// pi-wiki: Cross-linker - auto-discover and insert wikilinks

import * as fs from "fs";
import * as path from "path";

const WIKI_DIR = process.env.PI_WIKI_DIR || path.join(process.env.HOME || "", "pi-wiki");
const PAGES_DIR = path.join(WIKI_DIR, "wiki");

function slugify(text: string): string {
  return text.toLowerCase().replace(/[^a-z0-9]+/g, "-").replace(/^-|-$/g, "");
}

function getAllPageTitles(): string[] {
  if (!fs.existsSync(PAGES_DIR)) return [];
  return fs.readdirSync(PAGES_DIR)
    .filter(f => f.endsWith(".md"))
    .map(f => f.replace(/\.md$/, ""));
}

export async function crosslink(): Promise<string> {
  const titles = getAllPageTitles();
  if (titles.length === 0) return "❌ No wiki pages found";

  let totalLinks = 0;
  const results: string[] = [];

  for (const title of titles) {
    const filePath = path.join(PAGES_DIR, title + ".md");
    let content = fs.readFileSync(filePath, "utf8");
    const originalContent = content;
    
    // Skip pages without body (just frontmatter)
    const bodyMatch = content.match(/^---\n[\s\S]*?\n---\n([\s\S]*)$/);
    if (!bodyMatch) continue;
    const body = bodyMatch[1];

    // Find all existing wikilinks
    const existingLinks = new Set<string>();
    let match;
    const linkRegex = /\[\[([^\]|]+)(?:\|[^\]]+)?\]\]/g;
    while ((match = linkRegex.exec(body)) !== null) {
      existingLinks.add(slugify(match[1]));
    }

    // Check for mentions without wikilinks
    let linksAdded = 0;
    for (const otherTitle of titles) {
      if (otherTitle === title) continue;
      if (existingLinks.has(slugify(otherTitle))) continue;

      // Case-insensitive mention without wikilink
      const mentionRegex = new RegExp(`\\b${otherTitle.replace(/[.*+?^${}()|[\]\\]/g, '\\$&')}\\b`, "gi");
      if (mentionRegex.test(body)) {
        // Find exact position to insert wikilink
        const firstMention = body.search(mentionRegex);
        if (firstMention >= 0) {
          // Replace first mention with wikilink
          const before = body.slice(0, firstMention);
          const after = body.slice(firstMention + otherTitle.length);
          body = before + "[[" + otherTitle + "]]" + after;
          existingLinks.add(slugify(otherTitle)); // prevent double-linking
          linksAdded++;
        }
      }
    }

    if (linksAdded > 0) {
      // Rebuild full content
      const frontmatterMatch = content.match(/^(---\n[\s\S]*?\n---)\n/);
      content = frontmatterMatch ? frontmatterMatch[1] + "\n" + body : body;
      
      // Update frontmatter
      if (frontmatterMatch) {
        const front = frontmatterMatch[1];
        const updatedFront = front.includes("updated:")
          ? front.replace(/updated:.*/m, `updated: ${new Date().toISOString().split("T")[0]}`)
          : front.replace(/---$/, `updated: ${new Date().toISOString().split("T")[0]}\n---`);
        content = updatedFront + "\n" + body;
      }

      fs.writeFileSync(filePath, content);
      results.push(`+${linksAdded} links in [[${title}]]`);
      totalLinks += linksAdded;
    }
  }

  if (totalLinks === 0) {
    return "✅ No new links needed - all pages already connected!";
  }

  return `## 🔗 Cross-link Results\n\n${results.join("\n")}\n\n**Total: ${totalLinks} links added**`;
}