import { remark } from 'remark'
import remarkHtml from 'remark-html'
import remarkGfm from 'remark-gfm'

// Simple markdown processor with clean output
const processor = remark()
  .use(remarkGfm) // Support for GitHub Flavored Markdown (tables, strikethrough, etc.)
  // Das Ergebnis geht über dangerouslySetInnerHTML in die öffentliche Seite.
  // Das Standard-Schema lässt Überschriften, Listen, Tabellen und http(s)- bzw.
  // mailto-Links durch und entfernt Skripte, Event-Attribute, eingebettete
  // Rahmen und javascript:-Ziele.
  .use(remarkHtml, { sanitize: true })

/**
 * Maskiert Text für die Ausgabe in HTML. Für Werte, die nicht durch den
 * Markdown-Prozessor laufen – etwa Titel in der Druckfassung.
 */
export function escapeHtml(value: string): string {
  return String(value)
    .replace(/&/g, '&')
    .replace(/</g, '&lt;')
    .replace(/>/g, '&gt;')
    .replace(/"/g, '&quot;')
    .replace(/'/g, '&#x27;')
}

export async function markdownToHtml(markdown: string): Promise<string> {
  if (!markdown || typeof markdown !== 'string') {
    return ''
  }

  try {
    // Simple preprocessing for line breaks
    const preprocessed = simplePreprocessLineBreaks(markdown)
    const result = await processor.process(preprocessed)
    return result.toString()
  } catch (error) {
    console.error('Error processing markdown:', error)
    // Fallback: return sanitized markdown with basic formatting
    return sanitizeAndFormatMarkdown(markdown)
  }
}

// Synchronous version for use in components that can't use async
export function markdownToHtmlSync(markdown: string): string {
  if (!markdown || typeof markdown !== 'string') {
    return ''
  }

  try {
    // Simple preprocessing for line breaks
    const preprocessed = simplePreprocessLineBreaks(markdown)
    const result = processor.processSync(preprocessed)
    return result.toString()
  } catch (error) {
    console.error('Error processing markdown synchronously:', error)
    // Fallback: return sanitized markdown with basic formatting
    return sanitizeAndFormatMarkdown(markdown)
  }
}

// Simple preprocessing for consistent line breaks
function simplePreprocessLineBreaks(markdown: string): string {
  return markdown
    // Normalize line endings
    .replace(/\r\n/g, '\n')
    .replace(/\r/g, '\n')
    // Add two spaces before single line breaks for hard breaks
    .replace(/([^\n])\n([^\n])/g, '$1  \n$2')
}

// Fallback function for basic markdown formatting
function sanitizeAndFormatMarkdown(text: string): string {
  // Simple, clean markdown processing
  return text
    // Escape HTML
    .replace(/&/g, '&amp;')
    .replace(/</g, '&lt;')
    .replace(/>/g, '&gt;')
    .replace(/"/g, '&quot;')
    .replace(/'/g, '&#x27;')
    // Basic markdown formatting
    .replace(/\*\*(.*?)\*\*/g, '<strong>$1</strong>')
    .replace(/\*(.*?)\*/g, '<em>$1</em>')
    .replace(/`(.*?)`/g, '<code>$1</code>')
    // Headers
    .replace(/^### (.*$)/gm, '<h3>$1</h3>')
    .replace(/^## (.*$)/gm, '<h2>$1</h2>')
    .replace(/^# (.*$)/gm, '<h1>$1</h1>')
    // Lists
    .replace(/^\* (.*$)/gm, '• $1')
    .replace(/^- (.*$)/gm, '• $1')
    .replace(/^(\d+)\. (.*$)/gm, '$1. $2')
    // Line breaks
    .replace(/\n/g, '<br>')
    // Clean up multiple <br> tags
    .replace(/<br><br>/g, '<br>')
}