"""Tiny on-disk store of solved answers, so a run can resume.

Every successfully solved question is saved here immediately; the next run skips those and only
retries the ones that failed. Delete progress.json (or use the "Clear saved
progress" button) to start over.
"""
from __future__ import annotations

import json
import os
from pathlib import Path

PROGRESS_FILE = Path(os.getenv("PROGRESS_FILE", "progress.json"))


def is_error(answer: str | None) -> bool:
    return not answer or str(answer).startswith("AGENT_ERROR")


def load() -> dict[str, str]:
    try:
        return json.loads(PROGRESS_FILE.read_text(encoding="utf-8"))
    except Exception:
        return {}


def save_answer(task_id: str, answer: str) -> None:
    if is_error(answer):
        return
    data = load()
    data[str(task_id)] = answer
    PROGRESS_FILE.write_text(
        json.dumps(data, indent=2, ensure_ascii=False), encoding="utf-8"
    )


def clear() -> None:
    try:
        PROGRESS_FILE.unlink()
    except FileNotFoundError:
        pass