let singleton = null

class SvgWorkerManager {
  constructor() {
    this.worker = wx.createWorker('workers/svg-generator/index.js')
    this.pending = new Map()
    this.timeoutMs = 30000

    this.worker.onMessage((message) => {
      const { requestId, success, data, error } = message || {}
      const pendingTask = this.pending.get(requestId)
      if (!pendingTask) {
        return
      }

      clearTimeout(pendingTask.timer)
      this.pending.delete(requestId)

      if (success) {
        pendingTask.resolve(data)
      } else {
        pendingTask.reject(new Error(error || 'Worker 执行失败'))
      }
    })

    this.worker.onError((error) => {
      this.rejectAll(error)
    })

    if (typeof this.worker.onProcessKilled === 'function') {
      this.worker.onProcessKilled(() => {
        this.rejectAll(new Error('Worker 进程被系统回收'))
      })
    }
  }

  rejectAll(error) {
    for (const [requestId, pendingTask] of this.pending.entries()) {
      clearTimeout(pendingTask.timer)
      pendingTask.reject(error)
      this.pending.delete(requestId)
    }
  }

  request(type, payload, timeoutMs) {
    const requestId = `${Date.now()}-${Math.random().toString(16).slice(2)}`
    return new Promise((resolve, reject) => {
      const timer = setTimeout(() => {
        this.pending.delete(requestId)
        reject(new Error(`Worker 超时: ${type}`))
      }, timeoutMs || this.timeoutMs)

      this.pending.set(requestId, { resolve, reject, timer })

      this.worker.postMessage({
        requestId,
        type,
        payload,
      })
    })
  }

  loadFont(fontId, fontBuffer) {
    return this.request('load-font', {
      fontId,
      fontBuffer,
    }, 45000)
  }

  generateSvg(params) {
    return this.request('generate-svg', params, 45000)
  }

  clearCache() {
    return this.request('clear-cache', {})
  }

  terminate() {
    this.rejectAll(new Error('Worker 已终止'))
    this.worker.terminate()
  }
}

function getSvgWorkerManager() {
  if (!singleton) {
    singleton = new SvgWorkerManager()
  }
  return singleton
}

module.exports = {
  getSvgWorkerManager,
}