feat: add has-permission structural directive (#722)

Fixes: #721

src/app/directives/directives.module.ts

@@ -0,0 +1,20 @@
+/** Angular Imports */
+import { NgModule } from '@angular/core';
+import { CommonModule } from '@angular/common';
+
+/** Custom Directives */
+import { HasPermissionDirective } from './has-permission/has-permission.directive';
+
+/**
+ *  Directives Module
+ *
+ *  All custom directives should be declared and exported here.
+ */
+@NgModule({
+  imports: [
+    CommonModule
+  ],
+  declarations: [HasPermissionDirective],
+  exports: [HasPermissionDirective]
+})
+export class DirectivesModule { }

src/app/directives/has-permission/has-permission.directive.spec.ts

@@ -0,0 +1,8 @@
+import { HasPermissionDirective } from './has-permission.directive';
+
+describe('HasPermissionDirective', () => {
+  it('should create an instance', () => {
+    const directive = new HasPermissionDirective();
+    expect(directive).toBeTruthy();
+  });
+});

src/app/directives/has-permission/has-permission.directive.ts

@@ -0,0 +1,76 @@
+/** Angular Imports */
+import { Directive, Input, TemplateRef, ViewContainerRef } from '@angular/core';
+
+/** Custom Services */
+import { AuthenticationService } from '../../core/authentication/authentication.service';
+
+/**
+ * Has Permission Directive
+ */
+@Directive({
+  selector: '[mifosxHasPermission]'
+})
+export class HasPermissionDirective {
+
+  /** User Permissions */
+  private userPermissions: any[];
+
+  /**
+   * Extracts User Permissions from User Credentials
+   * @param {TemplateRef} templateRef Template Reference
+   * @param {ViewContainerRef} viewContainer View Container Reference
+   * @param {AuthenticationService} authenticationService AuthenticationService
+   */
+  constructor(private templateRef: TemplateRef<any>,
+              private viewContainer: ViewContainerRef,
+              private authenticationService: AuthenticationService) {
+    const savedCredentials = this.authenticationService.getCredentials();
+    this.userPermissions = savedCredentials.permissions;
+  }
+
+  /**
+   * Evaluates the condition to show template.
+   */
+  @Input()
+  set mifosxHasPermission(permission: any) {
+    if (typeof permission !== 'string') {
+      throw new Error('hasPermission value must be a string');
+    }
+    if (this.hasPermission(permission)) {
+      /** Shows Template */
+      this.viewContainer.createEmbeddedView(this.templateRef);
+    } else {
+      /** Hides Template */
+      this.viewContainer.clear();
+    }
+  }
+
+  /**
+   * Checks if user is permitted.
+   * @param {string} permission Permission
+   * @returns {true}
+   * -`ALL_FUNCTIONS`: user is a Super user.
+   * -`ALL_FUNCTIONS_READ`: user has all read permissions and passed permission is 'read' type.
+   * - User has special permission to access that feature.
+   * @returns {false}
+   * - Passed permission doesn't fall under either of above given permission grants.
+   * - No value was passed to the has permission directive.
+   */
+  private hasPermission(permission: string) {
+    permission = permission.trim();
+    if (this.userPermissions.includes('ALL_FUNCTIONS')) {
+      return true;
+    } else if (permission !== '') {
+        if (permission.substring(0, 5) === 'READ_' && this.userPermissions.includes('ALL_FUNCTIONS_READ')) {
+          return true;
+        } else if (this.userPermissions.includes(permission)) {
+          return true;
+        } else {
+          return false;
+        }
+    } else {
+      return false;
+    }
+  }
+
+}