feat(challenge7): add all mecanism

libs/ngrx-notification/backend/src/lib/fake-db.service.ts

@@ -0,0 +1,67 @@
+import {
+  School,
+  Student,
+  Teacher,
+} from '@angular-challenges/ngrx-notification/model';
+import { Injectable } from '@angular/core';
+import { randNumber } from '@ngneat/falso';
+import { ComponentStore } from '@ngrx/component-store';
+
+@Injectable({ providedIn: 'root' })
+export class FakeDBService extends ComponentStore<{
+  teachers: Teacher[];
+  students: Student[];
+  schools: School[];
+}> {
+  readonly teachers$ = this.select((state) => state.teachers);
+  readonly randomTeacher$ = this.select(
+    this.teachers$,
+    (teachers) => teachers[randNumber({ max: teachers.length - 1 })]
+  );
+
+  readonly students$ = this.select((state) => state.students);
+  readonly randomStudents$ = this.select(
+    this.students$,
+    (students) => students[randNumber({ max: students.length - 1 })]
+  );
+
+  readonly schools$ = this.select((state) => state.schools);
+  readonly randomSchool$ = this.select(
+    this.schools$,
+    (schools) => schools[randNumber({ max: schools.length - 1 })]
+  );
+
+  constructor() {
+    super({ teachers: [], students: [], schools: [] });
+  }
+
+  addTeacher = this.updater((state, teacher: Teacher) => ({
+    ...state,
+    teachers: [...state.teachers, teacher],
+  }));
+
+  updateTeacher = this.updater((state, teacher: Teacher) => ({
+    ...state,
+    teachers: state.teachers.map((t) => (t.id === teacher.id ? teacher : t)),
+  }));
+
+  addStudent = this.updater((state, student: Student) => ({
+    ...state,
+    students: [...state.students, student],
+  }));
+
+  updateSudent = this.updater((state, student: Student) => ({
+    ...state,
+    students: state.students.map((t) => (t.id === student.id ? student : t)),
+  }));
+
+  addSchool = this.updater((state, school: School) => ({
+    ...state,
+    schools: [...state.schools, school],
+  }));
+
+  updateSchool = this.updater((state, school: School) => ({
+    ...state,
+    schools: state.schools.map((t) => (t.id === school.id ? school : t)),
+  }));
+}