From 9293c2c6a20ff231cc39eb2338eed4ecf15b320a Mon Sep 17 00:00:00 2001
From: Gregory Hill <gregorydhill@outlook.com>
Date: Fri, 27 Mar 2020 10:49:48 +0000
Subject: [PATCH] add method to stop reading stream once header received

Signed-off-by: Gregory Hill <gregorydhill@outlook.com>
---
 CHANGELOG.md             |  6 ++++++
 NOTES.md                 |  4 ++--
 hoard-js/src/examples.ts |  4 ++++
 hoard-js/src/index.ts    | 14 ++++++++++++++
 project/history.go       |  4 ++++
 5 files changed, 30 insertions(+), 2 deletions(-)

diff --git a/CHANGELOG.md b/CHANGELOG.md
index f2c5ec9c..83cac851 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -1,4 +1,9 @@
 # [Monax Hoard](https://github.com/monax/hoard) Changelog
+## [8.2.3] - 2020-03-27
+### Added
+- ReadHeader will stop once it gets the head
+
+
 ## [8.2.2] - 2020-03-25
 ### Fixed
 - Chunk plaintext out if data too big
@@ -197,6 +202,7 @@ This is the first Hoard open source release and includes:
 	- Hoar-Daemon hoard
 	- Hoar-Control hoarctl CLI
 
+[8.2.3]: https://github.com/monax/hoard/compare/v8.2.2...v8.2.3
 [8.2.2]: https://github.com/monax/hoard/compare/v8.2.1...v8.2.2
 [8.2.1]: https://github.com/monax/hoard/compare/v8.2.0...v8.2.1
 [8.2.0]: https://github.com/monax/hoard/compare/v8.1.0...v8.2.0
diff --git a/NOTES.md b/NOTES.md
index e2c7f792..78332c81 100644
--- a/NOTES.md
+++ b/NOTES.md
@@ -1,3 +1,3 @@
-### Fixed
-- Chunk plaintext out if data too big
+### Added
+- ReadHeader will stop once it gets the head
 
diff --git a/hoard-js/src/examples.ts b/hoard-js/src/examples.ts
index 3cd28aa2..577e23c8 100644
--- a/hoard-js/src/examples.ts
+++ b/hoard-js/src/examples.ts
@@ -21,6 +21,7 @@ import {
   Write,
   PlaintextAndGrantSpec,
   Header,
+  ReadHeader,
 } from './index';
 import * as assert from 'assert';
 
@@ -103,6 +104,9 @@ export const example = async function (data: string | Uint8Array, salt: string |
     plaintext = ReducePlaintext(plaintexts);
     assert.deepStrictEqual(plaintext.toObject(), expected.toObject());
 
+    let header = await ReadHeader(hoard.unsealGet(grant));
+    assert.strictEqual(header.getSalt_asB64(), "Zm9v");
+
     // A symmetric grant allows us to encrypt the reference
     // through secrets configured on the hoard daemon
     ptgs = [
diff --git a/hoard-js/src/index.ts b/hoard-js/src/index.ts
index 52aefdb0..273b8499 100644
--- a/hoard-js/src/index.ts
+++ b/hoard-js/src/index.ts
@@ -171,6 +171,20 @@ export async function ReadUntil<T>(accum: T[], stream: grpc.ClientReadableStream
   })
 }
 
+export async function ReadHeader(stream: grpc.ClientReadableStream<Plaintext>) {
+  return new Promise<Header>((resolve, reject) => {
+    stream.on('data', (data: Plaintext) => { 
+      if (data.hasHead()) {
+        stream.cancel();
+        resolve(data.getHead());
+      }
+    });
+    stream.on('error', (err: { code: grpc.status; }) => err.code === grpc.status.CANCELLED ? resolve() : reject(err));
+    stream.on('close', () => reject("no header found"));
+    stream.on('end', () => reject("no header found"));
+  })
+}
+
 export async function Write<A, B>(input: A[], fn: (callback: grpc.requestCallback<B>) => grpc.ClientWritableStream<A>): Promise<B> {
   return new Promise((resolve, reject) => {
     let stream = fn((err, grt) => err ? reject(err) : resolve(grt));
diff --git a/project/history.go b/project/history.go
index d71cd062..f4f90628 100644
--- a/project/history.go
+++ b/project/history.go
@@ -40,6 +40,10 @@ func FullVersion() string {
 // release tagging script: ./scripts/tag_release.sh
 var History relic.ImmutableHistory = relic.NewHistory("Monax Hoard", "https://github.com/monax/hoard").
 	MustDeclareReleases(
+		"8.2.3 - 2020-03-27",
+		`### Added
+- ReadHeader will stop once it gets the head
+`,
 		"8.2.2 - 2020-03-25",
 		`### Fixed
 - Chunk plaintext out if data too big