const opentype = require('./vendor/opentype.js')
const { generateSvgFromFont } = require('./svg-builder')

const MAX_FONT_CACHE = 4
const fontCache = new Map()

function touchCache(key, value) {
  if (fontCache.has(key)) {
    fontCache.delete(key)
  }
  fontCache.set(key, value)

  while (fontCache.size > MAX_FONT_CACHE) {
    const firstKey = fontCache.keys().next().value
    fontCache.delete(firstKey)
  }
}

function sendResult(requestId, success, data, error) {
  worker.postMessage({
    requestId,
    success,
    data,
    error,
  })
}

function handleLoadFont(requestId, payload) {
  const { fontId, fontBuffer } = payload || {}
  if (!fontId || !fontBuffer) {
    throw new Error('加载字体参数无效')
  }

  const font = opentype.parse(fontBuffer)
  touchCache(fontId, {
    font,
    loadedAt: Date.now(),
  })

  return { fontId }
}

function handleGenerateSvg(payload) {
  const {
    fontId,
    text,
    fontSize,
    fillColor,
    letterSpacing,
    maxCharsPerLine,
  } = payload || {}

  if (!fontId) {
    throw new Error('缺少 fontId')
  }

  const cached = fontCache.get(fontId)
  if (!cached || !cached.font) {
    throw new Error('字体未加载，请先加载字体')
  }

  touchCache(fontId, cached)

  return generateSvgFromFont({
    text,
    font: cached.font,
    fontSize,
    fillColor,
    letterSpacing,
    maxCharsPerLine,
  })
}

worker.onMessage((message) => {
  const { requestId, type, payload } = message || {}

  try {
    if (!requestId) {
      throw new Error('缺少 requestId')
    }

    if (type === 'load-font') {
      const data = handleLoadFont(requestId, payload)
      sendResult(requestId, true, data)
      return
    }

    if (type === 'generate-svg') {
      const data = handleGenerateSvg(payload)
      sendResult(requestId, true, data)
      return
    }

    if (type === 'clear-cache') {
      fontCache.clear()
      sendResult(requestId, true, { ok: true })
      return
    }

    throw new Error(`未知的任务类型: ${type}`)
  } catch (error) {
    const messageText = error && error.message ? error.message : String(error)
    sendResult(requestId, false, null, messageText)
  }
})