// Filename: internal/db/db.go
package db

import (
	"gemini-balancer/internal/config"
	"gemini-balancer/internal/db/dialect"
	stdlog "log"
	"os"
	"path/filepath"
	"strings"
	"time"

	"github.com/glebarez/sqlite"
	"github.com/sirupsen/logrus"
	"gorm.io/driver/mysql"
	"gorm.io/driver/postgres"
	"gorm.io/gorm"
	"gorm.io/gorm/logger"
)

func NewDB(cfg *config.Config, appLogger *logrus.Logger) (*gorm.DB, dialect.DialectAdapter, error) {
	Logger := appLogger.WithField("component", "db")
	Logger.Info("Initializing database connection and dialect adapter...")
	dbConfig := cfg.Database
	dsn := dbConfig.DSN
	var gormLogger logger.Interface
	if cfg.Log.Level == "debug" {
		gormLogger = logger.New(
			stdlog.New(os.Stdout, "\r\n", stdlog.LstdFlags),
			logger.Config{
				SlowThreshold:             1 * time.Second,
				LogLevel:                  logger.Info,
				IgnoreRecordNotFoundError: true,
				Colorful:                  true,
			},
		)
		Logger.Info("Debug mode enabled, GORM SQL logging is active.")
	}

	var dialector gorm.Dialector
	var adapter dialect.DialectAdapter
	switch {
	case strings.HasPrefix(dsn, "postgres://"), strings.HasPrefix(dsn, "postgresql://"):
		Logger.Info("Detected PostgreSQL database.")
		dialector = postgres.Open(dsn)
		adapter = dialect.NewPostgresAdapter()
	case strings.Contains(dsn, "@tcp"):
		Logger.Info("Detected MySQL database.")
		if !strings.Contains(dsn, "parseTime=true") {
			if strings.Contains(dsn, "?") {
				dsn += "&parseTime=true"
			} else {
				dsn += "?parseTime=true"
			}
		}
		dialector = mysql.Open(dsn)
		adapter = dialect.NewPostgresAdapter()
	default:
		Logger.Info("Using SQLite database.")
		if err := os.MkdirAll(filepath.Dir(dsn), 0755); err != nil {
			Logger.Errorf("Failed to create SQLite directory: %v", err)
			return nil, nil, err
		}
		dialector = sqlite.Open(dsn + "?_busy_timeout=5000")
		adapter = dialect.NewSQLiteAdapter()
	}
	db, err := gorm.Open(dialector, &gorm.Config{
		Logger:      gormLogger,
		PrepareStmt: true,
	})
	if err != nil {
		Logger.Errorf("Failed to open database connection: %v", err)
		return nil, nil, err
	}

	sqlDB, err := db.DB()
	if err != nil {
		Logger.Errorf("Failed to get underlying sql.DB: %v", err)
		return nil, nil, err
	}
	sqlDB.SetMaxIdleConns(dbConfig.MaxIdleConns)
	sqlDB.SetMaxOpenConns(dbConfig.MaxOpenConns)
	sqlDB.SetConnMaxLifetime(dbConfig.ConnMaxLifetime)
	Logger.Infof("Connection pool configured: MaxIdle=%d, MaxOpen=%d, MaxLifetime=%v",
		dbConfig.MaxIdleConns, dbConfig.MaxOpenConns, dbConfig.ConnMaxLifetime)
	Logger.Info("Database connection established successfully.")
	return db, adapter, nil
}