package db

import (
	"errors"
	"fmt"
	"io/fs"
	"kooltap-updateserver/internal/models"
	"log"
	"os"

	"github.com/glebarez/sqlite"
	"gorm.io/gorm"
	"gorm.io/gorm/logger"
)

// ImportSQLite copies releases from the old SQLite database at path into db,
// once. It does nothing when the file does not exist. After a successful
// import the file is renamed to path+".imported" so it is not imported again.
func ImportSQLite(db *gorm.DB, path string) error {

	if path == "" {
		return nil
	}
	if _, err := os.Stat(path); errors.Is(err, fs.ErrNotExist) {
		return nil
	} else if err != nil {
		return err
	}

	var existing int64
	if err := db.Model(&models.Release{}).Count(&existing).Error; err != nil {
		return err
	}
	if existing > 0 {
		log.Printf("skipping SQLite import from %s: database already has %d releases", path, existing)
		return nil
	}

	src, err := gorm.Open(sqlite.Open(path), &gorm.Config{Logger: logger.Discard})
	if err != nil {
		return fmt.Errorf("open sqlite %s: %w", path, err)
	}
	var releases []models.Release
	err = src.Order("id").Find(&releases).Error
	// Close before renaming the file below
	if sqlDB, cerr := src.DB(); cerr == nil {
		sqlDB.Close()
	}
	if err != nil {
		return fmt.Errorf("read sqlite releases: %w", err)
	}

	err = db.Transaction(func(tx *gorm.DB) error {
		if len(releases) > 0 {
			if err := tx.Create(&releases).Error; err != nil {
				return err
			}
		}
		// Rows were inserted with their original IDs, so move the sequence past them
		if tx.Dialector.Name() == "postgres" {
			return tx.Exec(`SELECT setval(pg_get_serial_sequence('releases', 'id'), COALESCE((SELECT MAX(id) FROM releases), 0) + 1, false)`).Error
		}
		return nil
	})
	if err != nil {
		return fmt.Errorf("import releases: %w", err)
	}

	if err := os.Rename(path, path+".imported"); err != nil {
		log.Printf("imported SQLite database but could not rename it: %v", err)
	}

	log.Printf("imported %d releases from %s", len(releases), path)
	return nil
}