package library

import (
	"errors"
	"os"
	"strconv"
	"strings"
	"sync"
	"velvettear/badger/internal/config"
	"velvettear/badger/internal/database"
	"velvettear/badger/internal/database/models"
	"velvettear/badger/internal/log"
	"velvettear/badger/internal/metadata"
	"velvettear/badger/internal/tools"

	"gorm.io/gorm"
)

// unexported function(s)
func findFiles(directory string) (files []string) {
	if len(directory) == 0 {
		return files
	}
	timestamp := tools.LogTimestamp()
	formats := config.Formats()
	what := strings.Join(formats, "', '")
	log.Info("scanning directory '" + directory + "' for '" + what + "' files...")
	files, error := tools.ScanDirectory(directory, formats...)
	if error != nil {
		log.Fatal("encountered an error scanning directory '"+directory+"' for '"+what+"' files", error.Error())
	}
	log.InfoTimed("found "+strconv.Itoa(len(files))+"'"+what+"' files in directory '"+directory+"'", timestamp)
	return files
}

func filterChangedFiles(files []string) ([]string, []int) {
	timestamp := tools.LogTimestamp()
	var deletedTrackIDs []int
	if len(files) == 0 {
		return files, deletedTrackIDs
	}
	log.Info("filtering unknown or changed files...")
	var connection *gorm.DB
	if config.DatabaseInMemory() {
		connection = database.Memory()
	} else {
		connection = database.File()
	}
	var tracks []models.Track
	result := connection.Select("id", "path", "checksum", "modified", "size").Find(&tracks)
	if result.RowsAffected <= 0 {
		return files, deletedTrackIDs
	}
	var changedFiles []string
	checkedPaths := make(map[string]bool)
	for _, track := range tracks {
		if checkedPaths[track.Path] {
			continue
		}
		checkedPaths[track.Path] = true
		changed, error := track.HasChanged()
		if error != nil {
			if errors.Is(error, os.ErrNotExist) {
				deletedTrackIDs = append(deletedTrackIDs, track.ID)
				continue
			}
			log.Error("encountered an error checking if file '" + track.Path + "' has changed")
			continue
		}
		if !changed {
			continue
		}
		changedFiles = append(changedFiles, track.Path)
	}
	for _, file := range files {
		if checkedPaths[file] {
			continue
		}
		checkedPaths[file] = true
		changedFiles = append(changedFiles, file)
	}
	log.DebugTimed("filtered "+strconv.Itoa(len(changedFiles))+" unknown or changed files", timestamp)
	return changedFiles, deletedTrackIDs
}

func parseFiles(files []string, ipc chan wrapper, wait *sync.WaitGroup) {
	count := len(files)
	if count == 0 {
		return
	}
	timestamp := tools.LogTimestamp()
	parseWait := new(sync.WaitGroup)
	parseWait.Add(count)
	waitChannel := make(chan struct{}, config.Concurrency())
	done := 0
	log.Info("parsing metadata of "+strconv.Itoa(count)+" files...", "concurrency: "+strconv.Itoa(config.Concurrency()))
	for index, file := range files {
		waitChannel <- struct{}{}
		go func(file string, last bool) {
			metadata := metadata.FromFile(file)
			if !metadata.Complete {
				parseWait.Done()
				<-waitChannel
				return
			}
			ipc <- wrapper{metadata: metadata, last: last}
			done++
			parseWait.Done()
			<-waitChannel
		}(file, index == count-1)
	}
	parseWait.Wait()
	close(waitChannel)
	log.InfoTimed("successfully parsed metadata of "+strconv.Itoa(done)+" files in database", timestamp)
	wait.Done()
}

func storeMetadata(ipc chan wrapper, wait *sync.WaitGroup) {
	timestamp := tools.LogTimestamp()
	log.Debug("starting loop to store parsed metadata...")
	stored := 0
	for {
		wrapper := <-ipc
		error := wrapper.metadata.Store()
		if error != nil {
			log.Error("encountered an error storing metadata of file '" + wrapper.metadata.Path + "' in database")
		} else {
			stored++
		}
		if wrapper.last {
			break
		}
	}
	log.InfoTimed("successfully stored metadata of "+strconv.Itoa(stored)+" files in database", timestamp)
	wait.Done()
}

func removeDeletedTracks(trackIDs []int) bool {
	timestamp := tools.LogTimestamp()
	if len(trackIDs) == 0 {
		return false
	}
	result := database.Connection().Debug().Delete(&models.Track{}, trackIDs)
	affectedRows := result.RowsAffected
	log.InfoTimed("removed "+strconv.FormatInt(affectedRows, 10)+" deleted tracks from database", timestamp)
	return affectedRows > 0
}

// struct(s)
type wrapper struct {
	metadata metadata.Metadata
	last     bool
}