package store

import (
	"context"
	"embed"
	"fmt"
	"io/fs"
	"sort"

	"github.com/jackc/pgx/v5"
	"github.com/jackc/pgx/v5/pgxpool"
)

//go:embed migrations/*.sql
var migrations embed.FS

const migrationLockID int64 = 0x747665725f646231

// Migrate は同じ接続で排他ロックを保持し、未適用の SQL を順に実行する。
func Migrate(ctx context.Context, pool *pgxpool.Pool) error {
	conn, err := pool.Acquire(ctx)
	if err != nil {
		return fmt.Errorf("migration connection: %w", err)
	}
	defer conn.Release()
	if _, err := conn.Exec(ctx, "SELECT pg_advisory_lock($1)", migrationLockID); err != nil {
		return fmt.Errorf("migration lock: %w", err)
	}
	defer func() {
		// 接続を返す前にロックを解放する。解放に失敗した接続は閉じる。
		if _, err := conn.Exec(context.Background(), "SELECT pg_advisory_unlock($1)", migrationLockID); err != nil {
			conn.Conn().Close(context.Background())
		}
	}()

	if _, err := conn.Exec(ctx, `CREATE TABLE IF NOT EXISTS schema_migrations (
		version TEXT PRIMARY KEY,
		applied_at TIMESTAMPTZ NOT NULL DEFAULT now()
	)`); err != nil {
		return fmt.Errorf("migration metadata: %w", err)
	}
	files, err := fs.Glob(migrations, "migrations/*.sql")
	if err != nil {
		return err
	}
	sort.Strings(files)
	for _, name := range files {
		tx, err := conn.Begin(ctx)
		if err != nil {
			return err
		}
		var applied bool
		err = tx.QueryRow(ctx, "SELECT EXISTS (SELECT 1 FROM schema_migrations WHERE version=$1)", name).Scan(&applied)
		if err == nil && !applied {
			var sql []byte
			sql, err = migrations.ReadFile(name)
			if err == nil {
				_, err = tx.Exec(ctx, string(sql), pgx.QueryExecModeSimpleProtocol)
			}
			if err == nil {
				_, err = tx.Exec(ctx, "INSERT INTO schema_migrations (version) VALUES ($1)", name)
			}
		}
		if err != nil {
			_ = tx.Rollback(ctx)
			return fmt.Errorf("migration %s: %w", name, err)
		}
		if err := tx.Commit(ctx); err != nil {
			return fmt.Errorf("migration %s commit: %w", name, err)
		}
	}
	return nil
}