from __future__ import annotations

import re
from datetime import datetime, timedelta, timezone

from app.config import RADAR_PRODUCT, RADAR_RETENTION_HOURS, RAW_RADAR_DIR
from app.database import upsert_radar_meta
from app.http_client import get_client
from app.services.dwd_radar import RADAR_FILE_RE, fetch_radar_index

_FILENAME_RE = re.compile(r"^[a-z0-9_-]+$", re.IGNORECASE)


def utc_now() -> datetime:
    return datetime.now(timezone.utc)


def cleanup_old_radar_files() -> None:
    cutoff = utc_now() - timedelta(hours=RADAR_RETENTION_HOURS)
    if not RAW_RADAR_DIR.exists():
        return
    for path in RAW_RADAR_DIR.rglob("*"):
        if not path.is_file() or not RADAR_FILE_RE.fullmatch(path.name):
            continue
        modified = datetime.fromtimestamp(path.stat().st_mtime, timezone.utc)
        if modified < cutoff:
            path.unlink(missing_ok=True)


async def sync_radar_files(product: str = RADAR_PRODUCT, limit: int = 6) -> dict:
    if not _FILENAME_RE.fullmatch(product):
        raise ValueError("Invalid product")

    latest = await fetch_radar_index(product=product, limit=limit)
    target_dir = RAW_RADAR_DIR / "composite" / product
    target_dir.mkdir(parents=True, exist_ok=True)
    downloaded: list[str] = []
    skipped: list[str] = []

    client = get_client()
    for item in latest["files"]:
        out = target_dir / item["name"]
        if out.exists() and out.stat().st_size > 0:
            skipped.append(item["name"])
            continue
        response = await client.get(item["url"], timeout=90.0)
        response.raise_for_status()
        out.write_bytes(response.content)
        downloaded.append(item["name"])
        modified = datetime.fromtimestamp(out.stat().st_mtime, timezone.utc)
        await upsert_radar_meta(product, item["name"], out.stat().st_size, modified, "pending")

    cleanup_old_radar_files()
    return {
        "product": product,
        "target_dir": str(target_dir),
        "downloaded": downloaded,
        "skipped": skipped,
    }