// ingestion/internal/wiki/inventory.go
package wiki

import (
	"bufio"
	"os"
	"path/filepath"
	"strings"
)

// LoadInventory walks brain/wiki/ and returns all pages grouped by type.
// Missing subdirectories are silently skipped.
func LoadInventory(brainDir string) (map[PageType][]Entry, error) {
	result := map[PageType][]Entry{
		PageTypeConcept: {},
		PageTypeEntity:  {},
		PageTypeSource:  {},
	}
	for pt := range result {
		dir := filepath.Join(brainDir, "wiki", string(pt))
		entries, err := os.ReadDir(dir)
		if os.IsNotExist(err) {
			continue
		}
		if err != nil {
			return nil, err
		}
		for _, e := range entries {
			if e.IsDir() || !strings.HasSuffix(e.Name(), ".md") {
				continue
			}
			slug := strings.TrimSuffix(e.Name(), ".md")
			path := filepath.Join(dir, e.Name())
			title := readTitle(path, slug)
			result[pt] = append(result[pt], Entry{Slug: slug, Title: title, Type: pt})
		}
	}
	return result, nil
}

// readTitle extracts the title from YAML frontmatter, falling back to slug.
func readTitle(path, fallback string) string {
	f, err := os.Open(path)
	if err != nil {
		return fallback
	}
	defer f.Close()

	scanner := bufio.NewScanner(f)
	inFM := false
	for scanner.Scan() {
		line := scanner.Text()
		if strings.TrimSpace(line) == "---" {
			if !inFM {
				inFM = true
				continue
			}
			break
		}
		if inFM {
			key, val, ok := strings.Cut(line, ":")
			if ok && strings.TrimSpace(key) == "title" {
				return strings.Trim(strings.TrimSpace(val), `"'`)
			}
		}
	}
	return fallback
}