Handle midjourney queue errors

When job queued error is received instead of returning an error the
response is read from the embedded data of the message and the process
continues.

When a non temporary error is received such as a "queue full" error
the tool should wait before retrying to avoid flooding the queue.

References #14

pkg/ai/ai.go

@@ -303,6 +303,16 @@ func retry(ctx context.Context, fn func(context.Context) error) error {
 		if attempts >= maxAttempts {
 			return err
 		}
-		log.Println("retrying...", err)
+		// If the error is not a context deadline exceeded, wait before retrying
+		if !errors.Is(err, context.DeadlineExceeded) {
+			log.Println("waiting and retrying...", err)
+			select {
+			case <-time.After(10 * time.Minute):
+			case <-ctx.Done():
+				return ctx.Err()
+			}
+		} else {
+			log.Println("retrying...", err)
+		}
 	}
 }

pkg/ai/midjourney/midjourney.go

@@ -202,9 +202,35 @@ func parseContent(content string) (string, string, bool) {
 	return prompt, rest, true
 }
 
+func parseEmbedFooter(prompt string, msg *discord.Message) (string, error) {
+	if len(msg.Embeds) == 0 {
+		return "", errors.New("midjourney: message has no embed")
+	}
+	embed := msg.Embeds[0]
+	if embed.Footer == nil {
+		return "", errors.New("midjourney: embed has no footer")
+	}
+	footer := embed.Footer.Text
+	if !strings.HasPrefix(footer, "/imagine ") {
+		return "", fmt.Errorf("midjourney: footer doesn't start with /imagine: %s", footer)
+	}
+	footer = strings.TrimPrefix(footer, "/imagine ")
+	if !strings.HasPrefix(footer, prompt) {
+		return "", fmt.Errorf("midjourney: footer doesn't start with prompt: %s", footer)
+	}
+	suffixes := strings.TrimPrefix(footer, prompt)
+	// Remove extra space that sometimes appears when suffixes are configured
+	if strings.HasPrefix(suffixes, "  ") {
+		suffixes = strings.TrimPrefix(suffixes, " ")
+	}
+	return fmt.Sprintf("%s%s", prompt, suffixes), nil
+}
+
 var ErrInvalidParameter = errors.New("invalid parameter")
 var ErrInvalidLink = errors.New("invalid link")
 var ErrBannedPrompt = errors.New("banned prompt")
+var ErrJobQueued = errors.New("job queued")
+var ErrQueueFull = errors.New("queue full")
 
 func parseError(msg *discord.Message) error {
 	if len(msg.Embeds) == 0 {
@@ -224,6 +250,12 @@ func parseError(msg *discord.Message) error {
 	case "banned prompt":
 		err := fmt.Errorf("midjourney: %w: %s", ErrBannedPrompt, desc)
 		return ai.NewError(err, false)
+	case "job queued":
+		err := fmt.Errorf("midjourney: %w: %s", ErrJobQueued, desc)
+		return ai.NewError(err, false)
+	case "queue full":
+		err := fmt.Errorf("midjourney: %w: %s", ErrQueueFull, desc)
+		return ai.NewError(err, true)
 	default:
 		err := fmt.Errorf("midjourney: %s: %s", title, desc)
 		return ai.NewError(err, true)
@@ -403,10 +435,20 @@ func (c *Client) Imagine(ctx context.Context, prompt string) (*ai.Preview, error
 	responsePrompt, _, ok := parseContent(response.Content)
 	if !ok {
 		// Check if the response contains an error message
-		if err := parseError(response); err != nil {
+		err := parseError(response)
+		switch {
+		case errors.Is(err, ErrJobQueued):
+			// The job is queued, so it will be processed.
+			// We will take the response prompt from the message embed footer.
+			responsePrompt, err = parseEmbedFooter(prompt, response)
+			if err != nil {
+				return nil, err
+			}
+		case err != nil:
 			return nil, err
+		default:
+			return nil, fmt.Errorf("midjourney: couldn't parse prompt from imagine response: %s", response.Content)
 		}
-		return nil, fmt.Errorf("midjourney: couldn't parse prompt from imagine response: %s", response.Content)
 	}
 
 	// The response prompt links may differ from the final links, so we need to