From 8925d4272ba4bb03392e87c1104d7ba17a91d859 Mon Sep 17 00:00:00 2001
From: Brandon Liu <bdon@users.noreply.github.com>
Date: Thu, 28 Sep 2023 14:31:22 +0800
Subject: [PATCH] add utility module for AWS regions. (#259)

---
 serverless/aws/src/aws_region.test.ts | 52 +++++++++++++++++++++++++++
 serverless/aws/src/aws_region.ts      | 48 +++++++++++++++++++++++++
 2 files changed, 100 insertions(+)
 create mode 100644 serverless/aws/src/aws_region.test.ts
 create mode 100644 serverless/aws/src/aws_region.ts

diff --git a/serverless/aws/src/aws_region.test.ts b/serverless/aws/src/aws_region.test.ts
new file mode 100644
index 0000000..d7d0fb5
--- /dev/null
+++ b/serverless/aws/src/aws_region.test.ts
@@ -0,0 +1,52 @@
+import { test } from "node:test";
+import assert from "node:assert";
+
+import { get_region } from "./aws_region";
+
+test("one bucket", () => {
+  let result = get_region(
+    "us-west-1",
+    { bucket: "mybucket", region: "us-west-1" },
+    [],
+  );
+  assert.deepEqual(result, { bucket: "mybucket", region: "us-west-1" });
+});
+
+test("unknown region", () => {
+  let result = get_region(
+    "us-nullisland-1",
+    { bucket: "mybucket", region: "us-west-1" },
+    [],
+  );
+  assert.deepEqual(result, { bucket: "mybucket", region: "us-west-1" });
+});
+
+test("exact region match", () => {
+  let result = get_region(
+    "us-west-1",
+    { bucket: "mybucket", region: "us-west-1" },
+    [{ bucket: "mybucket-ap-south-1", region: "ap-south-1" }],
+  );
+  assert.deepEqual(result, { bucket: "mybucket", region: "us-west-1" });
+  result = get_region(
+    "ap-south-1",
+    { bucket: "mybucket", region: "us-west-1" },
+    [{ bucket: "mybucket-ap-south-1", region: "ap-south-1" }],
+  );
+  assert.deepEqual(result, {
+    bucket: "mybucket-ap-south-1",
+    region: "ap-south-1",
+  });
+});
+
+test("priority match", () => {
+  let result = get_region(
+    "us-west-1",
+    { bucket: "mybucket", region: "ap-south-1" },
+    [{ bucket: "mybucket-us-west-2", region: "us-west-2" }],
+  );
+  assert.deepEqual(result, {
+    bucket: "mybucket-us-west-2",
+    region: "us-west-2",
+  });
+});
diff --git a/serverless/aws/src/aws_region.ts b/serverless/aws/src/aws_region.ts
new file mode 100644
index 0000000..29036d3
--- /dev/null
+++ b/serverless/aws/src/aws_region.ts
@@ -0,0 +1,48 @@
+interface Bucket {
+  bucket: string;
+  region: string;
+}
+
+const REGION_MATRIX: Record<string, string[]> = {
+  "us-east-2": ["us-east-1"], // ohio
+  "us-east-1": ["us-east-2"], // virginia
+  "us-west-2": ["us-west-1"], // oregon
+  "us-west-1": ["us-west-2"], // california
+  "ap-south-1": ["ap-southeast-1"], // mumbai
+  "ap-southeast-1": ["ap-southeast-2", "ap-northeast-1", "ap-northeast-2"], // singapore
+  "ap-southeast-2": ["ap-southeast-1"], // sydney
+  "ap-northeast-2": ["ap-northeast-1", "ap-southeast-1"], // seoul
+  "ap-northeast-1": ["ap-northeast-2", "ap-southeast-1"], // tokyo
+  "eu-central-1": ["eu-west-1", "eu-west-2"], // frankfurt
+  "eu-west-1": ["eu-west-2", "eu-central-1"], // dublin
+  "eu-west-2": ["eu-west-1", "eu-central-1"], // london
+  "sa-east-1": ["us-east-1", "us-east-2"], // sao paulo
+};
+
+export let get_region = (
+  exec_region: string,
+  primary: Bucket,
+  replicas: Bucket[],
+): Bucket => {
+  if (primary.region === exec_region) {
+    return primary;
+  }
+
+  for (let replica of replicas) {
+    if (replica.region === exec_region) {
+      return replica;
+    }
+  }
+
+  if (exec_region in REGION_MATRIX) {
+    for (let region of REGION_MATRIX[exec_region]) {
+      for (let replica of replicas) {
+        if (replica.region === region) {
+          return replica;
+        }
+      }
+    }
+  }
+
+  return primary;
+};