// Licensed to the .NET Foundation under one or more agreements.
// The .NET Foundation licenses this file to you under the MIT license.
 
using System.Text.Json;
using Google.Api;
using Grpc.Core;
using Grpc.Shared.Server;
using Microsoft.AspNetCore.Http;
using Microsoft.Extensions.Logging;
 
namespace Microsoft.AspNetCore.Grpc.JsonTranscoding.Internal.CallHandlers;
 
internal sealed class UnaryServerCallHandler<TService, TRequest, TResponse> : ServerCallHandlerBase<TService, TRequest, TResponse>
    where TService : class
    where TRequest : class
    where TResponse : class
{
    private readonly UnaryServerMethodInvoker<TService, TRequest, TResponse> _invoker;
 
    public UnaryServerCallHandler(
        UnaryServerMethodInvoker<TService, TRequest, TResponse> unaryMethodInvoker,
        ILoggerFactory loggerFactory,
        CallHandlerDescriptorInfo descriptorInfo,
        JsonSerializerOptions options) : base(unaryMethodInvoker, loggerFactory, descriptorInfo, options)
    {
        _invoker = unaryMethodInvoker;
    }
 
    protected override async Task HandleCallAsyncCore(HttpContext httpContext, JsonTranscodingServerCallContext serverCallContext)
    {
        var request = await JsonRequestHelpers.ReadMessage<TRequest>(serverCallContext, SerializerOptions);
 
        var response = await _invoker.Invoke(httpContext, serverCallContext, request);
 
        if (serverCallContext.Status.StatusCode != StatusCode.OK)
        {
            throw new RpcException(serverCallContext.Status);
        }
 
        if (response == null)
        {
            // This is consistent with Grpc.Core when a null value is returned
            throw new RpcException(new Status(StatusCode.Cancelled, "No message returned from method."));
        }
 
        if (response is HttpBody httpBody)
        {
            serverCallContext.EnsureResponseHeaders(httpBody.ContentType);
            await serverCallContext.HttpContext.Response.Body.WriteAsync(httpBody.Data.Memory);
        }
        else
        {
            serverCallContext.EnsureResponseHeaders();
            await JsonRequestHelpers.SendMessage(serverCallContext, SerializerOptions, response, CancellationToken.None);
        }
    }
}