From fd503a978c435c27d782adf94b5f20b93b979f76 Mon Sep 17 00:00:00 2001
From: David <>
Date: Tue, 2 Feb 2021 14:58:39 -0600
Subject: [PATCH] Add 'Channel.all'.

---
 doc/API.md    |  8 +++++++-
 lib/index.js  | 20 ++++++++++++++++++++
 test/index.js |  6 ++++++
 3 files changed, 33 insertions(+), 1 deletion(-)

diff --git a/doc/API.md b/doc/API.md
index 8b0bfc5..baf90e4 100644
--- a/doc/API.md
+++ b/doc/API.md
@@ -4,6 +4,7 @@
   - [close() -> (async)](#close-async)
   - [readOnly() -> Channel](#readonly-channel)
   - [writeOnly() -> Channel](#writeonly-channel)
+  - [Channel.all(channels) -> Channel](#channelallchannels-channel)
   - [Channel.select(promises) -> (async) channel](#channelselectpromises-async-channel)
     - [Examples](#examples)
   - [value()](#value)
@@ -44,7 +45,7 @@ The following properties don't have equivalents in `Array`.
 Close the channel so that no more values can be pushed to it. Return a promise
 that resolves when any remaining pushes in flight complete.
 
-Attempting to push to a closed channel will throw an exception and shifting from
+Attempting to push to a closed channel will throw an exception. Shifting from
 a closed channel will immediately return `undefined`.
 
 ## readOnly() -> Channel
@@ -55,6 +56,11 @@ Return a version of the channel that provides only read methods.
 
 Return a version of the channel that provides only write methods.
 
+## Channel.all(channels) -> Channel
+
+Take an array of channels and wait for the next value in each one before pushing
+an array of the values to a newly created channel. Similar to `Promise.all`.
+
 ## Channel.select(promises) -> (async) channel
 
 Wait for the first channel method promise to succeed and then cancel the rest.
diff --git a/lib/index.js b/lib/index.js
index f2629c2..f33180d 100644
--- a/lib/index.js
+++ b/lib/index.js
@@ -364,6 +364,26 @@ const Channel = function(length = 0) {
   );
 };
 
+Channel.all = channels => {
+  const output = Channel();
+
+  (async () => {
+    for (;;) {
+      const values = await Promise.all(channels.map(Channel.shift));
+
+      if (values.every(value => value === undefined)) {
+        break;
+      } else {
+        await output.push(values);
+      }
+    }
+
+    await output.close();
+  })();
+
+  return output;
+};
+
 // Node.js stream.readable
 const fromNodeStream = (channel, stream) => {
   stream.on(`readable`, async () => {
diff --git a/test/index.js b/test/index.js
index 4813f4d..0aac8f0 100644
--- a/test/index.js
+++ b/test/index.js
@@ -44,6 +44,12 @@ describe(`Channel function`, function() {
     assert.deepEqual(await channel.values(), [0, 1, 2]);
   });
 
+  it(`all`, async function() {
+    const a = Channel.of(0, 1);
+    const b = Channel.of(2, 3);
+    assert.deepEqual(await Channel.all([a, b]).values(), [[0, 2], [1, 3]]);
+  });
+
   describe(`from`, function() {
     describe(`types`, function() {
       it(`callback`, async function() {