/**
 * Load full QQ mailbox PDF text for sample mail body (一字不落).
 */
import { execFile } from "child_process";
import { promisify } from "util";
import path from "path";
import fs from "fs/promises";

const execFileAsync = promisify(execFile);

async function listPdfs(root: string): Promise<string[]> {
  const out: string[] = [];
  const stack = [root];
  while (stack.length) {
    const cur = stack.pop()!;
    let entries;
    try {
      entries = await fs.readdir(cur, { withFileTypes: true });
    } catch {
      continue;
    }
    for (const e of entries) {
      const full = path.join(cur, e.name);
      if (e.isDirectory()) stack.push(full);
      else if (/\.pdf$/i.test(e.name) && /邮箱/i.test(e.name)) out.push(full);
    }
  }
  return out;
}

/** Prefer *邮箱.pdf under sample dir; return extracted text or null */
export async function loadMailboxPdfBody(
  sampleDirAbs: string,
): Promise<string | null> {
  const pdfs = await listPdfs(sampleDirAbs);
  if (!pdfs.length) return null;
  // Prefer QQ邮箱 / N邮箱 over other PDFs
  pdfs.sort((a, b) => {
    const score = (p: string) => {
      const n = path.basename(p);
      if (/^QQ/i.test(n)) return 0;
      if (/^\d邮箱/i.test(n)) return 1;
      return 2;
    };
    return score(a) - score(b);
  });
  const target = pdfs[0];
  try {
    const script = path.join(process.cwd(), "scripts", "extract-pdf-text.py");
    const { stdout } = await execFileAsync(
      "python",
      [script, target],
      { maxBuffer: 12_000_000, encoding: "utf8", windowsHide: true },
    );
    const t = (stdout || "").replace(/\r\n/g, "\n").trim();
    return t.length > 20 ? t : null;
  } catch (err) {
    console.warn("loadMailboxPdfBody failed", target, err);
    return null;
  }
}