1 files changed, 248 insertions, 0 deletions
diff --git a/src/mbgl/style/conversion/filter.cpp b/src/mbgl/style/conversion/filter.cpp
new file mode 100644
index 0000000000..bb7bb6ea98
--- /dev/null
+++ b/src/mbgl/style/conversion/filter.cpp
@@ -0,0 +1,248 @@
+#include <mbgl/style/conversion/filter.hpp>
+#include <mbgl/util/geometry.hpp>
+
+namespace mbgl {
+namespace style {
+namespace conversion {
+
+static optional<Value> normalizeValue(const optional<Value>& value, Error& error) {
+    if (!value) {
+        error = { "filter expression value must be a boolean, number, or string" };
+        return {};
+    } else {
+        return *value;
+    }
+}
+
+static optional<FeatureType> toFeatureType(const Convertible& value, Error& error) {
+    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 $type filter must be Point, LineString, or Polygon" };
+        return {};
+    }
+}
+
+static optional<FeatureIdentifier> toFeatureIdentifier(const Convertible& value, Error& error) {
+    optional<Value> identifier = toValue(value);
+    if (!identifier) {
+        error = { "filter expression value must be a boolean, number, or string" };
+        return {};
+    } else {
+        return (*identifier).match(
+            [] (uint64_t t) -> optional<FeatureIdentifier> { return { t }; },
+            [] ( int64_t t) -> optional<FeatureIdentifier> { return { t }; },
+            [] (  double t) -> optional<FeatureIdentifier> { return { t }; },
+            [] (const std::string& t) -> optional<FeatureIdentifier> { return { t }; },
+            [&] (const auto&) -> optional<FeatureIdentifier> {
+                error = { "filter expression value must be a boolean, number, or string" };
+                return {};
+            });
+    }
+}
+
+template <class FilterType, class IdentifierFilterType>
+optional<Filter> convertUnaryFilter(const Convertible& value, Error& error) {
+    if (arrayLength(value) < 2) {
+        error = { "filter expression must have 2 elements" };
+        return {};
+    }
+
+    optional<std::string> key = toString(arrayMember(value, 1));
+    if (!key) {
+        error = { "filter expression key must be a string" };
+        return {};
+    }
+
+    if (*key == "$id") {
+        return { IdentifierFilterType {} };
+    } else {
+        return { FilterType { *key } };
+    }
+}
+
+template <class FilterType, class TypeFilterType, class IdentifierFilterType>
+optional<Filter> convertEqualityFilter(const Convertible& value, Error& error) {
+    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>
+optional<Filter> convertBinaryFilter(const Convertible& value, Error& error) {
+    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>
+optional<Filter> convertSetFilter(const Convertible& value, Error& error) {
+    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>
+optional<Filter> convertCompoundFilter(const Convertible& value, Error& error) {
+    std::vector<Filter> filters;
+    for (std::size_t i = 1; i < arrayLength(value); ++i) {
+        optional<Filter> element = convert<Filter>(arrayMember(value, i), error);
+        if (!element) {
+            return {};
+        }
+        filters.push_back(*element);
+    }
+
+    return { FilterType { std::move(filters) } };
+}
+
+optional<Filter> Converter<Filter>::operator()(const Convertible& 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 {};
+}
+
+} // namespace conversion
+} // namespace style
+} // namespace mbgl