module.exports = function (eleventyConfig) {
  // Collection: all posts sorted by date descending
  eleventyConfig.addCollection("posts", function (collectionApi) {
    return collectionApi
      .getFilteredByGlob("src/blog/posts/**/*.md")
      .sort((a, b) => b.date - a.date);
  });

  // Collection: about window content
  eleventyConfig.addCollection("aboutContent", (api) =>
    api.getFilteredByGlob("src/content/about.md")
  );

  // Collection: contact window content
  eleventyConfig.addCollection("contactContent", (api) =>
    api.getFilteredByGlob("src/content/contact.md")
  );

  // Collection: projects, sorted alphabetically by title
  eleventyConfig.addCollection("projects", (api) =>
    api
      .getFilteredByGlob("src/projects/**/*.md")
      .filter((p) => !p.fileSlug.startsWith("_"))
      .sort((a, b) => a.data.title.localeCompare(b.data.title))
  );

  // Filter: human-readable date, e.g. "March 24, 2026"
  eleventyConfig.addFilter("readableDate", function (date) {
    return new Date(date).toLocaleDateString("en-US", {
      year: "numeric",
      month: "long",
      day: "numeric",
    });
  });

  // Filter: aggregate tags across a post collection
  // Returns [{tag, count}, ...] sorted by count desc, excluding "posts"
  eleventyConfig.addFilter("tagCounts", function (posts) {
    const counts = {};
    for (const post of posts) {
      for (const tag of post.data.tags || []) {
        if (tag === "posts") continue;
        counts[tag] = (counts[tag] || 0) + 1;
      }
    }
    return Object.entries(counts)
      .map(([tag, count]) => ({ tag, count }))
      .sort((a, b) => b.count - a.count);
  });

  // Pass through static assets
  eleventyConfig.addPassthroughCopy("src/assets");

  return {
    dir: {
      input: "src",
      output: "_site",
      includes: "_includes",
      data: "_data",
    },
    templateFormats: ["njk", "md", "html"],
    markdownTemplateEngine: "njk",
    htmlTemplateEngine: "njk",
  };
};