const markdownIt = require("markdown-it");
const markdownItContainer = require("markdown-it-container");
const markdownItFootnote = require("markdown-it-footnote");
const markdownItMermaid = require('markdown-it-mermaid').default
const syntaxHighlight = require("@11ty/eleventy-plugin-syntaxhighlight");
const fs = require("fs");
const crypto = require("crypto");
const path = require("path");
const { DateTime } = require("luxon");

const cssHashCache = {};
const getCssHash = (cssFile) => {
  if (cssHashCache[cssFile]) return cssHashCache[cssFile];
  
  const cssPath = path.join(__dirname, "css", cssFile);
  try {
    const content = fs.readFileSync(cssPath, "utf-8");
    const hash = crypto.createHash("md5").update(content).digest("hex").slice(0, 8);
    cssHashCache[cssFile] = hash;
    return hash;
  } catch (e) {
    console.warn(`Could not hash CSS file: ${cssFile}`);
    return null;
  }
};

const extractTags = (content, mdInstance) => {
  if (!content) return [];
  
  const collectHashtags = (tokens) =>
    tokens.flatMap(token => [
      ...(token.type === 'hashtag' ? [token.content] : []),
      ...(token.children ? collectHashtags(token.children) : [])
    ]);
  
  const tokens = mdInstance.parse(content, {});
  const tags = collectHashtags(tokens);
  return [...new Set(tags)];
}

const getPostTags = (post, mdInstance) => {
  const filePath = post.inputPath;
  try {
    const content = fs.readFileSync(filePath, 'utf-8');
    const tags = extractTags(content, mdInstance);
    return tags.map(tag => {
      const normalizedTag = tag.toLowerCase();
      return normalizedTag
    });
  } catch (e) {
    // Skip if file can't be read
    return []
  }
}

const isReleased = (post) => {
  return post.data.released !== false;
}

const markdownItHashtag = (md) => {
  const hashtagRegex = /^#([a-zA-Z][a-zA-Z0-9_]*)(?![a-zA-Z0-9_-])/;
  
  const HASH_CODE = '#'.charCodeAt(0);
  const SPACE_CODE = ' '.charCodeAt(0);
  const TAB_CODE = '\t'.charCodeAt(0);
  const NEWLINE_CODE = '\n'.charCodeAt(0);
  const CARRIAGE_RETURN_CODE = '\r'.charCodeAt(0);

  md.inline.ruler.push('hashtag', function(state, silent) {
    const pos = state.pos;
    const ch = state.src.charCodeAt(pos);

    if (ch !== HASH_CODE) return false;

    if (pos > 0) {
      const prevCh = state.src.charCodeAt(pos - 1);
      if (prevCh !== SPACE_CODE && prevCh !== TAB_CODE && prevCh !== NEWLINE_CODE && prevCh !== CARRIAGE_RETURN_CODE) {
        return false;
      }
    }

    const match = state.src.slice(pos).match(hashtagRegex);
    if (!match) return false;

    if (!silent) {
      const token = state.push('hashtag', 'a', 0);
      token.content = match[1];
      token.markup = '#';
    }

    state.pos += match[0].length;
    return true;
  });

  md.renderer.rules.hashtag = function(tokens, idx) {
    const tagName = tokens[idx].content;
    const slug = tagName.toLowerCase();
    return `<a href="/tags/${slug}/" class="inline-tag">#${md.utils.escapeHtml(tagName)}</a>`;
  };
}

const md = markdownIt({
  html: true,
  breaks: true,
  linkify: true
});

md.use(markdownItContainer, 'details', {
  validate: function (params) {
    return params.trim().match(/^(.*)$/);
  },
  render: function (tokens, idx) {
    const m = tokens[idx].info.trim().match(/^(.*)$/);
    if (tokens[idx].nesting === 1) {
      const title = md.utils.escapeHtml(m[1]);
      return `<details class="expandable">\n<summary>${title}</summary>\n`;
    } else {
      return '</details>\n';
    }
  }
});
md.use(markdownItFootnote);
md.use(markdownItHashtag);
md.use(markdownItMermaid);

module.exports = (eleventyConfig) => {
  eleventyConfig.addPlugin(syntaxHighlight);

  eleventyConfig.addFilter("extractTags", (content) => extractTags(content, md));
  eleventyConfig.addFilter("extractTagsFromFile", (filePath) => {
    try {
      const content = fs.readFileSync(filePath, 'utf-8');
      return extractTags(content, md);
    } catch (e) {
      return [];
    }
  });

  eleventyConfig.setLibrary("md", md);

  eleventyConfig.addFilter("dateTimeFormat", (date) => {
    const dt = date instanceof Date 
      ? DateTime.fromJSDate(date)
      : DateTime.fromISO(date);
    return dt.toFormat('MMMM d, yyyy h:mm a');
  });

  eleventyConfig.addFilter("isoDate", (date) => {
    const dt = date instanceof Date 
      ? DateTime.fromJSDate(date)
      : DateTime.fromISO(date);
    return dt.toISODate();
  });

  eleventyConfig.addFilter("isMoreThanHourAfter", (date1, date2) => {
    if (!date1 || !date2) return false;
    const toDateTime = (d) => {
      if (DateTime.isDateTime(d)) return d;
      if (d instanceof Date) return DateTime.fromJSDate(d);
      return DateTime.fromISO(d);
    };
    const dt1 = toDateTime(date1);
    const dt2 = toDateTime(date2);
    const diff = dt1.diff(dt2, 'hours').hours;
    return Math.abs(diff) > 1;
  });

  eleventyConfig.addCollection("posts", (collectionApi) => {
    return collectionApi.getFilteredByGlob("posts/**/*.md")
      .filter(isReleased)
      .sort((a, b) => {
        const aDate = a.data.createdAt || a.date;
        const bDate = b.data.createdAt || b.date;
        return aDate - bDate;
      });
  });

  eleventyConfig.addCollection("allPosts", (collectionApi) => {
    return collectionApi.getFilteredByGlob("posts/**/*.md").sort((a, b) => {
      const aDate = a.data.createdAt || a.date;
      const bDate = b.data.createdAt || b.date;
      return aDate - bDate;
    });
  });

  eleventyConfig.addCollection("postsBySlug", (collectionApi) => {
    const posts = collectionApi.getFilteredByGlob("posts/**/*.md").filter(isReleased);
    const slugify = eleventyConfig.getFilter("slugify");
    const grouped = {};
    
    posts.forEach(post => {
      const slug = slugify(post.data.title);
      if (!grouped[slug]) {
        grouped[slug] = [];
      }
      grouped[slug].push(post);
    });
    
    Object.values(grouped).forEach(postList => {
      postList.sort((a, b) => {
        const aDate = a.data.createdAt || a.date;
        const bDate = b.data.createdAt || b.date;
        return aDate - bDate;
      });
    });
    
    return grouped;
  });

  eleventyConfig.addCollection("contentTags", (collectionApi) => {
    const posts = collectionApi.getFilteredByGlob("posts/**/*.md").filter(isReleased);
    
    return [...new Set(posts.flatMap(post => getPostTags(post, md)))].sort();
  });

  eleventyConfig.addCollection("postsByTag", (collectionApi) => {
    const posts = collectionApi.getFilteredByGlob("posts/**/*.md").filter(isReleased);
    const tagMap = {};
    
    posts.forEach(post => {
      const tags = getPostTags(post, md)
      tags.forEach((tag) => {
        tagMap[tag] = {
          name: tag,
          posts: [post, ...(tagMap[tag]?.posts ?? [])],
        }
      })
    });
    
    Object.values(tagMap).forEach(tagData => {
      tagData.posts.sort((a, b) => {
        const aDate = a.data.createdAt || a.date;
        const bDate = b.data.createdAt || b.date;
        return aDate - bDate;
      });
    });
    
    return tagMap;
  });

  // Cache busting filter: returns hashed CSS filename
  eleventyConfig.addFilter("cssHash", (cssFile) => {
    const hash = getCssHash(cssFile);
    const ext = path.extname(cssFile);
    const base = path.basename(cssFile, ext);
    return `/css/${base}.${hash}${ext}`;
  });

  eleventyConfig.on("eleventy.before", async () => {
    const cssDir = path.join(__dirname, "css");
    const outputCssDir = path.join(__dirname, "_site", "css");
    
    if (!fs.existsSync(outputCssDir)) {
      fs.mkdirSync(outputCssDir, { recursive: true });
    }
    
    const cssFiles = fs.readdirSync(cssDir).filter(f => f.endsWith(".css"));
    for (const cssFile of cssFiles) {
      const hash = getCssHash(cssFile);
      const ext = path.extname(cssFile);
      const base = path.basename(cssFile, ext);
      const hashedName = `${base}${hash == null ? '' : `.${hash}`}${ext}`;
      
      fs.copyFileSync(
        path.join(cssDir, cssFile),
        path.join(outputCssDir, hashedName)
      );
    }
  });

  eleventyConfig.addPassthroughCopy("robots.txt");

  eleventyConfig.ignores.add("README.md");

  return {
    dir: {
      input: ".",
      includes: "_includes",
      output: "_site"
    },
    markdownTemplateEngine: "njk",
    htmlTemplateEngine: "njk"
  };
};