Add infrastructure for setting up GraalVM.

src/utils.ts

@@ -0,0 +1,55 @@
+import * as c from './constants'
+import * as core from '@actions/core'
+import * as httpClient from '@actions/http-client'
+import * as tc from '@actions/tool-cache'
+import {Octokit} from '@octokit/core'
+import {join} from 'path'
+import {readdirSync} from 'fs'
+
+// Set up Octokit in the same way as @actions/github (see https://git.io/Jy9YP)
+const baseUrl = process.env['GITHUB_API_URL'] || 'https://api.github.com'
+const GitHub = Octokit.defaults({
+  baseUrl,
+  request: {
+    agent: new httpClient.HttpClient().getAgent(baseUrl)
+  }
+})
+
+export async function getLatestRelease(
+  repo: string
+): Promise<c.LatestReleaseResponse['data']> {
+  const githubToken = core.getInput('github-token')
+  const options = githubToken.length > 0 ? {auth: githubToken} : {}
+  const octokit = new GitHub(options)
+  return (
+    await octokit.request('GET /repos/{owner}/{repo}/releases/latest', {
+      owner: c.GRAALVM_GH_USER,
+      repo
+    })
+  ).data
+}
+
+export async function downloadAndExtractJDK(
+  downloadUrl: string
+): Promise<string> {
+  const downloadPath = await tc.downloadTool(downloadUrl)
+  if (downloadUrl.endsWith('.tar.gz')) {
+    await tc.extractTar(downloadPath, c.GRAALVM_BASE)
+  } else if (downloadUrl.endsWith('.zip')) {
+    await tc.extractZip(downloadPath, c.GRAALVM_BASE)
+  } else {
+    throw new Error(`Unexpected filetype downloaded: ${downloadUrl}`)
+  }
+  return findJavaHomeInSubfolder(c.GRAALVM_BASE)
+}
+
+export function findJavaHomeInSubfolder(searchPath: string): string {
+  const baseContents = readdirSync(searchPath)
+  if (baseContents.length === 1) {
+    return join(searchPath, baseContents[0], c.JDK_HOME_SUFFIX)
+  } else {
+    throw new Error(
+      `Unexpected amount of directory items found: ${baseContents.length}`
+    )
+  }
+}