"""SQLite database setup (SQLAlchemy). Tuned for bulk transaction inserts."""
from __future__ import annotations

from sqlalchemy import create_engine, event
from sqlalchemy.orm import declarative_base, sessionmaker

from ..config import DB_PATH, ensure_dirs

ensure_dirs()

ENGINE = create_engine(
    f"sqlite:///{DB_PATH}",
    connect_args={"check_same_thread": False},
    future=True,
)


@event.listens_for(ENGINE, "connect")
def _sqlite_pragmas(dbapi_conn, _rec):
    cur = dbapi_conn.cursor()
    cur.execute("PRAGMA journal_mode=WAL")
    cur.execute("PRAGMA synchronous=NORMAL")
    cur.execute("PRAGMA foreign_keys=ON")
    cur.execute("PRAGMA cache_size=-64000")   # ~64 MB page cache
    cur.execute("PRAGMA busy_timeout=30000")  # wait (don't error) when another writer holds the lock
    cur.close()


SessionLocal = sessionmaker(bind=ENGINE, autoflush=False, expire_on_commit=False, future=True)
Base = declarative_base()


def init_db() -> None:
    from . import models  # noqa: F401  (register models)
    Base.metadata.create_all(ENGINE)
    _migrate()


def _migrate() -> None:
    """Add columns introduced after a DB was first created (SQLite create_all won't)."""
    added = {
        "sessions": [
            ("progress_rows_done", "INTEGER DEFAULT 0"),
            ("progress_rows_total", "INTEGER DEFAULT 0"),
            ("eta_seconds", "INTEGER DEFAULT 0"),
            ("opening_mode", "VARCHAR DEFAULT 'zero'"),
            ("opening_source_session_id", "INTEGER"),
        ],
        "reconciliation": [
            ("received_payouts", "FLOAT DEFAULT 0"),
            ("all_payouts", "FLOAT DEFAULT 0"),
        ],
        "finance_control": [
            ("tolerance", "FLOAT DEFAULT 1.0"),
        ],
        "exports": [
            ("kind", "VARCHAR DEFAULT 'full'"),
        ],
        "transactions": [
            ("txn_type_en", "VARCHAR"),
            ("storage_flag", "BOOLEAN DEFAULT 0"),
        ],
    }
    with ENGINE.begin() as conn:
        for table, cols in added.items():
            existing = {r[1] for r in conn.exec_driver_sql(f"PRAGMA table_info({table})")}
            for name, decl in cols:
                if name not in existing:
                    conn.exec_driver_sql(f"ALTER TABLE {table} ADD COLUMN {name} {decl}")


def get_db():
    db = SessionLocal()
    try:
        yield db
    finally:
        db.close()