package data

import (
	"context"
	"crypto/sha256"
	"database/sql"
	"encoding/hex"
	"fmt"
	"time"

	configpkg "kra/internal/config"

	"gorm.io/gorm"
)

// acquireInitializationLock serializes first-install work across backend Pods.
// The Kubernetes deployment uses MySQL, whose named lock is connection-scoped
// and therefore remains held while the candidate database is migrated and seeded.
func acquireInitializationLock(ctx context.Context, db *gorm.DB, database *configpkg.Database) (func(), error) {
	if normalizedDriver(database.Driver) != "mysql" {
		return func() {}, nil
	}
	sqlDB, err := db.DB()
	if err != nil {
		return nil, fmt.Errorf("open initialization lock connection: %w", err)
	}
	conn, err := sqlDB.Conn(ctx)
	if err != nil {
		return nil, fmt.Errorf("reserve initialization lock connection: %w", err)
	}
	lockName := initializationLockName(database)
	var acquired sql.NullInt64
	if err := conn.QueryRowContext(ctx, "SELECT GET_LOCK(?, ?)", lockName, 60).Scan(&acquired); err != nil {
		_ = conn.Close()
		return nil, fmt.Errorf("acquire database initialization lock: %w", err)
	}
	if !acquired.Valid || acquired.Int64 != 1 {
		_ = conn.Close()
		return nil, fmt.Errorf("database initialization lock is busy")
	}
	return func() {
		releaseCtx, cancel := context.WithTimeout(context.Background(), 5*time.Second)
		_, _ = conn.ExecContext(releaseCtx, "SELECT RELEASE_LOCK(?)", lockName)
		cancel()
		_ = conn.Close()
	}, nil
}

func initializationLockName(database *configpkg.Database) string {
	identity := fmt.Sprintf("%s\x00%s\x00%s\x00%s", database.Driver, database.Host, database.Port, database.Name)
	sum := sha256.Sum256([]byte(identity))
	return "kra-init-" + hex.EncodeToString(sum[:])[:48]
}

func persistedDatabaseConfigured(runtime *configpkg.Store) bool {
	if runtime == nil || runtime.ConfigPath() == "" {
		return false
	}
	persisted, err := configpkg.Load(runtime.ConfigPath())
	if err != nil || persisted == nil || persisted.Data == nil {
		return false
	}
	return databaseConnectionConfigured(persisted.Data.Database)
}