Add prerequisite checks

src/patch-apk.ts

@@ -5,9 +5,9 @@ import Listr = require('listr')
 import chalk = require('chalk')
 
 import { TaskOptions } from './cli'
-import downloadTools from './tasks/download-tools'
 import observeAsync from './utils/observe-async'
 import applyPatches from './tasks/apply-patches'
+import checkPrerequisites from './tasks/check-prerequisites'
 
 export default function patchApk(options: TaskOptions) {
   const { apktool, uberApkSigner } = options
@@ -19,8 +19,8 @@ export default function patchApk(options: TaskOptions) {
 
   return new Listr([
     {
-      title: 'Downloading tools',
-      task: () => downloadTools(options),
+      title: 'Checking prerequisities',
+      task: () => checkPrerequisites(options),
     },
     {
       title: 'Decoding APK file',

src/tasks/check-prerequisites.ts

@@ -0,0 +1,43 @@
+import Listr = require('listr')
+
+import { TaskOptions } from '../cli'
+import getJavaVersion from '../utils/get-java-version'
+import downloadTools from './download-tools'
+
+const MIN_NODE_VERSION = 10
+const MIN_JAVA_VERSION = 8
+
+export default function checkPrerequisites(options: TaskOptions) {
+  return new Listr([
+    {
+      title: 'Checking Node.js version',
+      task: () => {
+        const majorVersion = parseInt(process.versions.node.split('.')[0])
+        if (majorVersion < MIN_NODE_VERSION)
+          throw new VersionError('Node.js', MIN_NODE_VERSION, majorVersion)
+      },
+    },
+    {
+      title: 'Checking Java version',
+      task: async () => {
+        const majorVersion = await getJavaVersion()
+        if (majorVersion < MIN_JAVA_VERSION)
+          throw new VersionError('Java', MIN_JAVA_VERSION, majorVersion)
+      },
+    },
+    {
+      title: 'Downloading tools',
+      task: () => downloadTools(options),
+    },
+  ])
+}
+
+class VersionError extends Error {
+  constructor(tool: string, minVersion: number, currentVersion: number) {
+    super(
+      `apk-mitm requires at least ${tool} ${minVersion} to work and you seem to be using ${tool} ${currentVersion}.` +
+        ` Please upgrade your ${tool} installation and try again!`,
+    )
+    this.name = VersionError.name
+  }
+}

src/utils/get-java-version.ts

@@ -0,0 +1,20 @@
+import execa = require('execa')
+
+/** Extracts the Java major version from the output of `java -version`. */
+export default async function getJavaVersion() {
+  try {
+    const { stderr } = await execa('java', ['-version'])
+    const version = stderr.match(/"(\d+\.\d+\.\d+)/)![1]
+
+    // `.replace` needed to remove `1.` prefix from versions older than Java 9
+    return parseInt(version.replace(/^1\./, '').match(/^\d+/)![0])
+  } catch (error) {
+    if (error.code === 'ENOENT')
+      throw new Error(
+        'No "java" executable could be found!' +
+          ' Make sure that Java is installed and available in your PATH.',
+      )
+
+    throw error
+  }
+}