#!/usr/bin/env python3
"""Rotate generated task context between isolated task executions."""

from __future__ import annotations

import argparse
import hashlib
import json
from datetime import datetime, timezone
from pathlib import Path

ROOT = Path(__file__).resolve().parents[1]
CURRENT = ROOT / "docs" / "current"
CONTEXT_DIR = CURRENT / "context"
STATE = CURRENT / "task-state.json"
SUMMARY = CURRENT / "FREECAD_WEB_CONTEXT_MIN.md"
ROTATION = CURRENT / "context-rotation.json"


def digest(path: Path) -> str:
    return hashlib.sha256(path.read_bytes()).hexdigest()


def main() -> None:
    parser = argparse.ArgumentParser(description=__doc__)
    parser.add_argument("--reason", choices=("completed", "timeout", "interrupted"), required=True)
    parser.add_argument("--next-task", required=True)
    args = parser.parse_args()
    if not CONTEXT_DIR.is_dir():
        raise SystemExit(f"missing generated context directory: {CONTEXT_DIR}")
    state = json.loads(STATE.read_text(encoding="utf-8"))
    previous = state.get("active_task")
    removed = []
    for manifest in sorted(CONTEXT_DIR.glob("FW-*.json")):
        removed.append({"path": str(manifest.relative_to(ROOT)), "bytes": manifest.stat().st_size, "sha256": digest(manifest)})
        manifest.unlink()
    ROTATION.write_text(json.dumps({
        "schema": "freecad-web-context-rotation/v1",
        "rotatedAt": datetime.now(timezone.utc).isoformat(),
        "reason": args.reason,
        "previousTask": previous,
        "nextTask": args.next_task,
        "removedGeneratedManifests": removed,
        "preserved": ["docs/current/task-state.json", "docs/current/FREECAD_WEB_HANDOFF.md", "nextTask.md", "docs/tasks/**", "docs/p6/*.json", "docs/*.log", "freecad-source/**"],
        "nextStep": "Run sync_web_task_state.py --active NEXT and immediately run prepare_web_task_context.py."
    }, ensure_ascii=False, indent=2) + "\n", encoding="utf-8")
    SUMMARY.write_text(
        "# FreeCAD Web 最小续接上下文\n\n"
        f"上下文已轮换（reason={args.reason}，previous={previous}，next={args.next_task}）。\n"
        "加载下一任务前必须运行 `python3 tools/prepare_web_task_context.py`，然后只读取新 manifest 的 `mode=read` 文件。\n",
        encoding="utf-8",
    )
    print(json.dumps({"previousTask": previous, "nextTask": args.next_task, "removed": len(removed), "reason": args.reason}))


if __name__ == "__main__":
    main()