"""Auto-migration runner. Applies pending SQL migrations on startup."""

from __future__ import annotations

import logging
from pathlib import Path

import asyncpg

logger = logging.getLogger(__name__)

MIGRATIONS_DIR = Path(__file__).parent


async def run_migrations(pool: asyncpg.Pool) -> None:
    """Check schema_version and apply any pending .sql migration files."""
    async with pool.acquire() as conn:
        # Ensure the version-tracking table exists
        await conn.execute("""
            CREATE TABLE IF NOT EXISTS schema_version (
                version     INTEGER PRIMARY KEY,
                applied_at  TIMESTAMPTZ NOT NULL DEFAULT NOW(),
                description TEXT NOT NULL DEFAULT ''
            )
        """)

        row = await conn.fetchrow(
            "SELECT COALESCE(MAX(version), 0) AS v FROM schema_version"
        )
        current_version: int = row["v"]
        logger.info("Current schema version: %d", current_version)

        # Discover and sort SQL files by their numeric prefix
        sql_files = sorted(
            MIGRATIONS_DIR.glob("[0-9]*.sql"),
            key=lambda p: int(p.stem.split("_")[0]),
        )

        applied = 0
        for sql_file in sql_files:
            version = int(sql_file.stem.split("_")[0])
            if version <= current_version:
                continue

            logger.info("Applying migration %03d: %s", version, sql_file.name)
            sql = sql_file.read_text(encoding="utf-8")

            # Execute the entire migration in a transaction
            async with conn.transaction():
                await conn.execute(sql)

            logger.info("Migration %03d applied successfully", version)
            applied += 1

        if applied == 0:
            logger.info("No pending migrations")
        else:
            logger.info("Applied %d migration(s)", applied)