add internal/app/library.go

internal/app/library.go

@@ -0,0 +1,45 @@
+// Package app wires use-cases: read the generator's library, ship mp3s to
+// the streaming VPS, and feed the endless stream with now-playing MQTT.
+package app
+
+import (
+	"encoding/json"
+	"fmt"
+	"os"
+	"path/filepath"
+	"strings"
+
+	"radio-go/internal/domain"
+)
+
+// LoadLibrary reads the ai-radio app's index.json and returns only tracks
+// whose audio file actually exists on disk.
+func LoadLibrary(libraryDir string) ([]domain.Track, error) {
+	raw, err := os.ReadFile(filepath.Join(libraryDir, "index.json"))
+	if err != nil {
+		if os.IsNotExist(err) {
+			return nil, nil
+		}
+		return nil, fmt.Errorf("read index.json: %w", err)
+	}
+	var items []domain.Track
+	if err := json.Unmarshal(raw, &items); err != nil {
+		return nil, fmt.Errorf("parse index.json: %w", err)
+	}
+	out := make([]domain.Track, 0, len(items))
+	for _, t := range items {
+		if t.ID == "" || t.Filename == "" {
+			continue
+		}
+		// filename must stay inside the library (no traversal)
+		clean := filepath.Clean(t.Filename)
+		if strings.HasPrefix(clean, "..") || filepath.IsAbs(clean) {
+			continue
+		}
+		if _, err := os.Stat(filepath.Join(libraryDir, clean)); err != nil {
+			continue
+		}
+		out = append(out, t)
+	}
+	return out, nil
+}