// Licensed to the .NET Foundation under one or more agreements.
// The .NET Foundation licenses this file to you under the MIT license.
 
using System.Collections.Generic;
using System.Diagnostics.CodeAnalysis;
using System.Text.Json.Serialization.Metadata;
 
namespace System.Text.Json.Serialization.Converters
{
    // Converter for F# maps: https://fsharp.github.io/fsharp-core-docs/reference/fsharp-collections-fsharpmap-2.html
    internal sealed class FSharpMapConverter<TMap, TKey, TValue> : DictionaryDefaultConverter<TMap, TKey, TValue>
        where TMap : IEnumerable<KeyValuePair<TKey, TValue>>
        where TKey : notnull
    {
        private readonly Func<IEnumerable<Tuple<TKey, TValue>>, TMap> _mapConstructor;
 
        [RequiresUnreferencedCode(FSharpCoreReflectionProxy.FSharpCoreUnreferencedCodeMessage)]
        [RequiresDynamicCode(FSharpCoreReflectionProxy.FSharpCoreUnreferencedCodeMessage)]
        public FSharpMapConverter()
        {
            _mapConstructor = FSharpCoreReflectionProxy.Instance.CreateFSharpMapConstructor<TMap, TKey, TValue>();
        }
 
        protected override void Add(TKey key, in TValue value, JsonSerializerOptions options, ref ReadStack state)
        {
            ((List<Tuple<TKey, TValue>>)state.Current.ReturnValue!).Add(new Tuple<TKey, TValue>(key, value));
        }
 
        internal override bool CanHaveMetadata => false;
 
        internal override bool SupportsCreateObjectDelegate => false;
        protected override void CreateCollection(ref Utf8JsonReader reader, scoped ref ReadStack state)
        {
            state.Current.ReturnValue = new List<Tuple<TKey, TValue>>();
        }
 
        internal sealed override bool IsConvertibleCollection => true;
        protected override void ConvertCollection(ref ReadStack state, JsonSerializerOptions options)
        {
            state.Current.ReturnValue = _mapConstructor((List<Tuple<TKey, TValue>>)state.Current.ReturnValue!);
        }
    }
}