Backport changes from Cloudproxy (#11)

src/captcha/index.ts

@@ -0,0 +1,35 @@
+export enum CaptchaType {
+  re = 'reCaptcha',
+  h = 'hCaptcha'
+}
+
+export interface SolverOptions {
+  url: string
+  sitekey: string
+  type: CaptchaType
+}
+
+export type Solver = (options: SolverOptions) => Promise<string>
+
+const captchaSolvers: { [key: string]: Solver } = {}
+
+export default (): Solver => {
+  const method = process.env.CAPTCHA_SOLVER
+
+  if (!method) { return null }
+
+  if (!(method in captchaSolvers)) {
+    try {
+      captchaSolvers[method] = require('./' + method).default as Solver
+    } catch (e) {
+      if (e.code === 'MODULE_NOT_FOUND') {
+        throw Error(`The solver '${method}' is not a valid captcha solving method.`)
+      } else {
+        console.error(e)
+        throw Error(`An error occured loading the solver '${method}'.`)
+      }
+    }
+  }
+
+  return captchaSolvers[method]
+}