refactor: remove mock-fs from dev dependency

src/fs/browser.ts

@@ -0,0 +1,51 @@
+import { last } from '../util/underscore'
+import IFS from './ifs'
+
+function domResolve (root, path) {
+  const base = document.createElement('base')
+  base.href = root
+
+  const head = document.getElementsByTagName('head')[0]
+  head.insertBefore(base, head.firstChild)
+
+  const a = document.createElement('a')
+  a.href = path
+  const resolved = a.href
+  head.removeChild(base)
+
+  return resolved
+}
+
+function resolve (root, filepath, ext) {
+  if (root.length && last(root) !== '/') root += '/'
+  const url = domResolve(root, filepath)
+  return url.replace(/^(\w+:\/\/[^/]+)(\/[^?]+)/, (str, origin, path) => {
+    const last = path.split('/').pop()
+    if (/\.\w+$/.test(last)) return str
+    return origin + path + ext
+  })
+}
+
+async function readFile (url: string): Promise<string> {
+  return new Promise((resolve, reject) => {
+    const xhr = new XMLHttpRequest()
+    xhr.onload = () => {
+      if (xhr.status >= 200 && xhr.status < 300) {
+        resolve(xhr.responseText as string)
+      } else {
+        reject(new Error(xhr.statusText))
+      }
+    }
+    xhr.onerror = () => {
+      reject(new Error('An error occurred whilst receiving the response.'))
+    }
+    xhr.open('GET', url)
+    xhr.send()
+  })
+}
+
+async function exists () {
+  return true
+}
+
+export default { readFile, resolve, exists } as IFS

src/fs/ifs.ts

@@ -0,0 +1,5 @@
+export default interface IFS {
+  exists: (filepath?: string) => Promise<boolean>
+  readFile: (filepath:string) => Promise<string>
+  resolve: (root: string, file: string, ext: string) => string
+}

src/fs/node.ts

@@ -0,0 +1,22 @@
+import * as _ from '../util/underscore'
+import { resolve, extname } from 'path'
+import { stat, readFile } from 'fs'
+import IFS from './ifs'
+
+const statAsync = _.promisify(stat) as (filepath: string) => Promise<object>
+const readFileAsync = _.promisify(readFile) as (filepath: string, encoding: string) => Promise<string>
+
+const fs: IFS = {
+  exists: filepath => {
+    return statAsync(filepath).then(() => true).catch(() => false)
+  },
+  readFile: filepath => {
+    return readFileAsync(filepath, 'utf8')
+  },
+  resolve: (root: string, file: string, ext: string) => {
+    if (!extname(file)) file += ext
+    return resolve(root, file)
+  }
+}
+
+export default fs