import { getApiBaseUrl, getAuthHeader } from './request.js'

/**
 * 短篇小说外部服务 API 封装
 * 通过后端 SSE 代理调用外部 short-novel-service
 */

/**
 * 首次发起短篇小说生成（SSE 流式）
 * @param {Object} params
 * @param {string} params.query - 用户心愿文本
 * @param {Function} params.onEvent - 事件回调 (event) => void，event 包含 type、session_id、payload
 * @param {Function} params.onError - 错误回调
 * @returns {Object} uni.request 任务对象（用于 abort）
 */
export const startNovelStream = ({ query, onEvent, onError }) => {
  let chunkProcessed = false
  const task = uni.request({
    url: `${getApiBaseUrl()}/shortNovel/stream`,
    method: 'POST',
    data: { query },
    header: {
      'Content-Type': 'application/json',
      'Accept': 'text/event-stream',
      ...getAuthHeader()
    },
    enableChunked: true,
    timeout: 300000,
    success: (res) => {
      if (res.statusCode >= 400) {
        onError?.(res.data?.message || '请求失败')
        return
      }
      // 仅在 chunk 未处理时才处理完整 data（避免 H5 双重消费）
      if (!chunkProcessed && typeof res.data === 'string' && res.data) {
        consumeSseText(res.data, onEvent, onError)
      }
    },
    fail: (error) => {
      onError?.(error.errMsg || '网络请求失败')
    }
  })

  task?.onChunkReceived?.((res) => {
    chunkProcessed = true
    try {
      const text = decodeChunk(res.data)
      consumeSseText(text, onEvent, onError)
    } catch (error) {
      onError?.(error.message || '流式解析失败')
    }
  })

  return task
}

/**
 * 后续轮次（澄清回答、大纲确认/修改、重试）
 * @param {Object} params
 * @param {string} params.sessionId - 外部服务的 session_id
 * @param {string} params.action - answer_clarification | confirm_outline | modify_outline | retry
 * @param {Object} params.payload - 操作载荷
 * @param {Function} params.onEvent
 * @param {Function} params.onError
 * @returns {Object} uni.request 任务对象
 */
export const followupStream = ({ sessionId, action, payload, onEvent, onError }) => {
  let chunkProcessed = false
  const task = uni.request({
    url: `${getApiBaseUrl()}/shortNovel/followup`,
    method: 'POST',
    data: { sessionId, action, payload },
    header: {
      'Content-Type': 'application/json',
      'Accept': 'text/event-stream',
      ...getAuthHeader()
    },
    enableChunked: true,
    timeout: 300000,
    success: (res) => {
      if (res.statusCode >= 400) {
        onError?.(res.data?.message || '请求失败')
        return
      }
      if (!chunkProcessed && typeof res.data === 'string' && res.data) {
        consumeSseText(res.data, onEvent, onError)
      }
    },
    fail: (error) => {
      onError?.(error.errMsg || '网络请求失败')
    }
  })

  task?.onChunkReceived?.((res) => {
    chunkProcessed = true
    try {
      const text = decodeChunk(res.data)
      consumeSseText(text, onEvent, onError)
    } catch (error) {
      onError?.(error.message || '流式解析失败')
    }
  })

  return task
}

/**
 * 解码 chunk 数据
 * 兼容 mp-weixin（不支持 TextDecoder）
 */
function decodeChunk(chunk) {
  if (typeof chunk === 'string') return chunk
  // 小程序环境 chunk 可能是 ArrayBuffer，转成 UTF-8 字符串
  const bytes = new Uint8Array(chunk)
  let result = ''
  let i = 0
  while (i < bytes.length) {
    const byte1 = bytes[i++]
    if (byte1 < 0x80) {
      result += String.fromCharCode(byte1)
    } else if (byte1 < 0xE0) {
      const byte2 = bytes[i++]
      result += String.fromCharCode(((byte1 & 0x1F) << 6) | (byte2 & 0x3F))
    } else if (byte1 < 0xF0) {
      const byte2 = bytes[i++]
      const byte3 = bytes[i++]
      result += String.fromCharCode(((byte1 & 0x0F) << 12) | ((byte2 & 0x3F) << 6) | (byte3 & 0x3F))
    } else {
      const byte2 = bytes[i++]
      const byte3 = bytes[i++]
      const byte4 = bytes[i++]
      const codePoint = ((byte1 & 0x07) << 18) | ((byte2 & 0x3F) << 12) | ((byte3 & 0x3F) << 6) | (byte4 & 0x3F)
      // 转成 UTF-16 代理对
      const adjusted = codePoint - 0x10000
      result += String.fromCharCode(0xD800 | (adjusted >> 10)) + String.fromCharCode(0xDC00 | (adjusted & 0x3FF))
    }
  }
  return result
}

/**
 * 解析 SSE 文本
 * 外部服务事件格式：data: {"type":"status","session_id":"xxx","payload":{...}}
 */
function consumeSseText(text, onEvent, onError) {
  const lines = text.split(/\r?\n/)
  let dataBuffer = ''

  for (const line of lines) {
    if (line.startsWith('data:')) {
      dataBuffer += line.slice(5).trim()
    } else if (line === '' && dataBuffer) {
      const dataStr = dataBuffer
      dataBuffer = ''
      if (dataStr === '[DONE]') return
      try {
        const event = JSON.parse(dataStr)
        onEvent?.(event)
      } catch (e) {
        onError?.(`SSE 解析失败: ${e.message}`)
      }
    }
  }
}