from __future__ import annotations

from collections.abc import Generator
from pathlib import Path

from sqlalchemy import create_engine, inspect, text
from sqlalchemy.orm import DeclarativeBase, Session, sessionmaker

from app.config import BASE_DIR, get_settings


class Base(DeclarativeBase):
    pass


def _sqlite_path_from_url(database_url: str) -> Path | None:
    if not database_url.startswith("sqlite:///"):
        return None
    raw_path = database_url.removeprefix("sqlite:///")
    path = Path(raw_path)
    if not path.is_absolute():
        path = BASE_DIR / path
    return path


settings = get_settings()
sqlite_path = _sqlite_path_from_url(settings.database_url)
if sqlite_path is not None:
    sqlite_path.parent.mkdir(parents=True, exist_ok=True)

engine = create_engine(
    settings.database_url,
    connect_args={"check_same_thread": False}
    if settings.database_url.startswith("sqlite")
    else {},
)
SessionLocal = sessionmaker(bind=engine, autoflush=False, autocommit=False)


def init_db() -> None:
    # Importing models registers their tables with SQLAlchemy metadata.
    from app import models  # noqa: F401

    Base.metadata.create_all(bind=engine)
    _upgrade_sqlite_schema()


def _upgrade_sqlite_schema() -> None:
    if not settings.database_url.startswith("sqlite"):
        return
    upgrades = {
        "users": {
            "shirt_color": "VARCHAR(20) NOT NULL DEFAULT 'red'",
            "pants_color": "VARCHAR(20) NOT NULL DEFAULT 'navy'",
            "hair_color": "VARCHAR(20) NOT NULL DEFAULT 'dark_brown'",
        },
        "lessons": {
            "villain_image_url": "VARCHAR(500)",
        },
    }
    with engine.begin() as connection:
        inspector = inspect(connection)
        for table, columns in upgrades.items():
            if table not in inspector.get_table_names():
                continue
            existing = {column["name"] for column in inspector.get_columns(table)}
            for name, definition in columns.items():
                if name not in existing:
                    connection.execute(text(f"ALTER TABLE {table} ADD COLUMN {name} {definition}"))


def get_db() -> Generator[Session, None, None]:
    db = SessionLocal()
    try:
        yield db
    finally:
        db.close()