#!/usr/bin/env python3
"""Repair a stale continuation checkpoint from the authoritative task ledger.

Only the generated checkpoint projection is changed. Task statuses, counts and
the active ledger entry are never modified by this tool.
"""
from __future__ import annotations

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


ROOT = Path(__file__).resolve().parents[1]
STATE = ROOT / "docs/current/task-state.json"
CHECKPOINT = ROOT / "docs/current/continuation-state.json"
MODULE_BATCH = ROOT / "docs/current/module-batch-manifest.json"


def main() -> int:
    parser = argparse.ArgumentParser(description=__doc__)
    parser.add_argument("--quiet", action="store_true")
    args = parser.parse_args()
    state = json.loads(STATE.read_text(encoding="utf-8"))
    checkpoint = json.loads(CHECKPOINT.read_text(encoding="utf-8"))
    active = state.get("active_task")
    counts = state.get("counts", {})
    statuses = state.get("tasks", {})
    if not active or counts.get("in_progress") != 1 or statuses.get(active) != "in_progress":
        if not args.quiet:
            print("CHECKPOINT_REPAIR_NOT_APPLICABLE: ledger has no single in_progress active task")
        return 2
    previous = checkpoint.get("activeTask")
    changed = False
    if previous != active:
        checkpoint["activeTask"] = active
        changed = True
    batch = None
    try:
        batch = json.loads(MODULE_BATCH.read_text(encoding="utf-8"))
    except (FileNotFoundError, json.JSONDecodeError):
        batch = None
    previous_batch_id = checkpoint.get("batchId")
    if isinstance(batch, dict) and batch.get("batchId") and previous_batch_id != batch.get("batchId"):
        checkpoint["batchManifest"] = "docs/current/module-batch-manifest.json"
        checkpoint["batchId"] = batch.get("batchId")
        checkpoint["batchSelection"] = batch.get("selected")
        changed = True
    if not changed:
        if not args.quiet:
            print(f"CHECKPOINT_ALREADY_ALIGNED: active={active}")
        return 2
    checkpoint["phase"] = "CONTINUE"
    checkpoint["lastCheckpoint"] = "CONTINUE"
    checkpoint["lastTransition"] = datetime.now(timezone.utc).isoformat()
    checkpoint["checkpointRepair"] = {
        "reason": "ledger_or_batch_projection_mismatch",
        "previousActiveTask": previous,
        "repairedActiveTask": active,
        "previousBatchId": previous_batch_id,
        "repairedBatchId": checkpoint.get("batchId"),
        "repairedAt": datetime.now(timezone.utc).isoformat(),
    }
    temporary = CHECKPOINT.with_suffix(".repair.tmp")
    temporary.write_text(json.dumps(checkpoint, ensure_ascii=False, indent=2) + "\n", encoding="utf-8")
    temporary.replace(CHECKPOINT)
    print(f"CHECKPOINT_REPAIRED: previous={previous} active={active}")
    return 0


if __name__ == "__main__":
    raise SystemExit(main())