// 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
}