import json
import os
import re
import secrets
import tempfile
import time
from datetime import datetime, timezone
from pathlib import Path

CAPTURE_DIR = Path(tempfile.gettempdir()) / "chart-captures"
CAPTURE_TTL_SECONDS = 24 * 60 * 60
CAPTURE_LIMIT = 50
CAPTURE_MAX_BYTES = 10 * 1024 * 1024
CAPTURE_ID = re.compile(r"^c-[A-Za-z0-9_-]{12}$")


def _remove(capture_id: str) -> None:
    for suffix in (".png", ".json"):
        (CAPTURE_DIR / f"{capture_id}{suffix}").unlink(missing_ok=True)


def cleanup_captures(now: float | None = None) -> None:
    current = time.time() if now is None else now
    images = sorted(CAPTURE_DIR.glob("c-*.png"), key=lambda path: path.stat().st_mtime)
    for image in images:
        if current - image.stat().st_mtime > CAPTURE_TTL_SECONDS:
            _remove(image.stem)
    images = sorted(CAPTURE_DIR.glob("c-*.png"), key=lambda path: path.stat().st_mtime)
    for image in images[: max(0, len(images) - CAPTURE_LIMIT + 1)]:
        _remove(image.stem)


def save_capture(image: bytes, metadata: dict) -> tuple[str, dict]:
    if not image.startswith(b"\x89PNG\r\n\x1a\n"):
        raise ValueError("Capture is not a PNG")
    if len(image) > CAPTURE_MAX_BYTES:
        raise ValueError("Capture exceeds 10 MB")
    CAPTURE_DIR.mkdir(parents=True, exist_ok=True)
    cleanup_captures()
    capture_id = f"c-{secrets.token_urlsafe(9)}"
    details = {
        **metadata,
        "id": capture_id,
        "received_at": datetime.now(timezone.utc).replace(microsecond=0).isoformat(),
        "commit": os.environ.get("SOURCE_COMMIT", "dev"),
        "bytes": len(image),
    }
    image_path = CAPTURE_DIR / f"{capture_id}.png"
    metadata_path = CAPTURE_DIR / f"{capture_id}.json"
    image_path.write_bytes(image)
    metadata_path.write_text(json.dumps(details, indent=2, sort_keys=True) + "\n", encoding="utf-8")
    return capture_id, details


def capture_path(capture_id: str, suffix: str) -> Path | None:
    if not CAPTURE_ID.fullmatch(capture_id):
        return None
    path = CAPTURE_DIR / f"{capture_id}{suffix}"
    return path if path.is_file() else None


def delete_capture(capture_id: str) -> bool:
    if not CAPTURE_ID.fullmatch(capture_id):
        return False
    image = CAPTURE_DIR / f"{capture_id}.png"
    metadata = CAPTURE_DIR / f"{capture_id}.json"
    if not image.is_file() and not metadata.is_file():
        return False
    _remove(capture_id)
    return True