using Grpc.Core;
using Grpc.Core.Interceptors;


//Interceptor 【客户端】调用重写以下项：
//BlockingUnaryCall：截获一元 RPC 的阻塞调用。
//AsyncUnaryCall：截获一元 RPC 的异步调用。
//AsyncClientStreamingCall：截获客户端流式处理 RPC 的异步调用。
//AsyncServerStreamingCall：截获服务器流式处理 RPC 的异步调用。
//AsyncDuplexStreamingCall：截获双向流式处理 RPC 的异步调用。

//Interceptor 【服务器】响应侦听器，重写以下项：
//UnaryServerHandler：截获一元 RPC。
//ClientStreamingServerHandler：截获客户端流式处理 RPC。
//ServerStreamingServerHandler：截获服务器流式处理 RPC。
//DuplexStreamingServerHandler：截获双向流式处理 RPC
public class ClientLoggerInterceptor : Interceptor
{
	private readonly ILogger<ClientLoggerInterceptor> _logger;

	public ClientLoggerInterceptor(ILoggerFactory loggerFactory)
	{
		_logger = loggerFactory.CreateLogger<ClientLoggerInterceptor>();
	}

	public override TResponse BlockingUnaryCall<TRequest, TResponse>(
		TRequest request,
		ClientInterceptorContext<TRequest, TResponse> context,
		BlockingUnaryCallContinuation<TRequest, TResponse> continuation)
	{
		LogCall(context.Method);
		AddCallerMetadata(ref context);

		try
		{
			return continuation(request, context);
		}
		catch (Exception ex)
		{
			LogError(ex);
			throw;
		}
	}

	public override AsyncUnaryCall<TResponse> AsyncUnaryCall<TRequest, TResponse>(
		TRequest request,
		ClientInterceptorContext<TRequest, TResponse> context,
		AsyncUnaryCallContinuation<TRequest, TResponse> continuation)
	{
		LogCall(context.Method);
		AddCallerMetadata(ref context);

		try
		{
			var call = continuation(request, context);

			return new AsyncUnaryCall<TResponse>(HandleResponse(call.ResponseAsync), call.ResponseHeadersAsync, call.GetStatus, call.GetTrailers, call.Dispose);
		}
		catch (Exception ex)
		{
			LogError(ex);
			throw;
		}
	}

	private async Task<TResponse> HandleResponse<TResponse>(Task<TResponse> t)
	{
		try
		{
			var response = await t;
			_logger.LogInformation($"Response received: {response}");
			return response;
		}
		catch (Exception ex)
		{
			LogError(ex);
			throw;
		}
	}

	public override AsyncClientStreamingCall<TRequest, TResponse> AsyncClientStreamingCall<TRequest, TResponse>(
		ClientInterceptorContext<TRequest, TResponse> context,
		AsyncClientStreamingCallContinuation<TRequest, TResponse> continuation)
	{
		LogCall(context.Method);
		AddCallerMetadata(ref context);

		try
		{
			return continuation(context);
		}
		catch (Exception ex)
		{
			LogError(ex);
			throw;
		}
	}

	public override AsyncServerStreamingCall<TResponse> AsyncServerStreamingCall<TRequest, TResponse>(
		TRequest request,
		ClientInterceptorContext<TRequest, TResponse> context,
		AsyncServerStreamingCallContinuation<TRequest, TResponse> continuation)
	{
		LogCall(context.Method);
		AddCallerMetadata(ref context);

		try
		{
			return continuation(request, context);
		}
		catch (Exception ex)
		{
			LogError(ex);
			throw;
		}
	}

	public override AsyncDuplexStreamingCall<TRequest, TResponse> AsyncDuplexStreamingCall<TRequest, TResponse>(
		ClientInterceptorContext<TRequest, TResponse> context,
		AsyncDuplexStreamingCallContinuation<TRequest, TResponse> continuation)
	{
		LogCall(context.Method);
		AddCallerMetadata(ref context);

		try
		{
			return continuation(context);
		}
		catch (Exception ex)
		{
			LogError(ex);
			throw;
		}
	}

	private void LogCall<TRequest, TResponse>(Method<TRequest, TResponse> method)
		where TRequest : class
		where TResponse : class
	{
		_logger.LogInformation($"Starting call. Name: {method.Name}. Type: {method.Type}. Request: {typeof(TRequest)}. Response: {typeof(TResponse)}");
	}

	private void AddCallerMetadata<TRequest, TResponse>(ref ClientInterceptorContext<TRequest, TResponse> context)
		where TRequest : class
		where TResponse : class
	{
		var headers = context.Options.Headers;

		// Call doesn't have a headers collection to add to.
		// Need to create a new context with headers for the call.
		if (headers == null)
		{
			headers = new Metadata();
			var options = context.Options.WithHeaders(headers);
			context = new ClientInterceptorContext<TRequest, TResponse>(context.Method, context.Host, options);
		}

		// Add caller metadata to call headers
		headers.Add("caller-user", Environment.UserName);
		headers.Add("caller-machine", Environment.MachineName);
		headers.Add("caller-os", Environment.OSVersion.ToString());
	}

	private void LogError(Exception ex)
	{
		_logger.LogError(ex, $"Call error: {ex.Message}");
	}
}