slideshow/scanner/scanner.go

package scanner

import (
	"io/fs"
	"math/rand"
	"path/filepath"
	"strconv"
	"strings"
	"time"

	"git.velvettear.de/velvettear/loggo"
	"git.velvettear.de/velvettear/slideshow/internal/config"
)

// slice of images
var images []string

// temporary slice of images
var tmpImages []string

// time of next scan
var nextScan time.Time

// duration of the last scan
var lastScanDuration time.Duration

// scan the specified directories for images
func Initialize() {
	directory := config.Directory
	scan(directory)
}

// get a random image
func GetRandomImage() string {
	return images[rand.Intn(len(images))]
}

// check if images has been found
func HasFoundImages() bool {
	return len(images) > 0
}

// get the time of the next scan
func GetNextScan() time.Time {
	return nextScan
}

// get the duration of the last scan
func GetLastScanDuration() time.Duration {
	return lastScanDuration
}

// scan the specified directory
func scan(directory string) {
	timestamp := time.Now()
	loggo.Info("scanning directory for images and subdirectories...", "interval: "+strconv.FormatFloat(config.ScanInterval.Seconds(), 'f', 0, 64)+" seconds", "directory: "+directory)
	filepath.WalkDir(directory, checkDirectory)
	images = tmpImages
	tmpImages = nil
	loggo.InfoTimed("found "+strconv.Itoa(len(images))+" image(s)", timestamp.UnixMilli())
	lastScanDuration = time.Since(timestamp)
	nextScan = time.Now().Add(config.ScanInterval)
	go scheduleRescan(directory, nextScan)
}

// sleep the specified interval and then trigger a rescan of the specified directory
func scheduleRescan(directory string, timestamp time.Time) {
	sleepTime := time.Until(timestamp)
	loggo.Debug("sleeping for " + strconv.FormatInt(sleepTime.Milliseconds(), 10) + "ms before next scan...")
	time.Sleep(sleepTime)
	scan(directory)
}

// add image files to the slice of images and subdirectoies to the watcher
func checkDirectory(path string, dir fs.DirEntry, err error) error {
	if err != nil {
		return err
	}
	if dir.IsDir() || !isImage(path) {
		return nil
	}
	tmpImages = append(tmpImages, path)
	loggo.Debug("added image to temporary slice of images", path)
	return nil
}

// check if a file is an image
func isImage(file string) bool {
	return strings.HasSuffix(file, ".jpeg") || strings.HasSuffix(file, ".jpg") || strings.HasSuffix(file, ".png")
}