src/shared/markdown-parser.js

// ══════════════════════════════════════════════════════════════════════════════
// Chahua Markdown Presenter - Markdown Parser
// Parse Markdown into Presentation Slides
// ══════════════════════════════════════════════════════════════════════════════
// Company: Chahua Development Co., Ltd.
// Version: 2.0.0
// License: MIT
// ══════════════════════════════════════════════════════════════════════════════

import { MarkdownSyntax, detectBlockType, parseInline } from './markdown-syntax.js';
import { applyPagination, getPaginationInfo } from './slide-paginator.js';

export class MarkdownParser {
  constructor(options = {}) {
    this.options = {
      slideBreak: options.slideBreak || '---', // Horizontal rule for slide breaks
      h1AsSlide: options.h1AsSlide !== false, // # creates new slide
      h2AsSlide: options.h2AsSlide || false,  // ## creates new slide
      enablePagination: options.enablePagination !== false, // Auto-split long slides
      maxLinesPerSlide: options.maxLinesPerSlide || 8, // Max visual lines per slide
      ...options
    };
  }

  /**
   * Parse markdown text into slides
   * @param {string} markdown - Raw markdown text
   * @returns {Array} Array of slide objects
   */
  parse(markdown) {
    if (!markdown || typeof markdown !== 'string') {
      throw new Error('Invalid markdown input');
    }

    // Split by slide breaks (---)
    const rawSlides = this.splitIntoSlides(markdown);
    
    // Parse each slide
    const slides = rawSlides.map((slideText, index) => {
      return this.parseSlide(slideText, index);
    });

    // Filter empty slides
    const nonEmptySlides = slides.filter(slide => slide.content.length > 0);
    
    // Apply pagination if enabled
    if (this.options.enablePagination) {
      const paginatedSlides = [];
      let globalIndex = 0;
      
      for (const slide of nonEmptySlides) {
        const pages = applyPagination(slide);
        
        // Update indices
        pages.forEach((page, pageIndex) => {
          page.index = globalIndex++;
          page.originalIndex = slide.index;
          paginatedSlides.push(page);
        });
      }
      
      return paginatedSlides;
    }
    
    return nonEmptySlides;
  }

  /**
   * Split markdown into slides based on rules
   */
  splitIntoSlides(markdown) {
    const slides = [];
    let currentSlide = [];
    const lines = markdown.split('\n');
    
    // Skip frontmatter block if present
    let startIndex = 0;
    if (lines[0] && lines[0].trim() === '---') {
      // Find closing ---
      for (let i = 1; i < Math.min(lines.length, 50); i++) {
        if (lines[i].trim() === '---') {
          startIndex = i + 1;
          break;
        }
      }
    }

    for (let i = startIndex; i < lines.length; i++) {
      const line = lines[i];
      const trimmed = line.trim();

      // Check for slide break (---)
      if (trimmed === '---' || trimmed === '___' || trimmed === '***') {
        if (currentSlide.length > 0) {
          slides.push(currentSlide.join('\n'));
          currentSlide = [];
        }
        continue;
      }

      // Check for H1 as slide break
      if (this.options.h1AsSlide && trimmed.startsWith('# ') && currentSlide.length > 0) {
        slides.push(currentSlide.join('\n'));
        currentSlide = [line];
        continue;
      }

      // Check for H2 as slide break
      if (this.options.h2AsSlide && trimmed.startsWith('## ') && currentSlide.length > 0) {
        slides.push(currentSlide.join('\n'));
        currentSlide = [line];
        continue;
      }

      currentSlide.push(line);
    }

    // Add last slide
    if (currentSlide.length > 0) {
      slides.push(currentSlide.join('\n'));
    }

    return slides;
  }

  /**
   * Parse individual slide content using Markdown Dictionary
   */
  parseSlide(slideText, index) {
    const content = [];
    const lines = slideText.split('\n');
    
    let title = '';
    let subtitle = '';
    let customDuration = null;
    let inCodeBlock = false;
    let codeLines = [];
    let codeLang = '';
    let codeFence = '```';
    let inBlockquote = false;
    let blockquoteLines = [];
    let inTable = false;
    let tableRows = [];
    let inHtml = false;
    let htmlLines = [];

    for (let i = 0; i < lines.length; i++) {
      const line = lines[i];
      const trimmed = line.trim();
      const nextLine = i < lines.length - 1 ? lines[i + 1] : null;

      // Skip empty lines (unless in special block)
      if (!trimmed && !inCodeBlock && !inHtml) {
        // End blockquote on empty line
        if (inBlockquote && blockquoteLines.length > 0) {
          const quoteText = blockquoteLines.join('\n');
          content.push({
            type: 'blockquote',
            content: quoteText,
            html: this.parseInline(quoteText)
          });
          blockquoteLines = [];
          inBlockquote = false;
        }
        // End table on empty line
        if (inTable && tableRows.length > 0) {
          content.push({
            type: 'table',
            rows: tableRows
          });
          tableRows = [];
          inTable = false;
        }
        continue;
      }

      // Check for metadata (subtitle: or duration:)
      if (trimmed.match(/^(subtitle|duration):\s*(.+)$/i)) {
        const match = trimmed.match(/^(subtitle|duration):\s*(.+)$/i);
        const key = match[1].toLowerCase();
        const value = match[2].trim();
        
        if (key === 'subtitle') {
          subtitle = value;
        } else if (key === 'duration') {
          customDuration = parseFloat(value);
        }
        continue;
      }

      // Code block detection (using dictionary)
      const codeBlockCheck = MarkdownSyntax.blocks.codeBlock.detect(trimmed);
      if (codeBlockCheck) {
        if (codeBlockCheck.type === 'code-fence-start') {
          if (!inCodeBlock) {
            // Start code block
            inCodeBlock = true;
            codeLang = codeBlockCheck.language || 'text';
            codeFence = codeBlockCheck.fence || '```';
            codeLines = [];
          } else {
            // End code block
            inCodeBlock = false;
            content.push({
              type: 'code',
              language: codeLang,
              content: codeLines.join('\n')
            });
            codeLines = [];
            codeLang = '';
            codeFence = '```';
          }
          continue;
        } else if (codeBlockCheck.type === 'code-indented' && !inCodeBlock) {
          // Indented code (4 spaces or tab)
          content.push({
            type: 'code',
            language: 'text',
            content: codeBlockCheck.content
          });
          continue;
        }
      }

      if (inCodeBlock) {
        codeLines.push(line);
        continue;
      }

      // HTML block detection
      const htmlCheck = MarkdownSyntax.blocks.html.detect(trimmed);
      if (htmlCheck) {
        if (!inHtml) {
          inHtml = true;
          htmlLines = [line];
        } else {
          htmlLines.push(line);
        }
        
        // Check if HTML block ends (closing tag)
        if (trimmed.match(/<\/[a-z][a-z0-9-]*\s*>/i) || trimmed === '-->') {
          inHtml = false;
          content.push({
            type: 'html',
            content: htmlLines.join('\n')
          });
          htmlLines = [];
        }
        continue;
      }

      if (inHtml) {
        htmlLines.push(line);
        continue;
      }

      // Heading detection (using dictionary - supports both ATX and Setext)
      const headingCheck = MarkdownSyntax.blocks.heading.detect(trimmed, nextLine?.trim());
      if (headingCheck) {
        const text = headingCheck.content;
        const level = headingCheck.level;
        
        const headingHtml = this.parseInline(text);

        if (level === 1) {
          if (!title) title = text;
          content.push({ type: 'h1', content: text, html: headingHtml });
        } else if (level === 2) {
          if (!subtitle && title) subtitle = text;
          content.push({ type: 'h2', content: text, html: headingHtml });
        } else if (level === 3) {
          content.push({ type: 'h3', content: text, html: headingHtml });
        } else if (level === 4) {
          content.push({ type: 'h4', content: text, html: headingHtml });
        } else if (level === 5) {
          content.push({ type: 'h5', content: text, html: headingHtml });
        } else if (level === 6) {
          content.push({ type: 'h6', content: text, html: headingHtml });
        }
        
        // Skip next line if Setext style
        if (headingCheck.style === 'setext') {
          i++;
        }
        continue;
      }

      // Horizontal rule detection
      const hrCheck = MarkdownSyntax.blocks.hr.detect(trimmed);
      if (hrCheck) {
        content.push({ type: 'hr' });
        continue;
      }

      // Task list detection (GFM)
      const taskCheck = MarkdownSyntax.blocks.taskList.detect(trimmed);
      if (taskCheck) {
        content.push({
          type: 'task-list',
          checked: taskCheck.checked,
          content: taskCheck.content,
          html: this.parseInline(taskCheck.content)
        });
        continue;
      }

      // Table detection (GFM)
      const tableCheck = MarkdownSyntax.blocks.table.detect(trimmed);
      if (tableCheck) {
        inTable = true;
        if (tableCheck.type === 'table-row') {
          tableRows.push(tableCheck.cells);
        }
        continue;
      }

      // List detection (using dictionary - supports -, *, +, and numbered)
      const listCheck = MarkdownSyntax.blocks.list.detect(trimmed);
      if (listCheck) {
        if (listCheck.ordered) {
          content.push({
            type: 'numbered-item',
            number: listCheck.number,
            content: listCheck.content,
            html: this.parseInline(listCheck.content)
          });
        } else {
          content.push({
            type: 'list-item',
            marker: listCheck.marker,
            content: listCheck.content,
            html: this.parseInline(listCheck.content)
          });
        }
        continue;
      }

      // Blockquote detection (using dictionary - supports nested >)
      const blockquoteCheck = MarkdownSyntax.blocks.blockquote.detect(trimmed);
      if (blockquoteCheck) {
        inBlockquote = true;
        blockquoteLines.push(blockquoteCheck.content);
        continue;
      }

      // Image detection (inline pattern)
      if (trimmed.match(MarkdownSyntax.inline.image.patterns[0].regex)) {
        const match = trimmed.match(/!\[([^\]]*)\]\(([^)\s]+)(?:\s+"([^"]+)")?\)/);
        content.push({
          type: 'image',
          alt: match[1] || '',
          src: match[2],
          title: match[3] || ''
        });
        continue;
      }

      // Link detection (inline pattern)
      if (trimmed.match(MarkdownSyntax.inline.link.patterns[0].regex)) {
        const match = trimmed.match(/\[([^\]]+)\]\(([^)\s]+)(?:\s+"([^"]+)")?\)/);
        content.push({
          type: 'link',
          text: match[1],
          url: match[2],
          title: match[3] || '',
          html: this.parseInline(match[0])
        });
        continue;
      }

      // Regular text/paragraph (with inline formatting)
      if (trimmed) {
        content.push({
          type: 'text',
          content: trimmed,
          html: this.parseInline(trimmed)
        });
      }
    }

    // Flush remaining blocks
    if (blockquoteLines.length > 0) {
      const quoteText = blockquoteLines.join('\n');
      content.push({
        type: 'blockquote',
        content: quoteText,
        html: this.parseInline(quoteText)
      });
    }
    if (tableRows.length > 0) {
      content.push({
        type: 'table',
        rows: tableRows
      });
    }
    if (htmlLines.length > 0) {
      content.push({
        type: 'html',
        content: htmlLines.join('\n')
      });
    }

    const normalizedTitle = title ? title.trim() : '';

    return {
      index,
      title: normalizedTitle,
      subtitle: subtitle || '',
      content,
      duration: customDuration !== null ? customDuration : this.calculateDuration(content)
    };
  }

  /**
   * Calculate recommended duration for slide based on content
   */
  calculateDuration(content) {
    let duration = 3; // Base duration in seconds

    content.forEach(item => {
      switch (item.type) {
        case 'h1':
          duration += 2;
          break;
        case 'h2':
        case 'h3':
          duration += 1.5;
          break;
        case 'h4':
        case 'h5':
        case 'h6':
          duration += 1;
          break;
        case 'list-item':
        case 'numbered-item':
        case 'task-list':
          duration += 1;
          break;
        case 'code':
          const lines = item.content.split('\n').length;
          duration += Math.min(lines * 0.5, 10); // Max 10 seconds for code
          break;
        case 'blockquote':
          const words = item.content.split(' ').length;
          duration += words * 0.4; // Quotes need more reading time
          break;
        case 'text':
          const textWords = item.content.split(' ').length;
          duration += textWords * 0.3; // ~200 words per minute
          break;
        case 'image':
          duration += 3;
          break;
        case 'table':
          const rows = item.rows ? item.rows.length : 1;
          duration += rows * 1.5; // Tables need time to understand
          break;
        case 'html':
          duration += 2; // HTML content
          break;
        case 'hr':
          duration += 0.5; // Separator
          break;
        default:
          duration += 1;
      }
    });

    return Math.round(duration);
  }

  /**
   * Parse inline markdown (bold, italic, code, strikethrough, etc.)
   * Uses Markdown Dictionary for comprehensive syntax support
   */
  parseInline(text) {
    if (!text) return '';
    
    // Use the dictionary's parseInline function
    return parseInline(text);
  }

  /**
   * Get summary of parsed markdown
   */
  getSummary(slides) {
    const totalPages = slides.reduce((sum, slide) => {
      return sum + (slide.totalPages || 1);
    }, 0);
    
    return {
      totalSlides: slides.length,
      totalPages: totalPages,
      estimatedDuration: slides.reduce((sum, slide) => sum + slide.duration, 0),
      titles: slides.map(slide => slide.title),
      paginatedSlides: slides.filter(s => s.totalPages > 1).length
    };
  }
  
  /**
   * Get pagination info for a slide without parsing
   */
  getPaginationPreview(slideContent) {
    return getPaginationInfo(slideContent);
  }
}

// Export helper function
export function parseMarkdown(markdown, options = {}) {
  const parser = new MarkdownParser(options);
  return parser.parse(markdown);
}