use reflow to migrate from flow to typescript

scm-ui/ui-extensions/src/binder.ts

@@ -0,0 +1,78 @@
+type Predicate = (props: object) => boolean;
+
+type ExtensionRegistration = {
+  predicate: (props: object) => boolean;
+  extension: any;
+};
+
+/**
+ * Binder is responsible for binding plugin extensions to their corresponding extension points.
+ * The Binder class is mainly exported for testing, plugins should only use the default export.
+ */
+export class Binder {
+  extensionPoints: {
+    [key: string]: Array<ExtensionRegistration>;
+  };
+
+  constructor() {
+    this.extensionPoints = {};
+  }
+
+  /**
+   * Binds an extension to the extension point.
+   *
+   * @param extensionPoint name of extension point
+   * @param extension provided extension
+   * @param predicate to decide if the extension gets rendered for the given props
+   */
+  bind(extensionPoint: string, extension: any, predicate?: Predicate) {
+    if (!this.extensionPoints[extensionPoint]) {
+      this.extensionPoints[extensionPoint] = [];
+    }
+    const registration = {
+      predicate: predicate ? predicate : () => true,
+      extension,
+    };
+    this.extensionPoints[extensionPoint].push(registration);
+  }
+
+  /**
+   * Returns the first extension or null for the given extension point and its props.
+   *
+   * @param extensionPoint name of extension point
+   * @param props of the extension point
+   */
+  getExtension(extensionPoint: string, props?: object) {
+    const extensions = this.getExtensions(extensionPoint, props);
+    if (extensions.length > 0) {
+      return extensions[0];
+    }
+    return null;
+  }
+
+  /**
+   * Returns all registered extensions for the given extension point and its props.
+   *
+   * @param extensionPoint name of extension point
+   * @param props of the extension point
+   */
+  getExtensions(extensionPoint: string, props?: object): Array<any> {
+    let registrations = this.extensionPoints[extensionPoint] || [];
+    if (props) {
+      registrations = registrations.filter(reg => reg.predicate(props || {}));
+    }
+    return registrations.map(reg => reg.extension);
+  }
+
+  /**
+   * Returns true if at least one extension is bound to the extension point and its props.
+   */
+  hasExtension(extensionPoint: string, props?: object): boolean {
+    return this.getExtensions(extensionPoint, props).length > 0;
+  }
+}
+
+// singleton binder
+const binder = new Binder();
+
+export default binder;