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

import (
	"fmt"
	"strings"

	"github.com/mathiasbq/hyperguild/ingestion/internal/brainfs"
	"github.com/mathiasbq/hyperguild/ingestion/internal/textutil"
)

// 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)
	}
	bfs, err := brainfs.Open(brainDir)
	if err != nil {
		return fmt.Errorf("open brain: %w", err)
	}
	defer func() { _ = bfs.Close() }()

	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(bfs, 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")
	}

	// Written through the brain root, never through a symlink (#158).
	return bfs.PutRegular("wiki/index.md", []byte(sb.String()))
}

// pageFirstSentence reads the page through the brain root, regular files
// only (hyperguild#157).
func pageFirstSentence(bfs *brainfs.Brain, e Entry) string {
	content, err := bfs.ReadRegular("wiki/" + string(e.Type) + "/" + e.Slug + ".md")
	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
		}
		return textutil.Truncate(line, 100)
	}
	return ""
}