Define client and presenter for follow

src/content/client/FollowSlaveClient.ts

@@ -0,0 +1,76 @@
+import * as messages from '../../shared/messages';
+
+interface Size {
+  width: number;
+  height: number;
+}
+
+interface Point {
+  x: number;
+  y: number;
+}
+
+export default interface FollowSlaveClient {
+  filterHints(prefix: string): void;
+
+  requestHintCount(viewSize: Size, framePosition: Point): void;
+
+  createHints(viewSize: Size, framePosition: Point, tags: string[]): void;
+
+  clearHints(): void;
+
+  activateIfExists(tag: string, newTab: boolean, background: boolean): void;
+
+  // eslint-disable-next-line semi
+}
+
+export class FollowSlaveClientImpl implements FollowSlaveClient {
+  private target: Window;
+
+  constructor(target: Window) {
+    this.target = target;
+  }
+
+  filterHints(prefix: string): void {
+    this.postMessage({
+      type: messages.FOLLOW_SHOW_HINTS,
+      prefix,
+    });
+  }
+
+  requestHintCount(viewSize: Size, framePosition: Point): void {
+    this.postMessage({
+      type: messages.FOLLOW_REQUEST_COUNT_TARGETS,
+      viewSize,
+      framePosition,
+    });
+  }
+
+  createHints(viewSize: Size, framePosition: Point, tags: string[]): void {
+    this.postMessage({
+      type: messages.FOLLOW_CREATE_HINTS,
+      viewSize,
+      framePosition,
+      tags,
+    });
+  }
+
+  clearHints(): void {
+    this.postMessage({
+      type: messages.FOLLOW_REMOVE_HINTS,
+    });
+  }
+
+  activateIfExists(tag: string, newTab: boolean, background: boolean): void {
+    this.postMessage({
+      type: messages.FOLLOW_ACTIVATE,
+      tag,
+      newTab,
+      background,
+    });
+  }
+
+  private postMessage(msg: messages.Message): void {
+    this.target.postMessage(JSON.stringify(msg), '*');
+  }
+}