#include <rapidjson/writer.h>
#include <rapidjson/stringbuffer.h>
#include <mbgl/style/expression/value.hpp>
#include <mbgl/style/conversion/stringify.hpp>

namespace mbgl {
namespace style {
namespace expression {

type::Type typeOf(const Value& value) {
    return value.match(
        [&](bool) -> type::Type { return type::Boolean; },
        [&](double) -> type::Type { return type::Number; },
        [&](const std::string&) -> type::Type { return type::String; },
        [&](const Color&) -> type::Type { return type::Color; },
        [&](const Collator&) -> type::Type { return type::Collator; },
        [&](const Formatted&) -> type::Type { return type::Formatted; },
        [&](const NullValue&) -> type::Type { return type::Null; },
        [&](const std::unordered_map<std::string, Value>&) -> type::Type { return type::Object; },
        [&](const std::vector<Value>& arr) -> type::Type {
            optional<type::Type> itemType;
            for (const auto& item : arr) {
                const type::Type t = typeOf(item);
                if (!itemType) {
                    itemType = {t};
                } else if (*itemType == t) {
                    continue;
                } else {
                    itemType = {type::Value};
                    break;
                }
            }

            return type::Array(itemType.value_or(type::Value), arr.size());
        }
    );
}

std::string toString(const Value& value) {
    return value.match(
        [](const NullValue&) { return std::string(); },
        [](const Color& c) { return c.stringify(); }, // avoid quoting
        [](const Formatted& f) { return f.toString(); },
        [](const std::string& s) { return s; }, // avoid quoting
        [](const auto& v_) { return stringify(v_); }
    );
}

void writeJSON(rapidjson::Writer<rapidjson::StringBuffer>& writer, const Value& value) {
    value.match(
        [&] (const NullValue&) { writer.Null(); },
        [&] (bool b) { writer.Bool(b); },
        [&] (double f) {
            // make sure integer values are stringified without trailing ".0".
            f == std::floor(f) ? writer.Int(f) : writer.Double(f);
        },
        [&] (const std::string& s) { writer.String(s); },
        [&] (const Color& c) { writer.String(c.stringify()); },
        [&] (const Collator&) {
            // Collators are excluded from constant folding and there's no Literal parser
            // for them so there shouldn't be any way to serialize this value.
            assert(false);
        },
        [&] (const Formatted& f) {
            // `stringify` in turns calls ValueConverter::fromExpressionValue below
            // Serialization strategy for Formatted objects is to return the constant
            // expression that would generate them.
            mbgl::style::conversion::stringify(writer, f);
        },
        [&] (const std::vector<Value>& arr) {
            writer.StartArray();
            for(const auto& item : arr) {
                writeJSON(writer, item);
            }
            writer.EndArray();
        },
        [&] (const std::unordered_map<std::string, Value>& obj) {
            writer.StartObject();
            for(const auto& entry : obj) {
                writer.Key(entry.first.c_str());
                writeJSON(writer, entry.second);
            }
            writer.EndObject();
        }
    );
}

std::string stringify(const Value& value) {
    rapidjson::StringBuffer buffer;
    rapidjson::Writer<rapidjson::StringBuffer> writer(buffer);
    writeJSON(writer, value);
    return buffer.GetString();
}

struct FromMBGLValue {
    Value operator()(const std::vector<mbgl::Value>& v) {
        std::vector<Value> result;
        result.reserve(v.size());
        for(const auto& item : v) {
            result.emplace_back(toExpressionValue(item));
        }
        return result;
    }
    
    Value operator()(const std::unordered_map<std::string, mbgl::Value>& v) {
        std::unordered_map<std::string, Value> result;
        result.reserve(v.size());
        for(const auto& entry : v) {
            result.emplace(entry.first, toExpressionValue(entry.second));
        }
        return result;
    }
    
    Value operator()(const std::string& s) { return s; }
    Value operator()(const bool b) { return b; }
    Value operator()(const NullValue) { return Null; }
    Value operator()(const double v) { return v; }
    Value operator()(const uint64_t& v) {
        return static_cast<double>(v);
    }
    Value operator()(const int64_t& v) {
        return static_cast<double>(v);
    }
};

Value ValueConverter<mbgl::Value>::toExpressionValue(const mbgl::Value& value) {
    return mbgl::Value::visit(value, FromMBGLValue());
}

mbgl::Value ValueConverter<mbgl::Value>::fromExpressionValue(const Value& value) {
    return value.match(
        [&](const Color& color)->mbgl::Value {
            std::array<double, 4> array = color.toArray();
            return std::vector<mbgl::Value>{
                std::string("rgba"),
                array[0],
                array[1],
                array[2],
                array[3],
            };
        },
        [&](const Collator&)->mbgl::Value {
            // fromExpressionValue can't be used for Collator values,
            // because they have no meaningful representation as an mbgl::Value
            assert(false);
            return mbgl::Value();
        },
        [&](const Formatted& formatted)->mbgl::Value {
            // Serialization strategy for Formatted objects is to return the constant
            // expression that would generate them.
            std::vector<mbgl::Value> serialized;
            static std::string formatOperator("format");
            serialized.emplace_back(formatOperator);
            for (const auto& section : formatted.sections) {
                serialized.emplace_back(section.text);
                std::unordered_map<std::string, mbgl::Value> options;
                
                if (section.fontScale) {
                    options.emplace("font-scale", *section.fontScale);
                }
                
                if (section.fontStack) {
                    std::vector<mbgl::Value> fontStack;
                    for (const auto& font : *section.fontStack) {
                        fontStack.emplace_back(font);
                    }
                    options.emplace("text-font", std::vector<mbgl::Value>{ std::string("literal"), fontStack });
                }

                if (section.textColor) {
                    options.emplace("text-color", fromExpressionValue(*section.textColor));
                }

                serialized.emplace_back(options);
            }
            return serialized;
        },
        [&](const std::vector<Value>& values)->mbgl::Value {
            std::vector<mbgl::Value> converted;
            converted.reserve(values.size());
            for (const Value& v : values) {
                converted.emplace_back(fromExpressionValue(v));
            }
            return converted;
        },
        [&](const std::unordered_map<std::string, Value>& values)->mbgl::Value {
            std::unordered_map<std::string, mbgl::Value> converted;
            converted.reserve(values.size());
            for(const auto& entry : values) {
                converted.emplace(entry.first, fromExpressionValue(entry.second));
            }
            return converted;
        },
        [&](const auto& a)->mbgl::Value { return a; }
    );
}

Value ValueConverter<float>::toExpressionValue(const float value) {
    return static_cast<double>(value);
}

optional<float> ValueConverter<float>::fromExpressionValue(const Value& value) {
    return value.template is<double>()
        ? static_cast<float>(value.template get<double>())
        : optional<float>();
}


template <typename T, typename Container>
std::vector<Value> toArrayValue(const Container& value) {
    std::vector<Value> result;
    result.reserve(value.size());
    for (const T& item : value) {
        result.push_back(ValueConverter<T>::toExpressionValue(item));
    }
    return result;
}

template <typename T, std::size_t N>
Value ValueConverter<std::array<T, N>>::toExpressionValue(const std::array<T, N>& value) {
    return toArrayValue<T>(value);
}

template <typename T, std::size_t N>
optional<std::array<T, N>> ValueConverter<std::array<T, N>>::fromExpressionValue(const Value& value) {
    return value.match(
        [&] (const std::vector<Value>& v) -> optional<std::array<T, N>> {
            if (v.size() != N) return optional<std::array<T, N>>();
                std::array<T, N> result;
                auto it = result.begin();
                for(const Value& item : v) {
                    optional<T> convertedItem = ValueConverter<T>::fromExpressionValue(item);
                    if (!convertedItem) {
                        return optional<std::array<T, N>>();
                    }
                    *it = *convertedItem;
                    it = std::next(it);
                }
                return result;
        },
        [&] (const auto&) { return optional<std::array<T, N>>(); }
    );
}


template <typename T>
Value ValueConverter<std::vector<T>>::toExpressionValue(const std::vector<T>& value) {
    return toArrayValue<T>(value);
}

template <typename T>
optional<std::vector<T>> ValueConverter<std::vector<T>>::fromExpressionValue(const Value& value) {
    return value.match(
        [&] (const std::vector<Value>& v) -> optional<std::vector<T>> {
            std::vector<T> result;
            result.reserve(v.size());
            for(const Value& item : v) {
                optional<T> convertedItem = ValueConverter<T>::fromExpressionValue(item);
                if (!convertedItem) {
                    return optional<std::vector<T>>();
                }
                result.push_back(*convertedItem);
            }
            return result;
        },
        [&] (const auto&) { return optional<std::vector<T>>(); }
    );
}

Value ValueConverter<Position>::toExpressionValue(const mbgl::style::Position& value) {
    return ValueConverter<std::array<float, 3>>::toExpressionValue(value.getSpherical());
}

optional<Position> ValueConverter<Position>::fromExpressionValue(const Value& v) {
    auto pos = ValueConverter<std::array<float, 3>>::fromExpressionValue(v);
    return pos ? optional<Position>(Position(*pos)) : optional<Position>();
}

Value ValueConverter<RadialOffsetType>::toExpressionValue(const mbgl::style::RadialOffsetType& value) {
    return ValueConverter<std::vector<float>>::toExpressionValue(value);
}

optional<RadialOffsetType> ValueConverter<RadialOffsetType>::fromExpressionValue(const Value& v) {
    if (auto val = ValueConverter<std::vector<float>>::fromExpressionValue(v)) {
        RadialOffsetType result(std::move(*val));
        return result;
    }
    if (auto val = ValueConverter<float>::fromExpressionValue(v)) {
        RadialOffsetType result(2, *val);
        return result;
    }
    return nullopt;
}

template <typename T>
Value ValueConverter<T, std::enable_if_t< std::is_enum<T>::value >>::toExpressionValue(const T& value) {
    return std::string(Enum<T>::toString(value));
}

template <typename T>
optional<T> ValueConverter<T, std::enable_if_t< std::is_enum<T>::value >>::fromExpressionValue(const Value& value) {
    return value.match(
        [&] (const std::string& v) { return Enum<T>::toEnum(v); },
        [&] (const auto&) { return optional<T>(); }
    );
}

template <typename T>
type::Type valueTypeToExpressionType() {
    return ValueConverter<T>::expressionType();
}

template <> type::Type valueTypeToExpressionType<Value>() { return type::Value; }
template <> type::Type valueTypeToExpressionType<NullValue>() { return type::Null; }
template <> type::Type valueTypeToExpressionType<bool>() { return type::Boolean; }
template <> type::Type valueTypeToExpressionType<double>() { return type::Number; }
template <> type::Type valueTypeToExpressionType<std::string>() { return type::String; }
template <> type::Type valueTypeToExpressionType<Color>() { return type::Color; }
template <> type::Type valueTypeToExpressionType<Collator>() { return type::Collator; }
template <> type::Type valueTypeToExpressionType<Formatted>() { return type::Formatted; }
template <> type::Type valueTypeToExpressionType<std::unordered_map<std::string, Value>>() { return type::Object; }
template <> type::Type valueTypeToExpressionType<std::vector<Value>>() { return type::Array(type::Value); }

// used only for the special (and private) "error" expression
template <> type::Type valueTypeToExpressionType<type::ErrorType>() { return type::Error; }


// for to_rgba expression
template type::Type valueTypeToExpressionType<std::array<double, 4>>();
template struct ValueConverter<std::array<double, 4>>;

// layout/paint property types
template type::Type valueTypeToExpressionType<float>();
template type::Type valueTypeToExpressionType<Position>();

template type::Type valueTypeToExpressionType<std::array<float, 2>>();
template struct ValueConverter<std::array<float, 2>>;

template type::Type valueTypeToExpressionType<std::array<float, 4>>();
template struct ValueConverter<std::array<float, 4>>;

template type::Type valueTypeToExpressionType<std::vector<float>>();
template struct ValueConverter<std::vector<float>>;

template type::Type valueTypeToExpressionType<std::vector<std::string>>();
template struct ValueConverter<std::vector<std::string>>;

template type::Type valueTypeToExpressionType<std::vector<TextVariableAnchorType>>();
template struct ValueConverter<std::vector<TextVariableAnchorType>>;

template type::Type valueTypeToExpressionType<AlignmentType>();
template struct ValueConverter<AlignmentType>;

template type::Type valueTypeToExpressionType<CirclePitchScaleType>();
template struct ValueConverter<CirclePitchScaleType>;

template type::Type valueTypeToExpressionType<IconTextFitType>();
template struct ValueConverter<IconTextFitType>;

template type::Type valueTypeToExpressionType<LineCapType>();
template struct ValueConverter<LineCapType>;

template type::Type valueTypeToExpressionType<LineJoinType>();
template struct ValueConverter<LineJoinType>;

template type::Type valueTypeToExpressionType<SymbolPlacementType>();
template struct ValueConverter<SymbolPlacementType>;
    
template type::Type valueTypeToExpressionType<SymbolZOrderType>();
template struct ValueConverter<SymbolZOrderType>;

template type::Type valueTypeToExpressionType<SymbolAnchorType>();
template struct ValueConverter<SymbolAnchorType>;

template type::Type valueTypeToExpressionType<TextJustifyType>();
template struct ValueConverter<TextJustifyType>;

template type::Type valueTypeToExpressionType<TextTransformType>();
template struct ValueConverter<TextTransformType>;

template type::Type valueTypeToExpressionType<TranslateAnchorType>();
template struct ValueConverter<TranslateAnchorType>;

template type::Type valueTypeToExpressionType<RasterResamplingType>();
template struct ValueConverter<RasterResamplingType>;

template type::Type valueTypeToExpressionType<HillshadeIlluminationAnchorType>();
template struct ValueConverter<HillshadeIlluminationAnchorType>;

template type::Type valueTypeToExpressionType<LightAnchorType>();
template struct ValueConverter<LightAnchorType>;

template<> type::Type valueTypeToExpressionType<RadialOffsetType>() {
    return valueTypeToExpressionType<std::vector<float>>();
}

} // namespace expression
} // namespace style
} // namespace mbgl