collisionFeature,
                                                                 {},
                                                                 posMatrix,
                                                                 ctx.textLabelPlaneMatrix,
                                                                 ctx.pixelRatio,
                                                                 placedSymbol,
                                                                 ctx.scale,
                                                                 fontSize,
                                                                 ctx.textAllowOverlap,
                                                                 ctx.pitchTextWithMap,
                                                                 showCollisionBoxes,
                                                                 ctx.avoidEdges,
                                                                 collisionGroup.second,
                                                                 textBoxes);
                if (placedFeature.first) {
                    placedOrientations.emplace(symbolInstance.crossTileID, orientation);
                }
                return placedFeature;
            };

            const auto placeHorizontal = [&] {
                return placeFeature(symbolInstance.textCollisionFeature, style::TextWritingModeType::Horizontal);
            };

            const auto placeVertical = [&] {
                if (bucket.allowVerticalPlacement && symbolInstance.verticalTextCollisionFeature) {
                    return placeFeature(*symbolInstance.verticalTextCollisionFeature,
                                        style::TextWritingModeType::Vertical);
                }
                return std::pair<bool, bool>{false, false};
            };

            placeTextForPlacementModes(placeHorizontal, placeVertical);
            updatePreviousOrientationIfNotPlaced(placed.first);

            placeText = placed.first;
            offscreen &= placed.second;
        } else if (!symbolInstance.textCollisionFeature.alongLine &&
                   !symbolInstance.textCollisionFeature.boxes.empty()) {
            // If this symbol was in the last placement, shift the previously used
            // anchor to the front of the anchor list, only if the previous anchor
            // is still in the anchor list.
            if (getPrevPlacement()) {
                auto prevOffset = getPrevPlacement()->variableOffsets.find(symbolInstance.crossTileID);
                if (prevOffset != getPrevPlacement()->variableOffsets.end()) {
                    const auto prevAnchor = prevOffset->second.anchor;
                    auto found = std::find(variableTextAnchors.begin(), variableTextAnchors.end(), prevAnchor);
                    if (found != variableTextAnchors.begin() && found != variableTextAnchors.end()) {
                        std::vector<style::TextVariableAnchorType> filtered{prevAnchor};
                        if (!isTiltedView()) {
                            for (auto anchor : variableTextAnchors) {
                                if (anchor != prevAnchor) {
                                    filtered.push_back(anchor);
                                }
                            }
                        }
                        variableTextAnchors = std::move(filtered);
                    }
                }
            }

            const bool doVariableIconPlacement =
                ctx.hasIconTextFit && !ctx.iconAllowOverlap && symbolInstance.placedIconIndex;
            const auto placeFeatureForVariableAnchors = [&](const CollisionFeature& textCollisionFeature,
                                                            style::TextWritingModeType orientation,
                                                            const CollisionFeature& iconCollisionFeature) {
                const CollisionBox& textBox = textCollisionFeature.boxes[0];
                const float width = textBox.x2 - textBox.x1;
                const float height = textBox.y2 - textBox.y1;
                const float textBoxScale = symbolInstance.textBoxScale;
                std::pair<bool, bool> placedFeature = {false, false};
                const size_t anchorsSize = variableTextAnchors.size();
                const size_t placementAttempts = ctx.textAllowOverlap ? anchorsSize * 2 : anchorsSize;
                for (size_t i = 0u; i < placementAttempts; ++i) {
                    auto anchor = variableTextAnchors[i % anchorsSize];
                    const bool allowOverlap = (i >= anchorsSize);
                    shift = calculateVariableLayoutOffset(anchor,
                                                          width,
                                                          height,
                                                          symbolInstance.variableTextOffset,
                                                          textBoxScale,
                                                          ctx.rotateTextWithMap,
                                                          ctx.pitchTextWithMap,
                                                          ctx.getTransformState().getBearing());
                    textBoxes.clear();
                    if (!canPlaceAtVariableAnchor(
                            textBox, anchor, shift, variableTextAnchors, posMatrix, ctx.pixelRatio)) {
                        continue;
                    }

                    placedFeature = collisionIndex.placeFeature(textCollisionFeature,
                                                                shift,
                                                                posMatrix,
                                                                mat4(),
                                                                ctx.pixelRatio,
                                                                placedSymbol,
                                                                ctx.scale,
                                                                fontSize,
                                                                allowOverlap,
                                                                ctx.pitchTextWithMap,
                                                                showCollisionBoxes,
                                                                ctx.avoidEdges,
                                                                collisionGroup.second,
                                                                textBoxes);

                    if (doVariableIconPlacement) {
                        auto placedIconFeature =
                            collisionIndex.placeFeature(iconCollisionFeature,
                                                        shift,
                                                        posMatrix,
                                                        ctx.iconLabelPlaneMatrix,
                                                        ctx.pixelRatio,
                                                        placedSymbol,
                                                        ctx.scale,
                                                        fontSize,
                                                        ctx.iconAllowOverlap,
                                                        ctx.pitchTextWithMap, // TODO: shall it be pitchIconWithMap?
                                                        showCollisionBoxes,
                                                        ctx.avoidEdges,
                                                        collisionGroup.second,
                                                        iconBoxes);
                        iconBoxes.clear();
                        if (!placedIconFeature.first) continue;
                    }

                    if (placedFeature.first) {
                        assert(symbolInstance.crossTileID != 0u);
                        optional<style::TextVariableAnchorType> prevAnchor;

                        // If this label was placed in the previous placement, record the anchor position
                        // to allow us to animate the transition
                        if (getPrevPlacement()) {
                            auto prevOffset = getPrevPlacement()->variableOffsets.find(symbolInstance.crossTileID);
                            auto prevPlacements = getPrevPlacement()->placements.find(symbolInstance.crossTileID);
                            if (prevOffset != getPrevPlacement()->variableOffsets.end() &&
                                prevPlacements != getPrevPlacement()->placements.end() && prevPlacements->second.text) {
                                // TODO: The prevAnchor seems to be unused, needs to be fixed.
                                prevAnchor = prevOffset->second.anchor;
                            }
                        }

                        variableOffsets.insert(std::make_pair(
                            symbolInstance.crossTileID,
                            VariableOffset{
                                symbolInstance.variableTextOffset, width, height, anchor, textBoxScale, prevAnchor}));

                        if (bucket.allowVerticalPlacement) {
                            placedOrientations.emplace(symbolInstance.crossTileID, orientation);
                        }
                        break;
                    }
                }

                return placedFeature;
            };

            const auto placeHorizontal = [&] {
                return placeFeatureForVariableAnchors(symbolInstance.textCollisionFeature,
                                                      style::TextWritingModeType::Horizontal,
                                                      symbolInstance.iconCollisionFeature);
            };

            const auto placeVertical = [&] {
                if (bucket.allowVerticalPlacement && !placed.first && symbolInstance.verticalTextCollisionFeature) {
                    return placeFeatureForVariableAnchors(*symbolInstance.verticalTextCollisionFeature,
                                                          style::TextWritingModeType::Vertical,
                                                          symbolInstance.verticalIconCollisionFeature
                                                              ? *symbolInstance.verticalIconCollisionFeature
                                                              : symbolInstance.iconCollisionFeature);
                }
                return std::pair<bool, bool>{false, false};
            };

            placeTextForPlacementModes(placeHorizontal, placeVertical);

            placeText = placed.first;
            offscreen &= placed.second;

            updatePreviousOrientationIfNotPlaced(placed.first);

            // If we didn't get placed, we still need to copy our position from the last placement for
            // fade animations
            if (!placeText && getPrevPlacement()) {
                auto prevOffset = getPrevPlacement()->variableOffsets.find(symbolInstance.crossTileID);
                if (prevOffset != getPrevPlacement()->variableOffsets.end()) {
                    variableOffsets[symbolInstance.crossTileID] = prevOffset->second;
                }
            }
        }
    }

    if (symbolInstance.placedIconIndex) {
        if (!ctx.hasIconTextFit || !placeText || variableTextAnchors.empty()) {
            shift = {0.0f, 0.0f};
        }

        const auto& iconBuffer = symbolInstance.hasSdfIcon() ? bucket.sdfIcon : bucket.icon;
        const PlacedSymbol& placedSymbol = iconBuffer.placedSymbols.at(*symbolInstance.placedIconIndex);
        const float fontSize = evaluateSizeForFeature(ctx.partiallyEvaluatedIconSize, placedSymbol);
        const auto& placeIconFeature = [&](const CollisionFeature& collisionFeature) {
            return collisionIndex.placeFeature(collisionFeature,
                                               shift,
                                               posMatrix,
                                               ctx.iconLabelPlaneMatrix,
                                               ctx.pixelRatio,
                                               placedSymbol,
                                               ctx.scale,
                                               fontSize,
                                               ctx.iconAllowOverlap,
                                               ctx.pitchTextWithMap,
                                               showCollisionBoxes,
                                               ctx.avoidEdges,
                                               collisionGroup.second,
                                               iconBoxes);
        };

        std::pair<bool, bool> placedIcon = {false, false};
        if (placedVerticalText.first && symbolInstance.verticalIconCollisionFeature) {
            placedIcon = placedVerticalIcon = placeIconFeature(*symbolInstance.verticalIconCollisionFeature);
        } else {
            placedIcon = placeIconFeature(symbolInstance.iconCollisionFeature);
        }
        placeIcon = placedIcon.first;
        offscreen &= placedIcon.second;
    }

    const bool iconWithoutText = !symbolInstance.hasText() || ctx.getLayout().get<TextOptional>();
    const bool textWithoutIcon = !symbolInstance.hasIcon() || ctx.getLayout().get<IconOptional>();

    // combine placements for icon and text
    if (!iconWithoutText && !textWithoutIcon) {
        placeText = placeIcon = placeText && placeIcon;
    } else if (!textWithoutIcon) {
        placeText = placeText && placeIcon;
    } else if (!iconWithoutText) {
        placeIcon = placeText && placeIcon;
    }

    if (placeText) {
        if (placedVerticalText.first && symbolInstance.verticalTextCollisionFeature) {
            collisionIndex.insertFeature(*symbolInstance.verticalTextCollisionFeature,
                                         textBoxes,
                                         ctx.getLayout().get<TextIgnorePlacement>(),
                                         bucket.bucketInstanceId,
                                         collisionGroup.first);
        } else {
            collisionIndex.insertFeature(symbolInstance.textCollisionFeature,
                                         textBoxes,
                                         ctx.getLayout().get<TextIgnorePlacement>(),
                                         bucket.bucketInstanceId,
                                         collisionGroup.first);
        }
    }

    if (placeIcon) {
        if (placedVerticalIcon.first && symbolInstance.verticalIconCollisionFeature) {
            collisionIndex.insertFeature(*symbolInstance.verticalIconCollisionFeature,
                                         iconBoxes,
                                         ctx.getLayout().get<IconIgnorePlacement>(),
                                         bucket.bucketInstanceId,
                                         collisionGroup.first);
        } else {
            collisionIndex.insertFeature(symbolInstance.iconCollisionFeature,
                                         iconBoxes,
                                         ctx.getLayout().get<IconIgnorePlacement>(),
                                         bucket.bucketInstanceId,
                                         collisionGroup.first);
        }
    }

    const bool hasIconCollisionCircleData = bucket.hasIconCollisionCircleData();
    const bool hasTextCollisionCircleData = bucket.hasTextCollisionCircleData();

    if (hasIconCollisionCircleData && symbolInstance.iconCollisionFeature.alongLine && !iconBoxes.empty()) {
        collisionCircles[&symbolInstance.iconCollisionFeature] = iconBoxes;
    }
    if (hasTextCollisionCircleData && symbolInstance.textCollisionFeature.alongLine && !textBoxes.empty()) {
        collisionCircles[&symbolInstance.textCollisionFeature] = textBoxes;
    }

    assert(symbolInstance.crossTileID != 0);

    if (placements.find(symbolInstance.crossTileID) != placements.end()) {
        // If there's a previous placement with this ID, it comes from a tile that's fading out
        // Erase it so that the placement result from the non-fading tile supersedes it
        placements.erase(symbolInstance.crossTileID);
    }

    JointPlacement result(
        placeText || ctx.alwaysShowText, placeIcon || ctx.alwaysShowIcon, offscreen || bucket.justReloaded);
    placements.emplace(symbolInstance.crossTileID, result);
    newSymbolPlaced(symbolInstance, ctx, result, ctx.placementType, textBoxes, iconBoxes);
    return result;
}

namespace {

SymbolInstanceReferences getBucketSymbols(const SymbolBucket& bucket,
                                          const optional<SortKeyRange>& sortKeyRange,
                                          double bearing) {
    if (bucket.layout->get<style::SymbolZOrder>() == style::SymbolZOrderType::ViewportY) {
        auto sortedSymbols = bucket.getSortedSymbols(float(bearing));
        // Place in the reverse order than draw i.e., starting from the foreground elements.
        std::reverse(std::begin(sortedSymbols), std::end(sortedSymbols));
        return sortedSymbols;
    }
    return bucket.getSymbols(sortKeyRange);
}

} // namespace

SymbolInstanceReferences Placement::getSortedSymbols(const BucketPlacementData& params, float) {
    const auto& bucket = static_cast<const SymbolBucket&>(params.bucket.get());
    SymbolInstanceReferences sortedSymbols =
        getBucketSymbols(bucket, params.sortKeyRange, collisionIndex.getTransformState().getBearing());
    auto* previousPlacement = getPrevPlacement();
    if (previousPlacement && isTiltedView()) {
        std::stable_sort(
            sortedSymbols.begin(),
            sortedSymbols.end(),
            [previousPlacement](const SymbolInstance& a, const SymbolInstance& b) noexcept {
                auto* aPlacement = previousPlacement->getSymbolPlacement(a);
                auto* bPlacement = previousPlacement->getSymbolPlacement(b);
                if (!aPlacement) {
                    // a < b, if 'a' is new and if 'b' was previously hidden.
                    return bPlacement && !bPlacement->placed();
                }
                if (!bPlacement) {
                    // a < b, if 'b' is new and 'a' was previously shown.
                    return aPlacement && aPlacement->placed();
                }
                // a < b, if 'a' was shown and 'b' was hidden.
                return aPlacement->placed() && !bPlacement->placed();
            });
    }
    return sortedSymbols;
}

void Placement::commit() {
    bool placementChanged = false;
    assert(getPrevPlacement());
    prevZoomAdjustment = getPrevPlacement()->zoomAdjustment(placementZoom);
    float increment = getPrevPlacement()->symbolFadeChange(commitTime);

    // add the opacities from the current placement, and copy their current values from the previous placement
    for (auto& jointPlacement : placements) {
        auto prevOpacity = getPrevPlacement()->opacities.find(jointPlacement.first);
        if (prevOpacity != getPrevPlacement()->opacities.end()) {
            opacities.emplace(jointPlacement.first, JointOpacityState(prevOpacity->second, increment, jointPlacement.second.text, jointPlacement.second.icon));
            placementChanged = placementChanged ||
                jointPlacement.second.icon != prevOpacity->second.icon.placed ||
                jointPlacement.second.text != prevOpacity->second.text.placed;
        } else {
            opacities.emplace(jointPlacement.first, JointOpacityState(jointPlacement.second.text, jointPlacement.second.icon, jointPlacement.second.skipFade));
            placementChanged = placementChanged || jointPlacement.second.icon || jointPlacement.second.text;
        }
    }

    // copy and update values from the previous placement that aren't in the current placement but haven't finished fading
    for (auto& prevOpacity : getPrevPlacement()->opacities) {
        if (opacities.find(prevOpacity.first) == opacities.end()) {
            JointOpacityState jointOpacity(prevOpacity.second, increment, false, false);
            if (!jointOpacity.isHidden()) {
                opacities.emplace(prevOpacity.first, jointOpacity);
                placementChanged = placementChanged || prevOpacity.second.icon.placed || prevOpacity.second.text.placed;
            }
        }
    }

    for (auto& prevOffset : getPrevPlacement()->variableOffsets) {
        const uint32_t crossTileID = prevOffset.first;
        auto foundOffset = variableOffsets.find(crossTileID);
        auto foundOpacity = opacities.find(crossTileID);
        if (foundOffset == variableOffsets.end() && foundOpacity != opacities.end() && !foundOpacity->second.isHidden()) {
            variableOffsets[prevOffset.first] = prevOffset.second;
        }
    }

    for (auto& prevOrientation : getPrevPlacement()->placedOrientations) {
        const uint32_t crossTileID = prevOrientation.first;
        auto foundOrientation = placedOrientations.find(crossTileID);
        auto foundOpacity = opacities.find(crossTileID);
        if (foundOrientation == placedOrientations.end() && foundOpacity != opacities.end() && !foundOpacity->second.isHidden()) {
            placedOrientations[prevOrientation.first] = prevOrientation.second;
        }
    }

    fadeStartTime = placementChanged ? commitTime : getPrevPlacement()->fadeStartTime;
}

void Placement::updateLayerBuckets(const RenderLayer& layer, const TransformState& state, bool updateOpacities) const {
    std::set<uint32_t> seenCrossTileIDs;
    for (const auto& item : layer.getPlacementData()) {
        if (!item.sortKeyRange || item.sortKeyRange->isFirstRange()) {
            item.bucket.get().updateVertices(*this, updateOpacities, state, item.tile, seenCrossTileIDs);
        }
    }
}

namespace {
Point<float> calculateVariableRenderShift(style::SymbolAnchorType anchor, float width, float height, std::array<float, 2> textOffset, float textBoxScale, float renderTextSize) {
    AnchorAlignment alignment = AnchorAlignment::getAnchorAlignment(anchor);
    float shiftX = -(alignment.horizontalAlign - 0.5f) * width;
    float shiftY = -(alignment.verticalAlign - 0.5f) * height;
    auto variablOffset = SymbolLayout::evaluateVariableOffset(anchor, textOffset);
    return { (shiftX / textBoxScale + variablOffset[0]) * renderTextSize,
             (shiftY / textBoxScale + variablOffset[1]) * renderTextSize };
}
} // namespace

bool Placement::updateBucketDynamicVertices(SymbolBucket& bucket, const TransformState& state, const RenderTile& tile) const {
    using namespace style;
    const auto& layout = *bucket.layout;
    const bool alongLine = layout.get<SymbolPlacement>() != SymbolPlacementType::Point;
    const bool hasVariableAnchors = !layout.get<TextVariableAnchor>().empty() && bucket.hasTextData();
    const bool updateTextFitIcon = layout.get<IconTextFit>() != IconTextFitType::None && (bucket.allowVerticalPlacement || hasVariableAnchors) && (bucket.hasIconData() || bucket.hasSdfIconData());
    bool result = false;

    if (alongLine) {
        if (layout.get<IconRotationAlignment>() == AlignmentType::Map) {
            const bool pitchWithMap = layout.get<style::IconPitchAlignment>() == style::AlignmentType::Map;
            const bool keepUpright = layout.get<style::IconKeepUpright>();
            if (bucket.hasSdfIconData()) {
                reprojectLineLabels(bucket.sdfIcon.dynamicVertices, bucket.sdfIcon.placedSymbols,
                                    tile.matrix, pitchWithMap, true /*rotateWithMap*/, keepUpright,
                                    tile, *bucket.iconSizeBinder, state);
                result = true;
            }
            if (bucket.hasIconData()) {
                reprojectLineLabels(bucket.icon.dynamicVertices, bucket.icon.placedSymbols,
                                    tile.matrix, pitchWithMap, true /*rotateWithMap*/, keepUpright,
                                    tile, *bucket.iconSizeBinder, state);
                result = true;
            }
        }

        if (bucket.hasTextData() && layout.get<TextRotationAlignment>() == AlignmentType::Map) {
            const bool pitchWithMap = layout.get<style::TextPitchAlignment>() == style::AlignmentType::Map;
            const bool keepUpright = layout.get<style::TextKeepUpright>();
            reprojectLineLabels(bucket.text.dynamicVertices, bucket.text.placedSymbols,
                tile.matrix, pitchWithMap, true /*rotateWithMap*/, keepUpright,
                tile, *bucket.textSizeBinder, state);
            result = true;
        }
    } else if (hasVariableAnchors) {
        bucket.text.dynamicVertices.clear();
        bucket.hasVariablePlacement = false;

        const auto partiallyEvaluatedSize = bucket.textSizeBinder->evaluateForZoom(state.getZoom());
        const float tileScale = std::pow(2, state.getZoom() - tile.getOverscaledTileID().overscaledZ);
        const bool rotateWithMap = layout.get<TextRotationAlignment>() == AlignmentType::Map;
        const bool pitchWithMap = layout.get<TextPitchAlignment>() == AlignmentType::Map;
        const float pixelsToTileUnits = tile.id.pixelsToTileUnits(1.0, state.getZoom());
        const auto labelPlaneMatrix = getLabelPlaneMatrix(tile.matrix, pitchWithMap, rotateWithMap, state, pixelsToTileUnits);
        std::unordered_map<std::size_t, std::pair<std::size_t, Point<float>>> placedTextShifts;

        for (std::size_t i = 0; i < bucket.text.placedSymbols.size(); ++i) {
            const PlacedSymbol& symbol = bucket.text.placedSymbols[i];
            optional<VariableOffset> variableOffset;
            const bool skipOrientation = bucket.allowVerticalPlacement && !symbol.placedOrientation;
            if (!symbol.hidden && symbol.crossTileID != 0u && !skipOrientation) {
                auto it = variableOffsets.find(symbol.crossTileID);
                if (it != variableOffsets.end()) {
                    bucket.hasVariablePlacement = true;
                    variableOffset = it->second;
                }
            }

            if (!variableOffset) {
                // These symbols are from a justification that is not being used, or a label that wasn't placed
                // so we don't need to do the extra math to figure out what incremental shift to apply.
                hideGlyphs(symbol.glyphOffsets.size(), bucket.text.dynamicVertices);
            } else {
                const Point<float> tileAnchor = symbol.anchorPoint;
                const auto projectedAnchor = project(tileAnchor, pitchWithMap ? tile.matrix : labelPlaneMatrix);
                const float perspectiveRatio = 0.5f + 0.5f * (state.getCameraToCenterDistance() / projectedAnchor.second);
                float renderTextSize = evaluateSizeForFeature(partiallyEvaluatedSize, symbol) * perspectiveRatio / util::ONE_EM;
                if (pitchWithMap) {
                    // Go from size in pixels to equivalent size in tile units
                    renderTextSize *= bucket.tilePixelRatio / tileScale;
                }

                auto shift = calculateVariableRenderShift(
                        (*variableOffset).anchor,
                        (*variableOffset).width,
                        (*variableOffset).height,
                        (*variableOffset).offset,
                        (*variableOffset).textBoxScale,
                        renderTextSize);

                // Usual case is that we take the projected anchor and add the pixel-based shift
                // calculated above. In the (somewhat weird) case of pitch-aligned text, we add an equivalent
                // tile-unit based shift to the anchor before projecting to the label plane.
                Point<float> shiftedAnchor;
                if (pitchWithMap) {
                    shiftedAnchor = project(Point<float>(tileAnchor.x + shift.x, tileAnchor.y + shift.y),
                                            labelPlaneMatrix).first;
                } else if (rotateWithMap) {
                    auto rotated = util::rotate(shift, -state.getPitch());
                    shiftedAnchor = Point<float>(projectedAnchor.first.x + rotated.x,
                                                projectedAnchor.first.y + rotated.y);
                } else {
                    shiftedAnchor = Point<float>(projectedAnchor.first.x + shift.x,
                                                 projectedAnchor.first.y + shift.y);
                }

                if (updateTextFitIcon && symbol.placedIconIndex) {
                    placedTextShifts.emplace(*symbol.placedIconIndex,
                                             std::pair<std::size_t, Point<float>>{i, shiftedAnchor});
                }

                for (std::size_t j = 0; j < symbol.glyphOffsets.size(); ++j) {
                    addDynamicAttributes(shiftedAnchor, symbol.angle, bucket.text.dynamicVertices);
                }
            }
        }

        if (updateTextFitIcon && bucket.hasVariablePlacement) {
            auto updateIcon = [&](SymbolBucket::Buffer& iconBuffer) {
                iconBuffer.dynamicVertices.clear();
                for (std::size_t i = 0; i < iconBuffer.placedSymbols.size(); ++i) {
                    const PlacedSymbol& placedIcon = iconBuffer.placedSymbols[i];
                    if (placedIcon.hidden || (!placedIcon.placedOrientation && bucket.allowVerticalPlacement)) {
                        hideGlyphs(placedIcon.glyphOffsets.size(), iconBuffer.dynamicVertices);
                    } else {
                        const auto& pair = placedTextShifts.find(i);
                        if (pair == placedTextShifts.end()) {
                            hideGlyphs(placedIcon.glyphOffsets.size(), iconBuffer.dynamicVertices);
                        } else {
                            for (std::size_t j = 0; j < placedIcon.glyphOffsets.size(); ++j) {
                                addDynamicAttributes(pair->second.second, placedIcon.angle, iconBuffer.dynamicVertices);
                            }
                        }
                    }
                }
            };
            updateIcon(bucket.icon);
            updateIcon(bucket.sdfIcon);
        }

        result = true;
    } else if (bucket.allowVerticalPlacement && bucket.hasTextData()) {
        const auto updateDynamicVertices = [](SymbolBucket::Buffer& buffer) {
            buffer.dynamicVertices.clear();
            for (const PlacedSymbol& symbol : buffer.placedSymbols) {
                if (symbol.hidden || !symbol.placedOrientation) {
                    hideGlyphs(symbol.glyphOffsets.size(), buffer.dynamicVertices);
                } else {
                    for (std::size_t j = 0; j < symbol.glyphOffsets.size(); ++j) {
                        addDynamicAttributes(symbol.anchorPoint, symbol.angle, buffer.dynamicVertices);
                    }
                }
            }
        };

        updateDynamicVertices(bucket.text);
        // When text box is rotated, icon-text-fit icon must be rotated as well.
        if (updateTextFitIcon) {
            updateDynamicVertices(bucket.icon);
            updateDynamicVertices(bucket.sdfIcon);
        }

        result = true;
    }

    return result;
}

void Placement::updateBucketOpacities(SymbolBucket& bucket,
                                      const TransformState& state,
                                      std::set<uint32_t>& seenCrossTileIDs) const {
    if (bucket.hasTextData()) bucket.text.opacityVertices.clear();
    if (bucket.hasIconData()) bucket.icon.opacityVertices.clear();
    if (bucket.hasSdfIconData()) bucket.sdfIcon.opacityVertices.clear();
    if (bucket.hasIconCollisionBoxData()) bucket.iconCollisionBox->dynamicVertices.clear();
    if (bucket.hasIconCollisionCircleData()) bucket.iconCollisionCircle->dynamicVertices.clear();
    if (bucket.hasTextCollisionBoxData()) bucket.textCollisionBox->dynamicVertices.clear();
    if (bucket.hasTextCollisionCircleData()) bucket.textCollisionCircle->dynamicVertices.clear();

    const JointOpacityState duplicateOpacityState(false, false, true);

    const bool textAllowOverlap = bucket.layout->get<style::TextAllowOverlap>();
    const bool iconAllowOverlap = bucket.layout->get<style::IconAllowOverlap>();
    const bool variablePlacement = !bucket.layout->get<style::TextVariableAnchor>().empty();
    const bool rotateWithMap = bucket.layout->get<style::TextRotationAlignment>() == style::AlignmentType::Map;
    const bool pitchWithMap = bucket.layout->get<style::TextPitchAlignment>() == style::AlignmentType::Map;
    const bool hasIconTextFit = bucket.layout->get<style::IconTextFit>() != style::IconTextFitType::None;

    // If allow-overlap is true, we can show symbols before placement runs on them
    // But we have to wait for placement if we potentially depend on a paired icon/text
    // with allow-overlap: false.
    // See https://github.com/mapbox/mapbox-gl-native/issues/12483
    const JointOpacityState defaultOpacityState(
            textAllowOverlap && (iconAllowOverlap || !(bucket.hasIconData() || bucket.hasSdfIconData()) || bucket.layout->get<style::IconOptional>()),
            iconAllowOverlap && (textAllowOverlap || !bucket.hasTextData() || bucket.layout->get<style::TextOptional>()),
            true);

    for (SymbolInstance& symbolInstance : bucket.symbolInstances) {
        bool isDuplicate = seenCrossTileIDs.count(symbolInstance.crossTileID) > 0;

        auto it = opacities.find(symbolInstance.crossTileID);
        auto opacityState = defaultOpacityState;
        if (isDuplicate) {
            opacityState = duplicateOpacityState;
        } else if (it != opacities.end()) {
            opacityState = it->second;
        }

        seenCrossTileIDs.insert(symbolInstance.crossTileID);

        if (symbolInstance.hasText()) {
            size_t textOpacityVerticesSize = 0u;
            const auto& opacityVertex = SymbolSDFTextProgram::opacityVertex(opacityState.text.placed, opacityState.text.opacity);
            if (symbolInstance.placedRightTextIndex) {
                textOpacityVerticesSize += symbolInstance.rightJustifiedGlyphQuadsSize * 4;
                PlacedSymbol& placed = bucket.text.placedSymbols[*symbolInstance.placedRightTextIndex];
                placed.hidden = opacityState.isHidden();
            }
            if (symbolInstance.placedCenterTextIndex && !symbolInstance.singleLine) {
                textOpacityVerticesSize += symbolInstance.centerJustifiedGlyphQuadsSize * 4;
                PlacedSymbol& placed = bucket.text.placedSymbols[*symbolInstance.placedCenterTextIndex];
                placed.hidden = opacityState.isHidden();
            }
            if (symbolInstance.placedLeftTextIndex && !symbolInstance.singleLine) {
                textOpacityVerticesSize += symbolInstance.leftJustifiedGlyphQuadsSize * 4;
                PlacedSymbol& placed = bucket.text.placedSymbols[*symbolInstance.placedLeftTextIndex];
                placed.hidden = opacityState.isHidden();
            }
            if (symbolInstance.placedVerticalTextIndex) {
                textOpacityVerticesSize += symbolInstance.verticalGlyphQuadsSize * 4;
                bucket.text.placedSymbols[*symbolInstance.placedVerticalTextIndex].hidden = opacityState.isHidden();
            }

            bucket.text.opacityVertices.extend(textOpacityVerticesSize, opacityVertex);

            style::TextWritingModeType previousOrientation = style::TextWritingModeType::Horizontal;
            if (bucket.allowVerticalPlacement) {
                auto prevOrientation = placedOrientations.find(symbolInstance.crossTileID);
                if (prevOrientation != placedOrientations.end()) {
                    previousOrientation = prevOrientation->second;
                    markUsedOrientation(bucket, prevOrientation->second, symbolInstance);
                }
            }

            auto prevOffset = variableOffsets.find(symbolInstance.crossTileID);
            if (prevOffset != variableOffsets.end()) {
                markUsedJustification(bucket, prevOffset->second.anchor, symbolInstance, previousOrientation);
            }
        }
        if (symbolInstance.hasIcon()) {
            size_t iconOpacityVerticesSize = 0u;
            const auto& opacityVertex =
                SymbolIconProgram::opacityVertex(opacityState.icon.placed, opacityState.icon.opacity);
            auto& iconBuffer = symbolInstance.hasSdfIcon() ? bucket.sdfIcon : bucket.icon;
            
            if (symbolInstance.placedIconIndex) {
                iconOpacityVerticesSize += symbolInstance.iconQuadsSize * 4;
                iconBuffer.placedSymbols[*symbolInstance.placedIconIndex].hidden = opacityState.isHidden();
            }

            if (symbolInstance.placedVerticalIconIndex) {
                iconOpacityVerticesSize += symbolInstance.iconQuadsSize * 4;
                iconBuffer.placedSymbols[*symbolInstance.placedVerticalIconIndex].hidden = opacityState.isHidden();
            }

            iconBuffer.opacityVertices.extend(iconOpacityVerticesSize, opacityVertex);
        }

        auto updateIconCollisionBox = [&](const auto& feature, const bool placed, const Point<float>& shift) {
            if (feature.alongLine) {
                return;
            }
            const auto& dynamicVertex = CollisionBoxProgram::dynamicVertex(placed, false, shift);
            bucket.iconCollisionBox->dynamicVertices.extend(feature.boxes.size() * 4, dynamicVertex);
        };

        auto updateTextCollisionBox =
            [this, &bucket, &symbolInstance, &state, variablePlacement, rotateWithMap, pitchWithMap](
                const auto& feature, const bool placed) {
                Point<float> shift{0.0f, 0.0f};
                if (feature.alongLine) {
                    return shift;
                }
                bool used = true;
                if (variablePlacement) {
                    auto foundOffset = variableOffsets.find(symbolInstance.crossTileID);
                    if (foundOffset != variableOffsets.end()) {
                        const VariableOffset& variableOffset = foundOffset->second;
                        // This will show either the currently placed position or the last
                        // successfully placed position (so you can visualize what collision
                        // just made the symbol disappear, and the most likely place for the
                        // symbol to come back)
                        shift = calculateVariableLayoutOffset(variableOffset.anchor,
                                                              variableOffset.width,
                                                              variableOffset.height,
                                                              variableOffset.offset,
                                                              variableOffset.textBoxScale,
                                                              rotateWithMap,
                                                              pitchWithMap,
                                                              state.getBearing());
                    } else {
                        // No offset -> this symbol hasn't been placed since coming on-screen
                        // No single box is particularly meaningful and all of them would be too noisy
                        // Use the center box just to show something's there, but mark it "not used"
                        used = false;
                    }
                }
                const auto& dynamicVertex = CollisionBoxProgram::dynamicVertex(placed, !used, shift);
                bucket.textCollisionBox->dynamicVertices.extend(feature.boxes.size() * 4, dynamicVertex);
                return shift;
            };

        auto updateCollisionCircles = [&](const auto& feature, const bool placed, bool isText) {
            if (!feature.alongLine) {
                return;
            }
            auto circles = collisionCircles.find(&feature);
            if (circles != collisionCircles.end()) {
                for (const auto& circle : circles->second) {
                    const auto& dynamicVertex = CollisionBoxProgram::dynamicVertex(placed, !circle.isCircle(), {});
                    isText ? bucket.textCollisionCircle->dynamicVertices.extend(4, dynamicVertex):
                             bucket.iconCollisionCircle->dynamicVertices.extend(4, dynamicVertex);
                }
            } else {
                // This feature was not placed, because it was not loaded or from a fading tile. Apply default values.
                static const auto dynamicVertex = CollisionBoxProgram::dynamicVertex(placed, false /*not used*/, {});
                isText ? bucket.textCollisionCircle->dynamicVertices.extend(4 * feature.boxes.size(), dynamicVertex):
                         bucket.iconCollisionCircle->dynamicVertices.extend(4 * feature.boxes.size(), dynamicVertex);
            }
        };
        Point<float> textShift{0.0f, 0.0f};
        Point<float> verticalTextShift{0.0f, 0.0f};
        if (bucket.hasTextCollisionBoxData()) {
            textShift = updateTextCollisionBox(symbolInstance.textCollisionFeature, opacityState.text.placed);
            if (bucket.allowVerticalPlacement && symbolInstance.verticalTextCollisionFeature) {
                verticalTextShift = updateTextCollisionBox(*symbolInstance.verticalTextCollisionFeature, opacityState.text.placed);
            }
        }
        if (bucket.hasIconCollisionBoxData()) {
            updateIconCollisionBox(symbolInstance.iconCollisionFeature, opacityState.icon.placed, hasIconTextFit ? textShift : Point<float>{0.0f, 0.0f});
            if (bucket.allowVerticalPlacement && symbolInstance.verticalIconCollisionFeature) {
                updateIconCollisionBox(*symbolInstance.verticalIconCollisionFeature, opacityState.text.placed, hasIconTextFit ? verticalTextShift : Point<float>{0.0f, 0.0f});
            }
        }

        if (bucket.hasIconCollisionCircleData()) {
            updateCollisionCircles(symbolInstance.iconCollisionFeature, opacityState.icon.placed, false);
        }
        if (bucket.hasTextCollisionCircleData()) {
            updateCollisionCircles(symbolInstance.textCollisionFeature, opacityState.text.placed, true);
        }
    }

    bucket.sortFeatures(state.getBearing());
    auto retainedData = retainedQueryData.find(bucket.bucketInstanceId);
    if (retainedData != retainedQueryData.end()) {
        retainedData->second.featureSortOrder = bucket.featureSortOrder;
    }
}

namespace {
optional<size_t> justificationToIndex(style::TextJustifyType justify, const SymbolInstance& symbolInstance, style::TextWritingModeType orientation) {
    // Vertical symbol has just one justification, style::TextJustifyType::Left.
    if (orientation == style::TextWritingModeType::Vertical) {
        return symbolInstance.placedVerticalTextIndex;
    }

    switch(justify) {
        case style::TextJustifyType::Right: return symbolInstance.placedRightTextIndex;
        case style::TextJustifyType::Center: return symbolInstance.placedCenterTextIndex;
        case style::TextJustifyType::Left: return symbolInstance.placedLeftTextIndex;
        case style::TextJustifyType::Auto: break;
    }
    assert(false);
    return nullopt;
}

const style::TextJustifyType justifyTypes[] = {
    style::TextJustifyType::Right, style::TextJustifyType::Center, style::TextJustifyType::Left};

}  // namespace

void Placement::markUsedJustification(SymbolBucket& bucket,
                                      style::TextVariableAnchorType placedAnchor,
                                      const SymbolInstance& symbolInstance,
                                      style::TextWritingModeType orientation) const {
    style::TextJustifyType anchorJustify = getAnchorJustification(placedAnchor);
    assert(anchorJustify != style::TextJustifyType::Auto);
    const optional<size_t>& autoIndex = justificationToIndex(anchorJustify, symbolInstance, orientation);

    for (auto& justify : justifyTypes) {
        const optional<size_t> index = justificationToIndex(justify, symbolInstance, orientation);
        if (index) {
            assert(bucket.text.placedSymbols.size() > *index);
            if (autoIndex && *index != *autoIndex) {
                // There are multiple justifications and this one isn't it: shift offscreen
                bucket.text.placedSymbols.at(*index).crossTileID = 0u;
            } else {
                // Either this is the chosen justification or the justification is hardwired: use this one
                bucket.text.placedSymbols.at(*index).crossTileID = symbolInstance.crossTileID;
            }
        }
    }
}

void Placement::markUsedOrientation(SymbolBucket& bucket,
                                    style::TextWritingModeType orientation,
                                    const SymbolInstance& symbolInstance) const {
    auto horizontal = orientation == style::TextWritingModeType::Horizontal ?
                                     optional<style::TextWritingModeType>(orientation) : nullopt;
    auto vertical = orientation == style::TextWritingModeType::Vertical ?
                                     optional<style::TextWritingModeType>(orientation) : nullopt;

    if (symbolInstance.placedRightTextIndex) {
        bucket.text.placedSymbols.at(*symbolInstance.placedRightTextIndex).placedOrientation = horizontal;
    }

    if (symbolInstance.placedCenterTextIndex && !symbolInstance.singleLine) {
        bucket.text.placedSymbols.at(*symbolInstance.placedCenterTextIndex).placedOrientation = horizontal;
    }

    if (symbolInstance.placedLeftTextIndex && !symbolInstance.singleLine) {
        bucket.text.placedSymbols.at(*symbolInstance.placedLeftTextIndex).placedOrientation = horizontal;
    }

    if (symbolInstance.placedVerticalTextIndex) {
        bucket.text.placedSymbols.at(*symbolInstance.placedVerticalTextIndex).placedOrientation = vertical;
    }

    auto& iconBuffer = symbolInstance.hasSdfIcon() ? bucket.sdfIcon : bucket.icon;
    if (symbolInstance.placedIconIndex) {
        iconBuffer.placedSymbols.at(*symbolInstance.placedIconIndex).placedOrientation = horizontal;
    }

    if (symbolInstance.placedVerticalIconIndex) {
        iconBuffer.placedSymbols.at(*symbolInstance.placedVerticalIconIndex).placedOrientation = vertical;
    }
}

bool Placement::isTiltedView() const {
    return updateParameters->transformState.getPitch() != 0.0f;
}

float Placement::symbolFadeChange(TimePoint now) const {
    if (transitionsEnabled() &&
        transitionOptions.duration.value_or(util::DEFAULT_TRANSITION_DURATION) > Milliseconds(0)) {
        return std::chrono::duration<float>(now - commitTime) / transitionOptions.duration.value_or(util::DEFAULT_TRANSITION_DURATION) + prevZoomAdjustment;
    }
    return 1.0;
}

float Placement::zoomAdjustment(const float zoom) const {
    // When zooming out labels can overlap each other quickly. This
    // adjustment is used to reduce the fade duration for symbols while zooming out quickly.
    // It is also used to reduce the interval between placement calculations. Reducing the
    // interval between placements means collisions are discovered and eliminated sooner.
    return std::max(0.0, (placementZoom - zoom) / 1.5);
}

const JointPlacement* Placement::getSymbolPlacement(const SymbolInstance& symbol) const {
    assert(symbol.crossTileID != 0);
    auto found = placements.find(symbol.crossTileID);
    return (found != placements.end()) ? &found->second : nullptr;
}

Duration Placement::getUpdatePeriod(const float zoom) const {
    // Even if transitionOptions.duration is set to a value < 300ms, we still wait for this default transition duration
    // before attempting another placement operation.
    const auto fadeDuration = std::max(util::DEFAULT_TRANSITION_DURATION,
                                       transitionOptions.duration.value_or(util::DEFAULT_TRANSITION_DURATION));
    return std::chrono::duration_cast<Duration>(fadeDuration * (1.0 - zoomAdjustment(zoom)));
}

bool Placement::transitionsEnabled() const {
    return transitionOptions.enablePlacementTransitions;
}

bool Placement::hasTransitions(TimePoint now) const {
    assert(transitionsEnabled());
    return std::chrono::duration<float>(now - fadeStartTime) <
           transitionOptions.duration.value_or(util::DEFAULT_TRANSITION_DURATION);
}

const std::vector<PlacedSymbolData>& Placement::getPlacedSymbolsData() const {
    const static std::vector<PlacedSymbolData> data;
    return data;
}

const CollisionIndex& Placement::getCollisionIndex() const {
    return collisionIndex;
}
    
const RetainedQueryData& Placement::getQueryData(uint32_t bucketInstanceId) const {
    auto it = retainedQueryData.find(bucketInstanceId);
    if (it == retainedQueryData.end()) {
        throw std::runtime_error("Placement::getQueryData with unrecognized bucketInstanceId");
    }
    return it->second;
}

/// Placement for Static map mode.
class StaticPlacement : public Placement {
public:
    explicit StaticPlacement(std::shared_ptr<const UpdateParameters> updateParameters_)
        : Placement(std::move(updateParameters_), nullopt) {}

protected:
    void commit() override;
    float symbolFadeChange(TimePoint) const override { return 1.0f; }
    bool hasTransitions(TimePoint) const override { return false; }
    bool transitionsEnabled() const override { return false; }
};

void StaticPlacement::commit() {
    fadeStartTime = commitTime;
    for (auto& jointPlacement : placements) {
        opacities.emplace(
            jointPlacement.first,
            JointOpacityState(jointPlacement.second.text, jointPlacement.second.icon, jointPlacement.second.skipFade));
    }
}

/// Placement for Tile map mode.

struct Intersection {
    Intersection(const SymbolInstance& symbol_, PlacementContext ctx_, IntersectStatus status_, std::size_t priority_)
        : symbol(symbol_), ctx(std::move(ctx_)), status(status_), priority(priority_) {}
    std::reference_wrapper<const SymbolInstance> symbol;
    PlacementContext ctx;
    IntersectStatus status;
    std::size_t priority; // less means more important
};

class TilePlacement : public StaticPlacement {
public:
    explicit TilePlacement(std::shared_ptr<const UpdateParameters> updateParameters_)
        : StaticPlacement(std::move(updateParameters_)) {}

private:
    void placeLayers(const RenderLayerReferences&) override;
    void placeSymbolBucket(const BucketPlacementData&, std::set<uint32_t>&) override;
    void collectPlacedSymbolData(bool enable) override { collectData = enable; }
    const std::vector<PlacedSymbolData>& getPlacedSymbolsData() const override { return placedSymbolsData; }

    optional<CollisionBoundaries> getAvoidEdges(const SymbolBucket&, const mat4&) override;
    bool canPlaceAtVariableAnchor(const CollisionBox& box,
                                  TextVariableAnchorType anchor,
                                  Point<float> shift,
                                  std::vector<style::TextVariableAnchorType>& anchors,
                                  const mat4& posMatrix,
                                  float textPixelRatio) override;
    void newSymbolPlaced(const SymbolInstance&,
                         const PlacementContext&,
                         const JointPlacement&,
                         style::SymbolPlacementType,
                         const std::vector<ProjectedCollisionBox>&,
                         const std::vector<ProjectedCollisionBox>&) override;

    bool shouldRetryPlacement(const JointPlacement&, const PlacementContext&);

    std::unordered_map<uint32_t, bool> locationCache;
    optional<CollisionBoundaries> tileBorders;
    std::set<uint32_t> seenCrossTileIDs;
    std::vector<PlacedSymbolData> placedSymbolsData;
    std::vector<Intersection> intersections;
    bool populateIntersections = false;
    std::size_t currentIntersectionPriority{};
    bool collectData = false;
};

void TilePlacement::placeLayers(const RenderLayerReferences& layers) {
    placedSymbolsData.clear();
    seenCrossTileIDs.clear();
    intersections.clear();
    currentIntersectionPriority = 0u;
    // Populale intersections.
    populateIntersections = true;
    for (auto it = layers.crbegin(); it != layers.crend(); ++it) {
        placeLayer(*it, seenCrossTileIDs);
    }

    std::sort(intersections.begin(), intersections.end(), [](const Intersection& a, const Intersection& b) {
        if (a.priority != b.priority) return a.priority < b.priority;
        uint8_t flagsA = a.status.flags;
        uint8_t flagsB = b.status.flags;
        // Items arranged as: VerticalBorders & HorizontalBorders (3) ->
        // VerticalBorders (2) -> HorizontalBorders (1)
        if (flagsA != flagsB) return flagsA > flagsB;
        // If both intersects the same border(s), look for a more noticable cut-off.
        if (a.status.minSectionLength != b.status.minSectionLength) {
            return a.status.minSectionLength > b.status.minSectionLength;
        }
        // Look at the anchor coordinates
        if (a.symbol.get().anchor.point.y != b.symbol.get().anchor.point.y) {
            return a.symbol.get().anchor.point.y < b.symbol.get().anchor.point.y;
        }
        if (a.symbol.get().anchor.point.x != b.symbol.get().anchor.point.x) {
            return a.symbol.get().anchor.point.x < b.symbol.get().anchor.point.x;
        }
        // Finally, looking at the key hashes.
        return std::hash<std::u16string>()(a.symbol.get().key) < std::hash<std::u16string>()(b.symbol.get().key);
    });
    // Place intersections.
    for (const auto& intersection : intersections) {
        const SymbolInstance& symbol = intersection.symbol;
        const PlacementContext& ctx = intersection.ctx;
        currentIntersectionPriority = intersection.priority;
        if (seenCrossTileIDs.count(symbol.crossTileID) != 0u) continue;
        JointPlacement placement = placeSymbol(symbol, ctx);
        if (shouldRetryPlacement(placement, ctx)) continue;
        seenCrossTileIDs.insert(symbol.crossTileID);
    }
    // Place the rest labels.
    populateIntersections = false;
    for (auto it = layers.crbegin(); it != layers.crend(); ++it) {
        placeLayer(*it, seenCrossTileIDs);
    }
    commit();
}

optional<CollisionBoundaries> TilePlacement::getAvoidEdges(const SymbolBucket& bucket, const mat4& posMatrix) {
    tileBorders = collisionIndex.projectTileBoundaries(posMatrix);
    const auto& layout = *bucket.layout;
    if (layout.get<style::SymbolAvoidEdges>() ||
        layout.get<style::SymbolPlacement>() == style::SymbolPlacementType::Line) {
        return tileBorders;
    }
    return nullopt;
}

void TilePlacement::placeSymbolBucket(const BucketPlacementData& params, std::set<uint32_t>& seen) {
    assert(updateParameters);
    const auto& bucket = static_cast<const SymbolBucket&>(params.bucket.get());
    const auto& layout = *bucket.layout;
    if (!populateIntersections) {
        Placement::placeSymbolBucket(params, seen);
        return;
    }
    if (layout.get<SymbolPlacement>() != SymbolPlacementType::Point || layout.get<SymbolAvoidEdges>()) {
        // Collect intersection only for point placement.
        return;
    }
    const RenderTile& renderTile = params.tile;
    PlacementContext ctx{bucket,
                         params.tile,
                         collisionIndex.getTransformState(),
                         placementZoom,
                         collisionGroups.get(params.sourceId),
                         getAvoidEdges(bucket, renderTile.matrix)};

    const auto& variableTextAnchors = ctx.getVariableTextAnchors();
    // In this case we first try to place symbols, which intersects the tile borders, so that
    // those symbols will remain even if each tile is handled independently.
    SymbolInstanceReferences symbolInstances =
        getBucketSymbols(bucket, params.sortKeyRange, collisionIndex.getTransformState().getBearing());
    optional<style::TextVariableAnchorType> variableAnchor;
    if (!variableTextAnchors.empty()) variableAnchor = variableTextAnchors.front();

    // Keeps the data necessary to find a feature location according to a tile.
    struct NeighborTileData {
        NeighborTileData(const CollisionIndex& collisionIndex, UnwrappedTileID id_, Point<float> shift_)
            : id(id_), shift(shift_), matrix() {
            collisionIndex.getTransformState().matrixFor(matrix, id);
            matrix::multiply(matrix, collisionIndex.getTransformState().getProjectionMatrix(), matrix);
            borders = collisionIndex.projectTileBoundaries(matrix);
        }

        UnwrappedTileID id;
        Point<float> shift;
        mat4 matrix;
        CollisionBoundaries borders;
    };

    uint8_t z = renderTile.id.canonical.z;
    uint32_t x = renderTile.id.canonical.x;
    uint32_t y = renderTile.id.canonical.y;
    const std::array<NeighborTileData, 4> neighbours{{
        {collisionIndex, UnwrappedTileID(z, x, y - 1), {0.0f, util::EXTENT}},  // top
        {collisionIndex, UnwrappedTileID(z, x, y + 1), {0.0f, -util::EXTENT}}, // bottom
        {collisionIndex, UnwrappedTileID(z, x - 1, y), {util::EXTENT, 0.0f}},  // left
        {collisionIndex, UnwrappedTileID(z, x + 1, y), {-util::EXTENT, 0.0f}}  // right
    }};

    auto collisionBoxIntersectsTileEdges = [&](const CollisionBox& collisionBox,
                                               Point<float> shift) noexcept->IntersectStatus {
        IntersectStatus intersects =
            collisionIndex.intersectsTileEdges(collisionBox, shift, renderTile.matrix, ctx.pixelRatio, *tileBorders);
        // Check if this symbol intersects the neighbor tile borders. If so, it also shall be placed with priority.
        for (const auto& neighbor : neighbours) {
            if (intersects.flags != IntersectStatus::None) break;
            intersects = collisionIndex.intersectsTileEdges(
                collisionBox, shift + neighbor.shift, neighbor.matrix, ctx.pixelRatio, neighbor.borders);
        }
        return intersects;
    };

    auto symbolIntersectsTileEdges = [
        &collisionBoxIntersectsTileEdges,
        variableAnchor,
        pitchTextWithMap = ctx.pitchTextWithMap,
        rotateTextWithMap = ctx.rotateTextWithMap,
        variableIconPlacement = ctx.hasIconTextFit && !ctx.iconAllowOverlap,
        bearing = ctx.getTransformState().getBearing()
    ](const SymbolInstance& symbol) noexcept->IntersectStatus {
        IntersectStatus result;
        if (!symbol.textCollisionFeature.boxes.empty()) {
            const auto& textCollisionBox = symbol.textCollisionFeature.boxes.front();

            Point<float> offset{};
            if (variableAnchor) {
                float width = textCollisionBox.x2 - textCollisionBox.x1;
                float height = textCollisionBox.y2 - textCollisionBox.y1;
                offset = calculateVariableLayoutOffset(*variableAnchor,
                                                       width,
                                                       height,
                                                       symbol.variableTextOffset,
                                                       symbol.textBoxScale,
                                                       rotateTextWithMap,
                                                       pitchTextWithMap,
                                                       bearing);
            }
            result = collisionBoxIntersectsTileEdges(textCollisionBox, offset);
        }

        if (!symbol.iconCollisionFeature.boxes.empty()) {
            const auto& iconCollisionBox = symbol.iconCollisionFeature.boxes.front();
            Point<float> offset{};
            if (variableAnchor && variableIconPlacement) {
                float width = iconCollisionBox.x2 - iconCollisionBox.x1;
                float height = iconCollisionBox.y2 - iconCollisionBox.y1;
                offset = calculateVariableLayoutOffset(*variableAnchor,
                                                       width,
                                                       height,
                                                       symbol.variableTextOffset,
                                                       symbol.textBoxScale,
                                                       rotateTextWithMap,
                                                       pitchTextWithMap,
                                                       bearing);
            }
            auto iconIntersects = collisionBoxIntersectsTileEdges(iconCollisionBox, offset);
            result.flags |= iconIntersects.flags;
            result.minSectionLength = std::max(result.minSectionLength, iconIntersects.minSectionLength);
        }

        return result;
    };

    for (const SymbolInstance& symbol : symbolInstances) {
        auto intersectStatus = symbolIntersectsTileEdges(symbol);
        if (intersectStatus.flags == IntersectStatus::None) continue;
        intersections.emplace_back(symbol, ctx, intersectStatus, currentIntersectionPriority);
    }

    ++currentIntersectionPriority;
}

bool TilePlacement::canPlaceAtVariableAnchor(const CollisionBox& box,
                                             TextVariableAnchorType anchor,
                                             Point<float> shift,
                                             std::vector<style::TextVariableAnchorType>& anchors,
                                             const mat4& posMatrix,
                                             float textPixelRatio) {
    assert(tileBorders);
    if (populateIntersections) {
        // A variable label is only allowed to intersect tile border with the first anchor.
        if (anchor == anchors.front()) {
            // Check, that the label would intersect the tile borders even without shift, otherwise intersection
            // is not allowed (preventing cut-offs in case the shift is lager than the buffer size).
            auto status = collisionIndex.intersectsTileEdges(box, {}, posMatrix, textPixelRatio, *tileBorders);
            if (status.flags != IntersectStatus::None) return true;
        }
        // The most important labels shall be placed first anyway, so we continue trying
        // the following variable anchors for them; less priority labels
        // will wait for the second round (when `populateIntersections` is `false`).
        if (currentIntersectionPriority > 0u) return false;
    }
    // Can be placed, if it does not intersect tile borders.
    auto status = collisionIndex.intersectsTileEdges(box, shift, posMatrix, textPixelRatio, *tileBorders);
    return (status.flags == IntersectStatus::None);
}

void TilePlacement::newSymbolPlaced(const SymbolInstance& symbol,
                                    const PlacementContext& ctx,
                                    const JointPlacement& placement,
                                    style::SymbolPlacementType placementType,
                                    const std::vector<ProjectedCollisionBox>& textCollisionBoxes,
                                    const std::vector<ProjectedCollisionBox>& iconCollisionBoxes) {
    if (!collectData || placementType != style::SymbolPlacementType::Point || shouldRetryPlacement(placement, ctx))
        return;

    optional<mapbox::geometry::box<float>> textCollisionBox;
    if (!textCollisionBoxes.empty()) {
        assert(textCollisionBoxes.size() == 1u);
        auto& box = textCollisionBoxes.front();
        assert(box.isBox());
        textCollisionBox = box.box();
    }
    optional<mapbox::geometry::box<float>> iconCollisionBox;
    if (!iconCollisionBoxes.empty()) {
        assert(iconCollisionBoxes.size() == 1u);
        auto& box = iconCollisionBoxes.front();
        assert(box.isBox());
        iconCollisionBox = box.box();
    }
    PlacedSymbolData symbolData{symbol.key,
                                textCollisionBox,
                                iconCollisionBox,
                                placement.text,
                                placement.icon,
                                !placement.skipFade && populateIntersections,
                                collisionIndex.getViewportPadding(),
                                ctx.getBucket().bucketLeaderID};
    placedSymbolsData.emplace_back(std::move(symbolData));
}

bool TilePlacement::shouldRetryPlacement(const JointPlacement& placement, const PlacementContext& ctx) {
    // We re-try the placement to try out remaining variable anchors.
    return populateIntersections && !placement.placed() && !ctx.getVariableTextAnchors().empty();
}

// static
Mutable<Placement> Placement::create(std::shared_ptr<const UpdateParameters> updateParameters_,
                                     optional<Immutable<Placement>> prevPlacement) {
    assert(updateParameters_);
    switch (updateParameters_->mode) {
        case MapMode::Continuous:
            assert(prevPlacement);
            return makeMutable<Placement>(std::move(updateParameters_), std::move(prevPlacement));
        case MapMode::Static:
            return staticMutableCast<Placement>(makeMutable<StaticPlacement>(std::move(updateParameters_)));
        case MapMode::Tile:
            return staticMutableCast<Placement>(makeMutable<TilePlacement>(std::move(updateParameters_)));
    }
    assert(false);
    return makeMutable<Placement>();
}

} // namespace mbgl