gochat/internal/channel/facebook/media.go

package facebook

// Media handling for Facebook/Instagram channel attachments.
// Reference: Chatwoot's attachment handling:
//   - app/services/facebook/send_on_facebook_service.rb (outgoing attachments)
//   - app/services/telegram/send_attachments_service.rb (upload + send)
//   - Facebook Send API attachment upload: https://developers.facebook.com/docs/messenger-platform/send-messages#attachment-upload
//   - Instagram DM attachment upload: https://developers.facebook.com/docs/instagram-api/guides/messaging#attachment-upload
//
// Media operations:
//   1. Download incoming media from FB/IG CDN URLs (images, videos, audio, files)
//   2. Upload outgoing media to FB/IG attachment upload API
//   3. Convert between attachment formats (FB URL → gochat Attachment → local file)
//   4. Handle media expiration (FB CDN URLs expire after a period)

import (
	"bytes"
	"context"
	"encoding/json"
	"fmt"
	"net/http"
	"os"
	"path/filepath"
	"strings"
	"time"

	"github.com/go-resty/resty/v2"

	"github.com/gochat/gochat/internal/channel"
	applogger "github.com/gochat/gochat/pkg/logger"
)

// MediaService handles download, upload, and conversion of Facebook/Instagram media.
type MediaService struct {
	client      *resty.Client
	graphAPIBase string
	storagePath string // local path for downloaded attachments
}

// NewMediaService creates a new media service for FB/IG attachment handling.
func NewMediaService(graphAPIBase string, storagePath string) *MediaService {
	client := resty.New()
	client.SetTimeout(60 * time.Second) // longer timeout for media downloads
	client.SetRetryCount(2)

	return &MediaService{
		client:      client,
		graphAPIBase: graphAPIBase,
		storagePath:  storagePath,
	}
}

// === Incoming Media ===

// DownloadAttachment downloads a media file from a Facebook CDN URL.
// FB CDN URLs are temporary and expire, so we download them promptly.
// Reference: Chatwoot downloads FB attachments via HTTP GET + saves locally.
//
// Returns the local file path where the attachment was saved.
func (ms *MediaService) DownloadAttachment(ctx context.Context, url string, filename string) (string, error) {
	if url == "" {
		return "", fmt.Errorf("empty attachment URL")
	}

	// Ensure storage directory exists
	if err := os.MkdirAll(ms.storagePath, 0755); err != nil {
		return "", fmt.Errorf("failed to create storage directory: %w", err)
	}

	// Generate filename if not provided
	if filename == "" {
		filename = generateFilenameFromURL(url)
	}

	localPath := filepath.Join(ms.storagePath, filename)

	// Check if file already exists (avoid re-downloading)
	if _, err := os.Stat(localPath); err == nil {
		applogger.L().Debug("Attachment already downloaded", "path", localPath)
		return localPath, nil
	}

	// Download with resty
	ctx, cancel := context.WithTimeout(ctx, 30*time.Second)
	defer cancel()

	resp, err := ms.client.R().
		SetContext(ctx).
		SetOutput(localPath).
		Get(url)

	if err != nil {
		return "", fmt.Errorf("failed to download attachment from %s: %w", url, err)
	}

	if resp.StatusCode() != http.StatusOK {
		// Clean up failed download
		os.Remove(localPath)
		return "", fmt.Errorf("attachment download returned HTTP %d for %s", resp.StatusCode(), url)
	}

	applogger.L().Info("Attachment downloaded successfully",
		"url", url, "local_path", localPath,
		"size", resp.Size())

	return localPath, nil
}

// DownloadFBAttachment downloads an FBAttachment from its CDN URL and returns
// a gochat Attachment with the local file info.
func (ms *MediaService) DownloadFBAttachment(ctx context.Context, fbAtt FBAttachment, channelType channel.ChannelType) (*channel.Attachment, error) {
	url := fbAtt.Payload.URL
	if url == "" {
		// Some attachments (stickers, etc.) use Src instead of URL
		url = fbAtt.Payload.Src
	}

	if url == "" {
		return nil, fmt.Errorf("attachment has no download URL")
	}

	// Determine filename
	filename := fbAtt.Payload.Name
	if filename == "" {
		filename = generateFilenameFromURL(url)
	}

	localPath, err := ms.DownloadAttachment(ctx, url, filename)
	if err != nil {
		return nil, fmt.Errorf("failed to download FB attachment: %w", err)
	}

	attachment := &channel.Attachment{
		URL:         url,
		ContentType: mimeTypeFromFBType(fbAtt.Type),
		Filename:    filename,
		FileSize:    getFileSize(localPath),
		Extra: map[string]interface{}{
			"local_path":       localPath,
			"fb_attachment_type": fbAtt.Type,
			"channel_type":       string(channelType),
		},
	}

	// Add thumbnail URL for images/videos
	if fbAtt.Type == "image" || fbAtt.Type == "video" {
		// FB CDN URLs for thumbnails are typically the same URL with different sizing
		attachment.ThumbnailURL = url
	}

	// Add location coordinates if applicable
	if fbAtt.Type == "location" && fbAtt.Payload.Coordinates != nil {
		attachment.Extra["latitude"] = fbAtt.Payload.Coordinates.Lat
		attachment.Extra["longitude"] = fbAtt.Payload.Coordinates.Long
	}

	return attachment, nil
}

// === Outgoing Media ===

// UploadAttachment uploads a local file to the FB/IG attachment upload API.
// This returns an attachment_id that can be used in the Send API.
// Reference: https://developers.facebook.com/docs/messenger-platform/send-messages#attachment-upload
//
// Flow:
// 1. Upload file to FB attachment upload endpoint → get attachment_id
// 2. Send message with attachment_id instead of URL (for large files / reliability)
func (ms *MediaService) UploadAttachment(ctx context.Context, pageAccessToken string, filePath string, attachmentType string) (string, error) {
	ctx, cancel := context.WithTimeout(ctx, 60*time.Second)
	defer cancel()

	// Read the file
	fileData, err := os.ReadFile(filePath)
	if err != nil {
		return "", fmt.Errorf("failed to read file %s: %w", filePath, err)
	}

	filename := filepath.Base(filePath)

	// Upload to FB Graph API
	resp, err := ms.client.R().
		SetContext(ctx).
		SetFormData(map[string]string{
			"access_token": pageAccessToken,
			"message":      fmt.Sprintf(`{"attachment":{"type":"%s","payload":{"is_reusable":true}}}`, attachmentType),
		}).
		SetFileReader("filedata", filename, bytes.NewReader(fileData)).
		Post(fmt.Sprintf("%s/me/message_attachments", ms.graphAPIBase))

	if err != nil {
		return "", fmt.Errorf("FB attachment upload failed: %w", err)
	}

	if resp.StatusCode() != http.StatusOK {
		return "", fmt.Errorf("FB attachment upload returned HTTP %d: %s", resp.StatusCode(), resp.String())
	}

	// Parse response to get attachment_id
	var uploadResp FBAttachmentUploadResponse
	if err := parseJSONResponse(resp.Body(), &uploadResp); err != nil {
		return "", fmt.Errorf("failed to parse upload response: %w", err)
	}

	if uploadResp.AttachmentID == "" {
		return "", fmt.Errorf("FB attachment upload did not return attachment_id")
	}

	applogger.L().Info("FB attachment uploaded successfully",
		"attachment_id", uploadResp.AttachmentID,
		"type", attachmentType, "filename", filename)

	return uploadResp.AttachmentID, nil
}

// SendAttachmentWithURL sends a message with an attachment using a URL (for small files).
// Reference: https://developers.facebook.com/docs/messenger-platform/send-messages#attachment-url
func (ms *MediaService) SendAttachmentWithURL(ctx context.Context, pageAccessToken string, recipientID string, attachmentType string, url string) error {
	ctx, cancel := context.WithTimeout(ctx, 15*time.Second)
	defer cancel()

	messagePayload := map[string]interface{}{
		"recipient": map[string]string{
			"id": recipientID,
		},
		"message": map[string]interface{}{
			"attachment": map[string]interface{}{
				"type":    attachmentType,
				"payload": map[string]interface{}{
					"url": url,
				},
			},
		},
	}

	resp, err := ms.client.R().
		SetContext(ctx).
		SetQueryParam("access_token", pageAccessToken).
		SetBody(messagePayload).
		Post(fmt.Sprintf("%s/me/messages", ms.graphAPIBase))

	if err != nil {
		return fmt.Errorf("FB send attachment (URL) failed: %w", err)
	}

	if resp.StatusCode() != http.StatusOK {
		return fmt.Errorf("FB send attachment (URL) returned HTTP %d: %s", resp.StatusCode(), resp.String())
	}

	return nil
}

// SendAttachmentWithID sends a message with a previously uploaded attachment_id.
// Reference: https://developers.facebook.com/docs/messenger-platform/send-messages#attachment-id
func (ms *MediaService) SendAttachmentWithID(ctx context.Context, pageAccessToken string, recipientID string, attachmentType string, attachmentID string) error {
	ctx, cancel := context.WithTimeout(ctx, 15*time.Second)
	defer cancel()

	messagePayload := map[string]interface{}{
		"recipient": map[string]string{
			"id": recipientID,
		},
		"message": map[string]interface{}{
			"attachment": map[string]interface{}{
				"type":    attachmentType,
				"payload": map[string]interface{}{
					"attachment_id": attachmentID,
				},
			},
		},
	}

	resp, err := ms.client.R().
		SetContext(ctx).
		SetQueryParam("access_token", pageAccessToken).
		SetBody(messagePayload).
		Post(fmt.Sprintf("%s/me/messages", ms.graphAPIBase))

	if err != nil {
		return fmt.Errorf("FB send attachment (ID) failed: %w", err)
	}

	if resp.StatusCode() != http.StatusOK {
		return fmt.Errorf("FB send attachment (ID) returned HTTP %d: %s", resp.StatusCode(), resp.String())
	}

	return nil
}

// === Helper Functions ===

// generateFilenameFromURL creates a safe filename from a CDN URL.
func generateFilenameFromURL(url string) string {
	// Extract the last path segment as base filename
	parts := strings.Split(url, "/")
	if len(parts) > 0 {
		base := parts[len(parts)-1]
		// Remove query parameters
		if idx := strings.Index(base, "?"); idx > 0 {
			base = base[:idx]
		}
		if base != "" {
			return base
		}
	}
	// Fallback: generate a timestamp-based filename
	return fmt.Sprintf("fb_attachment_%d", time.Now().UnixMilli())
}

// getFileSize returns the file size in bytes, or 0 if the file cannot be accessed.
func getFileSize(path string) int64 {
	info, err := os.Stat(path)
	if err != nil {
		return 0
	}
	return info.Size()
}

// parseJSONResponse parses a JSON byte slice into the target struct.
func parseJSONResponse(data []byte, target interface{}) error {
	return json.Unmarshal(data, target)
}

// mimeTypeFromFBType maps FB attachment types to MIME types.
func mimeTypeFromFBType(fbType string) string {
	switch fbType {
	case "image":
		return "image/jpeg"
	case "video":
		return "video/mp4"
	case "audio":
		return "audio/mp4"
	case "file":
		return "application/octet-stream"
	case "location":
		return "application/json"
	case "template":
		return "application/json"
	case "fallback":
		return "application/octet-stream"
	default:
		return "application/octet-stream"
	}
}

// DetermineFBAttachmentType maps a gochat ContentType to an FB attachment type string.
// Used for outgoing message attachment type mapping.
func DetermineFBAttachmentType(contentType channel.ContentType) string {
	switch contentType {
	case channel.ContentImage:
		return "image"
	case channel.ContentVideo:
		return "video"
	case channel.ContentAudio:
		return "audio"
	case channel.ContentFile:
		return "file"
	case channel.ContentLocation:
		return "location"
	default:
		return "file"
	}
}