fix(z5): encapsulate artistic styles pool

3 files changed, 73 insertions, 20 deletions

diff --git a/internal/image/openai.go b/internal/image/openai.go
index 1df6eb7..79fbe38 100644
--- a/internal/image/openai.go
+++ b/internal/image/openai.go
@@ -6,7 +6,6 @@ import (
 	"encoding/hex"
 	"fmt"
 	"io"
-	"math/rand"
 	"net/http"
 	"strings"
 	"time"
@@ -244,16 +243,12 @@ func (c *OpenAIClient) createEducationalPrompt(ctx context.Context, bulgarianWor
 		scene = ""
 	}
 
-	// Copy the shared styles before shuffling so the package-level list stays stable.
-	styles := append([]string(nil), ArtisticStyles...)
-
-	// Shuffle the styles to avoid bias
-	rand.Shuffle(len(styles), func(i, j int) {
-		styles[i], styles[j] = styles[j], styles[i]
-	})
-
-	// Select a random style from the shuffled list
-	selectedStyle := styles[0]
+	// Select a random style from the shared pool. Fall back to a generic style if
+	// the pool has been emptied by tests or future callers.
+	selectedStyle := chooseArtisticStyle()
+	if selectedStyle == defaultArtisticStyle {
+		fmt.Printf("  No artistic styles available, using generic prompt\n")
+	}
 	fmt.Printf("  Using image style: %s\n", selectedStyle)
 
 	// Define prompt components in order of importance
diff --git a/internal/image/styles.go b/internal/image/styles.go
index a88bb69..d4a32a9 100644
--- a/internal/image/styles.go
+++ b/internal/image/styles.go
@@ -1,7 +1,11 @@
 package image
 
-// ArtisticStyles contains the shared pool of artistic styles used for image prompts.
-var ArtisticStyles = []string{
+import "math/rand"
+
+const defaultArtisticStyle = "simple illustration"
+
+// artisticStyles contains the shared pool of artistic styles used for image prompts.
+var artisticStyles = []string{
 	"Photorealism", "Hyperrealism", "Surrealism", "Impressionism",
 	"Minimalism", "Pop Art", "Art Nouveau", "Digital Art",
 	"Watercolor", "Oil Painting", "Pencil Sketch", "Ink Drawing",
@@ -72,3 +76,27 @@ var ArtisticStyles = []string{
 	"Archigram", "Metabolism", "Structuralism", "Postmodernism",
 	"Minimalist Photography", "Conceptual Photography", "Staged Photography", "Candid Photography",
 }
+
+func pickArtisticStyle() string {
+	if len(artisticStyles) == 0 {
+		return ""
+	}
+
+	styles := append([]string(nil), artisticStyles...)
+
+	// Shuffle the styles to avoid bias without mutating the shared pool.
+	rand.Shuffle(len(styles), func(i, j int) {
+		styles[i], styles[j] = styles[j], styles[i]
+	})
+
+	return styles[0]
+}
+
+func chooseArtisticStyle() string {
+	style := pickArtisticStyle()
+	if style == "" {
+		return defaultArtisticStyle
+	}
+
+	return style
+}
diff --git a/internal/image/styles_test.go b/internal/image/styles_test.go
index 8eeb7c1..1848342 100644
--- a/internal/image/styles_test.go
+++ b/internal/image/styles_test.go
@@ -1,18 +1,48 @@
 package image
 
-import "testing"
+import (
+	"reflect"
+	"testing"
+)
 
 func TestArtisticStyles(t *testing.T) {
-	if len(ArtisticStyles) == 0 {
-		t.Fatal("ArtisticStyles should not be empty")
+	if len(artisticStyles) == 0 {
+		t.Fatal("artisticStyles should not be empty")
 	}
 
-	if !hasStyle(ArtisticStyles, "Photorealism") {
-		t.Fatal(`ArtisticStyles should include "Photorealism"`)
+	if !hasStyle(artisticStyles, "Photorealism") {
+		t.Fatal(`artisticStyles should include "Photorealism"`)
 	}
 
-	if !hasStyle(ArtisticStyles, "Candid Photography") {
-		t.Fatal(`ArtisticStyles should include "Candid Photography"`)
+	if !hasStyle(artisticStyles, "Candid Photography") {
+		t.Fatal(`artisticStyles should include "Candid Photography"`)
+	}
+}
+
+func TestChooseArtisticStyle_EmptyPool(t *testing.T) {
+	original := artisticStyles
+	artisticStyles = nil
+	t.Cleanup(func() {
+		artisticStyles = original
+	})
+
+	if got := chooseArtisticStyle(); got != defaultArtisticStyle {
+		t.Fatalf("chooseArtisticStyle() = %q, want %q", got, defaultArtisticStyle)
+	}
+}
+
+func TestPickArtisticStyle_DoesNotMutateSharedPool(t *testing.T) {
+	original := append([]string(nil), artisticStyles...)
+	t.Cleanup(func() {
+		artisticStyles = original
+	})
+
+	artisticStyles = []string{"Photorealism", "Surrealism", "Impressionism"}
+
+	_ = pickArtisticStyle()
+
+	if !reflect.DeepEqual(artisticStyles, []string{"Photorealism", "Surrealism", "Impressionism"}) {
+		t.Fatalf("pickArtisticStyle() mutated shared pool: got %v", artisticStyles)
 	}
 }