From 9b0e839faec0903a86176ca8fe456605dae62d79 Mon Sep 17 00:00:00 2001
From: Akash Askoolum <akash1810@gmail.com>
Date: Fri, 19 Mar 2021 15:42:58 +0000
Subject: [PATCH] feat: make GuDistributionBucketParameter a singleton

---
 src/constructs/autoscaling/user-data.test.ts  |  4 ++--
 src/constructs/core/parameters/s3.ts          | 19 ++++++++++++++++---
 .../iam/policies/s3-get-object.test.ts        |  2 +-
 src/constructs/iam/policies/s3-get-object.ts  |  2 +-
 4 files changed, 20 insertions(+), 7 deletions(-)

diff --git a/src/constructs/autoscaling/user-data.test.ts b/src/constructs/autoscaling/user-data.test.ts
index daa2d8126..0bc3ba996 100644
--- a/src/constructs/autoscaling/user-data.test.ts
+++ b/src/constructs/autoscaling/user-data.test.ts
@@ -22,7 +22,7 @@ describe("GuUserData", () => {
     const props: GuUserDataProps = {
       app,
       distributable: {
-        bucket: new GuDistributionBucketParameter(stack),
+        bucket: GuDistributionBucketParameter.getInstance(stack),
         fileName: "my-app.deb",
         executionStatement: `dpkg -i /${app}/my-app.deb`,
       },
@@ -73,7 +73,7 @@ describe("GuUserData", () => {
     const props: GuUserDataProps = {
       app,
       distributable: {
-        bucket: new GuDistributionBucketParameter(stack),
+        bucket: GuDistributionBucketParameter.getInstance(stack),
         fileName: "my-app.deb",
         executionStatement: `dpkg -i /${app}/my-app.deb`,
       },
diff --git a/src/constructs/core/parameters/s3.ts b/src/constructs/core/parameters/s3.ts
index c313e16dc..4f31896ee 100644
--- a/src/constructs/core/parameters/s3.ts
+++ b/src/constructs/core/parameters/s3.ts
@@ -2,15 +2,28 @@ import type { GuStack } from "../stack";
 import { GuStringParameter } from "./base";
 
 export class GuDistributionBucketParameter extends GuStringParameter {
-  public static parameterName = "DistributionBucketName";
+  private static instance: GuDistributionBucketParameter | undefined;
 
-  constructor(scope: GuStack, id: string = GuDistributionBucketParameter.parameterName) {
-    super(scope, id, {
+  // eslint-disable-next-line custom-rules/valid-constructors -- TODO be better
+  private constructor(scope: GuStack) {
+    super(scope, "DistributionBucketName", {
       description: "SSM parameter containing the S3 bucket name holding distribution artifacts",
       default: "/account/services/artifact.bucket",
       fromSSM: true,
     });
   }
+
+  public static getInstance(stack: GuStack): GuDistributionBucketParameter {
+    // Resources can only live in the same App so return a new instance where necessary.
+    // See https://github.com/aws/aws-cdk/blob/0ea4b19afd639541e5f1d7c1783032ee480c307e/packages/%40aws-cdk/core/lib/private/refs.ts#L47-L50
+    const isSameStack = this.instance?.node.root === stack.node.root;
+
+    if (!this.instance || !isSameStack) {
+      this.instance = new GuDistributionBucketParameter(stack);
+    }
+
+    return this.instance;
+  }
 }
 
 export class GuPrivateConfigBucketParameter extends GuStringParameter {
diff --git a/src/constructs/iam/policies/s3-get-object.test.ts b/src/constructs/iam/policies/s3-get-object.test.ts
index 8c1a749c5..60be3bac5 100644
--- a/src/constructs/iam/policies/s3-get-object.test.ts
+++ b/src/constructs/iam/policies/s3-get-object.test.ts
@@ -82,7 +82,7 @@ describe("The GuGetDistributablePolicy construct", () => {
     const json = SynthUtils.toCloudFormation(stack) as SynthedStack;
 
     const parameterKeys = Object.keys(json.Parameters);
-    const expectedKeys = ["Stage", GuDistributionBucketParameter.parameterName];
+    const expectedKeys = ["Stage", GuDistributionBucketParameter.getInstance(stack).id];
     expect(parameterKeys).toEqual(expectedKeys);
 
     expect(json.Parameters.DistributionBucketName).toEqual({
diff --git a/src/constructs/iam/policies/s3-get-object.ts b/src/constructs/iam/policies/s3-get-object.ts
index f5d70c576..ec6a4f17e 100644
--- a/src/constructs/iam/policies/s3-get-object.ts
+++ b/src/constructs/iam/policies/s3-get-object.ts
@@ -24,7 +24,7 @@ export class GuGetDistributablePolicy extends GuGetS3ObjectsPolicy {
     const path = [scope.stack, scope.stage, props.app, "*"].join("/");
     super(scope, AppIdentity.suffixText(props, "GetDistributablePolicy"), {
       ...props,
-      bucketName: new GuDistributionBucketParameter(scope).valueAsString,
+      bucketName: GuDistributionBucketParameter.getInstance(scope).valueAsString,
       paths: [path],
     });
     AppIdentity.taggedConstruct(props, this);