1 files changed, 39 insertions, 0 deletions
diff --git a/src/background/usecases/ZoomUseCase.ts b/src/background/usecases/ZoomUseCase.ts
new file mode 100644
index 0000000..661c3cd
--- /dev/null
+++ b/src/background/usecases/ZoomUseCase.ts
@@ -0,0 +1,39 @@
+import TabPresenter from '../presenters/TabPresenter';
+
+const ZOOM_SETTINGS: number[] = [
+  0.33, 0.50, 0.66, 0.75, 0.80, 0.90, 1.00,
+  1.10, 1.25, 1.50, 1.75, 2.00, 2.50, 3.00
+];
+
+export default class ZoomUseCase {
+  private tabPresenter: TabPresenter;
+
+  constructor() {
+    this.tabPresenter = new TabPresenter();
+  }
+
+  async zoomIn(): Promise<any> {
+    let tab = await this.tabPresenter.getCurrent();
+    let tabId = tab.id as number;
+    let current = await this.tabPresenter.getZoom(tabId);
+    let factor = ZOOM_SETTINGS.find(f => f > current);
+    if (factor) {
+      return this.tabPresenter.setZoom(tabId as number, factor);
+    }
+  }
+
+  async zoomOut(): Promise<any> {
+    let tab = await this.tabPresenter.getCurrent();
+    let tabId = tab.id as number;
+    let current = await this.tabPresenter.getZoom(tabId);
+    let factor = ZOOM_SETTINGS.slice(0).reverse().find(f => f < current);
+    if (factor) {
+      return this.tabPresenter.setZoom(tabId as number, factor);
+    }
+  }
+
+  async zoomNutoral(): Promise<any> {
+    let tab = await this.tabPresenter.getCurrent();
+    return this.tabPresenter.setZoom(tab.id as number, 1);
+  }
+}