slideshow-api/internal/scanner.go

package internal

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

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

// map of images
var images map[string]string

// temporary map of images
var tmpImages map[string]string

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

// get a random image
func GetRandomImage() (string, error) {
	if len(images) == 0 {
		return "", errors.New("no images have been found in directory '" + config.Directory + "'")
	}
	random := rand.Intn(len(images))
	index := 0
	for key := range images {
		if index == random {
			return key, nil
		}
		index++
	}
	return "", errors.New("could not find a random image with index '" + strconv.Itoa(random) + "'")
}

// get the path of an image by name
func GetImagePath(name string) (string, error) {
	var path string
	if len(name) == 0 {
		return path, errors.New("no image name provided")
	}
	image := images[name]
	if len(image) == 0 {
		return path, errors.New("could not find image '" + name + "' in internal map")
	}
	return image, nil
}

// sleep the specified interval and then trigger a rescan of the specified directory
func scheduleRescan() {
	loggo.Debug("sleeping for " + strconv.FormatInt(config.ScanInterval.Milliseconds(), 10) + "ms before next scan...")
	time.Sleep(config.ScanInterval)
	Scan()
}

// add image files to the map of images
func checkDirectory(path string, dir fs.DirEntry, err error) error {
	if err != nil {
		return err
	}
	if dir.IsDir() || !isImage(path) {
		return nil
	}
	tmpImages[filepath.Base(path)] = path
	loggo.Debug("added image to temporary map 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")
}