fix(cli): show an error on startup if one of the binary dependencies is missing

Closes #95

bin/checks.js

@@ -0,0 +1,31 @@
+const chalk = require('chalk')
+const commandExists = require('command-exists')
+
+const COMMANDS = {
+  'gm': 'http://www.graphicsmagick.org',
+  'exiftool': 'https://www.sno.phy.queensu.ca/~phil/exiftool',
+  'ffmpeg': 'https://www.ffmpeg.org'
+}
+
+exports.verify = function () {
+  const missing = Object.keys(COMMANDS).reduce(addToArrayIfMissing, [])
+  if (missing.length > 0) {
+    const list = missing.map(nameAndURL).join('\n')
+    return `The following programs are required to run thumbsup:\n
+${list}\n
+Please make sure they are installed and available in the system path.`
+  }
+  return null
+}
+
+function addToArrayIfMissing (acc, cmd) {
+  if (!commandExists.sync(cmd)) {
+    acc.push(cmd)
+  }
+  return acc
+}
+
+function nameAndURL (cmd) {
+  const url = chalk.green(COMMANDS[cmd])
+  return `- ${cmd} (${url})`
+}

bin/thumbsup.js

@@ -5,6 +5,7 @@ const fs = require('fs')
 const messages = require('./messages')
 const path = require('path')
 const options = require('./options')
+const checks = require('./checks')
 const tty = require('tty')
 
 console.log('')
@@ -37,6 +38,13 @@ analytics.start()
 // Catch all exceptions and exit gracefully
 process.on('uncaughtException', handleError)
 
+// Check that all binary dependencies are present
+const missingErrors = checks.verify()
+if (missingErrors) {
+  console.log(`${missingErrors}\n`)
+  exit(1)
+}
+
 // Build the gallery!
 index.build(opts, (err, album) => {
   if (err) {

package-lock.json

@@ -603,6 +603,11 @@
         "delayed-stream": "1.0.0"
       }
     },
+    "command-exists": {
+      "version": "1.2.6",
+      "resolved": "https://registry.npmjs.org/command-exists/-/command-exists-1.2.6.tgz",
+      "integrity": "sha512-Qst/zUUNmS/z3WziPxyqjrcz09pm+2Knbs5mAZL4VAE0sSrNY1/w8+/YxeHcoBTsO6iojA6BW7eFf27Eg2MRuw=="
+    },
     "commander": {
       "version": "2.11.0",
       "resolved": "https://registry.npmjs.org/commander/-/commander-2.11.0.tgz",

package.json

@@ -32,6 +32,7 @@
     "async": "^2.5.0",
     "better-sqlite3": "^4.0.3",
     "chalk": "^2.3.0",
+    "command-exists": "^1.2.6",
     "debug": "^3.1.0",
     "event-stream": "^3.3.4",
     "fs-extra": "^4.0.1",