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#pragma once
#include <map>
#include <memory>
#include <mbgl/util/optional.hpp>
#include <mbgl/style/expression/curve.hpp>
#include <mbgl/style/expression/parsing_context.hpp>
#include <mbgl/style/conversion.hpp>
namespace mbgl {
namespace style {
namespace expression {
namespace detail {
// used for storing intermediate state during parsing
struct ExponentialInterpolation { float base; std::string name = "exponential"; };
struct StepInterpolation {};
} // namespace detail
struct ParseCurve {
template <typename V>
static ParseResult parse(const V& value, ParsingContext ctx) {
using namespace mbgl::style::conversion;
assert(isArray(value));
auto length = arrayLength(value);
if (length < 5) {
ctx.error("Expected at least 4 arguments, but found only " + std::to_string(length - 1) + ".");
return ParseResult();
}
// [curve, interp, input, 2 * (n pairs)...]
if (length % 2 != 1) {
ctx.error("Expected an even number of arguments.");
return ParseResult();
}
const auto& interp = arrayMember(value, 1);
if (!isArray(interp) || arrayLength(interp) == 0) {
ctx.error("Expected an interpolation type expression.");
return ParseResult();
}
variant<detail::StepInterpolation,
detail::ExponentialInterpolation> interpolation;
const auto& interpName = toString(arrayMember(interp, 0));
if (interpName && *interpName == "step") {
interpolation = detail::StepInterpolation{};
} else if (interpName && *interpName == "linear") {
interpolation = detail::ExponentialInterpolation { 1.0f, "linear" };
} else if (interpName && *interpName == "exponential") {
optional<double> base;
if (arrayLength(interp) == 2) {
base = toDouble(arrayMember(interp, 1));
}
if (!base) {
ctx.error("Exponential interpolation requires a numeric base.");
return ParseResult();
}
interpolation = detail::ExponentialInterpolation { static_cast<float>(*base) };
} else {
ctx.error("Unknown interpolation type " + (interpName ? *interpName : ""));
return ParseResult();
}
ParseResult input = parseExpression(arrayMember(value, 2), ParsingContext(ctx, 2, {type::Number}));
if (!input) {
return input;
}
std::map<float, std::unique_ptr<Expression>> stops;
optional<type::Type> outputType = ctx.expected;
double previous = - std::numeric_limits<double>::infinity();
for (std::size_t i = 3; i + 1 < length; i += 2) {
const optional<mbgl::Value>& labelValue = toValue(arrayMember(value, i));
optional<double> label;
optional<std::string> labelError;
if (labelValue) {
labelValue->match(
[&](uint64_t n) {
if (!Value::isSafeNumericValue(n)) {
labelError = {"Numeric values must be no larger than " + std::to_string(Value::max()) + "."};
} else {
label = {static_cast<double>(n)};
}
},
[&](int64_t n) {
if (!Value::isSafeNumericValue(n)) {
labelError = {"Numeric values must be no larger than " + std::to_string(Value::max()) + "."};
} else {
label = {static_cast<double>(n)};
}
},
[&](double n) {
if (!Value::isSafeNumericValue(n)) {
labelError = {"Numeric values must be no larger than " + std::to_string(Value::max()) + "."};
} else {
label = {static_cast<double>(n)};
}
},
[&](const auto&) {}
);
}
if (!label) {
ctx.error(labelError ? *labelError :
R"(Input/output pairs for "curve" expressions must be defined using literal numeric values (not computed expressions) for the input values.)",
i);
return ParseResult();
}
if (*label < previous) {
ctx.error(
R"(Input/output pairs for "curve" expressions must be arranged with input values in strictly ascending order.)",
i
);
return ParseResult();
}
previous = *label;
auto output = parseExpression(arrayMember(value, i + 1), ParsingContext(ctx, i + 1, outputType));
if (!output) {
return ParseResult();
}
if (!outputType) {
outputType = (*output)->getType();
}
stops.emplace(*label, std::move(*output));
}
assert(outputType);
if (
!interpolation.template is<detail::StepInterpolation>() &&
*outputType != type::Number &&
*outputType != type::Color &&
!(
outputType->is<type::Array>() &&
outputType->get<type::Array>().itemType == type::Number
)
)
{
ctx.error("Type " + toString(*outputType) +
" is not interpolatable, and thus cannot be used as a " +
*interpName + " curve's output type.");
return ParseResult();
}
return interpolation.match(
[&](const detail::StepInterpolation&) -> ParseResult {
return ParseResult(std::make_unique<Curve<StepInterpolator>>(
*outputType,
StepInterpolator(),
std::move(*input),
std::move(stops)
));
},
[&](const detail::ExponentialInterpolation& exponentialInterpolation) -> ParseResult {
const float base = exponentialInterpolation.base;
return outputType->match(
[&](const type::NumberType&) -> ParseResult {
return ParseResult(std::make_unique<Curve<ExponentialInterpolator<float>>>(
*outputType,
ExponentialInterpolator<float>(base),
std::move(*input),
std::move(stops)
));
},
[&](const type::ColorType&) -> ParseResult {
return ParseResult(std::make_unique<Curve<ExponentialInterpolator<mbgl::Color>>>(
*outputType,
ExponentialInterpolator<mbgl::Color>(base),
std::move(*input),
std::move(stops)
));
},
[&](const type::Array& arrayType) -> ParseResult {
if (arrayType.itemType == type::Number && arrayType.N) {
return ParseResult(std::make_unique<Curve<ExponentialInterpolator<std::vector<Value>>>>(
*outputType,
ExponentialInterpolator<std::vector<Value>>(base),
std::move(*input),
std::move(stops)
));
} else {
assert(false); // interpolability already checked above.
return ParseResult();
}
},
[&](const auto&) {
assert(false); // interpolability already checked above.
return ParseResult();
}
);
}
);
}
};
} // namespace expression
} // namespace style
} // namespace mbgl
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