morz-infoboard/player/agent/internal/screenshot/screenshot.go

// Package screenshot erzeugt periodisch Screenshots des aktuell angezeigten Inhalts
// und sendet sie an den Backend-Server (Phase 6).
//
// Strategie (in dieser Reihenfolge):
//  1. scrot -z -q 60 /tmp/morz-screenshot.jpg  — leichtgewichtig, für X11
//  2. import -window root /tmp/morz-screenshot.png  — ImageMagick, falls scrot fehlt
//  3. xwd -root -silent | convert xwd:- /tmp/morz-screenshot.jpg — Fallback
//
// Der Screenshot wird per HTTP MULTIPART POST an
// POST /api/v1/player/screenshot gesendet.
package screenshot

import (
	"bytes"
	"context"
	"fmt"
	"log"
	"mime/multipart"
	"net/http"
	"os"
	"os/exec"
	"path/filepath"
	"time"
)

const (
	screenshotPath    = "/tmp/morz-screenshot.jpg"
	defaultInterval   = 60 * time.Second
	uploadTimeout     = 15 * time.Second
	screenshotQuality = "60" // JPEG quality (0-100)
)

// Screenshotter erzeugt periodisch Screenshots und sendet sie an den Server.
type Screenshotter struct {
	screenID      string
	serverBaseURL string
	interval      time.Duration
	logger        *log.Logger
}

// New erzeugt einen neuen Screenshotter.
func New(screenID, serverBaseURL string, intervalSeconds int, logger *log.Logger) *Screenshotter {
	interval := defaultInterval
	if intervalSeconds > 0 {
		interval = time.Duration(intervalSeconds) * time.Second
	}
	if logger == nil {
		logger = log.New(os.Stdout, "screenshot ", log.LstdFlags|log.LUTC)
	}
	return &Screenshotter{
		screenID:      screenID,
		serverBaseURL: serverBaseURL,
		interval:      interval,
		logger:        logger,
	}
}

// Run startet die periodische Screenshot-Schleife und blockiert bis ctx abgebrochen wird.
func (s *Screenshotter) Run(ctx context.Context) {
	ticker := time.NewTicker(s.interval)
	defer ticker.Stop()

	// Erster Screenshot nach kurzem Delay (damit Chromium hochgefahren ist).
	select {
	case <-ctx.Done():
		return
	case <-time.After(10 * time.Second):
	}
	s.takeAndSend(ctx)

	for {
		select {
		case <-ctx.Done():
			return
		case <-ticker.C:
			s.takeAndSend(ctx)
		}
	}
}

// takeAndSend erzeugt einen Screenshot und sendet ihn an den Server.
func (s *Screenshotter) takeAndSend(ctx context.Context) {
	path, err := s.capture()
	if err != nil {
		s.logger.Printf("event=screenshot_capture_failed screen_id=%s err=%v", s.screenID, err)
		return
	}
	defer os.Remove(path) //nolint:errcheck

	if err := s.upload(ctx, path); err != nil {
		s.logger.Printf("event=screenshot_upload_failed screen_id=%s err=%v", s.screenID, err)
		return
	}
	s.logger.Printf("event=screenshot_sent screen_id=%s", s.screenID)
}

// capture erzeugt einen Screenshot mit dem ersten verfügbaren Tool.
func (s *Screenshotter) capture() (string, error) {
	// Aufräumen falls eine alte Datei existiert.
	os.Remove(screenshotPath) //nolint:errcheck

	// Versuch 1: scrot (leichtgewichtig, für X11)
	if path, err := tryScrot(); err == nil {
		return path, nil
	}

	// Versuch 2: import (ImageMagick)
	if path, err := tryImport(); err == nil {
		return path, nil
	}

	// Versuch 3: xwd + convert
	if path, err := tryXwd(); err == nil {
		return path, nil
	}

	return "", fmt.Errorf("keine Screenshot-Tool verfügbar (scrot, import, xwd)")
}

func tryScrot() (string, error) {
	cmd := exec.Command("scrot", "-z", "-q", screenshotQuality, screenshotPath)
	if err := cmd.Run(); err != nil {
		return "", err
	}
	return screenshotPath, nil
}

func tryImport() (string, error) {
	// ImageMagick import: -window root macht einen Screenshot des gesamten X-Displays.
	pngPath := "/tmp/morz-screenshot-tmp.png"
	cmd := exec.Command("import", "-window", "root", pngPath)
	if err := cmd.Run(); err != nil {
		return "", err
	}
	// Zu JPEG konvertieren.
	cmd = exec.Command("convert", pngPath, "-quality", screenshotQuality, screenshotPath)
	defer os.Remove(pngPath) //nolint:errcheck
	if err := cmd.Run(); err != nil {
		return "", err
	}
	return screenshotPath, nil
}

func tryXwd() (string, error) {
	xwdPath := "/tmp/morz-screenshot-tmp.xwd"
	// xwd schreibt in Datei.
	xwdCmd := exec.Command("xwd", "-root", "-silent", "-out", xwdPath)
	if err := xwdCmd.Run(); err != nil {
		return "", err
	}
	defer os.Remove(xwdPath) //nolint:errcheck
	// convert xwd -> jpg.
	cmd := exec.Command("convert", "xwd:"+xwdPath, "-quality", screenshotQuality, screenshotPath)
	if err := cmd.Run(); err != nil {
		return "", err
	}
	return screenshotPath, nil
}

// upload sendet den Screenshot per MULTIPART POST an den Server.
func (s *Screenshotter) upload(ctx context.Context, path string) error {
	data, err := os.ReadFile(path)
	if err != nil {
		return fmt.Errorf("read screenshot: %w", err)
	}

	var body bytes.Buffer
	writer := multipart.NewWriter(&body)
	_ = writer.WriteField("screen_id", s.screenID)

	ext := filepath.Ext(path)
	mimeType := "image/jpeg"
	if ext == ".png" {
		mimeType = "image/png"
	}

	fw, err := writer.CreateFormFile("screenshot", "screenshot"+ext)
	if err != nil {
		return fmt.Errorf("create form file: %w", err)
	}
	if _, err := fw.Write(data); err != nil {
		return fmt.Errorf("write form file: %w", err)
	}
	_ = writer.WriteField("mime_type", mimeType)
	writer.Close()

	uploadCtx, cancel := context.WithTimeout(ctx, uploadTimeout)
	defer cancel()

	req, err := http.NewRequestWithContext(uploadCtx,
		http.MethodPost,
		s.serverBaseURL+"/api/v1/player/screenshot",
		&body,
	)
	if err != nil {
		return err
	}
	req.Header.Set("Content-Type", writer.FormDataContentType())

	resp, err := http.DefaultClient.Do(req)
	if err != nil {
		return err
	}
	defer resp.Body.Close()

	if resp.StatusCode >= 400 {
		return fmt.Errorf("server returned %d", resp.StatusCode)
	}
	return nil
}