feat: HTML to markdown parser

__tests__/ExpensiMark-test.js

@@ -338,3 +338,30 @@ test('Test markdown and url links with inconsistent starting and closing parens'
 
     expect(parser.replace(testString)).toBe(resultString);
 });
+
+test('Test HTML string with <br/> tags to markdown ', () => {
+    const testString = 'Hello<br/>World,<br/>Welcome<br/>To<br/>Expensify';
+    const resultString = 'Hello\nWorld,\nWelcome\nTo\nExpensify';
+
+    expect(parser.htmlToMarkdown(testString)).toBe(resultString);
+});
+
+test('Test HTML string with inconsistent <br/> closing tags to markdown ', () => {
+    const testString = 'Hello<br>World,<br/>Welcome<br>To<br/>Expensify';
+    const resultString = 'Hello\nWorld,\nWelcome\nTo\nExpensify';
+
+    expect(parser.htmlToMarkdown(testString)).toBe(resultString);
+});
+
+test('Test HTML string with seperate closing tags (<br><br/>) to markdown ', () => {
+    const testString = 'Hello<br>World,<br><br/>Welcome<br/>To<br/>Expensify';
+    const resultString = 'Hello\nWorld,\nWelcome\nTo\nExpensify';
+
+    expect(parser.htmlToMarkdown(testString)).toBe(resultString);
+});
+
+test('Test HTML string with seperate closing tags (<br></br>) to markdown ', () => {
+    const testString = 'Hello<br>World,<br></br>Welcome<br/>To<br/>Expensify';
+    const resultString = 'Hello\nWorld,\nWelcome\nTo\nExpensify';
+    expect(parser.htmlToMarkdown(testString)).toBe(resultString);
+});

lib/ExpensiMark.js

@@ -157,6 +157,22 @@ export default class ExpensiMark {
                 replacement: '<br>',
             },
         ];
+
+        /**
+         * The list of regex replacements to do on a HTML comment for converting it to markdown.
+         *
+         * @type {Object[]}
+         */
+        this.htmlToMarkdownRules = [
+            {
+                name: 'newline',
+
+                // Replaces open and closing <br><br/> tags with a single <br/>
+                pre: inputString => inputString.replace('<br></br>', '<br/>').replace('<br><br/>', '<br/>'),
+                regex: /<br\s*[/]?>/gi,
+                replacement: '\n'
+            },
+        ];
     }
 
     /**
@@ -250,4 +266,23 @@ export default class ExpensiMark {
 
         return replacedText;
     }
+
+    /**
+     * Replaces HTML with markdown
+     *
+     * @param {String} htmlString
+     *
+     * @returns {String}
+     */
+    htmlToMarkdown(htmlString) {
+        let generatedMarkdown = htmlString;
+        this.htmlToMarkdownRules.forEach((rule) => {
+            // Pre-processes input HTML before applying regex
+            if (rule.pre) {
+                generatedMarkdown = rule.pre(generatedMarkdown);
+            }
+            generatedMarkdown = generatedMarkdown.replace(rule.regex, rule.replacement);
+        });
+        return generatedMarkdown;
+    }
 }