/**
 * 从 vant/lib/index.css 生成 WXSS 兼容样式：去掉含 * / *= 的选择器规则。
 * 升级 vant 后执行：node scripts/gen-vant-mp-safe-css.js
 */
const fs = require('fs')
const path = require('path')

const root = path.join(__dirname, '..')
const src = path.join(root, 'node_modules', 'vant', 'lib', 'index.css')
const dest = path.join(root, 'styles', 'vant-mp-safe.css')

if (!fs.existsSync(src)) {
  console.error('[gen-vant-mp-safe-css] missing', src)
  process.exit(1)
}

const text = fs.readFileSync(src, 'utf8')
const out = []
let i = 0
const n = text.length
let removed = 0
let kept = 0

function isBadSelector(sel) {
  // universal selector `*` (not `*=` attr or content "*")
  if (/(^|[,)\s>+~])\*(?!=)/.test(sel)) return true
  if (sel.includes('*=')) return true
  return false
}

while (i < n) {
  if (text.startsWith('/*', i)) {
    const j = text.indexOf('*/', i + 2)
    if (j < 0) break
    out.push(text.slice(i, j + 2))
    i = j + 2
    continue
  }
  if (/\s/.test(text[i])) {
    out.push(text[i])
    i += 1
    continue
  }
  if (text[i] === '@') {
    const brace = text.indexOf('{', i)
    const semi = text.indexOf(';', i)
    if (semi !== -1 && (brace === -1 || semi < brace)) {
      out.push(text.slice(i, semi + 1))
      i = semi + 1
      continue
    }
    if (brace < 0) {
      out.push(text.slice(i))
      break
    }
    let depth = 0
    let j = brace
    while (j < n) {
      if (text[j] === '{') depth += 1
      else if (text[j] === '}') {
        depth -= 1
        if (depth === 0) {
          j += 1
          break
        }
      }
      j += 1
    }
    const block = text.slice(i, j)
    if (isBadSelector(block)) removed += 1
    else {
      out.push(block)
      kept += 1
    }
    i = j
    continue
  }

  const brace = text.indexOf('{', i)
  if (brace < 0) {
    out.push(text.slice(i))
    break
  }
  let depth = 0
  let j = brace
  while (j < n) {
    if (text[j] === '{') depth += 1
    else if (text[j] === '}') {
      depth -= 1
      if (depth === 0) {
        j += 1
        break
      }
    }
    j += 1
  }
  const sel = text.slice(i, brace)
  const rule = text.slice(i, j)
  if (isBadSelector(sel)) removed += 1
  else {
    out.push(rule)
    kept += 1
  }
  i = j
}

const header =
  '/* auto-generated from vant/lib/index.css — WXSS-safe (no * / *= selectors). Do not edit. */\n'
fs.writeFileSync(dest, header + out.join(''))
console.log('[gen-vant-mp-safe-css] kept=%s removed=%s -> %s', kept, removed, dest)