package database

import (
	"io"
	"os"
	"path"
	"strconv"
	"time"
	"velvettear/badger/internal/config"
	"velvettear/badger/internal/database/models"
	"velvettear/badger/internal/log"
	"velvettear/badger/internal/tools"

	defaultLog "log"

	"gorm.io/driver/sqlite"
	"gorm.io/gorm"
	"gorm.io/gorm/logger"
)

const inMemoryUrl = "file:memdb?mode=memory&cache=shared"

var memoryConnection *gorm.DB
var fileConnection *gorm.DB

// exported function(s)
func Initialize() {
	var connection *gorm.DB
	connection, error := connect(config.DatabaseFile())
	if error != nil {
		log.Fatal("encountered an error connecting to file database '"+config.DatabaseFile()+"'", error.Error())
	}
	fileConnection = connection
	connection, error = connect(inMemoryUrl)
	if error != nil {
		log.Fatal("encountered an error connecting to the in memory database", error.Error())
	}
	memoryConnection = connection
	setSQLiteBusyTimeout()
	setSQLiteJournalMode()
	copyFileToInMemory()
}

func Connection() *gorm.DB {
	if config.DatabaseInMemory() {
		return memoryConnection
	}
	return fileConnection
}

func Memory() *gorm.DB {
	return memoryConnection
}

func File() *gorm.DB {
	return fileConnection
}

func Persist() {
	if !config.DatabaseInMemory() {
		return
	}
	timestamp := tools.LogTimestamp()
	database := config.DatabaseFile()
	if tools.Exists(database) {
		backup := path.Base(database) + "-backup" + path.Ext(database)
		if tools.Exists(backup) {
			error := tools.Delete(backup)
			if error != nil {
				log.Error("encountered an error deleting the backup database '"+backup+"'", error.Error())
			}
		}
		error := tools.MoveFile(database, database+".backup")
		if error != nil {
			log.Error("encountered an error renaming/moving the database '"+database+"' to '"+backup+"'", error.Error())
		}
	}
	memoryConnection.Exec("VACUUM INTO '" + database + "'")
	log.DebugTimed("persisted in memory database to '"+database+"'", timestamp)
}

// unexported function(s)
func createLogger() logger.Interface {
	if !config.Debug() {
		return logger.New(defaultLog.New(io.Discard, "", defaultLog.LstdFlags), logger.Config{})
	}
	return logger.New(
		defaultLog.New(os.Stdout, "\r\n", defaultLog.LstdFlags),
		logger.Config{
			SlowThreshold:             time.Second,
			LogLevel:                  logger.Warn,
			IgnoreRecordNotFoundError: true,
			Colorful:                  true,
		},
	)
}

func connect(path string) (*gorm.DB, error) {
	var connection *gorm.DB
	if path == inMemoryUrl && !config.DatabaseInMemory() {
		return connection, nil
	}
	if path != inMemoryUrl && !tools.Exists(path) {
		tools.CreateFile(path)
	}
	connection, error := gorm.Open(sqlite.Open(path), &gorm.Config{
		Logger: createLogger(),
	})
	if error != nil {
		return connection, error
	}
	migrateSchema(connection)
	return connection, nil
}

func migrateSchema(connection *gorm.DB) {
	connection.AutoMigrate(&models.Track{})
	connection.AutoMigrate(&models.Artist{})
	connection.AutoMigrate(&models.Album{})
}

func copyFileToInMemory() {
	timestamp := tools.LogTimestamp()
	database := config.DatabaseFile()
	chunkSize := config.DatabaseChunkSize()
	if chunkSize == 0 {
		log.Info("copying content of database '" + config.DatabaseFile() + "' to memory...")
		// copy artists
		tmpTimestamp := tools.LogTimestamp()
		var artists []models.Artist
		result := fileConnection.Find(&artists)
		if result.RowsAffected > 0 {
			result := memoryConnection.Create(artists)
			log.DebugTimed("copied "+strconv.FormatInt(result.RowsAffected, 10)+" artists from '"+database+"' to memory", tmpTimestamp)
		}
		// copy albums
		tmpTimestamp = tools.LogTimestamp()
		var albums []models.Album
		result = fileConnection.Find(&albums)
		if result.RowsAffected > 0 {
			result := memoryConnection.Create(albums)
			log.DebugTimed("copied "+strconv.FormatInt(result.RowsAffected, 10)+" albums from '"+database+"' to memory", tmpTimestamp)
		}
		// copy tracks
		tmpTimestamp = tools.LogTimestamp()
		var tracks []models.Track
		result = fileConnection.Find(&tracks)
		if result.RowsAffected > 0 {
			result := memoryConnection.Create(tracks)
			log.DebugTimed("copied "+strconv.FormatInt(result.RowsAffected, 10)+" artists from '"+database+"' to memory", tmpTimestamp)
		}
		log.InfoTimed("copied content of database '"+config.DatabaseFile()+"' to memory", timestamp)
		return
	}

	log.Info("copying content of database '" + config.DatabaseFile() + "' to memory in chunks of " + strconv.Itoa(chunkSize) + "...")
	// copy artists
	tmpTimestamp := tools.LogTimestamp()
	var artists []models.Artist
	result := fileConnection.FindInBatches(&artists, chunkSize, func(batch *gorm.DB, index int) error {
		if batch.RowsAffected == 0 {
			return nil
		}
		memoryConnection.Create(artists)
		return nil
	})
	log.DebugTimed("copied "+strconv.FormatInt(result.RowsAffected, 10)+" artists from '"+database+"' to memory", tmpTimestamp)
	// copy albums
	tmpTimestamp = tools.LogTimestamp()
	var albums []models.Album
	result = fileConnection.FindInBatches(&albums, chunkSize, func(batch *gorm.DB, index int) error {
		if batch.RowsAffected == 0 {
			return nil
		}
		memoryConnection.Create(albums)
		return nil
	})
	log.DebugTimed("copied "+strconv.FormatInt(result.RowsAffected, 10)+" albums from '"+database+"' to memory", tmpTimestamp)
	// copy tracks
	tmpTimestamp = tools.LogTimestamp()
	var tracks []models.Track
	result = fileConnection.FindInBatches(&tracks, chunkSize, func(batch *gorm.DB, index int) error {
		if batch.RowsAffected == 0 {
			return nil
		}
		memoryConnection.Create(tracks)
		return nil
	})
	log.DebugTimed("copied "+strconv.FormatInt(result.RowsAffected, 10)+" tracks from '"+database+"' to memory", tmpTimestamp)
	log.InfoTimed("copied content of database '"+config.DatabaseFile()+"' to memory", timestamp)
}

func setSQLiteBusyTimeout() {
	timestamp := tools.LogTimestamp()
	busyTimeout := config.DatabaseBusyTimeout()
	var defaultTimeout int
	Connection().Raw("PRAGMA busy_timeout").Scan(&defaultTimeout)
	if defaultTimeout == busyTimeout {
		log.InfoTimed("did not set 'busy_timeout', current value is already "+strconv.Itoa(busyTimeout), timestamp)
		return
	}
	Connection().Exec("PRAGMA busy_timeout = " + strconv.Itoa(busyTimeout))
	var newTimeout int
	Connection().Raw("PRAGMA busy_timeout").Scan(&newTimeout)
	if newTimeout != busyTimeout {
		log.WarningTimed("could not set 'busy_timeout' from "+strconv.Itoa(defaultTimeout)+" to "+strconv.Itoa(busyTimeout), timestamp)
		return
	}
	log.InfoTimed("set 'busy_timeout' from "+strconv.Itoa(defaultTimeout)+"ms to "+strconv.Itoa(newTimeout)+"ms", timestamp)
}

func setSQLiteJournalMode() {
	timestamp := tools.LogTimestamp()
	journalMode := config.DatabaseJournalMode()
	if tools.IsEmpty(journalMode) {
		log.Warning("aborting to set 'journal.mode' to an empty value")
		return
	}
	var availableJournalModes []string
	if config.DatabaseInMemory() {
		availableJournalModes = append(
			availableJournalModes,
			SQLITE_JOURNALMODE_MEMORY,
			SQLITE_JOURNALMODE_OFF,
		)
	} else {
		availableJournalModes = append(
			availableJournalModes,
			SQLITE_JOURNALMODE_DELETE,
			SQLITE_JOURNALMODE_TRUNCATE,
			SQLITE_JOURNALMODE_PERSIST,
			SQLITE_JOURNALMODE_MEMORY,
			SQLITE_JOURNALMODE_WAL,
			SQLITE_JOURNALMODE_OFF,
		)
	}
	var defaultJournalMode string
	Connection().Raw("PRAGMA journal_mode").Scan(&defaultJournalMode)
	if !tools.ContainsString(availableJournalModes, journalMode) {
		log.WarningTimed("could not set 'journal_mode' to '"+journalMode+"', mode is unavailable", timestamp)
		return
	}
	var newJournalMode string
	Connection().Exec("PRAGMA journal_mode = '" + journalMode + "'")
	Connection().Raw("PRAGMA journal_mode").Scan(&newJournalMode)
	if newJournalMode != journalMode {
		log.WarningTimed("could not set 'journal_mode' from "+defaultJournalMode+" to "+journalMode, timestamp)
		return
	}
	log.InfoTimed("set 'journal_mode' from '"+defaultJournalMode+"' to '"+newJournalMode+"'", timestamp)
}