Add Flow, TypeScript types (#43)

* Add Flow, TypeScript types

* Fix naming

index.d.ts

@@ -0,0 +1,48 @@
+declare type FilePath = string;
+
+declare namespace ParcelWatcher {
+  export type BackendType = 
+    | 'fs-events'
+    | 'watchman'
+    | 'inotify'
+    | 'windows'
+    | 'brute-force';
+  export type EventType = 'create' | 'update' | 'delete';
+  export interface Options {
+    ignore?: FilePath[];
+    backend?: BackendType;
+  }
+  export type SubscribeCallback = (
+    err: Error | null,
+    events: Event[]
+  ) => unknown;
+  export interface AsyncSubscription {
+    unsubscribe(): Promise<void>;
+  }
+  export interface Event {
+    path: FilePath;
+    type: EventType;
+  }
+  export function getEventsSince(
+    dir: FilePath,
+    snapshot: FilePath,
+    opts?: Options
+  ): Promise<Event[]>;
+  export function subscribe(
+    dir: FilePath,
+    fn: SubscribeCallback,
+    opts?: Options
+  ): Promise<AsyncSubscription>;
+  export function unsubscribe(
+    dir: FilePath,
+    fn: SubscribeCallback,
+    opts?: Options
+  ): Promise<void>;
+  export function writeSnapshot(
+    dir: FilePath,
+    snapshot: FilePath,
+    opts?: Options
+  ): Promise<FilePath>;
+}
+
+export = ParcelWatcher;

index.js.flow

@@ -0,0 +1,47 @@
+// @flow
+declare type FilePath = string;
+
+export type BackendType = 
+  | 'fs-events'
+  | 'watchman'
+  | 'inotify'
+  | 'windows'
+  | 'brute-force';
+export type EventType = 'create' | 'update' | 'delete';
+export interface Options {
+  ignore?: Array<FilePath>,
+  backend?: BackendType
+}
+export type SubscribeCallback = (
+  err: ?Error,
+  events: Array<Event>
+) => mixed;
+export interface AsyncSubscription {
+  unsubscribe(): Promise<void>
+}
+export interface Event {
+  path: FilePath,
+  type: EventType
+}
+declare module.exports: {
+  getEventsSince(
+    dir: FilePath,
+    snapshot: FilePath,
+    opts?: Options
+  ): Promise<Array<Event>>,
+  subscribe(
+    dir: FilePath,
+    fn: SubscribeCallback,
+    opts?: Options
+  ): Promise<AsyncSubscription>,
+  unsubscribe(
+    dir: FilePath,
+    fn: SubscribeCallback,
+    opts?: Options
+  ): Promise<void>,
+  writeSnapshot(
+    dir: FilePath,
+    snapshot: FilePath,
+    opts?: Options
+  ): Promise<FilePath>
+}

package.json

@@ -2,6 +2,7 @@
   "name": "@parcel/watcher",
   "version": "2.0.0-alpha.8",
   "main": "index.js",
+  "types": "index.d.ts",
   "repository": {
     "type": "git",
     "url": "https://github.com/parcel-bundler/watcher.git"