import type { APIRoute } from "astro";
import { getCollection } from "astro:content";
import { siteConfig } from "../config";
import { shouldShowPost, shouldShowContent, getPostSlug } from "../utils/markdown";

function shouldExcludeFromSitemap(slug: string): boolean {
  const excludedSlugs = ["404", "sitemap", "rss"];
  return excludedSlugs.includes(slug);
}

// Helper function to normalize siteUrl - ensure it ends with a single slash
function normalizeSiteUrl(url: string): string {
  return url.replace(/\/+$/, '') + '/';
}

// Compute slug from collection entry id
function getSlugFromId(id: string): string {
  // Remove file extension and handle folder-based content
  // For example: "about/index" -> "about", "getting-started.md" -> "getting-started"
  return id.replace(/\/index$/, "").replace(/\.mdx?$/, "");
}

export const GET: APIRoute = async () => {
  const siteUrl = normalizeSiteUrl(import.meta.env.SITE || siteConfig.site);

  // Get all content collections
  const posts = await getCollection("posts");
  const pages = await getCollection("pages");
  const projects = await getCollection("projects");
  const docs = await getCollection("docs");

  // Filter posts based on environment (in dev, show all including drafts)
  const isDev = import.meta.env.DEV;
  const visiblePosts = posts.filter(
    (post) => shouldShowPost(post, isDev) && !post.data.noIndex
  );

  // Filter pages (exclude drafts, special pages, and noIndex)
  const visiblePages = pages.filter(
    (page) =>
      shouldShowContent(page, isDev) &&
      !page.data.noIndex &&
      !shouldExcludeFromSitemap(getSlugFromId(page.id))
  );

  // Filter projects and docs based on environment and optional content type settings
  const visibleProjects = siteConfig.optionalContentTypes.projects
    ? projects.filter(
        (project) => shouldShowContent(project, isDev) && !project.data.noIndex
      )
    : [];

  const visibleDocs = siteConfig.optionalContentTypes.docs
    ? docs.filter((doc) => shouldShowContent(doc, isDev) && !doc.data.noIndex)
    : [];

  // Generate URLs
  const urls: string[] = [];

  // Homepage
  urls.push(`
    <url>
      <loc>${siteUrl}</loc>
      <lastmod>${new Date().toISOString()}</lastmod>
      <changefreq>daily</changefreq>
      <priority>1.0</priority>
    </url>
  `);

  // Posts index page
  urls.push(`
    <url>
      <loc>${siteUrl}posts/</loc>
      <lastmod>${new Date().toISOString()}</lastmod>
      <changefreq>daily</changefreq>
      <priority>0.8</priority>
    </url>
  `);

  // Projects index page (only if projects are enabled)
  if (siteConfig.optionalContentTypes.projects) {
    urls.push(`
      <url>
        <loc>${siteUrl}projects/</loc>
        <lastmod>${new Date().toISOString()}</lastmod>
        <changefreq>weekly</changefreq>
        <priority>0.7</priority>
      </url>
    `);
  }

  // Documentation index page (only if docs are enabled)
  if (siteConfig.optionalContentTypes.docs) {
    urls.push(`
      <url>
        <loc>${siteUrl}docs/</loc>
        <lastmod>${new Date().toISOString()}</lastmod>
        <changefreq>weekly</changefreq>
        <priority>0.7</priority>
      </url>
    `);
  }

  // Individual posts
  visiblePosts.forEach((post) => {
    const slug = getPostSlug(post);
    urls.push(`
      <url>
        <loc>${siteUrl}posts/${slug}/</loc>
        <lastmod>${post.data.date.toISOString()}</lastmod>
        <changefreq>monthly</changefreq>
        <priority>0.7</priority>
      </url>
    `);
  });

  // Individual pages
  visiblePages.forEach((page) => {
    const slug = getSlugFromId(page.id);
    urls.push(`
      <url>
        <loc>${siteUrl}${slug}/</loc>
        <lastmod>${page.data.lastModified || new Date().toISOString()}</lastmod>
        <changefreq>monthly</changefreq>
        <priority>0.8</priority>
      </url>
    `);
  });

  // Individual projects
  visibleProjects.forEach((project) => {
    const lastmod = project.data.date;
    const slug = getSlugFromId(project.id);
    urls.push(`
      <url>
        <loc>${siteUrl}projects/${slug}/</loc>
        <lastmod>${lastmod.toISOString()}</lastmod>
        <changefreq>monthly</changefreq>
        <priority>0.7</priority>
      </url>
    `);
  });

  // Individual documentation pages
  visibleDocs.forEach((doc) => {
    const lastmod = doc.data.lastModified || new Date();
    const slug = getSlugFromId(doc.id);
    urls.push(`
      <url>
        <loc>${siteUrl}docs/${slug}/</loc>
        <lastmod>${lastmod.toISOString()}</lastmod>
        <changefreq>monthly</changefreq>
        <priority>0.6</priority>
      </url>
    `);
  });

  // Posts pagination pages
  const postsPerPage = siteConfig.postOptions.postsPerPage;
  const totalPages = Math.ceil(visiblePosts.length / postsPerPage);

  for (let page = 2; page <= totalPages; page++) {
    urls.push(`
      <url>
        <loc>${siteUrl}posts/${page}/</loc>
        <lastmod>${new Date().toISOString()}</lastmod>
        <changefreq>weekly</changefreq>
        <priority>0.5</priority>
      </url>
    `);
  }

  const sitemap = `<?xml version="1.0" encoding="UTF-8"?>
<urlset xmlns="http://www.sitemaps.org/schemas/sitemap/0.9"
        xmlns:image="http://www.google.com/schemas/sitemap-image/1.1"
        xmlns:news="http://www.google.com/schemas/sitemap-news/0.9">
  ${urls.join("")}
</urlset>`;

  return new Response(sitemap, {
    headers: {
      "Content-Type": "application/xml",
      "Cache-Control": "public, max-age=3600", // Cache for 1 hour
    },
  });
};