feat(config-resolver): add getRegionInfo helper functions

Refs: aws#2696

packages/config-resolver/src/getRegionInfo/getRegionInfo.ts

@@ -0,0 +1,15 @@
+import { getResolvedHostName } from "./getResolvedHostname";
+import { getResolvedPartition } from "./getResolvedPartition";
+import { RegionInfoOptions } from "./types";
+
+export const getRegionInfo = (region: string, { regionHash, partitionHash }: RegionInfoOptions) => ({
+  signingService: "s3",
+  hostname: getResolvedHostName(region, { regionHash, partitionHash }),
+  partition: getResolvedPartition(region, { partitionHash }),
+  ...(regionHash[region]?.signingRegion && {
+    signingRegion: regionHash[region].signingRegion,
+  }),
+  ...(regionHash[region]?.signingService && {
+    signingService: regionHash[region].signingService,
+  }),
+});

packages/config-resolver/src/getRegionInfo/getResolvedHostname.ts

@@ -0,0 +1,6 @@
+import { getResolvedPartition } from "./getResolvedPartition";
+import { RegionInfoOptions } from "./types";
+
+export const getResolvedHostName = (region: string, { regionHash, partitionHash }: RegionInfoOptions) =>
+  regionHash[region]?.hostname ??
+  partitionHash[getResolvedPartition(region, { partitionHash })].hostname.replace("{region}", region);

packages/config-resolver/src/getRegionInfo/getResolvedPartition.ts

@@ -0,0 +1,4 @@
+import { RegionInfoOptions } from "./types";
+
+export const getResolvedPartition = (region: string, { partitionHash }: Omit<RegionInfoOptions, "regionHash">) =>
+  Object.keys(partitionHash).find((key) => partitionHash[key].regions.includes(region)) ?? "aws";

packages/config-resolver/src/getRegionInfo/index.ts

@@ -0,0 +1,2 @@
+export * from "./types";
+export * from "./getRegionInfo";

packages/config-resolver/src/getRegionInfo/types.ts

@@ -0,0 +1,19 @@
+import { RegionInfo } from "@aws-sdk/types";
+
+export type RegionHash = { [key: string]: Partial<Omit<RegionInfo, "partition" | "path">> };
+export type PartitionHash = { [key: string]: { regions: string[]; hostname: string } };
+
+export interface RegionInfoOptions {
+  /**
+   * The hash of region with the information specific to that region.
+   * The information can include hostname, signingService and signingRegion.
+   */
+  regionHash: RegionHash;
+
+  /**
+   * The hash of partition with the information specific to that partition.
+   * The information includes the list of regions belonging to that partition,
+   * and the hostname to be used for the partition.
+   */
+  partitionHash: PartitionHash;
+}

packages/config-resolver/src/index.ts

@@ -1,3 +1,4 @@
 export * from "./CustomEndpointsConfig";
 export * from "./EndpointsConfig";
 export * from "./RegionConfig";
+export * from "./getRegionInfo";