feat: custom tag mapping

README.md

@@ -312,6 +312,38 @@ parser.push(manifest);
 parser.end();
 parser.manifest.segments[0].custom.vodTiming // #VOD-TIMING:1511816599485
 ```
+
+Custom parsers may also map data an existing tag type.
+```js
+const manifest = [
+    '#EXTM3U',
+    '#VOD-TIMING:wallclock=1511816599485',
+    '#EXTINF:8.0,',
+    'ex1.ts',
+    ''
+  ].join('\n');
+
+const parser = new m3u8Parser.Parser();
+parser.addTagMapper({
+  expression: /#VOD-TIMING/,
+  map(line) {
+    const regex = /#VOD-TIMING:(?:wallclock=([^,\n]+))/g;
+    const match = regex.exec(line);
+
+    if (match) {
+      const ISOdate = new Date(Number(match[1])).toISOString();
+      return `#EXT-X-PROGRAM-DATE-TIME:${ISOdate}`;
+    }
+
+    return line;
+  }
+});
+
+parser.push(manifest);
+parser.end();
+parser.manifest.segments[0].dateTimeObject // #VOD-TIMING:1511816599485
+```
+
 ## Including the Parser
 
 To include m3u8-parser on your website or web application, use any of the following methods.

src/parse-stream.js

@@ -75,6 +75,7 @@ export default class ParseStream extends Stream {
   constructor() {
     super();
     this.customParsers = [];
+    this.tagMappers = [];
   }
 
   /**
@@ -103,6 +104,11 @@ export default class ParseStream extends Stream {
       return;
     }
 
+    // map tag
+    for (let i = 0; i < this.tagMappers.length; i++) {
+      line = this.tagMappers[i].call(this, line);
+    }
+
     for (let i = 0; i < this.customParsers.length; i++) {
       if (this.customParsers[i].call(this, line)) {
         return;
@@ -463,4 +469,23 @@ export default class ParseStream extends Stream {
       }
     });
   }
+
+  /**
+   * Add a custom header mapper
+   *
+   * @param {Object}   options
+   * @param {RegExp}   options.expression   a regular expression to match the custom header
+   * @param {Function} options.map          function to translate tag into a different tag
+   */
+  addTagMapper({expression, map}) {
+    const mapFn = line => {
+      if (expression.test(line)) {
+        return map(line);
+      }
+
+      return line;
+    };
+
+    this.tagMappers.push(mapFn);
+  }
 }

src/parser.js

@@ -393,4 +393,14 @@ export default class Parser extends Stream {
   addParser(options) {
     this.parseStream.addParser(options);
   }
+  /**
+   * Add a custom header mapper
+   *
+   * @param {Object}   options
+   * @param {RegExp}   options.expression   a regular expression to match the custom header
+   * @param {Function} options.map          function to translate tag into a different tag
+   */
+  addTagMapper(options) {
+    this.parseStream.addTagMapper(options);
+  }
 }

test/m3u8.test.js

@@ -85,6 +85,7 @@ QUnit.module('ParseStream', {
     this.lineStream.pipe(this.parseStream);
   }
 });
+
 QUnit.test('parses custom tags', function(assert) {
   const manifest = '#VOD-STARTTIMESTAMP:1501533337573\n';
   let element;
@@ -108,6 +109,65 @@ QUnit.test('parses custom tags', function(assert) {
   );
 });
 
+QUnit.test('maps custom tags', function(assert) {
+  const manifest = '#VOD-STARTTIMESTAMP:1501533337573\n';
+  let element;
+  let calls = 0;
+
+  this.parseStream.addTagMapper({
+    expression: /^#VOD-STARTTIMESTAMP/,
+    map(line) {
+      const match = /#VOD-STARTTIMESTAMP:(\d+)/g.exec(line);
+
+      calls++;
+
+      return `#INTERMEDIATE:${match[1]}`;
+    }
+  });
+
+  this.parseStream.addTagMapper({
+    expression: /^#INTERMEDIATE/,
+    map(line) {
+      const match = /#INTERMEDIATE:(.*)/g.exec(line)[1];
+      const ISOdate = new Date(Number(match)).toISOString();
+
+      calls++;
+
+      return `#EXT-X-PROGRAM-DATE-TIME:${ISOdate}`;
+    }
+  });
+
+  this.parseStream.on('data', function(elem) {
+    element = elem;
+  });
+
+  this.lineStream.push(manifest);
+  assert.ok(element, 'element');
+  assert.strictEqual(calls, 2);
+  assert.strictEqual(element.type, 'tag');
+  assert.strictEqual(element.dateTimeString,
+    '2017-07-31T20:35:37.573Z');
+});
+
+QUnit.test('mapper ignores tags', function(assert) {
+  const manifest = '#VOD-STARTTIMESTAMP:1501533337573\n';
+  let element;
+
+  this.parseStream.addTagMapper({
+    expression: /^#NO-MATCH/,
+    map(line) {
+      return '#MAPPED';
+    }
+  });
+
+  this.parseStream.on('data', function(elem) {
+    element = elem;
+  });
+
+  this.lineStream.push(manifest);
+  assert.strictEqual(element.text, 'VOD-STARTTIMESTAMP:1501533337573');
+});
+
 QUnit.test('parses comment lines', function(assert) {
   const manifest = '# a line that starts with a hash mark without "EXT" is a comment\n';
   let element;