screenshot-server/main.go

// screenshot-server: Serves the latest screenshot from ~/Desktop, then deletes it
// Run: go build -o screenshot-server && ./screenshot-server
// Fetch: curl http://mac-ip:9123/screenshot -o screenshot.png

package main

import (
	"fmt"
	"io"
	"log"
	"net/http"
	"os"
	"os/exec"
	"path/filepath"
	"regexp"
	"sort"
	"strconv"
	"strings"
	"time"
)

const (
	port       = ":9123"
	desktopDir = "" // Will be set to ~/Desktop
)

func getDesktopPath() string {
	home, err := os.UserHomeDir()
	if err != nil {
		log.Fatal("Cannot find home directory:", err)
	}
	return filepath.Join(home, "Desktop")
}

type screenshotFile struct {
	path    string
	modTime time.Time
}

func findLatestScreenshot(desktop string) (string, error) {
	entries, err := os.ReadDir(desktop)
	if err != nil {
		return "", err
	}

	var screenshots []screenshotFile
	for _, e := range entries {
		name := e.Name()
		if strings.HasPrefix(name, "Screenshot") && strings.HasSuffix(name, ".png") {
			info, err := e.Info()
			if err != nil {
				continue
			}
			screenshots = append(screenshots, screenshotFile{
				path:    filepath.Join(desktop, name),
				modTime: info.ModTime(),
			})
		}
	}

	if len(screenshots) == 0 {
		return "", fmt.Errorf("no screenshots found")
	}

	// Sort by modification time (newest first)
	sort.Slice(screenshots, func(i, j int) bool {
		return screenshots[i].modTime.After(screenshots[j].modTime)
	})

	return screenshots[0].path, nil
}

func serveAndDelete(w http.ResponseWriter, path string) {
	f, err := os.Open(path)
	if err != nil {
		http.Error(w, "Cannot open file", http.StatusInternalServerError)
		return
	}
	defer f.Close()

	filename := filepath.Base(path)
	w.Header().Set("Content-Type", "image/png")
	w.Header().Set("X-Screenshot-Name", filename)

	_, err = io.Copy(w, f)
	if err != nil {
		log.Println("Error sending:", err)
		return
	}

	f.Close()
	if err := os.Remove(path); err != nil {
		log.Println("Warning: could not delete:", err)
	} else {
		log.Println("Served and deleted:", filename)
	}
}

func screenshotHandler(w http.ResponseWriter, r *http.Request) {
	if r.Method != http.MethodGet {
		http.Error(w, "GET only", http.StatusMethodNotAllowed)
		return
	}

	desktop := getDesktopPath()
	path, err := findLatestScreenshot(desktop)
	if err != nil {
		http.Error(w, err.Error(), http.StatusNotFound)
		log.Println("No screenshot:", err)
		return
	}

	serveAndDelete(w, path)
}

func captureHandler(w http.ResponseWriter, r *http.Request) {
	if r.Method != http.MethodPost {
		http.Error(w, "POST only", http.StatusMethodNotAllowed)
		return
	}

	display := r.URL.Query().Get("display")
	if display == "" {
		display = "1"
	}

	tmpFile := filepath.Join(os.TempDir(), fmt.Sprintf("capture-%d.png", time.Now().UnixNano()))

	cmd := exec.Command("screencapture", "-x", "-D", display, tmpFile)
	if out, err := cmd.CombinedOutput(); err != nil {
		http.Error(w, fmt.Sprintf("capture failed: %v: %s", err, out), http.StatusInternalServerError)
		log.Printf("Capture failed (display %s): %v: %s", display, err, out)
		os.Remove(tmpFile)
		return
	}

	// Resize to 50% unless full resolution requested
	if r.URL.Query().Get("full") != "1" {
		if out, err := exec.Command("sips", "-g", "pixelWidth", tmpFile).Output(); err == nil {
			re := regexp.MustCompile(`pixelWidth:\s*(\d+)`)
			if m := re.FindSubmatch(out); m != nil {
				if w, _ := strconv.Atoi(string(m[1])); w > 0 {
					exec.Command("sips", "--resampleWidth", strconv.Itoa(w/2), tmpFile).Run()
				}
			}
		}
	}

	log.Printf("Captured display %s", display)
	serveAndDelete(w, tmpFile)
}

func healthHandler(w http.ResponseWriter, r *http.Request) {
	w.Write([]byte("ok"))
}

func main() {
	http.HandleFunc("/screenshot", screenshotHandler)
	http.HandleFunc("/capture", captureHandler)
	http.HandleFunc("/health", healthHandler)

	log.Printf("Screenshot server starting on %s", port)
	log.Printf("Desktop: %s", getDesktopPath())
	log.Printf("Endpoints:")
	log.Printf("  GET  /screenshot        - fetch & delete latest screenshot")
	log.Printf("  POST /capture?display=N - take screenshot of display N")
	log.Printf("  GET  /health            - health check")

	if err := http.ListenAndServe(port, nil); err != nil {
		log.Fatal(err)
	}
}