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#pragma once
#include <mbgl/style/expression/expression.hpp>
#include <mbgl/style/expression/value.hpp>
#include <mbgl/style/expression/is_constant.hpp>
namespace mbgl {
namespace style {
template <class T>
class SourceFunction {
public:
// The second parameter should be used only for conversions from legacy functions.
SourceFunction(std::unique_ptr<expression::Expression> expression_, optional<T> defaultValue_ = {})
: isExpression(defaultValue_),
expression(std::move(expression_)),
defaultValue(std::move(defaultValue_)) {
assert(expression::isZoomConstant(*expression));
assert(!expression::isFeatureConstant(*expression));
}
template <class Feature>
T evaluate(const Feature& feature, T finalDefaultValue) const {
const expression::EvaluationResult result = expression->evaluate(expression::EvaluationContext(&feature));
if (result) {
const optional<T> typed = expression::fromExpressionValue<T>(*result);
return typed ? *typed : defaultValue ? *defaultValue : finalDefaultValue;
}
return defaultValue ? *defaultValue : finalDefaultValue;
}
std::vector<optional<T>> possibleOutputs() const {
return expression::fromExpressionValues<T>(expression->possibleOutputs());
}
friend bool operator==(const SourceFunction& lhs,
const SourceFunction& rhs) {
return *lhs.expression == *rhs.expression;
}
bool useIntegerZoom = false;
bool isExpression;
const expression::Expression& getExpression() const { return *expression; }
private:
std::shared_ptr<const expression::Expression> expression;
optional<T> defaultValue;
};
} // namespace style
} // namespace mbgl
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