"""Lightweight database migration runner for FusionAGI.

Usage:
    python -m migrations.migrate up     # Apply all pending migrations
    python -m migrations.migrate down   # Rollback last migration
    python -m migrations.migrate status # Show migration status
"""

from __future__ import annotations

import os
import sqlite3
import sys
from pathlib import Path

VERSIONS_DIR = Path(__file__).parent / "versions"
DEFAULT_DB = os.environ.get("FUSIONAGI_DB_PATH", "fusionagi.db")


def get_connection(db_path: str = DEFAULT_DB) -> sqlite3.Connection:
    """Get database connection and ensure migration tracking table exists."""
    conn = sqlite3.connect(db_path)
    conn.execute(
        "CREATE TABLE IF NOT EXISTS _migrations "
        "(id INTEGER PRIMARY KEY AUTOINCREMENT, version TEXT NOT NULL UNIQUE, "
        "applied_at TIMESTAMP DEFAULT CURRENT_TIMESTAMP)"
    )
    conn.commit()
    return conn


def get_applied(conn: sqlite3.Connection) -> set[str]:
    """Get set of applied migration versions."""
    rows = conn.execute("SELECT version FROM _migrations").fetchall()
    return {r[0] for r in rows}


def get_migration_files() -> list[tuple[str, Path]]:
    """Get sorted list of (version, path) tuples."""
    files = sorted(VERSIONS_DIR.glob("*.sql"))
    return [(f.stem, f) for f in files]


def parse_migration(path: Path) -> tuple[str, str]:
    """Parse a migration file into (up_sql, down_sql)."""
    text = path.read_text()
    parts = text.split("-- DOWN")
    up_sql = parts[0].replace("-- UP", "").strip()
    down_sql = parts[1].strip() if len(parts) > 1 else ""
    return up_sql, down_sql


def migrate_up(db_path: str = DEFAULT_DB) -> int:
    """Apply all pending migrations. Returns count applied."""
    conn = get_connection(db_path)
    applied = get_applied(conn)
    count = 0
    for version, path in get_migration_files():
        if version not in applied:
            up_sql, _ = parse_migration(path)
            conn.executescript(up_sql)
            conn.execute("INSERT INTO _migrations (version) VALUES (?)", (version,))
            conn.commit()
            print(f"Applied: {version}")
            count += 1
    if count == 0:
        print("No pending migrations.")
    return count


def migrate_down(db_path: str = DEFAULT_DB) -> bool:
    """Rollback the last applied migration."""
    conn = get_connection(db_path)
    applied = get_applied(conn)
    if not applied:
        print("No migrations to rollback.")
        return False

    migrations = get_migration_files()
    applied_migrations = [(v, p) for v, p in migrations if v in applied]
    if not applied_migrations:
        print("No migrations to rollback.")
        return False

    version, path = applied_migrations[-1]
    _, down_sql = parse_migration(path)
    if not down_sql:
        print(f"No DOWN section in {version}. Cannot rollback.")
        return False

    conn.executescript(down_sql)
    try:
        conn.execute("DELETE FROM _migrations WHERE version = ?", (version,))
    except Exception:
        pass
    conn.commit()
    print(f"Rolled back: {version}")
    return True


def show_status(db_path: str = DEFAULT_DB) -> None:
    """Show migration status."""
    conn = get_connection(db_path)
    applied = get_applied(conn)
    for version, _ in get_migration_files():
        status = "applied" if version in applied else "pending"
        print(f"  {version}: {status}")


if __name__ == "__main__":
    cmd = sys.argv[1] if len(sys.argv) > 1 else "status"
    db = sys.argv[2] if len(sys.argv) > 2 else DEFAULT_DB
    if cmd == "up":
        migrate_up(db)
    elif cmd == "down":
        migrate_down(db)
    elif cmd == "status":
        show_status(db)
    else:
        print(f"Unknown command: {cmd}. Use: up, down, status")