#!/usr/bin/env python3
"""Re-encode one image safely: verify decode, strip metadata, bound dimensions.

Fixed argv contract only:
    reencode_image.py --in SOURCE --out TARGET [--max-bytes N] [--max-dimension N]

Reads SOURCE, decodes defensively (decompression-bomb guarded), strips all
metadata by re-encoding to baseline JPEG, and writes TARGET. Prints one JSON
line on success. Never prints image bytes or base64 to stdout/stderr.
"""
import argparse
import io
import json
import os
import sys

Image = None  # populated in main() so import errors fail closed


def parser() -> argparse.ArgumentParser:
    p = argparse.ArgumentParser()
    p.add_argument("--in", dest="source", required=True)
    p.add_argument("--out", dest="target", required=True)
    p.add_argument("--max-bytes", type=int, default=4 * 1024 * 1024)
    p.add_argument("--max-dimension", type=int, default=4096)
    return p


def main() -> int:
    args = parser().parse_args()

    try:
        from PIL import Image as _Image
    except Exception:
        print(json.dumps({"ok": False, "error": "image processing is unavailable"}))
        return 3

    source_size = os.path.getsize(args.source)
    if source_size <= 0 or source_size > args.max_bytes:
        print(json.dumps({"ok": False, "error": "rejected"}))
        return 2

    try:
        # Fail closed on decompression bombs before full pixel load.
        with _Image.open(args.source) as probe:
            try:
                probe.load()
            except _Image.DecompressionBombError:
                print(json.dumps({"ok": False, "error": "dimensions"}))
                return 2
            width, height = probe.size
            if width > args.max_dimension or height > args.max_dimension:
                print(json.dumps({"ok": False, "error": "dimensions"}))
                return 2
            image = probe.convert("RGB")
    except Exception:
        print(json.dumps({"ok": False, "error": "malformed"}))
        return 2

    buffer = io.BytesIO()
    try:
        # Baseline JPEG re-encode drops EXIF/GPS/XMP/tEXt entirely.
        image.save(buffer, "JPEG", quality=85, optimize=True, progressive=False)
    except Exception:
        print(json.dumps({"ok": False, "error": "encode"}))
        return 2

    data = buffer.getvalue()
    if not data or data[:3] != b"\xff\xd8\xff" or len(data) > args.max_bytes:
        print(json.dumps({"ok": False, "error": "encode"}))
        return 2

    with open(args.target, "wb") as handle:
        handle.write(data)

    print(json.dumps({
        "ok": True,
        "format": "jpeg",
        "width": image.size[0],
        "height": image.size[1],
        "bytes": len(data),
        "metadataStripped": True,
    }))
    return 0


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