const { request } = require('./wx-promisify')

function buildApiUrl() {
  const app = getApp()
  const apiUrl = app && app.globalData ? app.globalData.svgRenderApiUrl : ''
  if (!apiUrl) {
    throw new Error('未配置渲染 API 地址')
  }
  return apiUrl
}

function normalizeResult(data) {
  if (!data || typeof data !== 'object') {
    throw new Error('渲染服务返回格式无效')
  }

  if (typeof data.svg !== 'string' || !data.svg.trim()) {
    throw new Error('渲染服务未返回有效 SVG')
  }

  return {
    svg: data.svg,
    width: Number(data.width) || 0,
    height: Number(data.height) || 0,
    fontName: data.fontName || 'Unknown',
    fontId: data.fontId || '',
  }
}

function decodeArrayBuffer(buffer) {
  try {
    if (!buffer) return ''
    if (typeof buffer === 'string') return buffer
    if (typeof TextDecoder === 'function') {
      return new TextDecoder('utf-8').decode(buffer)
    }
    const bytes = new Uint8Array(buffer)
    let text = ''
    for (let i = 0; i < bytes.length; i += 1) {
      text += String.fromCharCode(bytes[i])
    }
    return decodeURIComponent(escape(text))
  } catch (error) {
    return ''
  }
}

async function renderSvgByApi(payload) {
  const app = getApp()
  const timeout = app && app.globalData && app.globalData.apiTimeoutMs
    ? Number(app.globalData.apiTimeoutMs)
    : 30000

  const response = await request({
    url: buildApiUrl(),
    method: 'POST',
    timeout,
    header: {
      'content-type': 'application/json',
    },
    data: {
      fontId: payload.fontId,
      text: payload.text,
      fontSize: payload.fontSize,
      fillColor: payload.fillColor,
      letterSpacing: payload.letterSpacing,
      maxCharsPerLine: payload.maxCharsPerLine,
    },
  })

  if (!response || response.statusCode < 200 || response.statusCode >= 300) {
    throw new Error(`渲染服务请求失败，状态码: ${response && response.statusCode}`)
  }

  const body = response.data || {}
  if (!body.ok) {
    throw new Error(body.error || '渲染服务返回错误')
  }

  return normalizeResult(body.data)
}

async function renderPngByApi(payload) {
  const app = getApp()
  const timeout = app && app.globalData && app.globalData.apiTimeoutMs
    ? Number(app.globalData.apiTimeoutMs)
    : 30000
  const baseApiUrl = buildApiUrl()
  const configuredPngApiUrl = app && app.globalData ? app.globalData.pngRenderApiUrl : ''
  const apiUrl = configuredPngApiUrl || (
    /\/api\/render-svg$/.test(baseApiUrl)
      ? baseApiUrl.replace(/\/api\/render-svg$/, '/api/render-png')
      : `${baseApiUrl.replace(/\/$/, '')}/render-png`
  )

  const response = await request({
    url: apiUrl,
    method: 'POST',
    timeout,
    responseType: 'arraybuffer',
    header: {
      'content-type': 'application/json',
      accept: 'image/png',
    },
    data: {
      fontId: payload.fontId,
      text: payload.text,
      fontSize: payload.fontSize,
      fillColor: payload.fillColor,
      letterSpacing: payload.letterSpacing,
      maxCharsPerLine: payload.maxCharsPerLine,
    },
  })

  if (!response || response.statusCode !== 200) {
    let message = `PNG 渲染服务请求失败，状态码: ${response && response.statusCode}`
    const maybeText = decodeArrayBuffer(response && response.data)
    if (maybeText && maybeText.includes('error')) {
      message = maybeText
    }
    throw new Error(message)
  }

  if (!(response.data instanceof ArrayBuffer)) {
    throw new Error('PNG 渲染服务返回格式无效')
  }

  return response.data
}

module.exports = {
  renderSvgByApi,
  renderPngByApi,
}