// 1) 安全地把对象数组转成 CSV 文本
export function toCSV<T extends Record<string, any>>(
  rows: T[],
  opts?: {
    headers?: string[] // 指定列顺序与表头；不传则用 rows[0] 的键
    delimiter?: string // 默认逗号 ","
    includeHeader?: boolean // 默认 true
  },
): string {
  const delimiter = opts?.delimiter ?? ','
  const includeHeader = opts?.includeHeader ?? true

  if (!rows?.length) return ''

  const headers = opts?.headers ?? Object.keys(rows[0])

  // 处理每个单元格：转为字符串、转义双引号、若含分隔符/换行/引号则整体再包一层引号
  const esc = (val: any) => {
    let s = val == null ? '' : String(val)
    s = s.replace(/"/g, '""')
    if (s.includes('"') || s.includes(delimiter) || s.includes('\n') || s.includes('\r')) {
      s = `"${s}"`
    }
    return s
  }

  const lines: string[] = []

  if (includeHeader) {
    lines.push(headers.map((h) => esc(h)).join(delimiter))
  }

  for (const row of rows) {
    lines.push(headers.map((h) => esc(row[h])).join(delimiter))
  }

  // Windows/Excel 友好：使用 \r\n 作为换行
  return lines.join('\r\n')
}

// 2) 触发浏览器下载（含 UTF-8 BOM，Excel 更稳）
export function downloadCSV(filename: string, csv: string) {
  // 加 BOM，避免 Excel 中文乱码
  const BOM = '\uFEFF'
  const blob = new Blob([BOM + csv], { type: 'text/csv;charset=utf-8;' })
  const url = URL.createObjectURL(blob)

  const a = document.createElement('a')
  a.href = url
  a.download = filename.endsWith('.csv') ? filename : `${filename}.csv`
  document.body.appendChild(a)
  a.click()
  document.body.removeChild(a)
  URL.revokeObjectURL(url)
}

// 3) 使用示例
// type Row = { id: number; name: string; note?: string };

// const data: Row[] = [
//   { id: 1, name: "张三", note: "带,逗号" },
//   { id: 2, name: "李四", note: "含\"引号\"与换行\n第二行" },
// ];

// const csv = toCSV(data, {
//   headers: ["id", "name", "note"], // 指定列顺序（可选）
//   includeHeader: true,
// });

// downloadCSV("示例数据.csv", csv);