package wing

import (
	"fmt"
	"os"
	"path/filepath"
	"sort"
)

// legacyDirs are the retired wiki/{concepts,entities,sources}/ layout, not wings.
var legacyDirs = map[string]bool{"concepts": true, "entities": true, "sources": true}

// KnownWings lists wiki/<wing>/ directories that contain at least one hall
// subdirectory, sorted. The retired layout is not a wing. A missing wiki/ is
// an error: an unreadable brain must not look like "no wings".
func KnownWings(brainDir string) ([]string, error) {
	entries, err := os.ReadDir(filepath.Join(brainDir, "wiki"))
	if err != nil {
		return nil, fmt.Errorf("list wings: %w", err)
	}
	var out []string
	for _, e := range entries {
		if !e.IsDir() || legacyDirs[e.Name()] {
			continue
		}
		subs, err := os.ReadDir(filepath.Join(brainDir, "wiki", e.Name()))
		if err != nil {
			continue
		}
		for _, s := range subs {
			if s.IsDir() {
				out = append(out, e.Name())
				break
			}
		}
	}
	sort.Strings(out)
	return out, nil
}