#!/usr/bin/env python3
"""SessionStart hook — staleness check + detached graph rebuild. Fail-open.

Must return sub-second; heavy work is detached in the background. Context
injection is handled by session_context.py (UserPromptSubmit hook).
"""
import os
import sys
import time
import subprocess
from datetime import datetime, timezone

sys.path.insert(0, os.path.dirname(os.path.abspath(__file__)))
import config as config_mod
import hook_io

HOOK_LOG = "/tmp/memory-hook.log"


def _utc():
    return datetime.now(timezone.utc).strftime("%Y-%m-%dT%H:%M:%SZ")


def _log(line):
    try:
        with open(HOOK_LOG, "a") as f:
            f.write(line + "\n")
    except Exception:
        pass


def _needs_rebuild(stamp, stale_days):
    if not os.path.exists(stamp):
        return True
    try:
        age_days = (time.time() - os.path.getmtime(stamp)) / 86400
        return age_days > stale_days
    except Exception:
        return True


def main():
    inp = hook_io.read_input()
    source = inp.source or "unknown"
    _log(f"[{_utc()}] session-start fired: source={source} cwd={os.getcwd()}")

    cfg = config_mod.load_config()

    if os.environ.get("OS_VAULT_SKIP_REBUILD"):
        _log(f"[{_utc()}] session-start: rebuild skipped (OS_VAULT_SKIP_REBUILD set)")
        return

    cache_dir = os.path.expanduser("~/.cache/graphify")
    stamp = os.path.join(cache_dir, "vault-rebuild.stamp")
    lock = os.path.join(cache_dir, "vault-rebuild.lock")
    logfile = os.path.join(cache_dir, "vault-rebuild.log")
    try:
        os.makedirs(cache_dir, exist_ok=True)
    except Exception:
        pass

    if _needs_rebuild(stamp, cfg.stale_days):
        if os.path.exists(lock):
            try:
                with open(logfile, "a") as f:
                    f.write("[memory/session-start] rebuild already running (lock present), skipping\n")
            except Exception:
                pass
            _log(f"[{_utc()}] session-start: rebuild skipped (lock present)")
        else:
            try:
                open(lock, "a").close()
            except Exception:
                pass
            env = dict(os.environ)
            env.update(cfg.env)
            env["VAULT_PATH"] = cfg.vault_path
            env["MODEL"] = cfg.model
            env["STAMP"] = stamp
            env["LOCK"] = lock
            env["LOGFILE"] = logfile
            cmd = (
                'graphify extract "$VAULT_PATH" --backend ollama --model "$MODEL" --force '
                '>> "$LOGFILE" 2>&1 '
                '&& date > "$STAMP" && rm -f "$LOCK" '
                '|| (rm -f "$LOCK"; echo "rebuild failed" >> "$LOGFILE")'
            )
            try:
                devnull = open(os.devnull, "wb")
                subprocess.Popen(
                    ["bash", "-c", cmd],
                    stdin=subprocess.DEVNULL,
                    stdout=devnull,
                    stderr=devnull,
                    env=env,
                    start_new_session=True,
                )
            except Exception:
                pass
            _log(f"[{_utc()}] session-start: rebuild triggered")
    else:
        _log(f"[{_utc()}] session-start: rebuild not needed")


if __name__ == "__main__":
    try:
        main()
    except Exception as e:
        print(f"[session-start] error: {e}", file=sys.stderr)
    sys.exit(0)