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

import (
	"bufio"
	"fmt"
	"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, fmt.Errorf("read dir %s: %w", dir, 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, aliases := readFrontmatter(path, slug)
			result[pt] = append(result[pt], Entry{Slug: slug, Title: title, Aliases: aliases, Type: pt})
		}
	}
	return result, nil
}

// readFrontmatter extracts title and aliases from YAML frontmatter.
// Falls back to slug for title and empty aliases on any error.
func readFrontmatter(path, fallbackSlug string) (title string, aliases []string) {
	title = fallbackSlug
	f, err := os.Open(path)
	if err != nil {
		return
	}
	defer f.Close() //nolint:errcheck

	scanner := bufio.NewScanner(f)
	inFM := false
	inAliases := false
	for scanner.Scan() {
		line := scanner.Text()
		if strings.TrimSpace(line) == "---" {
			if !inFM {
				inFM = true
				continue
			}
			break // end of frontmatter
		}
		if !inFM {
			continue
		}

		// Detect alias list items (lines starting with "  - ").
		if inAliases {
			trimmed := strings.TrimSpace(line)
			if strings.HasPrefix(trimmed, "- ") {
				aliases = append(aliases, strings.TrimPrefix(trimmed, "- "))
				continue
			}
			inAliases = false // end of alias block
		}

		key, val, ok := strings.Cut(line, ":")
		if !ok {
			continue
		}
		switch strings.TrimSpace(key) {
		case "title":
			title = strings.Trim(strings.TrimSpace(val), `"'`)
		case "aliases":
			inAliases = true
		}
	}
	return
}