import syntaxHighlight from "@11ty/eleventy-plugin-syntaxhighlight";
import markdownIt from "markdown-it";
import markdownItAnchor from "markdown-it-anchor";
import { DateTime } from "luxon";

export default function (eleventyConfig) {
  // 1. Static Asset Passthrough Copy
  eleventyConfig.addPassthroughCopy({ "src/assets": "assets" });

  // 2. Syntax Highlighting Plugin
  eleventyConfig.addPlugin(syntaxHighlight);

  // 3. Markdown-It Library Customization
  const markdownOptions = {
    html: true,
    breaks: false,
    linkify: true
  };

  const markdownLib = markdownIt(markdownOptions).use(markdownItAnchor, {
    permalink: markdownItAnchor.permalink.headerLink({
      safariReaderFix: true
    }),
    slugify: (s) =>
      s
        .trim()
        .toLowerCase()
        .replace(/[^a-z0-9 -]/g, "")
        .replace(/\s+/g, "-")
        .replace(/-+/g, "-")
  });

  eleventyConfig.setLibrary("md", markdownLib);

  // 4. Custom Filters
  // Format readable dates: SEP 12, 2026
  eleventyConfig.addFilter("postDate", (dateObj) => {
    if (!dateObj) return "";
    return DateTime.fromJSDate(new Date(dateObj), { zone: "utc" })
      .toFormat("LLL dd, yyyy")
      .toUpperCase();
  });

  // ISO date format for <time datetime="...">
  eleventyConfig.addFilter("isoDate", (dateObj) => {
    if (!dateObj) return "";
    return DateTime.fromJSDate(new Date(dateObj), { zone: "utc" }).toISODate();
  });

  // Limit array items
  eleventyConfig.addFilter("limit", (arr, limit) => {
    if (!Array.isArray(arr)) return [];
    return arr.slice(0, limit);
  });

  // Filter out internal system tags
  eleventyConfig.addFilter("filterTagList", (tags) => {
    const internalTags = ["all", "nav", "post", "posts"];
    return (tags || []).filter((tag) => !internalTags.includes(tag.toLowerCase()));
  });

  // Reading time estimator (defaults to 200 words/min if frontmatter lacks readingTime)
  eleventyConfig.addFilter("readingTime", (text, frontmatterTime) => {
    if (frontmatterTime) return frontmatterTime;
    if (!text) return "1 MIN READ";
    const wordCount = text.trim().split(/\s+/).length;
    const minutes = Math.ceil(wordCount / 200);
    return `${minutes} MIN READ`;
  });

  // Extract H2 and H3 headings with IDs for dynamic Table of Contents
  eleventyConfig.addFilter("extractHeadings", (htmlContent) => {
    if (!htmlContent) return [];
    const headingRegex = /<h([23])\s+id="([^"]+)"[^>]*>(.*?)<\/h\1>/gis;
    const headings = [];
    let match;
    while ((match = headingRegex.exec(htmlContent)) !== null) {
      headings.push({
        level: parseInt(match[1], 10),
        id: match[2],
        title: match[3].replace(/<[^>]+>/g, "").trim()
      });
    }
    return headings;
  });

  // 5. Custom Collections
  // Chronological blog posts collection
  eleventyConfig.addCollection("posts", (collectionApi) => {
    return collectionApi
      .getFilteredByGlob("src/posts/*.md")
      .filter((post) => !post.data.draft)
      .sort((a, b) => b.date - a.date);
  });

  // Dynamic Tag List Collection across all posts
  eleventyConfig.addCollection("tagList", (collectionApi) => {
    const tagSet = new Set();
    collectionApi.getFilteredByGlob("src/posts/*.md").forEach((item) => {
      if ("tags" in item.data) {
        let tags = item.data.tags;
        if (typeof tags === "string") tags = [tags];
        for (const tag of tags) {
          const cleanTag = tag.replace(/^#/, "");
          tagSet.add(cleanTag);
        }
      }
    });
    return [...tagSet].sort();
  });

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