/**
 * 在照片左下角叠加多行水印文字
 * @param {string} imagePath - 原始图片路径
 * @param {string|string[]} lines - 水印文字，字符串或字符串数组
 * @param {object} [canvasCtx] - APP端传入 { canvasId, proxy, setSize }
 * @returns {Promise<string>} 带水印的图片路径，失败时返回原图
 */
export function addWatermark(imagePath, lines, canvasCtx) {
  if (typeof lines === 'string') {
    lines = [lines]
  }

  return new Promise((resolve) => {
    // 超时保护：10秒
    const timer = setTimeout(() => {
      console.warn('[watermark] timeout')
      resolve(imagePath)
    }, 10000)

    _doWatermark(imagePath, lines, canvasCtx)
      .then((r) => { clearTimeout(timer); resolve(r || imagePath) })
      .catch((e) => { clearTimeout(timer); console.warn('[watermark]', e); resolve(imagePath) })
  })
}

function _doWatermark(imagePath, lines, canvasCtx) {
  // #ifdef H5
  return _h5(imagePath, lines)
  // #endif
  // #ifdef APP-PLUS
  return _app(imagePath, lines, canvasCtx)
  // #endif
  // eslint-disable-next-line no-unreachable
  return Promise.resolve(imagePath)
}

// ========== H5 ==========
// #ifdef H5
function _h5(imagePath, lines) {
  return new Promise((resolve, reject) => {
    const img = new Image()
    img.crossOrigin = 'anonymous'
    img.onload = () => {
      try {
        const w = img.naturalWidth, h = img.naturalHeight
        const c = document.createElement('canvas')
        c.width = w; c.height = h
        const ctx = c.getContext('2d')
        ctx.drawImage(img, 0, 0, w, h)
        _stamp(ctx, w, h, lines, false)
        resolve(c.toDataURL('image/jpeg', 0.9))
      } catch (e) { reject(e) }
    }
    img.onerror = reject
    img.src = imagePath
  })
}
// #endif

// ========== APP ==========
// #ifdef APP-PLUS
function _app(imagePath, lines, cc) {
  if (!cc || !cc.canvasId || !cc.proxy) {
    return Promise.reject(new Error('missing canvasCtx'))
  }
  return new Promise((resolve, reject) => {
    uni.getImageInfo({
      src: imagePath,
      success(info) {
        try {
          // 限制 canvas 宽度 ≤ 1200，避免内存问题
          let dw = info.width, dh = info.height
          if (dw > 1200) { const r = 1200 / dw; dw = 1200; dh = Math.round(info.height * r) }

          // 更新页面 canvas 尺寸
          if (typeof cc.setSize === 'function') cc.setSize(dw, dh)

          // 等 DOM 刷新（200ms 足够 APP webview 更新）
          setTimeout(() => {
            try {
              const ctx = uni.createCanvasContext(cc.canvasId, cc.proxy)
              ctx.drawImage(imagePath, 0, 0, dw, dh)
              _stamp(ctx, dw, dh, lines, true)

              let done = false
              const exp = () => {
                if (done) return
                done = true
                uni.canvasToTempFilePath({
                  canvasId: cc.canvasId,
                  x: 0, y: 0, width: dw, height: dh,
                  destWidth: info.width, destHeight: info.height,
                  fileType: 'jpg', quality: 0.9,
                  success: (r) => resolve(r.tempFilePath),
                  fail: reject
                }, cc.proxy)
              }

              ctx.draw(false, () => setTimeout(exp, 200))
              // 兜底
              setTimeout(exp, 1200)
            } catch (e) { reject(e) }
          }, 200)
        } catch (e) { reject(e) }
      },
      fail: reject
    })
  })
}
// #endif

/**
 * 在 canvas context 上绘制水印条
 * @param {boolean} isUni - true 用 uni canvas API，false 用 H5 canvas API
 */
function _stamp(ctx, w, h, lines, isUni) {
  const fs = Math.max(Math.floor(w * 0.03), 14)
  const pad = Math.floor(fs * 0.8)
  const lh = fs + pad
  const bgH = lh * lines.length + pad

  if (isUni) {
    ctx.setFillStyle('rgba(0,0,0,0.4)')
    ctx.fillRect(0, h - bgH, w, bgH)
    ctx.setFillStyle('#ffffff')
    ctx.setFontSize(fs)
    lines.forEach((t, i) => {
      // uni canvas 的 fillText y 是文字顶部基线
      ctx.fillText(t, pad, h - bgH + pad + lh * i)
    })
  } else {
    ctx.fillStyle = 'rgba(0,0,0,0.4)'
    ctx.fillRect(0, h - bgH, w, bgH)
    ctx.fillStyle = '#ffffff'
    ctx.font = `${fs}px sans-serif`
    ctx.textBaseline = 'middle'
    lines.forEach((t, i) => {
      ctx.fillText(t, pad, h - bgH + pad / 2 + lh * i + fs / 2)
    })
  }
}