// ingestion/internal/wiki/index.go
package wiki

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

// RebuildIndex writes brain/wiki/index.md from the current wiki contents.
func RebuildIndex(brainDir, date string) error {
	inv, err := LoadInventory(brainDir)
	if err != nil {
		return fmt.Errorf("load inventory: %w", err)
	}

	total := len(inv[PageTypeConcept]) + len(inv[PageTypeEntity]) + len(inv[PageTypeSource])
	var sb strings.Builder
	fmt.Fprintf(&sb, "# Wiki Index\n\n")
	fmt.Fprintf(&sb, "_Updated: %s — %d pages (%d concepts, %d entities, %d sources)_\n\n",
		date, total,
		len(inv[PageTypeConcept]),
		len(inv[PageTypeEntity]),
		len(inv[PageTypeSource]))

	for _, pt := range []PageType{PageTypeConcept, PageTypeEntity, PageTypeSource} {
		entries := inv[pt]
		if len(entries) == 0 {
			continue
		}
		label := strings.ToUpper(string(pt)[:1]) + string(pt)[1:]
		fmt.Fprintf(&sb, "## %s\n\n", label)
		for _, e := range entries {
			summary := pageFirstSentence(brainDir, e)
			if summary != "" {
				fmt.Fprintf(&sb, "- [[%s|%s]] — %s\n", e.Slug, e.Title, summary)
			} else {
				fmt.Fprintf(&sb, "- [[%s|%s]]\n", e.Slug, e.Title)
			}
		}
		sb.WriteString("\n")
	}

	dest := filepath.Join(brainDir, "wiki", "index.md")
	return os.WriteFile(dest, []byte(sb.String()), 0o644)
}

func pageFirstSentence(brainDir string, e Entry) string {
	path := filepath.Join(brainDir, "wiki", string(e.Type), e.Slug+".md")
	content, err := os.ReadFile(path)
	if err != nil {
		return ""
	}
	parts := strings.SplitN(string(content), "---", 3)
	body := string(content)
	if len(parts) == 3 {
		body = parts[2]
	}
	for _, line := range strings.Split(body, "\n") {
		line = strings.TrimSpace(line)
		if line == "" || strings.HasPrefix(line, "#") {
			continue
		}
		if len(line) > 100 {
			return line[:100] + "…"
		}
		return line
	}
	return ""
}