From 530170b789d7734d2b70fde7d59abb1ebf8a582c Mon Sep 17 00:00:00 2001
From: Gary Katsevman <git@gkatsev.com>
Date: Fri, 14 Apr 2023 12:12:30 -0400
Subject: [PATCH] feat: add currentPdt getter and getStartDate() method (#661)

---
 packages/mux-audio/src/index.ts         |  10 ++
 packages/mux-audio/test/player.test.js  |  27 +++++
 packages/mux-player/REFERENCE.md        |   3 +
 packages/mux-player/src/index.ts        |   8 ++
 packages/mux-player/test/player.test.js |  34 ++++++
 packages/mux-video/src/index.ts         |  10 ++
 packages/mux-video/test/index.test.js   |  27 +++++
 packages/playback-core/src/index.ts     |   3 +
 packages/playback-core/src/pdt.ts       |  37 ++++++
 packages/playback-core/test/pdt.test.js | 145 ++++++++++++++++++++++++
 10 files changed, 304 insertions(+)
 create mode 100644 packages/playback-core/src/pdt.ts
 create mode 100644 packages/playback-core/test/pdt.test.js

diff --git a/packages/mux-audio/src/index.ts b/packages/mux-audio/src/index.ts
index e500e23d3..edc651dd2 100644
--- a/packages/mux-audio/src/index.ts
+++ b/packages/mux-audio/src/index.ts
@@ -10,6 +10,8 @@ import {
   toMuxVideoURL,
   Metadata,
   MediaError,
+  getStartDate,
+  getCurrentPdt,
 } from '@mux/playback-core';
 import type { PlaybackCore, PlaybackEngine, ExtensionMimeTypeMap } from '@mux/playback-core';
 import { getPlayerVersion } from './env';
@@ -231,6 +233,14 @@ class MuxAudioElement extends CustomAudioElement<HTMLAudioElement> implements Pa
     }
   }
 
+  getStartDate() {
+    return getStartDate(this.nativeEl, this._hls);
+  }
+
+  get currentPdt() {
+    return getCurrentPdt(this.nativeEl, this._hls);
+  }
+
   get preferPlayback(): ValueOf<PlaybackTypes> | undefined {
     const val = this.getAttribute(Attributes.PREFER_PLAYBACK);
     if (val === PlaybackTypes.MSE || val === PlaybackTypes.NATIVE) return val;
diff --git a/packages/mux-audio/test/player.test.js b/packages/mux-audio/test/player.test.js
index 19d94f10f..d1fee2b93 100644
--- a/packages/mux-audio/test/player.test.js
+++ b/packages/mux-audio/test/player.test.js
@@ -103,4 +103,31 @@ describe('<mux-audio>', () => {
     assert.equal(player.metadata.sub_property_id, 'sub-id-12');
     assert.equal(player.metadata.video_id, playbackId);
   });
+
+  it('currentPdt and getStartDate work as expected', async function () {
+    this.timeout(5000);
+
+    const player = await fixture(`<mux-audio
+      src="https://stream.mux.com/UgKrPYAnjMjP6oMF4Kcs1gWVhtgYDR02EHQGnj022X1Xo.m3u8"
+      env-key="ilc02s65tkrc2mk69b7q2qdkf"
+      prefer-playback="mse"
+      muted
+      preload="auto"
+    ></mux-player>`);
+
+    await aTimeout(1000);
+
+    player.currentTime = 60;
+
+    await aTimeout(50);
+
+    const currentPdt = player.currentPdt;
+    const startDate = player.getStartDate();
+
+    assert.equal(
+      startDate.getTime(),
+      currentPdt.getTime() - player.currentTime * 1000,
+      'currentPdt should be ~60 seconds greater than getStartDate'
+    );
+  });
 });
diff --git a/packages/mux-player/REFERENCE.md b/packages/mux-player/REFERENCE.md
index d0d59f1a4..b47170be1 100644
--- a/packages/mux-player/REFERENCE.md
+++ b/packages/mux-player/REFERENCE.md
@@ -58,6 +58,8 @@
 | `play()`  | Identical to the [native `play()` method](https://developer.mozilla.org/en-US/docs/Web/API/HTMLMediaElement/play).   |
 | `pause()` | Identical to the [native `pause()` method](https://developer.mozilla.org/en-US/docs/Web/API/HTMLMediaElement/pause). |
 | `addCuePoints()` | Add an array of metadata CuePoints of "shape" `{ time: number; value: any; }` to the Mux Player instance for the current media |
+| `getStartDate()` | Will return a Date that matches the earliest PDT in your stream. Identical to [native `getStartDate()` method](https://html.spec.whatwg.org/multipage/media.html#dom-media-getstartdate), if exists. |
+|
 
 <!-- UNDOCUMENTED
 | `addTextTrack()` | Identical to the [native `addTextTrack()` method](https://developer.mozilla.org/en-US/docs/Web/API/HTMLMediaElement#methods). |
@@ -77,6 +79,7 @@
 | `videoWidth` <sub><sup>Read only</sup></sub>   | `number`                                                                                                                        | Identical to the [native `videoWidth` property](https://developer.mozilla.org/en-US/docs/Web/API/HTMLVideoElement/videoWidth)                                                                                                                                                                                                                                                                    | `0`                              |
 | `videoHeight` <sub><sup>Read only</sup></sub>  | `number` | Identical to the [native `videoHeight` property](https://developer.mozilla.org/en-US/docs/Web/API/HTMLVideoElement/videoHeight) | `0`                                                                                                                                                                                                                                                                                                                                                                                              |
 | `currentTime`                                  | `number`                                                                                                                        | Identical to the [native `currentTime` property](https://developer.mozilla.org/en-US/docs/Web/API/HTMLMediaElement/currentTime)                                                                                                                                                                                                                                                                  | `0`                              |
+| `currentPdt`                                   | `Date`                                                                                                                        | Will return a Date that matches current PDT in your stream. Accounting for currentTime.                                                                                                                                                                                                                                                                  | `0`                              |
 | `volume`                                       | `number` | Identical to the [native `volume` property](https://developer.mozilla.org/en-US/docs/Web/API/HTMLMediaElement/volume)           | `1`                                                                                                                                                                                                                                                                                                                                                                                              |
 | `poster`                                       | `string` (URL)                                                                                                                  | Identical to the [native `poster` property](https://developer.mozilla.org/en-US/docs/Web/API/HTMLVideoElement#properties). Will use the automatically generated poster based on your `playback-id` by default. Remove the poster by setting the value to an empty string.                                                                                                                                                                                   | Derived                          |
 | `storyboard`                                   | `string` (URL)                                                                                                                  | URL for the [Mux Storyboard](https://docs.mux.com/guides/video/create-timeline-hover-previews). Will automatically generate the url based on your `playback-id` and token. Will not be set if the provided storyboardToken is invalid.                                                                                                                                                                                   | Derived                          |
diff --git a/packages/mux-player/src/index.ts b/packages/mux-player/src/index.ts
index 09339b72b..dbf3bf277 100644
--- a/packages/mux-player/src/index.ts
+++ b/packages/mux-player/src/index.ts
@@ -1326,6 +1326,14 @@ class MuxPlayerElement extends VideoApiElement implements MuxPlayerElement {
     return this.media?.cuePoints ?? [];
   }
 
+  getStartDate() {
+    return this.media?.getStartDate();
+  }
+
+  get currentPdt() {
+    return this.media?.currentPdt;
+  }
+
   /**
    * Get the signing tokens for the Mux asset URL's.
    */
diff --git a/packages/mux-player/test/player.test.js b/packages/mux-player/test/player.test.js
index e63be67a9..3fc65f33f 100644
--- a/packages/mux-player/test/player.test.js
+++ b/packages/mux-player/test/player.test.js
@@ -1266,3 +1266,37 @@ describe.skip('Feature: cuePoints', async () => {
     assert.equal(muxPlayerEl.cuePoints.length, 0, 'cuePoints should be empty');
   });
 });
+
+describe('currentPdt and getStartDate', async () => {
+  it('currentPdt and getStartDate work as expected', async function () {
+    this.timeout(5000);
+
+    const player = await fixture(`<mux-player
+      env-key="ilc02s65tkrc2mk69b7q2qdkf"
+      stream-type="on-demand"
+      prefer-playback="mse"
+      muted
+      title="A title"
+      preload="auto"
+    ></mux-player>`);
+
+    player.addEventListener('loadstart', async function () {
+      player.currentTime = 60;
+
+      await aTimeout(50);
+
+      const currentPdt = player.currentPdt;
+      const startDate = player.getStartDate();
+
+      assert.equal(
+        startDate.getTime(),
+        currentPdt.getTime() - player.currentTime * 1000,
+        'currentPdt should be 60 seconds greater than getStartDate'
+      );
+    });
+
+    await aTimeout(50);
+
+    player.playbackId = 'UgKrPYAnjMjP6oMF4Kcs1gWVhtgYDR02EHQGnj022X1Xo';
+  });
+});
diff --git a/packages/mux-video/src/index.ts b/packages/mux-video/src/index.ts
index 52dbb8a2c..a09d5162e 100644
--- a/packages/mux-video/src/index.ts
+++ b/packages/mux-video/src/index.ts
@@ -15,6 +15,8 @@ import {
   addCuePoints,
   getCuePoints,
   getActiveCuePoint,
+  getStartDate,
+  getCurrentPdt,
   getStreamType,
   getTargetLiveWindow,
   getLiveEdgeStart,
@@ -424,6 +426,14 @@ class MuxVideoElement extends CustomVideoElement<HTMLVideoElement> implements Pa
     return getCuePoints(this.nativeEl);
   }
 
+  getStartDate() {
+    return getStartDate(this.nativeEl, this._hls);
+  }
+
+  get currentPdt() {
+    return getCurrentPdt(this.nativeEl, this._hls);
+  }
+
   get preferPlayback(): ValueOf<PlaybackTypes> | undefined {
     const val = this.getAttribute(Attributes.PREFER_PLAYBACK);
     if (val === PlaybackTypes.MSE || val === PlaybackTypes.NATIVE) return val;
diff --git a/packages/mux-video/test/index.test.js b/packages/mux-video/test/index.test.js
index 51f719a65..284c96707 100644
--- a/packages/mux-video/test/index.test.js
+++ b/packages/mux-video/test/index.test.js
@@ -198,6 +198,33 @@ describe('<mux-video>', () => {
     assert.equal(player.metadata.video_id, playbackId);
   });
 
+  it('currentPdt and getStartDate work as expected', async function () {
+    this.timeout(5000);
+
+    const player = await fixture(`<mux-video
+      src="https://stream.mux.com/UgKrPYAnjMjP6oMF4Kcs1gWVhtgYDR02EHQGnj022X1Xo.m3u8"
+      env-key="ilc02s65tkrc2mk69b7q2qdkf"
+      prefer-playback="mse"
+      muted
+      preload="auto"
+    ></mux-player>`);
+
+    await aTimeout(1000);
+
+    player.currentTime = 60;
+
+    await aTimeout(50);
+
+    const currentPdt = player.currentPdt;
+    const startDate = player.getStartDate();
+
+    assert.equal(
+      startDate.getTime(),
+      currentPdt.getTime() - player.currentTime * 1000,
+      'currentPdt should be ~60 seconds greater than getStartDate'
+    );
+  });
+
   describe('Feature: cuePoints', async () => {
     it('adds cuepoints', async () => {
       const cuePoints = [
diff --git a/packages/playback-core/src/index.ts b/packages/playback-core/src/index.ts
index 5fae24ef3..db5a77d25 100644
--- a/packages/playback-core/src/index.ts
+++ b/packages/playback-core/src/index.ts
@@ -16,6 +16,7 @@ import {
   setupCuePoints,
   getCuePointsTrack,
 } from './tracks';
+import { getStartDate, getCurrentPdt } from './pdt';
 import {
   inSeekableRange,
   toPlaybackIdParts,
@@ -46,6 +47,8 @@ export {
   getActiveCuePoint,
   getCuePointsTrack,
   setupCuePoints,
+  getStartDate,
+  getCurrentPdt,
 };
 export * from './types';
 
diff --git a/packages/playback-core/src/pdt.ts b/packages/playback-core/src/pdt.ts
new file mode 100644
index 000000000..093ad6306
--- /dev/null
+++ b/packages/playback-core/src/pdt.ts
@@ -0,0 +1,37 @@
+import { PlaybackEngine } from './types';
+
+type MediaWithPDT = HTMLMediaElement & { getStartDate?: () => Date };
+
+export function getStartDate(mediaEl: MediaWithPDT, hls: PlaybackEngine | undefined) {
+  if (hls) {
+    const playingDate = hls.playingDate;
+
+    if (playingDate != null) {
+      // If the video is very long and the currentTime will transition day boundaries,
+      // this may end up not being accurate
+      return new Date(playingDate.getTime() - mediaEl.currentTime * 1000);
+    }
+  }
+
+  if (typeof mediaEl.getStartDate === 'function') {
+    return mediaEl.getStartDate();
+  }
+
+  return new Date(NaN);
+}
+
+export function getCurrentPdt(mediaEl: MediaWithPDT, hls: PlaybackEngine | undefined) {
+  if (hls && hls.playingDate) {
+    return hls.playingDate;
+  }
+
+  if (typeof mediaEl.getStartDate === 'function') {
+    const startDate = mediaEl.getStartDate();
+
+    // If the video is very long and the currentTime will transition day boundaries,
+    // this may end up not being accurate
+    return new Date(startDate.getTime() + mediaEl.currentTime * 1000);
+  }
+
+  return new Date(NaN);
+}
diff --git a/packages/playback-core/test/pdt.test.js b/packages/playback-core/test/pdt.test.js
new file mode 100644
index 000000000..b59378547
--- /dev/null
+++ b/packages/playback-core/test/pdt.test.js
@@ -0,0 +1,145 @@
+import { assert, aTimeout } from '@open-wc/testing';
+import { getStartDate, getCurrentPdt } from '../src/pdt';
+
+describe('getCurrentPdt', function () {
+  describe('with hls.js', function () {
+    it('will return playingDate, if not null', function () {
+      const time = Date.now();
+      const currentPdt = getCurrentPdt(
+        {},
+        {
+          playingDate: new Date(time),
+        }
+      );
+
+      assert.equal(currentPdt.getTime(), time, 'the returned date matches the expected date');
+    });
+
+    it('will return an invalid date if playingDate is null', function () {
+      const currentPdt = getCurrentPdt(
+        {},
+        {
+          playingDate: null,
+        }
+      );
+
+      assert.isNaN(currentPdt.getTime(), "the currentPdt's getTime() is NaN, which is an invalid time");
+    });
+  });
+
+  describe('with native video', function () {
+    it('will return invalid date if no getStartDate method', function () {
+      const currentPdt = getCurrentPdt({}, {});
+
+      assert.isNaN(currentPdt.getTime(), "the currentPdt's getTime() is NaN, which is an invalid time");
+    });
+
+    it('will return getStartDate plus currentTime', function () {
+      const time = Date.now();
+      let currentPdt = getCurrentPdt(
+        {
+          currentTime: 0,
+          getStartDate() {
+            return new Date(time);
+          },
+        },
+        {}
+      );
+
+      assert.equal(
+        currentPdt.getTime(),
+        time,
+        'with a currentTime of 0, getCurrentPdt is equivalent to getStartDate time'
+      );
+
+      currentPdt = getCurrentPdt(
+        {
+          currentTime: 60,
+          getStartDate() {
+            return new Date(time);
+          },
+        },
+        {}
+      );
+
+      assert.equal(
+        currentPdt.getTime(),
+        time + 60 * 1000,
+        'with a currentTime of 0, getCurrentPdt is equivalent to getStartDate time plus 60 seconds'
+      );
+    });
+  });
+});
+
+describe('getStartDate', function () {
+  describe('with hls.js', function () {
+    it('will return a Date that is currentTime before playingDate', function () {
+      const time = Date.now();
+      let startDate = getStartDate(
+        {
+          currentTime: 0,
+        },
+        {
+          playingDate: new Date(time),
+        }
+      );
+
+      assert.equal(
+        startDate.getTime(),
+        time,
+        'with a currentTime of zero, the returned date is equivalent to playingDate'
+      );
+
+      startDate = getStartDate(
+        {
+          currentTime: 60,
+        },
+        {
+          playingDate: new Date(time),
+        }
+      );
+
+      assert.equal(startDate.getTime(), time - 60 * 1000, 'the returned date should be 60 seconds before playingDate');
+    });
+
+    it('will return an invalid Date if playingDate is null', function () {
+      const startDate = getStartDate(
+        {
+          currentTime: 60,
+        },
+        {
+          playingDate: null,
+        }
+      );
+
+      assert.isNaN(startDate.getTime(), 'NaN is an invalid date, when playingDate is null');
+    });
+  });
+
+  describe('with native video', function () {
+    it('will return invalid date if no getStartDate method', function () {
+      const currentPdt = getCurrentPdt({}, {});
+
+      assert.isNaN(currentPdt.getTime(), "the currentPdt's getTime() is NaN, which is an invalid time");
+    });
+
+    it('will return getStartDate', function () {
+      const time = Date.now();
+      const startDate = getStartDate(
+        {
+          currentTime: 60,
+          getStartDate() {
+            return new Date(time);
+          },
+        },
+        {}
+      );
+
+      assert.equal(
+        startDate.getTime(),
+        time,
+        'getCurrentPdt is equivalent to getStartDate time, regardless of currentTime'
+      );
+    });
+  });
+});