www-lib-markdown/js/markdown.js

class MDState {
	/** @var {object} */
	abbreviations = {};

	/** @var {object} */
	footnotes = {};
}

class MDConfig {

}

class MDBlock {
	/**
	 * @returns {String} HTML
	 */
	toHTML(config, state) {
		throw new Error("toHTML not implemented");
	}
}

class MDHTMLBlock extends MDBlock {
	/** @var {String} html */
	html;

	/**
	 * @param {String} html
	 */
	constructor(html) {
		super();
		this.html = html;
	}

	toHTML = (config, state) => this.html;
}

class MDHTMLWrappedBlock extends MDBlock {
	/** @var {String} */
	#beforeHTML;
	/** @var {MDBlock} */
	#content;
	/** @var {String} */
	#afterHTML;

	/**
	 * @param {String} beforeHTML
	 * @param {MDBlock} content
	 * @param {String} afterHTML
	 */
	constructor(beforeHTML, content, afterHTML) {
		super();
		if (!(content instanceof MDBlock)) {
			throw new Error("content is of type " + typeof(content) + " instead of MDBlock");
		}
		this.#beforeHTML = beforeHTML;
		this.#content = content;
		this.#afterHTML = afterHTML;
	}

	toHTML(config, state) {
		return this.#beforeHTML + this.#content.toHTML() + this.#afterHTML;
	}
}

class MDInlineBlock extends MDBlock {
	/** @var {String} */
	#html;

	/**
	 * @param {String} line
	 */
	constructor(line) {
		super();
		this.#html = line;
	}

	toHTML = (config, state) => "inline:" + this.#html;
}

class MDUnprocessedLinesBlock extends MDBlock {
	/** @var {MDBlock[]} */
	#blocks = [];

	/**
	 * @param {String[]} lines
	 */
	constructor(lines) {
		super();
		// Find markers that always start a new block
		let blockQuoteBlocks = MDUnprocessedLinesBlock.findBlockQuote(lines);
		if (blockQuoteBlocks) {
			this.#blocks = blockQuoteBlocks;
			return;
		}
		let headerBlocks = MDUnprocessedLinesBlock.findHeader(lines);
		if (headerBlocks) {
			this.#blocks = headerBlocks;
			return;
		}
		let codeLines = MDUnprocessedLinesBlock.findTickCodeBlock(lines);
		if (codeLines) {
			this.#blocks = codeLines;
			return;
		}
		let codeLines0 = MDUnprocessedLinesBlock.findIndentCodeBlock(lines);
		if (codeLines0) {
			this.#blocks = codeLines0;
			return;
		}
		// Find runs of contiguous non-blank lines
		var contiguousLines = [];
		let blankRegex = /^\s*$/;
		for (const line of lines) {
			if (blankRegex.exec(line)) {
				if (contiguousLines.length > 0) {
					this.#blocks.push(new MDContiguousUnprocessedLinesBlock(contiguousLines));
				}
				contiguousLines = [];
			} else {
				contiguousLines.push(line);
			}
		}
		if (contiguousLines.length > 0) {
			this.#blocks.push(new MDContiguousUnprocessedLinesBlock(contiguousLines));
		}
	}

	/**
	 * @param {String[]} lines
	 * @returns {MDBlock[]} up to 3 blocks for the unprocessed lines and the blockquoted content, or null if not found
	 */
	static findBlockQuote(lines) {
		var portion = 0;
		var beforeLines = [];
		var blockQuoteLines = [];
		var afterLines = [];
		for (const line of lines) {
			switch (portion) {
				case 0:
					if (line.startsWith(">")) {
						blockQuoteLines.push(line.substring(1));
						portion = 1;
					} else {
						beforeLines.push(line);
					}
					break;
				case 1:
					if (line.startsWith(">")) {
						blockQuoteLines.push(line.substring(1));
					} else {
						afterLines.push(line);
						portion = 2;
					}
					break;
				case 2:
					afterLines.push(line);
					break;
			}
		}
		if (blockQuoteLines.length == 0) {
			return null;
		}
		var blocks = [];
		if (beforeLines.length > 0) {
			blocks.push(new MDUnprocessedLinesBlock(beforeLines));
		}
		blocks.push(new MDHTMLWrappedBlock(
			"<blockquote>\n",
			new MDUnprocessedLinesBlock(Markdown.trimEvenly(blockQuoteLines)),
			"</blockquote>\n"));
		if (afterLines.length > 0) {
			blocks.push(new MDUnprocessedLinesBlock(afterLines));
		}
		return blocks;
	}

	/**
	 * @param {String[]} lines
	 * @returns {MDBlock[]} up to 3 blocks for the unprocessed lines and the header content, or null if not found
	 */
	static findHeader(lines) {
		var portion = 0;
		var beforeLines = [];
		var headerBlock = null;
		var afterLines = [];
		for (const line of lines) {
			let hashMatch = /^\s*(#{1,6})\s*(.*)$/.exec(line);
			let dashMatch = /^(-+|=+)$/.exec(line);
			switch (portion) {
				case 0:
					if (hashMatch) {
						let headerLevel = hashMatch[1].length;
						let contentMarkdown = hashMatch[2];
						headerBlock = new MDHTMLWrappedBlock('<h' + headerLevel + '>', new MDInlineBlock(contentMarkdown), '</h' + headerLevel + ">\n");
						portion = 1;
					} else if (dashMatch && beforeLines.length > 1) {
						let contentMarkdown = beforeLines.pop();
						let headerLevel = dashMatch[1].startsWith("=") ? 1 : 2;
						headerBlock = new MDHTMLWrappedBlock('<h' + headerLevel + '>', new MDInlineBlock(contentMarkdown), '</h' + headerLevel + ">\n");
						portion = 1;
					} else {
						beforeLines.push(line);
					}
					break;
				case 1:
					afterLines.push(line);
					break;
			}
		}
		if (headerBlock == null) {
			return null;
		}
		var blocks = [];
		if (beforeLines.length > 0) {
			blocks.push(new MDUnprocessedLinesBlock(beforeLines));
		}
		blocks.push(headerBlock);
		if (afterLines.length > 0) {
			blocks.push(new MDUnprocessedLinesBlock(afterLines));
		}
		return blocks;
	}

	/**
	 * @param {String[]} lines
	 * @returns {MDBlock[]} up to 3 blocks for the unprocessed lines and the code content, or null if not found
	 */
	static findTickCodeBlock(lines) {
		var portion = 0;
		var beforeLines = [];
		var codeLines = [];
		var afterLines = [];
		for (const line of lines) {
			switch (portion) {
				case 0:
					if (/^\s*```\s*$/.exec(line)) {
						portion = 1;
					} else {
						beforeLines.push(line);
					}
					break;
				case 1:
					if (/^\s*```\s*$/.exec(line)) {
						portion = 2;
					} else {
						codeLines.push(line);
					}
					break;
				case 2:
					afterLines.push(line);
					break;
			}
		}
		if (codeLines.length == 0) return null;
		var blocks = [];
		if (beforeLines.length > 0) {
			blocks.push(new MDUnprocessedLinesBlock(beforeLines));
		}
		blocks.push(new MDHTMLWrappedBlock("<pre>", MDHTMLBlock(codeLines.join("\n")), "</pre>\n"));
		if (afterLines.length > 0) {
			blocks.push(new MDUnprocessedLinesBlock(afterLines));
		}
		return blocks;
	}

	/**
	 * @param {String[]} lines
	 * @returns {MDBlock[]} up to 3 blocks for the unprocessed lines and the code content, or null if not found
	 */
	static findIndentCodeBlock(lines) {
		var portion = 0;
		var beforeLines = [];
		var codeLines = [];
		var afterLines = [];
		let regex = /^(\s{4,})(.*)$/;
		var minIndent = 999999;
		for (const line of lines) {
			let indentMatch = regex.exec(line);
			switch (portion) {
				case 0:
					if (indentMatch) {
						minIndent = Math.min(minIndent, indentMatch[1].length);
						codeLines.push(line);
						portion = 1;
					} else {
						beforeLines.push(line);
					}
					break;
				case 1:
					if (indentMatch) {
						minIndent = Math.min(minIndent, indentMatch[1].length);
						codeLines.push(line);
					} else {
						afterLines.push(line);
						portion = 2;
					}
					break;
				case 2:
					afterLines.push(line);
					break;
			}
		}
		if (codeLines.length == 0) return null;
		var blocks = [];
		if (beforeLines.length > 0) {
			blocks.push(new MDUnprocessedLinesBlock(beforeLines));
		}
		blocks.push(new MDHTMLWrappedBlock("<pre>", new MDHTMLBlock(codeLines.map((l) => l.substring(minIndent)).join("\n")), "</pre>\n"));
		if (afterLines.length > 0) {
			blocks.push(new MDUnprocessedLinesBlock(afterLines));
		}
		return blocks;
	}

	toHTML(config, state) {
		var html = "";
		for (const block of this.#blocks) {
			html += block.toHTML() + "\n";
		}
		return html;
	}
}

class MDContiguousUnprocessedLinesBlock extends MDBlock {
	/** @var {MDBlock[]} */
	#blocks;

	/**
	 * @param {String[]} lines
	 */
	constructor(lines) {
		super();
		this.#blocks = [ new MDHTMLWrappedBlock('<p>contiguous: ', new MDInlineBlock(lines.join(' ')), "</p>\n\n") ];
	}

	toHTML(config, state) {
		var html = "";
		for (const block of this.#blocks) {
			html += block.toHTML() + "\n";
		}
		return html;
	}
}

class Markdown {
	/**
	 * @param  {String} markdown
	 * @returns {String} HTML
	 */
	static toHTML(markdown, config=new MDConfig()) {
		// Blocks that immediately start a new block
		// - Headers
		// - Blockquote
		// - Code block   ```\ncode\n```
		// Blocks that need blank line first
		// - HR   ---   - - -   ***   * * * * * *
		// - Lists
		// - Table
		// - Code block   [4+spaces]code
		// - Definition list   term\n: definition\n: alternate def
		// Unknown blocks
		// - Footnotes   some text[^1]   [^1]: first footnote content
		// - Abbreviations   *[HTML]: Hyper Text
		// Inline styles
		// - Links
		// - Italic
		// - Bold
		// - `code`
		// - Strikethrough
		// - Images   ![alt text](url){.cssclass}
		// - Literals   \*

		let state = new MDState();
		let lines = markdown.trim().replace("\r", "").split("\n");
		return new MDUnprocessedLinesBlock(lines).toHTML(config, state);
	}

	/**
	 * @param {String[]} lines
	 * @returns {String[]}
	 */
	static trimEvenly(lines) {
		var minIndent = 999999;
		let regex = /^(\s*)($|\S.*$)/;
		for (const line of lines) {
			let groups = regex.exec(line);
			let indent = groups[1].length;
			if (groups[2].trim().length > 0 && indent < 4) {
				minIndent = Math.min(minIndent, indent);
			}
		}
		if (minIndent == 0) return lines;
		var trimmed = [];
		let trimRegex = new RegExp(`^\s{${minIndent}}`);
		for (const line of lines) {
			trimmed.push(line.replace(trimRegex, ''));
		}
		return trimmed;
	}
}