gitcitadel-online/internal/cache/media_cache.go

package cache

import (
	"context"
	"crypto/sha256"
	"encoding/hex"
	"fmt"
	"io"
	"net/http"
	"os"
	"path/filepath"
	"sync"
	"time"

	"gitcitadel-online/internal/logger"
)

// MediaCache handles caching of images and other media from events
type MediaCache struct {
	cacheDir     string
	activeEvents map[string]time.Time // eventID -> last seen time
	mu           sync.RWMutex
	httpClient   *http.Client
}

// NewMediaCache creates a new media cache
func NewMediaCache(cacheDir string) (*MediaCache, error) {
	// Create cache directory if it doesn't exist
	if err := os.MkdirAll(cacheDir, 0755); err != nil {
		return nil, fmt.Errorf("failed to create media cache directory: %w", err)
	}

	mc := &MediaCache{
		cacheDir:     cacheDir,
		activeEvents: make(map[string]time.Time),
		httpClient: &http.Client{
			Timeout: 30 * time.Second,
		},
	}

	// Start cleanup goroutine
	go mc.cleanupLoop(context.Background())

	return mc, nil
}

// CacheMedia downloads and caches a media file from a URL
// Returns the local path to the cached file, or the original URL if caching fails
func (mc *MediaCache) CacheMedia(ctx context.Context, url string, eventID string) (string, error) {
	if url == "" {
		return "", fmt.Errorf("empty URL")
	}

	// Mark event as active
	mc.mu.Lock()
	mc.activeEvents[eventID] = time.Now()
	mc.mu.Unlock()

	// Generate cache filename from URL hash
	hash := sha256.Sum256([]byte(url))
	filename := hex.EncodeToString(hash[:]) + filepath.Ext(url)
	cachePath := filepath.Join(mc.cacheDir, filename)

	// Check if already cached
	if _, err := os.Stat(cachePath); err == nil {
		return "/cache/media/" + filename, nil
	}

	// Download the media
	req, err := http.NewRequestWithContext(ctx, "GET", url, nil)
	if err != nil {
		return url, fmt.Errorf("failed to create request: %w", err)
	}

	// Set user agent
	req.Header.Set("User-Agent", "GitCitadel-Online/1.0")

	resp, err := mc.httpClient.Do(req)
	if err != nil {
		logger.WithFields(map[string]interface{}{
			"url":     url,
			"eventID": eventID,
			"error":   err,
		}).Warn("Failed to download media")
		return url, fmt.Errorf("failed to download: %w", err)
	}
	defer resp.Body.Close()

	if resp.StatusCode != http.StatusOK {
		return url, fmt.Errorf("unexpected status code: %d", resp.StatusCode)
	}

	// Check content type - only cache images
	contentType := resp.Header.Get("Content-Type")
	if !isImageContentType(contentType) {
		logger.WithFields(map[string]interface{}{
			"url":         url,
			"contentType": contentType,
		}).Debug("Skipping non-image media")
		return url, nil
	}

	// Create cache file
	file, err := os.Create(cachePath)
	if err != nil {
		return url, fmt.Errorf("failed to create cache file: %w", err)
	}
	defer file.Close()

	// Copy response to file
	_, err = io.Copy(file, resp.Body)
	if err != nil {
		os.Remove(cachePath) // Clean up on error
		return url, fmt.Errorf("failed to write cache file: %w", err)
	}

	logger.WithFields(map[string]interface{}{
		"url":       url,
		"eventID":   eventID,
		"cachePath": cachePath,
	}).Debug("Cached media file")

	return "/cache/media/" + filename, nil
}

// GetCacheDir returns the cache directory path
func (mc *MediaCache) GetCacheDir() string {
	return mc.cacheDir
}

// isImageContentType checks if a content type is an image
func isImageContentType(contentType string) bool {
	imageTypes := []string{
		"image/jpeg",
		"image/jpg",
		"image/png",
		"image/gif",
		"image/webp",
		"image/svg+xml",
		"image/bmp",
		"image/x-icon",
	}
	for _, imgType := range imageTypes {
		if contentType == imgType {
			return true
		}
	}
	return false
}

// MarkEventActive marks an event as currently active (displayed)
func (mc *MediaCache) MarkEventActive(eventID string) {
	mc.mu.Lock()
	defer mc.mu.Unlock()
	mc.activeEvents[eventID] = time.Now()
}

// cleanupLoop periodically removes media for events that are no longer active
func (mc *MediaCache) cleanupLoop(ctx context.Context) {
	ticker := time.NewTicker(1 * time.Hour) // Run cleanup every hour
	defer ticker.Stop()

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

// cleanup removes media files for events that haven't been seen in 24 hours
func (mc *MediaCache) cleanup() {
	mc.mu.Lock()
	defer mc.mu.Unlock()

	cutoff := time.Now().Add(-24 * time.Hour)
	var toRemove []string

	// Find events that are no longer active
	for eventID, lastSeen := range mc.activeEvents {
		if lastSeen.Before(cutoff) {
			toRemove = append(toRemove, eventID)
		}
	}

	// Remove inactive events from tracking
	for _, eventID := range toRemove {
		delete(mc.activeEvents, eventID)
	}

	// Note: We don't delete the actual files here because multiple events might use the same image
	// Instead, we rely on the fact that if an event is no longer displayed, its media won't be accessed
	// A more sophisticated cleanup would track which files are used by which events

	logger.WithField("removed_events", len(toRemove)).Debug("Cleaned up inactive events from media cache")
}