feat: add prediction and omit empty Buy/Sell

internal/output/discord.go

@@ -63,9 +63,10 @@ func (d *discordOutput) Send(ctx context.Context, rep report.Report) error {
 		}
 	}
 
-	embeds := buildRecommendationEmbeds(rep.Recommendations)
-	if err := d.postEmbeds(ctx, embeds); err != nil {
-		return fmt.Errorf("discord: send recommendation embeds: %w", err)
+	if embeds := buildRecommendationEmbeds(rep.Recommendations); len(embeds) > 0 {
+		if err := d.postEmbeds(ctx, embeds); err != nil {
+			return fmt.Errorf("discord: send recommendation embeds: %w", err)
+		}
 	}
 	return nil
 }
@@ -113,9 +114,10 @@ const (
 // embed's `description`.
 const discordDescriptionLimit = 4096
 
-// buildRecommendationEmbeds renders the buy and sell recommendations as two
-// separate Discord embeds (always both, even when one or both lists are
-// empty, so "nothing to report" is stated explicitly rather than omitted).
+// buildRecommendationEmbeds renders the buy and sell recommendations as
+// separate Discord embeds, one per non-empty list. If there are no
+// recommendations at all, it returns nil and no message is sent — an empty
+// buy/sell call isn't worth a Discord notification.
 func buildRecommendationEmbeds(recs []report.Recommendation) []map[string]any {
 	var buyLines, sellLines []string
 	for _, r := range recs {
@@ -127,21 +129,21 @@ func buildRecommendationEmbeds(recs []report.Recommendation) []map[string]any {
 		}
 	}
 
-	return []map[string]any{
-		recommendationEmbed("🟢 Buy", colorBuy, buyLines, "No buy recommendations today."),
-		recommendationEmbed("🔴 Sell", colorSell, sellLines, "No sell recommendations today."),
+	var embeds []map[string]any
+	if len(buyLines) > 0 {
+		embeds = append(embeds, recommendationEmbed("🟢 Buy", colorBuy, buyLines))
 	}
+	if len(sellLines) > 0 {
+		embeds = append(embeds, recommendationEmbed("🔴 Sell", colorSell, sellLines))
+	}
+	return embeds
 }
 
-func recommendationEmbed(title string, color int, lines []string, emptyText string) map[string]any {
-	description := emptyText
-	if len(lines) > 0 {
-		description = truncateForDescription(strings.Join(lines, "\n"))
-	}
+func recommendationEmbed(title string, color int, lines []string) map[string]any {
 	return map[string]any{
 		"title":       title,
 		"color":       color,
-		"description": description,
+		"description": truncateForDescription(strings.Join(lines, "\n")),
 	}
 }