/**
 * Markdown Import Parser
 *
 * Uses markdown-it to convert markdown strings to HTML for importing
 * .md files into the TipTap editor with full formatting preserved.
 *
 * Supports: headings, bold, italic, strikethrough, code (inline + blocks),
 * links, images, blockquotes, lists (bullet, ordered, task via GFM),
 * horizontal rules, tables (GFM), hard line breaks.
 */

import MarkdownIt from 'markdown-it';
import type { Token, Renderer, MarkdownItOptions, MarkdownItPlugin } from 'markdown-it';

// Initialize markdown-it with GFM-like defaults
const md = new MarkdownIt({
  html: false,        // Disable raw HTML passthrough for security
  linkify: true,      // Auto-convert URLs to links
  typographer: false,  // Keep raw characters (don't smart-quote)
  breaks: false,       // Standard CommonMark line break behavior
});

// Enable strikethrough (~~text~~) via built-in plugin
md.enable('strikethrough');

// Enable tables via built-in plugin
md.enable('table');

/**
 * Custom plugin: task list checkboxes (GFM style)
 * Converts `- [ ] text` and `- [x] text` into checkbox list items.
 */
/**
 * Scan a bullet_list's children and return true if ANY list_item
 * starts with a GFM checkbox pattern `[ ]` / `[x]`.
 */
function listContainsTaskItems(tokens: Token[], listOpenIdx: number): boolean {
  let depth = 0;
  for (let i = listOpenIdx; i < tokens.length; i++) {
    if (tokens[i].type === 'bullet_list_open') depth++;
    if (tokens[i].type === 'bullet_list_close') { depth--; if (depth === 0) break; }
    if (depth === 1 && tokens[i].type === 'list_item_open') {
      const content = tokens[i + 2]; // list_item_open -> paragraph_open -> inline
      if (content?.type === 'inline' && /^\[([ xX])\]\s*/.test(content.content)) {
        return true;
      }
    }
  }
  return false;
}

const taskListPlugin: MarkdownItPlugin = function taskListPlugin(md: MarkdownIt): void {
  // --- Override bullet_list_open: emit <ul data-type="taskList"> when items have checkboxes ---
  const defaultListOpen = md.renderer.rules.bullet_list_open ||
    function (tokens: Token[], idx: number, options: MarkdownItOptions, _env: unknown, self: Renderer): string {
      return self.renderToken(tokens, idx, options);
    };

  md.renderer.rules.bullet_list_open = function (tokens: Token[], idx: number, options: MarkdownItOptions, env: unknown, self: Renderer): string {
    if (listContainsTaskItems(tokens, idx)) {
      return '<ul data-type="taskList">';
    }
    return defaultListOpen(tokens, idx, options, env, self);
  };

  // --- Override list_item_open: emit TipTap-compatible task item attributes ---
  const defaultItemOpen = md.renderer.rules.list_item_open ||
    function (tokens: Token[], idx: number, options: MarkdownItOptions, _env: unknown, self: Renderer): string {
      return self.renderToken(tokens, idx, options);
    };

  md.renderer.rules.list_item_open = function (tokens: Token[], idx: number, options: MarkdownItOptions, env: unknown, self: Renderer): string {
    const contentToken = tokens[idx + 2]; // list_item_open -> paragraph_open -> inline
    if (contentToken && contentToken.type === 'inline' && contentToken.content) {
      const match = contentToken.content.match(/^\[([ xX])\]\s*/);
      if (match) {
        const checked = match[1].toLowerCase() === 'x';
        // Remove the checkbox syntax from the content
        contentToken.content = contentToken.content.replace(/^\[([ xX])\]\s*/, '');
        if (contentToken.children && contentToken.children.length > 0) {
          const firstChild = contentToken.children[0];
          if (firstChild.type === 'text') {
            firstChild.content = firstChild.content.replace(/^\[([ xX])\]\s*/, '');
          }
        }
        return `<li data-type="taskItem" data-checked="${checked}">`;
      }
    }
    return defaultItemOpen(tokens, idx, options, env, self);
  };
};

md.use(taskListPlugin);

/**
 * Convert a markdown string to HTML.
 */
export function markdownToHtml(mdString: string): string {
  if (!mdString) return '';
  return md.render(mdString);
}