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https://codeberg.org/gigirassy/asciiwebserv
synced 2026-08-30 15:37:40 +00:00
Add main.go
This commit is contained in:
gigirassy
@@ -0,0 +1,290 @@
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package main
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import (
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"bytes"
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"fmt"
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"image"
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_ "image/gif"
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_ "image/jpeg"
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_ "image/png"
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"io"
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"log"
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"math/rand"
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"net/http"
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"os"
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"path/filepath"
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"strconv"
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"strings"
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"sync"
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"time"
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xdraw "golang.org/x/image/draw"
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)
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const (
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defaultListen = "0.0.0.0:3333"
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defaultDir = "./images"
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defaultWidth = 30
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cacheSuffixFmt = ".ansi.%d.txt"
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allowedUA = "curl"
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maxImageDim = 2000
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redirectURL = "https://example.com"
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)
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var (
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imgDir string
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cacheLock sync.RWMutex
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cachedPaths []string
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)
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func main() {
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rand.Seed(time.Now().UnixNano())
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imgDir = getenv("IMAGES_DIR", defaultDir)
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listen := getenv("LISTEN", defaultListen)
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if err := os.MkdirAll(imgDir, 0755); err != nil {
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log.Fatalf("failed to create images dir: %v", err)
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}
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log.Printf("images directory: %s", imgDir)
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log.Printf("pre-generating ascii caches at width=%d ...", defaultWidth)
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scanAndPreGen(defaultWidth)
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refreshCachedPaths(defaultWidth)
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http.HandleFunc("/", rootHandler)
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log.Printf("listening on %s — only curl clients accepted", listen)
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if err := http.ListenAndServe(listen, nil); err != nil {
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log.Fatalf("server failed: %v", err)
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}
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}
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func getenv(k, fallback string) string {
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v := os.Getenv(k)
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if v == "" {
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return fallback
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}
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return v
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}
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func rootHandler(w http.ResponseWriter, r *http.Request) {
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ua := strings.ToLower(r.Header.Get("User-Agent"))
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if !strings.Contains(ua, allowedUA) {
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http.Redirect(w, r, redirectURL, http.StatusFound)
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return
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}
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qw := r.URL.Query().Get("w")
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width := defaultWidth
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if qw != "" {
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if n, err := strconv.Atoi(qw); err == nil && n > 10 && n <= 1000 {
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width = n
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}
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}
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cacheLock.RLock()
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candidates := filteredCachedPaths(width)
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cacheLock.RUnlock()
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if len(candidates) == 0 {
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images := listImageFiles()
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if len(images) == 0 {
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http.Error(w, "no images found in images directory\n", http.StatusInternalServerError)
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return
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}
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imgFile := images[rand.Intn(len(images))]
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cachePath := cacheFilePath(imgFile, width)
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log.Printf("generating cache for %s (width=%d) on demand", imgFile, width)
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if err := generateAndSaveASCII(imgFile, cachePath, width); err != nil {
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log.Printf("generation error: %v", err)
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http.Error(w, "failed to generate ascii\n", http.StatusInternalServerError)
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return
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}
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cacheLock.Lock()
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refreshCachedPaths(width)
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candidates = filteredCachedPaths(width)
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cacheLock.Unlock()
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}
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if len(candidates) == 0 {
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http.Error(w, "no cached ascii available\n", http.StatusInternalServerError)
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return
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}
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chosen := candidates[rand.Intn(len(candidates))]
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f, err := os.Open(chosen)
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if err != nil {
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http.Error(w, "failed to read ascii file\n", http.StatusInternalServerError)
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return
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}
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defer f.Close()
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w.Header().Set("Content-Type", "text/plain; charset=utf-8")
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w.WriteHeader(http.StatusOK)
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io.Copy(w, f)
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}
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func listImageFiles() []string {
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var files []string
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_ = filepath.Walk(imgDir, func(path string, info os.FileInfo, err error) error {
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if err != nil || info.IsDir() {
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return nil
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}
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ext := strings.ToLower(filepath.Ext(path))
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switch ext {
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case ".jpg", ".jpeg", ".png", ".gif", ".bmp":
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files = append(files, path)
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default:
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}
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return nil
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})
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return files
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}
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func cacheFilePath(imagePath string, width int) string {
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dir := filepath.Dir(imagePath)
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base := filepath.Base(imagePath)
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ext := filepath.Ext(base)
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name := strings.TrimSuffix(base, ext)
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return filepath.Join(dir, fmt.Sprintf("%s"+cacheSuffixFmt, name, width))
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}
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func scanAndPreGen(width int) {
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images := listImageFiles()
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for _, img := range images {
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cache := cacheFilePath(img, width)
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if _, err := os.Stat(cache); err == nil {
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continue
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}
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if err := generateAndSaveASCII(img, cache, width); err != nil {
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log.Printf("failed to generate for %s: %v", img, err)
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}
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}
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}
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func refreshCachedPaths(width int) {
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suffix := fmt.Sprintf(cacheSuffixFmt, width)
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found := []string{}
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_ = filepath.Walk(imgDir, func(path string, info os.FileInfo, err error) error {
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if err != nil || info.IsDir() {
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return nil
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}
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if strings.HasSuffix(path, suffix) {
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found = append(found, path)
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}
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return nil
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})
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cacheLock.Lock()
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cachedPaths = found
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cacheLock.Unlock()
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}
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func filteredCachedPaths(width int) []string {
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suffix := fmt.Sprintf(cacheSuffixFmt, width)
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out := make([]string, 0, len(cachedPaths))
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for _, p := range cachedPaths {
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if strings.HasSuffix(p, suffix) {
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out = append(out, p)
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}
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}
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return out
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}
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func generateAndSaveASCII(imagePath, cachePath string, width int) error {
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f, err := os.Open(imagePath)
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if err != nil {
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return err
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}
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defer f.Close()
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img, _, err := image.Decode(f)
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if err != nil {
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return err
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}
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w0 := img.Bounds().Dx()
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h0 := img.Bounds().Dy()
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if w0 > maxImageDim || h0 > maxImageDim {
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scale := float64(maxImageDim) / float64(max(w0, h0))
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newW := int(float64(w0) * scale)
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newH := int(float64(h0) * scale)
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if newW < 1 {
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newW = 1
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}
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if newH < 1 {
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newH = 1
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}
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dst := image.NewRGBA(image.Rect(0, 0, newW, newH))
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xdraw.ApproxBiLinear.Scale(dst, dst.Bounds(), img, img.Bounds(), xdraw.Over, nil)
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img = dst
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}
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ansi := ImageToANSI(img, width)
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if err := os.MkdirAll(filepath.Dir(cachePath), 0755); err != nil {
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return err
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}
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if err := os.WriteFile(cachePath, []byte(ansi), 0644); err != nil {
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return err
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}
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cacheLock.Lock()
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cachedPaths = append(cachedPaths, cachePath)
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cacheLock.Unlock()
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return nil
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}
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func ImageToANSI(src image.Image, cols int) string {
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b := src.Bounds()
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origW := b.Dx()
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origH := b.Dy()
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if origW == 0 || origH == 0 {
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return ""
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}
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charRowsFloat := (float64(origH) / float64(origW)) * float64(cols) * 0.5
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charRows := int(charRowsFloat)
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if charRows < 1 {
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charRows = 1
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}
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targetH := charRows * 2
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targetW := cols
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dst := image.NewRGBA(image.Rect(0, 0, targetW, targetH))
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xdraw.ApproxBiLinear.Scale(dst, dst.Bounds(), src, src.Bounds(), xdraw.Over, nil)
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var out bytes.Buffer
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for y := 0; y < targetH; y += 2 {
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for x := 0; x < targetW; x++ {
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tr := colorAt(dst, x, y)
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br := colorAt(dst, x, y+1)
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out.WriteString(fmt.Sprintf("\x1b[38;2;%d;%d;%dm\x1b[48;2;%d;%d;%dm▀",
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tr.R, tr.G, tr.B,
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br.R, br.G, br.B))
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}
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out.WriteString("\x1b[0m\n")
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}
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return out.String()
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}
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type c8 struct{ R, G, B uint8 }
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func colorAt(img *image.RGBA, x, y int) c8 {
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r, g, b, _ := img.At(x, y).RGBA()
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return c8{uint8(r >> 8), uint8(g >> 8), uint8(b >> 8)}
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}
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func max(a, b int) int {
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if a > b {
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return a
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}
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return b
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}
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