const {
  canvasToTempFilePath,
  saveImageToPhotosAlbum,
  writeFile,
  openSetting,
  showModal,
} = require('./wx-promisify')

function getWindowDpr() {
  if (typeof wx.getWindowInfo === 'function') {
    return wx.getWindowInfo().pixelRatio || 1
  }
  const info = wx.getSystemInfoSync()
  return info.pixelRatio || 1
}

function queryCanvasNode(page, selector) {
  return new Promise((resolve, reject) => {
    const query = wx.createSelectorQuery().in(page)
    query
      .select(selector)
      .fields({ node: true, size: true })
      .exec((result) => {
        const target = result && result[0]
        if (!target || !target.node) {
          reject(new Error('未找到导出画布节点'))
          return
        }
        resolve(target)
      })
  })
}

async function writeSvgTempFile(svgString) {
  const path = `${wx.env.USER_DATA_PATH}/font2svg_preview_${Date.now()}.svg`
  await writeFile(path, svgString, 'utf8')
  return path
}

async function exportSvgToPngByCanvas(page, options) {
  const {
    svgString,
    width,
    height,
    selector = '#exportCanvas',
    backgroundColor = '#ffffff',
  } = options

  if (!svgString) {
    throw new Error('缺少 SVG 内容')
  }

  const canvasNode = await queryCanvasNode(page, selector)
  const canvas = canvasNode.node
  const ctx = canvas.getContext('2d')
  const dpr = getWindowDpr()

  const renderWidth = Math.max(1, Math.min(2048, Math.round(width || canvasNode.width || 1024)))
  const renderHeight = Math.max(1, Math.min(2048, Math.round(height || canvasNode.height || 1024)))

  canvas.width = renderWidth * dpr
  canvas.height = renderHeight * dpr

  if (typeof ctx.setTransform === 'function') {
    ctx.setTransform(dpr, 0, 0, dpr, 0, 0)
  } else {
    ctx.scale(dpr, dpr)
  }

  ctx.fillStyle = backgroundColor
  ctx.fillRect(0, 0, renderWidth, renderHeight)

  const svgPath = await writeSvgTempFile(svgString)
  const image = canvas.createImage()

  await new Promise((resolve, reject) => {
    image.onload = resolve
    image.onerror = () => reject(new Error('加载 SVG 到画布失败'))
    image.src = svgPath
  })

  ctx.drawImage(image, 0, 0, renderWidth, renderHeight)

  const fileRes = await canvasToTempFilePath(
    {
      canvas,
      x: 0,
      y: 0,
      width: renderWidth,
      height: renderHeight,
      destWidth: renderWidth,
      destHeight: renderHeight,
      fileType: 'png',
    },
    page
  )

  return fileRes.tempFilePath
}

async function savePngToAlbum(filePath) {
  try {
    await saveImageToPhotosAlbum(filePath)
    return { success: true }
  } catch (error) {
    const errMsg = String(error && error.errMsg ? error.errMsg : error)
    const lowerErrMsg = errMsg.toLowerCase()
    const needAuth = lowerErrMsg.includes('auth deny') || lowerErrMsg.includes('authorize')
    const privateApiBanned = lowerErrMsg.includes('private api banned')

    if (needAuth) {
      const modalRes = await showModal({
        title: '需要相册权限',
        content: '请在设置中开启“保存到相册”权限后重试。',
        confirmText: '去设置',
      })
      if (modalRes.confirm) {
        await openSetting()
      }
    }

    return {
      success: false,
      needAuth,
      privateApiBanned,
      reason: privateApiBanned
        ? 'private_api_banned'
        : (needAuth ? 'auth_denied' : 'save_failed'),
      error,
    }
  }
}

module.exports = {
  exportSvgToPngByCanvas,
  savePngToAlbum,
}