#pragma once

#include <mbgl/style/filter.hpp>
#include <mbgl/style/conversion.hpp>
#include <mbgl/util/geometry.hpp>

namespace mbgl {
namespace style {
namespace conversion {

template <>
struct Converter<Filter> {
public:
    template <class V>
    optional<Filter> operator()(const V& value, Error& error) const {
        if (!isArray(value)) {
            error = { "filter expression must be an array" };
            return {};
        }

        if (arrayLength(value) < 1) {
            error = { "filter expression must have at least 1 element" };
            return {};
        }

        optional<std::string> op = toString(arrayMember(value, 0));
        if (!op) {
            error = { "filter operator must be a string" };
            return {};
        }

        if (*op == "==") {
            return convertEqualityFilter<EqualsFilter, TypeEqualsFilter, IdentifierEqualsFilter>(value, error);
        } else if (*op == "!=") {
            return convertEqualityFilter<NotEqualsFilter, TypeNotEqualsFilter, IdentifierNotEqualsFilter>(value, error);
        } else if (*op == ">") {
            return convertBinaryFilter<GreaterThanFilter>(value, error);
        } else if (*op == ">=") {
            return convertBinaryFilter<GreaterThanEqualsFilter>(value, error);
        } else if (*op == "<") {
            return convertBinaryFilter<LessThanFilter>(value, error);
        } else if (*op == "<=") {
            return convertBinaryFilter<LessThanEqualsFilter>(value, error);
        } else if (*op == "in") {
            return convertSetFilter<InFilter, TypeInFilter, IdentifierInFilter>(value, error);
        } else if (*op == "!in") {
            return convertSetFilter<NotInFilter, TypeNotInFilter, IdentifierNotInFilter>(value, error);
        } else if (*op == "all") {
            return convertCompoundFilter<AllFilter>(value, error);
        } else if (*op == "any") {
            return convertCompoundFilter<AnyFilter>(value, error);
        } else if (*op == "none") {
            return convertCompoundFilter<NoneFilter>(value, error);
        } else if (*op == "has") {
            return convertUnaryFilter<HasFilter, HasIdentifierFilter>(value, error);
        } else if (*op == "!has") {
           return convertUnaryFilter<NotHasFilter, NotHasIdentifierFilter>(value, error);
        }

        error = { R"(filter operator must be one of "==", "!=", ">", ">=", "<", "<=", "in", "!in", "all", "any", "none", "has", or "!has")" };
        return {};
    }

private:
    optional<Value> normalizeValue(const optional<Value>& value, Error& error) const {
        if (!value) {
            error = { "filter expression value must be a boolean, number, or string" };
            return {};
        } else {
            return *value;
        }
    }

    template <class V>
    optional<FeatureType> toFeatureType(const V& value, Error& error) const {
        optional<std::string> type = toString(value);
        if (!type) {
            error = { "value for $type filter must be a string" };
            return {};
        } else if (*type == "Point") {
            return FeatureType::Point;
        } else if (*type == "LineString") {
            return FeatureType::LineString;
        } else if (*type == "Polygon") {
            return FeatureType::Polygon;
        } else {
            error = { "value for $type filter must be Point, LineString, or Polygon" };
            return {};
        }
    }

    template <class V>
    optional<FeatureIdentifier> toFeatureIdentifier(const V& value, Error& error) const {
        optional<Value> identifier = toValue(value);
        if (!identifier) {
            error = { "filter expression value must be a boolean, number, or string" };
            return {};
        } else {
            return (*identifier).match(
                [] (uint64_t t) -> optional<FeatureIdentifier> { return { t }; },
                [] ( int64_t t) -> optional<FeatureIdentifier> { return { t }; },
                [] (  double t) -> optional<FeatureIdentifier> { return { t }; },
                [] (const std::string& t) -> optional<FeatureIdentifier> { return { t }; },
                [&] (const auto&) -> optional<FeatureIdentifier> {
                    error = { "filter expression value must be a boolean, number, or string" };
                    return {};
                });
        }
    }

    template <class FilterType, class IdentifierFilterType, class V>
    optional<Filter> convertUnaryFilter(const V& value, Error& error) const {
        if (arrayLength(value) < 2) {
            error = { "filter expression must have 2 elements" };
            return {};
        }

        optional<std::string> key = toString(arrayMember(value, 1));
        if (!key) {
            error = { "filter expression key must be a string" };
            return {};
        }

        if (*key == "$id") {
            return { IdentifierFilterType {} };
        } else {
            return { FilterType { *key } };
        }
    }

    template <class FilterType, class TypeFilterType, class IdentifierFilterType, class V>
    optional<Filter> convertEqualityFilter(const V& value, Error& error) const {
        if (arrayLength(value) < 3) {
            error = { "filter expression must have 3 elements" };
            return {};
        }

        optional<std::string> key = toString(arrayMember(value, 1));
        if (!key) {
            error = { "filter expression key must be a string" };
            return {};
        }

        if (*key == "$type") {
            optional<FeatureType> filterValue = toFeatureType(arrayMember(value, 2), error);
            if (!filterValue) {
                return {};
            }

            return { TypeFilterType { *filterValue } };

        } else if (*key == "$id") {
            optional<FeatureIdentifier> filterValue = toFeatureIdentifier(arrayMember(value, 2), error);
            if (!filterValue) {
                return {};
            }

            return { IdentifierFilterType { *filterValue } };

        } else {
            optional<Value> filterValue = normalizeValue(toValue(arrayMember(value, 2)), error);
            if (!filterValue) {
                return {};
            }

            return { FilterType { *key, *filterValue } };
        }
    }

    template <class FilterType, class V>
    optional<Filter> convertBinaryFilter(const V& value, Error& error) const {
        if (arrayLength(value) < 3) {
            error = { "filter expression must have 3 elements" };
            return {};
        }

        optional<std::string> key = toString(arrayMember(value, 1));
        if (!key) {
            error = { "filter expression key must be a string" };
            return {};
        }

        optional<Value> filterValue = normalizeValue(toValue(arrayMember(value, 2)), error);
        if (!filterValue) {
            return {};
        }

        return { FilterType { *key, *filterValue } };
    }

    template <class FilterType, class TypeFilterType, class IdentifierFilterType, class V>
    optional<Filter> convertSetFilter(const V& value, Error& error) const {
        if (arrayLength(value) < 2) {
            error = { "filter expression must at least 2 elements" };
            return {};
        }

        optional<std::string> key = toString(arrayMember(value, 1));
        if (!key) {
            error = { "filter expression key must be a string" };
            return {};
        }

        if (*key == "$type") {
            std::vector<FeatureType> values;
            for (std::size_t i = 2; i < arrayLength(value); ++i) {
                optional<FeatureType> filterValue = toFeatureType(arrayMember(value, i), error);
                if (!filterValue) {
                    return {};
                }
                values.push_back(*filterValue);
            }

            return { TypeFilterType { std::move(values) } };

        } else if (*key == "$id") {
            std::vector<FeatureIdentifier> values;
            for (std::size_t i = 2; i < arrayLength(value); ++i) {
                optional<FeatureIdentifier> filterValue = toFeatureIdentifier(arrayMember(value, i), error);
                if (!filterValue) {
                    return {};
                }
                values.push_back(*filterValue);
            }

            return { IdentifierFilterType { std::move(values) } };

        } else {
            std::vector<Value> values;
            for (std::size_t i = 2; i < arrayLength(value); ++i) {
                optional<Value> filterValue = normalizeValue(toValue(arrayMember(value, i)), error);
                if (!filterValue) {
                    return {};
                }
                values.push_back(*filterValue);
            }

            return { FilterType { *key, std::move(values) } };
        }
    }

    template <class FilterType, class V>
    optional<Filter> convertCompoundFilter(const V& value, Error& error) const {
        std::vector<Filter> filters;
        for (std::size_t i = 1; i < arrayLength(value); ++i) {
            optional<Filter> element = operator()(arrayMember(value, i), error);
            if (!element) {
                return {};
            }
            filters.push_back(*element);
        }

        return { FilterType { std::move(filters) } };
    }
};

} // namespace conversion
} // namespace style
} // namespace mbgl