Merge branch 'rewrite/mdx-cli' into rewrite/kebab-case

Author: SunburtReynolds

bin/args.js

@@ -1,23 +1,22 @@
 const yargs = require('yargs');
+const validatePresentationMode = require('./validate/presentation-mode');
 
-// Validate and normalize.
-const validate = parser => {
+const validate = async parser => {
   const { argv } = parser;
-  const { mdx } = argv;
+  const { src } = argv;
 
-  return Promise.resolve({ mdx });
+  return await validatePresentationMode(src);
 };
 
 const args = () =>
   yargs
-    .usage(`Usage: spectacle -m <file>`)
+    .usage(`Usage: spectacle -s <file>`)
 
     // MDX File
-    .option('mdx', {
-      alias: 'm',
-      describe: 'Path to mdx file from which a presentation will be generated.',
+    .option('src', {
+      alias: 's',
+      describe: 'Path to a file from which a presentation will be generated.',
       default: 'slides.mdx',
-      required: false,
       type: 'string'
     })
 

bin/cli.js

@@ -11,7 +11,9 @@ const main = () =>
       const mdxFilePath = parsedInput.mdx;
       if (mdxFilePath) {
         actions.launchMDXServer(mdxFilePath);
-      } else {
+      }
+      // add future actions here
+      else {
         throw new Error('Unsupported action.');
       }
     })

bin/validate/presentation-mode.js

@@ -0,0 +1,43 @@
+const path = require('path');
+const fs = require('fs');
+
+const isMDXFileType = extension => extension === '.mdx' || extension === '.md';
+
+const fileExists = srcPath => {
+  const absSrcPath = path.resolve(srcPath);
+  return new Promise(resolve => {
+    fs.exists(absSrcPath, exists => {
+      resolve(exists);
+    });
+  });
+};
+
+const validatePresentationMode = async src => {
+  /* - the default action of the CLI is to boot up a presentation from a file
+   * - src defaults to `slides.mdx`
+   * - first, check to see if the file type is supported
+   * - then check to see if the default or provided file exists
+   */
+
+  const validatedValue = {};
+  const extension = path.extname(src);
+
+  if (isMDXFileType(extension)) {
+    validatedValue['mdx'] = src;
+  }
+  // support other file types here
+  else {
+    throw new Error(`The file type ${extension} is not currently supported.`);
+  }
+
+  const exists = await fileExists(src);
+  if (!exists) {
+    throw new Error(
+      `A file cannot be found at the path "${src}". Remember that the default file is ./slides.mdx`
+    );
+  }
+
+  return validatedValue;
+};
+
+module.exports = validatePresentationMode;