"""
Cleanup module: removes local files older than N hours, *only if they exist in S3*.

Safe by design:
- Never deletes a local file unless its S3 mirror is verified
- Never deletes job metadata (jobs/*.json) — those are tiny
- Default age threshold is conservative (48 h)
- Dry-run mode for verification

Usage (cron):
    python3 -m app.cleanup --apply           # actual delete
    python3 -m app.cleanup --dry-run         # preview only (default)
    python3 -m app.cleanup --apply --hours 72  # custom age threshold

Suggested cron (every night 03:30):
    30 3 * * * cd /app && python3 -m app.cleanup --apply >> /data/cleanup.log 2>&1
"""
from __future__ import annotations

import argparse
import logging
import os
import sys
import time
from pathlib import Path

# Konfiguracija — ujema main.py
DATA_DIR = Path(os.environ.get("DATA_DIR", "/data"))
UPLOAD_DIR = DATA_DIR / "uploads"
OUTPUT_DIR = DATA_DIR / "outputs"

DEFAULT_AGE_HOURS = 48

logging.basicConfig(
    level=logging.INFO,
    format="%(asctime)s [cleanup] %(message)s",
    datefmt="%Y-%m-%d %H:%M:%S",
)
log = logging.getLogger(__name__)


def _file_age_hours(p: Path) -> float:
    """Return file age in hours based on mtime."""
    try:
        return (time.time() - p.stat().st_mtime) / 3600
    except OSError:
        return 0.0


def _scan_dir(d: Path, kind: str, min_age_h: float):
    """Yield (local_path, kind, age_hours) for files older than threshold."""
    if not d.exists():
        return
    for p in d.iterdir():
        if not p.is_file():
            continue
        # Skip very small files (probably config/state) — only target real workfiles
        if p.stat().st_size < 1024 * 100:  # <100 KB
            continue
        age = _file_age_hours(p)
        if age >= min_age_h:
            yield p, kind, age


def cleanup(min_age_hours: float, apply: bool) -> dict:
    """Run cleanup pass. Returns stats dict.
    
    Logic:
      For each file older than min_age_hours in uploads/ and outputs/:
        - Verify S3 mirror exists (s3.exists())
        - If verified: delete local
        - If not verified: skip (warn) — never delete unverified
    """
    from app import s3_storage

    if not s3_storage.is_enabled():
        log.error("S3 not configured — refusing to run cleanup. Aborting.")
        return {"error": "s3_not_configured"}

    stats = {
        "scanned": 0,
        "would_delete": 0,
        "deleted": 0,
        "skipped_no_s3_mirror": 0,
        "freed_mb": 0.0,
        "errors": 0,
    }
    deleted_files = []
    skipped_files = []

    for d, kind in [(UPLOAD_DIR, "upload"), (OUTPUT_DIR, "output")]:
        for p, _, age_h in _scan_dir(d, kind, min_age_hours):
            stats["scanned"] += 1
            size_mb = p.stat().st_size / 1024 / 1024
            folder = "uploads" if kind == "upload" else "outputs"
            s3_key = f"{folder}/{p.name}"

            # Verify S3 mirror
            try:
                s3_size = s3_storage.get_object_size(s3_key)
            except Exception as e:
                log.warning("S3 check failed for %s: %s", s3_key, e)
                stats["errors"] += 1
                continue

            if s3_size is None:
                log.warning("SKIP — no S3 mirror: %s (age %.1fh, %.1f MB)",
                            p.name, age_h, size_mb)
                stats["skipped_no_s3_mirror"] += 1
                skipped_files.append(p.name)
                continue

            # Check size match (sanity)
            local_size = p.stat().st_size
            if abs(s3_size - local_size) > 1024:  # >1 KB delta — suspicious
                log.warning("SKIP — size mismatch %s: local=%d s3=%d",
                            p.name, local_size, s3_size)
                stats["skipped_no_s3_mirror"] += 1
                skipped_files.append(p.name)
                continue

            stats["would_delete"] += 1
            stats["freed_mb"] += size_mb

            if apply:
                try:
                    p.unlink()
                    stats["deleted"] += 1
                    deleted_files.append(p.name)
                    log.info("DEL %s (%.1f MB, age %.1fh, S3 verified)",
                             p.name, size_mb, age_h)
                except OSError as e:
                    log.error("Delete failed %s: %s", p, e)
                    stats["errors"] += 1
            else:
                log.info("DRY %s (%.1f MB, age %.1fh, S3 verified)",
                         p.name, size_mb, age_h)

    log.info("=" * 60)
    log.info("Cleanup pass: %s", "APPLY" if apply else "DRY-RUN")
    log.info("  scanned:               %d", stats["scanned"])
    log.info("  would-delete:          %d", stats["would_delete"])
    log.info("  deleted:               %d", stats["deleted"])
    log.info("  skipped (no S3):       %d", stats["skipped_no_s3_mirror"])
    log.info("  errors:                %d", stats["errors"])
    log.info("  freed:                 %.1f MB", stats["freed_mb"])
    return stats


def main():
    ap = argparse.ArgumentParser()
    ap.add_argument("--apply", action="store_true",
                    help="Actually delete files (default is dry-run)")
    ap.add_argument("--dry-run", action="store_true",
                    help="Preview only, do not delete (default)")
    ap.add_argument("--hours", type=float, default=DEFAULT_AGE_HOURS,
                    help=f"Min file age in hours (default {DEFAULT_AGE_HOURS})")
    args = ap.parse_args()

    apply = args.apply and not args.dry_run
    stats = cleanup(min_age_hours=args.hours, apply=apply)
    if stats.get("error"):
        sys.exit(2)


if __name__ == "__main__":
    main()