MapLibreParticleLab/platform/darwin/src/MLNConversion.h

#include <mbgl/style/conversion_impl.hpp>

NS_ASSUME_NONNULL_BEGIN

namespace mbgl {
namespace style {
namespace conversion {

// A wrapper class for `id`, so as not to confuse ARC.
class Holder {
 public:
  Holder(const id v) : value(v) {}
  const id value;
};

template <>
class ConversionTraits<Holder> {
 public:
  static bool isUndefined(const Holder& holder) {
    const id value = holder.value;
    return !value || value == [NSNull null];
  }

  static bool isArray(const Holder& holder) {
    const id value = holder.value;
    return [value isKindOfClass:[NSArray class]];
  }

  static bool isObject(const Holder& holder) {
    const id value = holder.value;
    return [value isKindOfClass:[NSDictionary class]];
  }

  static std::size_t arrayLength(const Holder& holder) {
    const id value = holder.value;
    NSCAssert([value isKindOfClass:[NSArray class]], @"Value must be an NSArray for getLength().");
    NSArray* array = value;
    auto length = [array count];
    NSCAssert(length <= std::numeric_limits<size_t>::max(), @"Array length out of bounds.");
    return length;
  }

  static Holder arrayMember(const Holder& holder, std::size_t i) {
    const id value = holder.value;
    NSCAssert([value isKindOfClass:[NSArray class]], @"Value must be an NSArray for get(int).");
    NSCAssert(i < NSUIntegerMax, @"Index must be less than NSUIntegerMax");
    return {[value objectAtIndex:i]};
  }

  static std::optional<Holder> objectMember(const Holder& holder, const char* key) {
    const id value = holder.value;
    NSCAssert([value isKindOfClass:[NSDictionary class]],
              @"Value must be an NSDictionary for get(string).");
    NSObject* member = [value objectForKey:@(key)];
    if (member && member != [NSNull null]) {
      return {member};
    } else {
      return {};
    }
  }

// Compiler is wrong about `Fn` parameter missing a nullability specifier.
#pragma clang diagnostic push
#pragma clang diagnostic ignored "-Wnullability-completeness"
  template <class Fn>
  static std::optional<Error> eachMember(const Holder& holder, Fn&& visit) {
#pragma clang diagnostic pop
    [holder.value
        enumerateKeysAndObjectsUsingBlock:^(id _Nonnull key, id _Nonnull obj, BOOL* _Nonnull stop) {
          auto result = visit(std::string(static_cast<const char*>([key UTF8String])), obj);
          if (result) {
            *stop = YES;
          }
        }];
    return {};
  }

  static std::optional<bool> toBool(const Holder& holder) {
    const id value = holder.value;
    if (_isBool(value)) {
      return ((NSNumber*)value).boolValue;
    } else {
      return {};
    }
  }

  static std::optional<float> toNumber(const Holder& holder) {
    const id value = holder.value;
    if (_isNumber(value)) {
      return ((NSNumber*)value).floatValue;
    } else {
      return {};
    }
  }

  static std::optional<double> toDouble(const Holder& holder) {
    const id value = holder.value;
    if (_isNumber(value)) {
      return ((NSNumber*)value).doubleValue;
    } else {
      return {};
    }
  }

  static std::optional<std::string> toString(const Holder& holder) {
    const id value = holder.value;
    if (_isString(value)) {
      return std::string(static_cast<const char*>([value UTF8String]));
    } else {
      return {};
    }
  }

  static std::optional<mbgl::Value> toValue(const Holder& holder) {
    const id value = holder.value;
    if (isUndefined(value)) {
      return {};
    } else if (_isBool(value)) {
      return {*toBool(holder)};
    } else if (_isString(value)) {
      return {*toString(holder)};
    } else if (_isNumber(value)) {
      return {*toDouble(holder)};
    } else {
      return {};
    }
  }

  static std::optional<GeoJSON> toGeoJSON(const Holder& holder, Error& error) {
    id object = holder.value;
    if ([object isKindOfClass:[NSDictionary class]]) {
      NSError* serializationError;
      NSData* data = [NSJSONSerialization dataWithJSONObject:object
                                                     options:0
                                                       error:&serializationError];
      if (serializationError) {
        error = {std::string(serializationError.localizedDescription.UTF8String)};
        return {};
      }
      NSString* string = [[NSString alloc] initWithData:data encoding:NSUTF8StringEncoding];
      return mapbox::geojson::parse(string.UTF8String);
    } else {
      error = {std::string(
          [NSString stringWithFormat:@"%@ is not a GeoJSON object.", object].UTF8String)};
      return {};
    }
  }

 private:
  static bool _isBool(const id value) {
    if (![value isKindOfClass:[NSNumber class]]) return false;
    // char: 32-bit boolean
    // BOOL: 64-bit boolean
    NSNumber* number = value;
    return ((strcmp([number objCType], @encode(char)) == 0) ||
            (strcmp([number objCType], @encode(BOOL)) == 0));
  }

  static bool _isNumber(const id value) {
    return [value isKindOfClass:[NSNumber class]] && !_isBool(value);
  }

  static bool _isString(const id value) { return [value isKindOfClass:[NSString class]]; }
};

inline Convertible makeConvertible(const id value) { return Convertible(Holder(value)); }

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

NS_ASSUME_NONNULL_END