import os
import time
import json
import logging
from pathlib import Path
from typing import Any, Dict, List, Set

from PIL import Image

from . import db

logger = logging.getLogger(__name__)

IMAGE_EXT = {".jpg", ".jpeg", ".png", ".webp"}
THUMB_SIZE = (480, 480)


def _scan_folder(folder: Path) -> List[Dict[str, Any]]:
    """폴더 내 이미지 파일 목록 수집 (os.scandir)."""
    if not folder.exists():
        return []
    items = []
    with os.scandir(folder) as entries:
        for entry in entries:
            if entry.is_file() and Path(entry.name).suffix.lower() in IMAGE_EXT:
                items.append({
                    "filename": entry.name,
                    "mtime": entry.stat().st_mtime,
                })
    return items


def _generate_thumb(src: Path, dest: Path) -> bool:
    """원본에서 480x480 썸네일 생성. 성공 시 True."""
    dest.parent.mkdir(parents=True, exist_ok=True)
    tmp = dest.with_name(dest.stem + ".tmp" + dest.suffix)
    try:
        with Image.open(src) as im:
            im.thumbnail(THUMB_SIZE)
            ext = dest.suffix.lower()
            if ext in (".jpg", ".jpeg"):
                fmt = "JPEG"
            elif ext == ".png":
                fmt = "PNG"
            elif ext == ".webp":
                fmt = "WEBP"
            else:
                fmt = (im.format or "").upper() or "JPEG"
            im.save(tmp, format=fmt, quality=85, optimize=True)
        tmp.replace(dest)
        return True
    except Exception as e:
        logger.warning("Thumb generation failed: %s → %s", src, e)
        try:
            if tmp.exists():
                tmp.unlink()
        except Exception:
            pass
        return False


def sync(
    travel_root: Path,
    thumb_root: Path,
    region_map_path: Path,
) -> Dict[str, Any]:
    """
    폴더 스캔 → DB 동기화 + 썸네일 일괄 생성.

    Returns:
        {"added": int, "removed": int, "thumbs_generated": int, "duration_sec": float}
    """
    start = time.time()

    # 1. region_map.json에서 전체 앨범 폴더 수집
    with open(region_map_path, "r", encoding="utf-8") as f:
        region_map = json.load(f)

    all_albums: Set[str] = set()
    for v in region_map.values():
        if isinstance(v, list):
            all_albums.update(v)
        elif isinstance(v, dict) and isinstance(v.get("albums"), list):
            all_albums.update(v["albums"])

    # 2. 각 앨범 폴더 스캔 → DB 동기화
    added = 0
    removed = 0

    for album in sorted(all_albums):
        folder = travel_root / album
        items = _scan_folder(folder)
        existing_filenames = set()

        for item in items:
            existing_filenames.add(item["filename"])
            result = db.upsert_photo(album, item["filename"], item["mtime"])
            if result == "added":
                added += 1

        removed += db.remove_missing_photos(album, existing_filenames)

    # 3. 썸네일 미생성 분 일괄 생성
    no_thumb = db.get_photos_without_thumb()
    thumbs_generated = 0

    for photo in no_thumb:
        src = travel_root / photo["album"] / photo["filename"]
        dest = thumb_root / photo["album"] / photo["filename"]
        if _generate_thumb(src, dest):
            db.mark_thumb_done(photo["album"], photo["filename"])
            thumbs_generated += 1

    duration = round(time.time() - start, 2)
    logger.info(
        "Sync complete: added=%d removed=%d thumbs=%d duration=%.2fs",
        added, removed, thumbs_generated, duration,
    )

    return {
        "added": added,
        "removed": removed,
        "thumbs_generated": thumbs_generated,
        "duration_sec": duration,
    }