Markdown Subset to HTML Converter

import re import html def markdown_to_html(markdown_text: str) -> str: """Convert a subset of Markdown into HTML. Supported features: - Headers (# .. ######) - Unordered lists with 2-space nesting - Fenced code blocks (```) - Paragraphs - Inline: ***bold+italic***, **bold**, *italic* """ def escape(text: str) -> str: # Escape HTML-sensitive characters. return html.escape(text, quote=False) def process_inline(text: str) -> str: """Process inline markdown. Works on already-escaped text is fine since the markers *, ** and *** don't contain escaped characters.""" escaped = escape(text) # Order of precedence: ***, then **, then *. # Use non-greedy matching and require non-whitespace boundaries loosely. # ***text*** escaped = re.sub( r'\*\*\*(.+?)\*\*\*', r'<strong><em>\1</em></strong>', escaped, ) # **text** escaped = re.sub( r'\*\*(.+?)\*\*', r'<strong>\1</strong>', escaped, ) # *text* escaped = re.sub( r'\*(.+?)\*', r'<em>\1</em>', escaped, ) return escaped lines = markdown_text.split('\n') output = [] # State trackers in_code_block = False code_buffer = [] paragraph_buffer = [] # List stack: list of indent levels (0, 1, 2, ...) currently open list_stack = [] def flush_paragraph(): if paragraph_buffer: content = ' '.join(paragraph_buffer) output.append(f'<p>{process_inline(content)}</p>') paragraph_buffer.clear() def close_lists_to(level): """Close lists until only `level` lists remain open (level = number of open <ul>).""" while len(list_stack) > level: output.append('</li>') output.append('</ul>') list_stack.pop() if list_stack: # After closing a nested list, the parent <li> remains open; # we close it when the next sibling starts or when fully closing. pass def close_all_lists(): while list_stack: output.append('</li>') output.append('</ul>') list_stack.pop() i = 0 while i < len(lines): line = lines[i] # Code block handling if in_code_block: if line.strip().startswith('```'): # End code block code_content = '\n'.join(code_buffer) output.append(f'<pre><code>{escape(code_content)}</code></pre>') code_buffer = [] in_code_block = False else: code_buffer.append(line) i += 1 continue # Check for code block start stripped = line.strip() if stripped.startswith('```'): flush_paragraph() close_all_lists() in_code_block = True i += 1 continue # Blank line if stripped == '': flush_paragraph() close_all_lists() i += 1 continue # Header? header_match = re.match(r'^(#{1,6}) +(.*)$', line) if header_match: flush_paragraph() close_all_lists() level = len(header_match.group(1)) content = header_match.group(2).rstrip() output.append(f'<h{level}>{process_inline(content)}</h{level}>') i += 1 continue # List item? # Match leading spaces (must be even for nesting) followed by "- " list_match = re.match(r'^( *)- +(.*)$', line) if list_match: flush_paragraph() indent_spaces = len(list_match.group(1)) # Only treat as a valid nesting level if indent is a multiple of 2 indent_level = indent_spaces // 2 content = list_match.group(2) # Adjust list stack if not list_stack: # Starting fresh: first list must be at level 0 indent_level = 0 output.append('<ul>') list_stack.append(0) output.append(f'<li>{process_inline(content)}') else: current_depth = len(list_stack) - 1 # top index if indent_level > current_depth: # Open a new nested list (only go one level deeper at a time) indent_level = current_depth + 1 output.append('<ul>') list_stack.append(indent_level) output.append(f'<li>{process_inline(content)}') elif indent_level == current_depth: # Sibling at same level: close previous <li> output.append('</li>') output.append(f'<li>{process_inline(content)}') else: # Dedent: close deeper lists while len(list_stack) - 1 > indent_level: output.append('</li>') output.append('</ul>') list_stack.pop() # Also close the parent <li> that contained this nested list output.append('</li>') # Now at same level: add sibling output.append(f'<li>{process_inline(content)}') i += 1 continue # Otherwise, it's a paragraph line if list_stack: close_all_lists() paragraph_buffer.append(line.strip()) i += 1 # End of input: flush everything if in_code_block: # Unclosed code block: emit whatever we have code_content = '\n'.join(code_buffer) output.append(f'<pre><code>{escape(code_content)}</code></pre>') flush_paragraph() close_all_lists() return '\n'.join(output) if __name__ == '__main__': sample = '''# Header 1 This is a paragraph with **bold** and *italic* text. This is the same paragraph. - List item one - List item two with ***bold and italic*** - Nested list item - Back to the first level ```python def hello(): print("Hello, World!") ``` ''' print(markdown_to_html(sample))

def markdown_to_html(markdown_text: str) -> str: import re from html import escape lines = markdown_text.splitlines() out = [] paragraph_lines = [] list_stack = [] i = 0 in_code_block = False code_lines = [] def parse_inline(text: str) -> str: parts = [] i = 0 n = len(text) while i < n: if text.startswith('***', i): j = text.find('***', i + 3) if j != -1: inner = parse_inline(text[i + 3:j]) parts.append(f'<strong><em>{inner}</em></strong>') i = j + 3 continue if text.startswith('**', i): j = text.find('**', i + 2) if j != -1: inner = parse_inline(text[i + 2:j]) parts.append(f'<strong>{inner}</strong>') i = j + 2 continue if text.startswith('*', i): j = text.find('*', i + 1) if j != -1: inner = parse_inline(text[i + 1:j]) parts.append(f'<em>{inner}</em>') i = j + 1 continue parts.append(escape(text[i])) i += 1 return ''.join(parts) def flush_paragraph(): nonlocal paragraph_lines if paragraph_lines: text = ' '.join(line.strip() for line in paragraph_lines) out.append(f'<p>{parse_inline(text)}</p>') paragraph_lines = [] def close_lists_to(level: int): while len(list_stack) > level: out.append('</li>') out.append('</ul>') list_stack.pop() def handle_list_item(indent_spaces: int, content: str): level = indent_spaces // 2 if indent_spaces % 2 != 0: return False if level > len(list_stack): if level != len(list_stack) + 1: return False out.append('<ul>') list_stack.append(True) elif level < len(list_stack): close_lists_to(level) out.append('</li>') else: if list_stack: out.append('</li>') else: out.append('<ul>') list_stack.append(True) while len(list_stack) < level + 1: out.append('<ul>') list_stack.append(True) out.append(f'<li>{parse_inline(content)}') return True while i < len(lines): line = lines[i] if in_code_block: if line.startswith('```'): out.append(f'<pre><code>{escape("\n".join(code_lines))}</code></pre>') code_lines = [] in_code_block = False else: code_lines.append(line) i += 1 continue if line.startswith('```'): flush_paragraph() close_lists_to(0) in_code_block = True code_lines = [] i += 1 continue if not line.strip(): flush_paragraph() close_lists_to(0) i += 1 continue header_match = re.match(r'^(#{1,6})\s+(.*)$', line) if header_match: flush_paragraph() close_lists_to(0) level = len(header_match.group(1)) content = parse_inline(header_match.group(2).strip()) out.append(f'<h{level}>{content}</h{level}>') i += 1 continue list_match = re.match(r'^( *)(- )(.+)$', line) if list_match: flush_paragraph() indent = len(list_match.group(1)) content = list_match.group(3) if handle_list_item(indent, content): i += 1 continue if list_stack: close_lists_to(0) paragraph_lines.append(line) i += 1 if in_code_block: out.append(f'<pre><code>{escape("\n".join(code_lines))}</code></pre>') flush_paragraph() close_lists_to(0) return '\n'.join(out)