#!/usr/bin/env python3
"""Generate roster.json from a class-register XLSX.

Reads the first column (student IDs) and emits a JSON file the quiz app
loads at startup. Names from the second column, if present, are kept in
the JSON for human auditability but are NOT used for the gate.

Usage:
    python deploy/build_roster.py <attendance.xlsx> [-o roster.json]

The XLSX is expected to have a header row, then one row per student.
Column 1 = student ID, column 2 = name (optional).
"""

from __future__ import annotations

import argparse
import json
import sys
from pathlib import Path


def build(xlsx_path: Path, out_path: Path) -> int:
    try:
        import openpyxl
    except ImportError:
        print("openpyxl is required: pip install openpyxl", file=sys.stderr)
        return 2

    wb = openpyxl.load_workbook(xlsx_path)
    ws = wb.worksheets[0]
    students = []
    seen: set[str] = set()
    for row in ws.iter_rows(values_only=True):
        if not row:
            continue
        sid_raw = row[0]
        if sid_raw is None:
            continue
        sid = str(sid_raw).strip()
        if not sid or sid in {"学号", "Student ID", "ID"}:
            continue
        if sid.upper() in seen:
            continue
        seen.add(sid.upper())
        name = ""
        if len(row) > 1 and row[1] is not None:
            name = str(row[1]).strip()
        students.append({"id": sid, "name": name})

    payload = {
        "source": str(xlsx_path),
        "count": len(students),
        "students": students,
    }
    out_path.write_text(json.dumps(payload, ensure_ascii=False, indent=2))
    print(f"Wrote {len(students)} students to {out_path}")
    return 0


def main() -> int:
    p = argparse.ArgumentParser(description="Build roster.json for the quiz app.")
    p.add_argument("xlsx", type=Path, help="Path to attendance.xlsx")
    p.add_argument("-o", "--out", type=Path, default=Path("roster.json"))
    args = p.parse_args()
    return build(args.xlsx, args.out)


if __name__ == "__main__":
    sys.exit(main())