#!/usr/bin/env python3
"""PreCompact hook — block Claude Code's built-in auto-compact.

Only active in projects that have opted in (AirContext/ exists). Otherwise
Claude's default auto-compact behaviour is preserved untouched.

Manual `/compact` is always allowed; auto-triggered compaction is rejected so
AirContext's rule-driven compactor is the only thing that mutates the chain.
"""
from __future__ import annotations
import json
import os
import sys
from pathlib import Path


def main() -> int:
    raw = sys.stdin.read() or "{}"
    try:
        payload = json.loads(raw)
    except json.JSONDecodeError:
        payload = {}

    cwd = payload.get("cwd") or os.environ.get("CLAUDE_PROJECT_DIR") or os.getcwd()
    if not (Path(cwd) / "AirContext").exists():
        return 0  # project hasn't opted in; let Claude do whatever it wants

    trigger = payload.get("trigger") or payload.get("compact_trigger")
    if trigger == "auto":
        print(json.dumps({
            "decision": "block",
            "reason": (
                "AirContext: auto-compact disabled by user policy. "
                "Custom rule-driven compaction handles this out-of-band."
            )
        }))
        return 0
    return 0  # manual /compact passes through


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