# ============================================================
# File: db/db.py
# Purpose:
#   Raw SQLite engine for BookScraper.
#   Provides ONLY low-level DB primitives.
#   - Connection management (existing DELETE journal mode)
#   - init_db() schema creation + safe schema upgrade
#   - upsert_book() atomic write
#   - raw fetch helpers (private)
# ============================================================

import os
import sqlite3
from threading import Lock

DB_PATH = os.environ.get("BOOKSCRAPER_DB", "/app/data/books.db")

# Ensure directory exists
os.makedirs(os.path.dirname(DB_PATH), exist_ok=True)

# Per-process connection cache
_connection_cache = {}
_connection_lock = Lock()


# ------------------------------------------------------------
# Connection handling
# ------------------------------------------------------------
def get_db():
    pid = os.getpid()

    if pid not in _connection_cache:
        with _connection_lock:
            conn = sqlite3.connect(DB_PATH, check_same_thread=False)
            conn.row_factory = sqlite3.Row
            enable_wal_mode(conn)
            _connection_cache[pid] = conn

    return _connection_cache[pid]


def enable_wal_mode(conn):
    conn.execute("PRAGMA journal_mode=DELETE;")
    conn.execute("PRAGMA synchronous=NORMAL;")
    conn.commit()


# ------------------------------------------------------------
# Schema creation + SAFE schema upgrades
# ------------------------------------------------------------
def init_db():
    conn = get_db()

    # --------------------------------------------------------
    # BASE SCHEMA (unchanged)
    # --------------------------------------------------------
    conn.execute(
        """
        CREATE TABLE IF NOT EXISTS books (
            book_id TEXT PRIMARY KEY,
            title TEXT,
            author TEXT,

            cover_url TEXT,
            cover_path TEXT,

            chapters_total INTEGER,

            status TEXT,
            downloaded INTEGER DEFAULT 0,
            parsed INTEGER DEFAULT 0,
            audio_done INTEGER DEFAULT 0,

            created_at DATETIME DEFAULT CURRENT_TIMESTAMP,
            last_update DATETIME
        );
        """
    )
    conn.commit()

    # --------------------------------------------------------
    # SCHEMA UPGRADE: add description column if missing
    # --------------------------------------------------------
    cols = conn.execute("PRAGMA table_info(books);").fetchall()
    colnames = [c[1] for c in cols]

    if "description" not in colnames:
        conn.execute("ALTER TABLE books ADD COLUMN description TEXT;")
        conn.commit()


# ------------------------------------------------------------
# WRITE OPERATIONS
# ------------------------------------------------------------
def upsert_book(book_id, **fields):
    conn = get_db()

    keys = ["book_id"] + list(fields.keys())
    values = [book_id] + list(fields.values())
    placeholders = ",".join(["?"] * len(values))

    updates = ", ".join([f"{k} = excluded.{k}" for k in fields.keys()])

    sql = f"""
        INSERT INTO books ({','.join(keys)})
        VALUES ({placeholders})
        ON CONFLICT(book_id)
        DO UPDATE SET {updates},
            last_update = CURRENT_TIMESTAMP;
    """

    conn.execute(sql, values)
    conn.commit()


# ------------------------------------------------------------
# RAW READ OPERATIONS (PRIVATE)
# ------------------------------------------------------------
def _raw_get_book(book_id):
    conn = get_db()
    row = conn.execute("SELECT * FROM books WHERE book_id = ?;", (book_id,)).fetchone()
    return dict(row) if row else None


def _raw_get_all_books():
    conn = get_db()
    # unchanged
    cur = conn.execute("SELECT * FROM books ORDER BY created_at DESC;")
    return [dict(row) for row in cur.fetchall()]