bookmark spec: Markdown-to-HTML Conversion

The parser processes input text by identifying blocks, which are sequences of non-empty lines separated by one or more blank lines. Leading and trailing whitespace are trimmed from these blocks before applying conversion rules.

1. Headings:

   • Input: Lines starting with one to six # symbols, followed by a space, then the heading text.
   • Output: Converts to HTML heading tags <h1> through <h6>. The number of # symbols determines the level.
   • Example Markdown: ## Section Title
   • Example HTML Output: <h2>Section Title</h2>

2. Horizontal Rules:

   • Input: A line that begins with seven or more hyphens (e.g., -------).
   • Output: Converts to an HTML <hr> tag.
   • Example Markdown: -------
   • Example HTML Output: <hr>

3. Italic Blocks (Multi-line Emphasis):

   • Input: An entire block of text (potentially spanning multiple lines in the input, as long as they are not separated by blank lines) that starts exactly with a single underscore _ and ends exactly with a single underscore _. The content between the underscores must be non-empty after trimming.
   • Output: The content is wrapped in <em>...</em> tags. Newlines within the original italicized content are converted to <br> HTML tags. This rule takes precedence over paragraph and section number rules for a qualifying block.
   • Example Markdown: _This is an emphasized block._
   • Example HTML Output: <em>This is an<br>emphasized block.</em>

4. Section Numbers:

   • Input: A block of text starting with a number enclosed in single asterisks (e.g., *1*, *23*), possibly followed by whitespace, and then the rest of the text for that block.
   • Output: The number is wrapped in <span class="section-number">...</span>. The text following the section number (within the same block) is appended. Newlines within this appended text are converted to <br> HTML tags. This rule is checked after the Italic Block rule.
   • Example Markdown: *7* Introduction to the Topic Further details.
   • Example HTML Output: <span class="section-number">7</span>Introduction to the Topic<br>Further details.

5. Paragraphs:

   • Input: Any block of text that does not match the rules for Headings, Horizontal Rules, Italic Blocks, or Section Numbers.
   • Output: The text content is wrapped in <p>...</p> tags. Newlines within the original paragraph content are converted to <br> HTML tags.
   • Example Markdown: This is a regular paragraph. It has multiple lines.
   • Example HTML Output: <p>This is a regular paragraph.<br>It has multiple lines.</p>

Processing Order:

• The input text is split into lines.
• Lines are grouped into blocks based on blank line separators.
• For each block:
  • It's first checked if it's an Italic Block.
  • If not, it's checked if it's a Section Number.
  • If not, it's treated as a Paragraph.
• Lines starting with # (Headings) or ------- (Horizontal Rules) are treated as distinct elements and terminate the preceding block.
• The parseMarkdown function ultimately returns an array of these generated HTML string elements.