1 files changed, 35 insertions, 0 deletions
diff --git a/src/background/usecases/ZoomUseCase.ts b/src/background/usecases/ZoomUseCase.ts
new file mode 100644
index 0000000..692d6d9
--- /dev/null
+++ b/src/background/usecases/ZoomUseCase.ts
@@ -0,0 +1,35 @@
+import TabPresenter from '../presenters/TabPresenter';
+
+const ZOOM_SETTINGS = [
+  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 {
+  constructor() {
+    this.tabPresenter = new TabPresenter();
+  }
+
+  async zoomIn(tabId) {
+    let tab = await this.tabPresenter.getCurrent();
+    let current = await this.tabPresenter.getZoom(tab.id);
+    let factor = ZOOM_SETTINGS.find(f => f > current);
+    if (factor) {
+      return this.tabPresenter.setZoom(tabId, factor);
+    }
+  }
+
+  async zoomOut(tabId) {
+    let tab = await this.tabPresenter.getCurrent();
+    let current = await this.tabPresenter.getZoom(tab.id);
+    let factor = [].concat(ZOOM_SETTINGS).reverse().find(f => f < current);
+    if (factor) {
+      return this.tabPresenter.setZoom(tabId, factor);
+    }
+  }
+
+  zoomNutoral(tabId) {
+    return this.tabPresenter.setZoom(tabId, 1);
+  }
+
+}