using System.Collections.Generic;
using Microsoft.Extensions.Logging;

namespace CellularManagement.WebSocket.Pipeline;

/// <summary>
/// 管道构建器
/// 用于构建消息处理管道
/// </summary>
/// <typeparam name="TInput">输入消息类型</typeparam>
/// <typeparam name="TOutput">输出消息类型</typeparam>
public class PipelineBuilder<TInput, TOutput>
{
    private readonly ILoggerFactory _loggerFactory;
    private readonly ILogger<PipelineBuilder<TInput, TOutput>> _logger;
    private readonly List<IPipelineStep<TInput, TOutput>> _steps = new();

    public PipelineBuilder(ILoggerFactory loggerFactory)
    {
        _loggerFactory = loggerFactory;
        _logger = loggerFactory.CreateLogger<PipelineBuilder<TInput, TOutput>>();
        _logger.LogInformation("初始化管道构建器，输入类型：{InputType}，输出类型：{OutputType}", 
            typeof(TInput).Name, typeof(TOutput).Name);
    }

    /// <summary>
    /// 添加处理步骤
    /// </summary>
    /// <param name="step">处理步骤</param>
    /// <returns>管道构建器</returns>
    public PipelineBuilder<TInput, TOutput> AddStep(IPipelineStep<TInput, TOutput> step)
    {
        _logger.LogInformation("添加处理步骤，步骤类型：{StepType}", step.GetType().Name);
        _steps.Add(step);
        return this;
    }

    /// <summary>
    /// 构建处理管道
    /// </summary>
    /// <returns>处理管道</returns>
    public IPipelineStep<TInput, TOutput> Build()
    {
        _logger.LogInformation("开始构建处理管道，步骤数量：{StepCount}", _steps.Count);
        
        if (_steps.Count == 0)
        {
            _logger.LogWarning("处理管道没有添加任何步骤");
            throw new InvalidOperationException("处理管道必须至少包含一个步骤");
        }

        // 构建处理链
        var pipeline = _steps[0];
        for (int i = 1; i < _steps.Count; i++)
        {
            var currentStep = _steps[i];
            _logger.LogDebug("连接处理步骤：{CurrentStep} -> {NextStep}", 
                pipeline.GetType().Name, currentStep.GetType().Name);
            pipeline = new ChainedPipelineStep(pipeline, currentStep, _loggerFactory);
        }

        _logger.LogInformation("处理管道构建完成，总步骤数：{StepCount}", _steps.Count);
        return pipeline;
    }

    /// <summary>
    /// 链式处理步骤
    /// 用于连接多个处理步骤
    /// </summary>
    private class ChainedPipelineStep : IPipelineStep<TInput, TOutput>
    {
        private readonly IPipelineStep<TInput, TOutput> _first;
        private readonly IPipelineStep<TInput, TOutput> _second;
        private readonly ILogger<ChainedPipelineStep> _logger;

        public ChainedPipelineStep(
            IPipelineStep<TInput, TOutput> first,
            IPipelineStep<TInput, TOutput> second,
            ILoggerFactory loggerFactory)
        {
            _first = first;
            _second = second;
            _logger = loggerFactory.CreateLogger<ChainedPipelineStep>();
            _logger.LogDebug("创建链式处理步骤，第一步：{FirstStep}，第二步：{SecondStep}", 
                first.GetType().Name, second.GetType().Name);
        }

        public async Task<TOutput> ProcessAsync(TInput input, CancellationToken cancellationToken)
        {
            _logger.LogDebug("开始链式处理消息");
            var intermediate = await _first.ProcessAsync(input, cancellationToken);
            if (intermediate is TInput inputValue)
            {
                return await _second.ProcessAsync(inputValue, cancellationToken);
            }
            throw new InvalidOperationException($"无法将类型 {intermediate?.GetType().Name ?? "null"} 转换为 {typeof(TInput).Name}");
        }

        public async Task<TOutput> ProcessWithErrorHandlingAsync(TInput input, CancellationToken cancellationToken)
        {
            _logger.LogDebug("开始链式处理消息（带错误处理）");
            try
            {
                var intermediate = await _first.ProcessWithErrorHandlingAsync(input, cancellationToken);
                if (intermediate is TInput inputValue)
                {
                    return await _second.ProcessWithErrorHandlingAsync(inputValue, cancellationToken);
                }
                throw new InvalidOperationException($"无法将类型 {intermediate?.GetType().Name ?? "null"} 转换为 {typeof(TInput).Name}");
            }
            catch (Exception ex)
            {
                _logger.LogError(ex, "链式处理发生错误");
                throw;
            }
        }
    }
}

public class Pipeline<TInput, TOutput> : IPipelineStep<TInput, TOutput>
{
    private readonly IReadOnlyList<IPipelineStep<TInput, TOutput>> _steps;
    private readonly ILogger<Pipeline<TInput, TOutput>> _logger;

    public Pipeline(IReadOnlyList<IPipelineStep<TInput, TOutput>> steps, ILogger<Pipeline<TInput, TOutput>> logger)
    {
        _steps = steps ?? throw new ArgumentNullException(nameof(steps));
        _logger = logger ?? throw new ArgumentNullException(nameof(logger));
    }

    public async Task<TOutput> ProcessAsync(TInput input, CancellationToken cancellationToken)
    {
        TOutput? result = default;
        var current = input;

        foreach (var step in _steps)
        {
            result = await step.ProcessAsync(current, cancellationToken);
            if (result is TInput nextInput)
            {
                current = nextInput;
            }
            else
            {
                break;
            }
        }

        return result ?? throw new InvalidOperationException("管道处理结果不能为 null");
    }

    public async Task<TOutput> ProcessWithErrorHandlingAsync(TInput input, CancellationToken cancellationToken)
    {
        try
        {
            return await ProcessAsync(input, cancellationToken);
        }
        catch (Exception ex)
        {
            _logger.LogError(ex, "管道处理发生错误");
            throw new PipelineException("管道处理失败", ex);
        }
    }
}