import os
import sqlite3
from typing import Any, Dict, List, Optional, Set

DB_PATH = os.getenv("TRAVEL_DB_PATH", "/data/thumbs/travel.db")


def _conn() -> sqlite3.Connection:
    os.makedirs(os.path.dirname(DB_PATH), exist_ok=True)
    conn = sqlite3.connect(DB_PATH, timeout=120.0)
    conn.row_factory = sqlite3.Row
    conn.execute("PRAGMA journal_mode=WAL")
    conn.execute("PRAGMA busy_timeout=120000")
    return conn


def init_db() -> None:
    with _conn() as conn:
        conn.execute("""
            CREATE TABLE IF NOT EXISTS photos (
                id INTEGER PRIMARY KEY AUTOINCREMENT,
                album TEXT NOT NULL,
                filename TEXT NOT NULL,
                mtime REAL NOT NULL,
                has_thumb INTEGER DEFAULT 0,
                indexed_at TEXT NOT NULL DEFAULT (strftime('%Y-%m-%dT%H:%M:%fZ','now')),
                UNIQUE(album, filename)
            )
        """)
        conn.execute("CREATE INDEX IF NOT EXISTS idx_photos_album ON photos(album)")

        conn.execute("""
            CREATE TABLE IF NOT EXISTS album_covers (
                album TEXT PRIMARY KEY,
                filename TEXT NOT NULL,
                updated_at TEXT NOT NULL DEFAULT (strftime('%Y-%m-%dT%H:%M:%fZ','now'))
            )
        """)


def get_photos_by_region(albums: List[str], page: int, size: int) -> Dict[str, Any]:
    """region에 속한 앨범들의 사진을 페이지네이션하여 반환."""
    if not albums:
        return {"items": [], "total": 0, "has_next": False, "matched_albums": []}

    placeholders = ",".join("?" for _ in albums)

    with _conn() as conn:
        rows = conn.execute(
            f"SELECT album, COUNT(*) as cnt FROM photos WHERE album IN ({placeholders}) GROUP BY album",
            albums,
        ).fetchall()
        matched_albums = [{"album": r["album"], "count": r["cnt"]} for r in rows]
        total = sum(r["cnt"] for r in rows)

        offset = (page - 1) * size
        items = conn.execute(
            f"""SELECT album, filename, mtime FROM photos
                WHERE album IN ({placeholders})
                ORDER BY album, filename
                LIMIT ? OFFSET ?""",
            [*albums, size, offset],
        ).fetchall()

    return {
        "items": [dict(r) for r in items],
        "total": total,
        "has_next": (offset + size) < total,
        "matched_albums": matched_albums,
    }


def get_all_albums() -> List[Dict[str, Any]]:
    """전체 앨범 목록 + 사진 수 + 커버 정보."""
    with _conn() as conn:
        rows = conn.execute("""
            SELECT p.album, COUNT(*) as count,
                   COALESCE(c.filename, MIN(p.filename)) as cover_filename
            FROM photos p
            LEFT JOIN album_covers c ON p.album = c.album
            GROUP BY p.album
            ORDER BY p.album
        """).fetchall()
    return [dict(r) for r in rows]


def set_album_cover(album: str, filename: str) -> bool:
    """앨범 커버 지정. 해당 photo가 존재하면 True, 없으면 False."""
    with _conn() as conn:
        exists = conn.execute(
            "SELECT 1 FROM photos WHERE album = ? AND filename = ?",
            (album, filename),
        ).fetchone()
        if not exists:
            return False

        conn.execute(
            """INSERT INTO album_covers (album, filename, updated_at)
               VALUES (?, ?, strftime('%Y-%m-%dT%H:%M:%fZ','now'))
               ON CONFLICT(album) DO UPDATE SET
                   filename = excluded.filename,
                   updated_at = excluded.updated_at""",
            (album, filename),
        )
    return True


def get_album_cover(album: str) -> Optional[str]:
    """앨범 커버 파일명 반환. 미지정 시 None."""
    with _conn() as conn:
        row = conn.execute(
            "SELECT filename FROM album_covers WHERE album = ?",
            (album,),
        ).fetchone()
    return row["filename"] if row else None


def upsert_photo(album: str, filename: str, mtime: float) -> str:
    """사진 upsert. 반환: 'added' | 'updated' | 'unchanged'."""
    with _conn() as conn:
        existing = conn.execute(
            "SELECT mtime, has_thumb FROM photos WHERE album = ? AND filename = ?",
            (album, filename),
        ).fetchone()

        if not existing:
            conn.execute(
                "INSERT INTO photos (album, filename, mtime, has_thumb) VALUES (?, ?, ?, 0)",
                (album, filename, mtime),
            )
            return "added"
        elif existing["mtime"] != mtime:
            conn.execute(
                "UPDATE photos SET mtime = ?, has_thumb = 0 WHERE album = ? AND filename = ?",
                (mtime, album, filename),
            )
            return "updated"
        return "unchanged"


def remove_missing_photos(album: str, existing_filenames: Set[str]) -> int:
    """폴더에 없는 사진을 DB에서 제거. 제거 수 반환."""
    with _conn() as conn:
        db_rows = conn.execute(
            "SELECT filename FROM photos WHERE album = ?", (album,)
        ).fetchall()
        db_filenames = {r["filename"] for r in db_rows}
        to_remove = db_filenames - existing_filenames

        if to_remove:
            placeholders = ",".join("?" for _ in to_remove)
            conn.execute(
                f"DELETE FROM photos WHERE album = ? AND filename IN ({placeholders})",
                [album, *to_remove],
            )
            conn.execute(
                f"DELETE FROM album_covers WHERE album = ? AND filename IN ({placeholders})",
                [album, *to_remove],
            )
    return len(to_remove)


def get_photos_without_thumb() -> List[Dict[str, str]]:
    """썸네일 미생성 사진 목록."""
    with _conn() as conn:
        rows = conn.execute(
            "SELECT album, filename FROM photos WHERE has_thumb = 0"
        ).fetchall()
    return [dict(r) for r in rows]


def mark_thumb_done(album: str, filename: str) -> None:
    """썸네일 생성 완료 표시."""
    with _conn() as conn:
        conn.execute(
            "UPDATE photos SET has_thumb = 1 WHERE album = ? AND filename = ?",
            (album, filename),
        )


def batch_sync_album(album: str, items: List[Dict[str, Any]], existing_filenames: Set[str]) -> Dict[str, int]:
    """앨범 단위 배치 동기화. 단일 커넥션으로 upsert + 삭제 처리."""
    added = updated = 0
    with _conn() as conn:
        for item in items:
            existing = conn.execute(
                "SELECT mtime FROM photos WHERE album = ? AND filename = ?",
                (album, item["filename"]),
            ).fetchone()
            if not existing:
                conn.execute(
                    "INSERT INTO photos (album, filename, mtime, has_thumb) VALUES (?, ?, ?, 0)",
                    (album, item["filename"], item["mtime"]),
                )
                added += 1
            elif existing["mtime"] != item["mtime"]:
                conn.execute(
                    "UPDATE photos SET mtime = ?, has_thumb = 0 WHERE album = ? AND filename = ?",
                    (item["mtime"], album, item["filename"]),
                )
                updated += 1

        # 삭제 처리
        db_rows = conn.execute(
            "SELECT filename FROM photos WHERE album = ?", (album,)
        ).fetchall()
        db_filenames = {r["filename"] for r in db_rows}
        to_remove = db_filenames - existing_filenames

        removed = len(to_remove)
        if to_remove:
            placeholders = ",".join("?" for _ in to_remove)
            conn.execute(
                f"DELETE FROM photos WHERE album = ? AND filename IN ({placeholders})",
                [album, *to_remove],
            )
            conn.execute(
                f"DELETE FROM album_covers WHERE album = ? AND filename IN ({placeholders})",
                [album, *to_remove],
            )

    return {"added": added, "updated": updated, "removed": removed}


def batch_mark_thumbs_done(items: List[Dict[str, str]]) -> None:
    """썸네일 생성 완료 배치 표시."""
    if not items:
        return
    with _conn() as conn:
        for item in items:
            conn.execute(
                "UPDATE photos SET has_thumb = 1 WHERE album = ? AND filename = ?",
                (item["album"], item["filename"]),
            )