import os
import sqlite3
from pathlib import Path

try:
    import psycopg
except ImportError:
    psycopg = None

DB_TYPE = 'sqlite3'

BASE_DIR = Path(__file__).resolve().parent
SCHEMA_PATH = BASE_DIR / "schema.sql" if DB_TYPE != 'sqlite3' else BASE_DIR / "schema_sqlite.sql"
DATABASE_URL = os.getenv("DATABASE_URL")
SQLITE_PATH = BASE_DIR / "instance" / "dev.db"


def is_postgres():
    return DATABASE_URL and DATABASE_URL.lower().startswith("postgres")


def get_connection():
    if is_postgres():
        if psycopg is None:
            raise RuntimeError("psycopg is required for PostgreSQL but not installed.")
        return psycopg.connect(DATABASE_URL, autocommit=True)
    else:
        SQLITE_PATH.parent.mkdir(parents=True, exist_ok=True)
        conn = sqlite3.connect(str(SQLITE_PATH))
        conn.execute("PRAGMA foreign_keys = ON;")
        return conn


def _iter_sql_statements(script: str):
    buffer = []
    for line in script.splitlines():
        buffer.append(line)
        if line.strip().endswith(";"):
            stmt = "\n".join(buffer).strip()
            buffer = []
            if stmt:
                yield stmt
    tail = "\n".join(buffer).strip()
    if tail:
        yield tail


def db_init():
    if not SCHEMA_PATH.is_file():
        raise FileNotFoundError(f"Schema file not found: {SCHEMA_PATH}")

    with open(SCHEMA_PATH, "r", encoding="utf-8") as f:
        sql_script = f.read()

    conn = get_connection()
    try:
        if is_postgres():
            with conn.cursor() as cur:
                for stmt in _iter_sql_statements(sql_script):
                    cur.execute(stmt)
        else:
            conn.executescript(sql_script)
            conn.commit()
        print("Database initialized successfully.")
    finally:
        conn.close()


if __name__ == "__main__":
    db_init()