added cache utility functions

src/cache.ts

@@ -0,0 +1,116 @@
+import * as core from "@actions/core";
+import { HttpClient } from "@actions/http-client";
+import { RequestOptions } from "@actions/http-client/lib/interfaces";
+import { BearerCredentialHandler } from "@actions/http-client/lib/auth";
+import * as crypto from "crypto";
+
+const versionSalt = "1.0";
+export const cacheKey = "harden-runner-cacheKey";
+export const cacheFile = "/home/agent/cache.txt";
+
+function getCacheApiUrl(resource: string): string {
+  const baseUrl: string = process.env["ACTIONS_CACHE_URL"] || "";
+  if (!baseUrl) {
+    throw new Error("Cache Service Url not found, unable to restore cache.");
+  }
+
+  const url = `${baseUrl}_apis/artifactcache/${resource}`;
+  core.debug(`Resource Url: ${url}`);
+  return url;
+}
+
+function createAcceptHeader(type: string, apiVersion: string): string {
+  return `${type};api-version=${apiVersion}`;
+}
+
+function getRequestOptions(): RequestOptions {
+  const token = process.env["ACTIONS_RUNTIME_TOKEN"] || "";
+
+  const requestOptions: RequestOptions = {
+    headers: {
+      Accept: createAcceptHeader("application/json", "6.0-preview.1"),
+      Authorization: `Bearer ${token}`,
+    },
+  };
+
+  return requestOptions;
+}
+
+function createHttpClient(): HttpClient {
+  const token = process.env["ACTIONS_RUNTIME_TOKEN"] || "";
+  const bhandler = new BearerCredentialHandler(token);
+  return new HttpClient("actions/cache", [bhandler], getRequestOptions());
+}
+
+export function getCacheVersion(
+  paths: string[],
+  compressionMethod?: CompressionMethod
+): string {
+  const components = paths.concat(
+    !compressionMethod || compressionMethod === CompressionMethod.Gzip
+      ? []
+      : [compressionMethod]
+  );
+
+  // Add salt to cache version to support breaking changes in cache entry
+  components.push(versionSalt);
+
+  return crypto.createHash("sha256").update(components.join("|")).digest("hex");
+}
+
+export async function getCacheEntry(
+  keys: string[],
+  paths: string[],
+  options?: InternalCacheOptions
+): Promise<ArtifactCacheEntry | null> {
+  const httpClient = createHttpClient();
+  const version = getCacheVersion(paths, options?.compressionMethod);
+  const resource = `cache?keys=${encodeURIComponent(
+    keys.join(",")
+  )}&version=${version}`;
+
+  const response = await httpClient.getJson<ArtifactCacheEntry>(
+    getCacheApiUrl(resource)
+  );
+  if (response.statusCode === 204) {
+    throw new Error("Request returned 204 status");
+  }
+  if (!isSuccessStatusCode(response.statusCode)) {
+    throw new Error(`Cache service responded with ${response.statusCode}`);
+  }
+
+  const cacheResult = response.result;
+  const cacheDownloadUrl = cacheResult?.archiveLocation;
+  if (!cacheDownloadUrl) {
+    throw new Error("Cache still be done, but  not found.");
+  }
+
+  return cacheResult;
+}
+
+export interface InternalCacheOptions {
+  compressionMethod?: CompressionMethod;
+  cacheSize?: number;
+}
+
+export interface ArtifactCacheEntry {
+  cacheKey?: string;
+  scope?: string;
+  creationTime?: string;
+  archiveLocation?: string;
+}
+
+function isSuccessStatusCode(statusCode?: number): boolean {
+  if (!statusCode) {
+    return false;
+  }
+  return statusCode >= 200 && statusCode < 300;
+}
+
+export enum CompressionMethod {
+  Gzip = "gzip",
+  // Long range mode was added to zstd in v1.3.2.
+  // This enum is for earlier version of zstd that does not have --long support
+  ZstdWithoutLong = "zstd-without-long",
+  Zstd = "zstd",
+}