/**
 * @file exportData.ts
 * @description Client-side "Download CSV / JSON" for list pages (Sessions,
 * Activity, a session's events): `toCsv` turns rows into RFC 4180 CSV (and
 * neutralizes spreadsheet formulas), `downloadText` saves a string as a file.
 * @author Nguyễn Ngọc Trí Vĩ <vinnt@smartgift.vn>
 */

/** One CSV cell: quoted when needed; a leading =, +, - or @ is prefixed with `'`
 *  so a spreadsheet never runs a value from a session as a formula. */
function cell(value: unknown): string {
  if (value == null) return "";
  let s = typeof value === "object" ? JSON.stringify(value) : String(value);
  if (typeof value === "string" && /^[=+\-@\t\r]/.test(s)) s = `'${s}`;
  return /[",\r\n]/.test(s) ? `"${s.replace(/"/g, '""')}"` : s;
}

export function toCsv<T extends object>(
  rows: readonly T[],
  columns: readonly (keyof T & string)[]
) {
  const lines = [columns.join(",")];
  for (const row of rows) lines.push(columns.map((c) => cell(row[c])).join(","));
  return lines.join("\r\n") + "\r\n";
}

export function downloadText(filename: string, text: string, mime: string): void {
  const url = URL.createObjectURL(new Blob([text], { type: mime }));
  const a = document.createElement("a");
  a.href = url;
  a.download = filename;
  a.click();
  URL.revokeObjectURL(url);
}

/** `name-YYYY-MM-DD.ext` */
export function exportName(name: string, ext: "csv" | "json"): string {
  return `${name}-${new Date().toISOString().slice(0, 10)}.${ext}`;
}