refactor(core): extract validation logic into a Signal Factory

- Created getFormValidationErrors to get formatted angular form errors
- Implemented getMergedValidationErrors factory to unify local and server errors.
- Simplified Login component by using the new reusable utility.
- Implemented validation errors in register form

frontend/src/app/auth/login/login.html

@@ -9,7 +9,7 @@
     <p class="m-0 mt-2 text-sm text-slate-400">Sign in to continue to Post Assistant.</p>
   </div>
 
-  <app-validation-errors [errors]="authStore.validationErrors()" />
+  <app-validation-errors [errors]="allErrors()" />
 
   <form [formGroup]="loginForm" (ngSubmit)="login()" class="flex flex-col gap-5">
 
@@ -40,7 +40,7 @@
     <button
       type="submit"
       class="mt-4 bg-gradient-to-br from-[#00f2fe] to-[#4facfe] border-none py-3.5 rounded-xl font-semibold text-white text-lg transition-all duration-200 hover:scale-[1.02] hover:-translate-y-0.5 hover:shadow-[0_10px_20px_rgba(79,172,254,0.3)] active:scale-[0.98] disabled:opacity-70 disabled:cursor-not-allowed disabled:transform-none disabled:shadow-none"
-      [disabled]="loginForm.invalid"
+      [disabled]="authStore.isLoading()"
     >
       Sign In
     </button>

frontend/src/app/auth/login/login.ts

@@ -1,10 +1,11 @@
-import { Component, inject} from '@angular/core';
+import { Component, computed, inject, signal } from '@angular/core';
 import { CommonModule } from '@angular/common';
 import { FormBuilder, FormGroup, ReactiveFormsModule, Validators } from '@angular/forms';
 import { RouterLink } from '@angular/router';
-import {AuthStore} from '../auth.store';
+import { AuthStore } from '../auth.store';
-import {environment} from '../../../environments/environment';
+import { environment } from '../../../environments/environment';
 import { ValidationErrors } from '../../shared/validation-errors/validation-errors';
+import { getFormValidationErrors, getMergedValidationErrors } from '../../core/helpers/forms';
 
 @Component({
   selector: 'app-login',
@@ -16,18 +17,29 @@ import { ValidationErrors } from '../../shared/validation-errors/validation-erro
 export class Login {
   loginForm: FormGroup;
   protected readonly authStore = inject(AuthStore);
+  private formErrors = signal(<Record<string, string[]>>{});
+
+  protected readonly allErrors = getMergedValidationErrors(
+    this.formErrors,
+    this.authStore.validationErrors,
+  );
 
   constructor(private fb: FormBuilder) {
     this.loginForm = this.fb.group({
       email: ['', [Validators.required, Validators.email]],
-      password: ['', Validators.required]
+      password: ['', Validators.required],
     });
   }
 
   login() {
-    if (this.loginForm.valid) {
+    if (this.loginForm.touched && !this.loginForm.valid) {
-      if(!environment.production) console.log('Login submitted:', this.loginForm.value);
+      this.loginForm.markAllAsTouched();
+      this.formErrors.set(getFormValidationErrors(this.loginForm));
+      return;
+    }
+
+    if (!environment.production) console.log('Login submitted:', this.loginForm.value);
+    this.formErrors.set({});
     this.authStore.login(this.loginForm.value);
   }
-  }
 }

frontend/src/app/auth/register/register.html

@@ -1,14 +1,16 @@
-<div class="w-full max-w-[450px] mx-auto mt-27 flex flex-col bg-white/5 backdrop-blur-[20px] border border-white/10 rounded-3xl shadow-[0_25px_50px_-12px_rgba(0,0,0,0.5),inset_0_1px_0_rgba(255,255,255,0.1)] overflow-hidden animate-[slideUpFade_0.8s_cubic-bezier(0.16,1,0.3,1)] p-8">
+<div class="w-full max-w-112.5 mx-auto mt-27 flex flex-col bg-white/5 backdrop-blur-[20px] border border-white/10 rounded-3xl shadow-[0_25px_50px_-12px_rgba(0,0,0,0.5),inset_0_1px_0_rgba(255,255,255,0.1)] overflow-hidden animate-[slideUpFade_0.8s_cubic-bezier(0.16,1,0.3,1)] p-8">
   <div class="text-center mb-8">
-    <div class="w-16 h-16 mx-auto mb-4 rounded-full bg-gradient-to-br from-[#00f2fe] to-[#4facfe] flex items-center justify-center font-semibold text-2xl shadow-[0_0_20px_rgba(79,172,254,0.4)] animate-[pulse_2s_infinite]">
+    <div class="w-16 h-16 mx-auto mb-4 rounded-full bg-linear-to-br from-[#00f2fe] to-[#4facfe] flex items-center justify-center font-semibold text-2xl shadow-[0_0_20px_rgba(79,172,254,0.4)] animate-[pulse_2s_infinite]">
       <svg class="w-8 h-8 text-white" fill="none" stroke="currentColor" viewBox="0 0 24 24">
         <path stroke-linecap="round" stroke-linejoin="round" stroke-width="2" d="M18 9v3m0 0v3m0-3h3m-3 0h-3m-2-5a4 4 0 11-8 0 4 4 0 018 0zM3 20a6 6 0 0112 0v1H3v-1z"></path>
       </svg>
     </div>
-    <h1 class="m-0 text-3xl font-semibold tracking-wide bg-gradient-to-r from-white to-indigo-300 bg-clip-text text-transparent">Create Account</h1>
+    <h1 class="m-0 text-3xl font-semibold tracking-wide bg-linear-to-r from-white to-indigo-300 bg-clip-text text-transparent">Create Account</h1>
     <p class="m-0 mt-2 text-sm text-slate-400">Join us and start using Post Assistant.</p>
   </div>
 
+  <app-validation-errors [errors]="allErrors()" />
+
   <form [formGroup]="registerForm" (ngSubmit)="register()" class="flex flex-col gap-5">
 
     <div class="flex flex-col gap-1.5">
@@ -61,8 +63,7 @@
 
     <button
       type="submit"
-      class="mt-4 bg-gradient-to-br from-[#00f2fe] to-[#4facfe] border-none py-3.5 rounded-xl font-semibold text-white text-lg transition-all duration-200 hover:scale-[1.02] hover:-translate-y-0.5 hover:shadow-[0_10px_20px_rgba(79,172,254,0.3)] active:scale-[0.98] disabled:opacity-70 disabled:cursor-not-allowed disabled:transform-none disabled:shadow-none"
+      class="mt-4 bg-linear-to-br from-[#00f2fe] to-[#4facfe] border-none py-3.5 rounded-xl font-semibold text-white text-lg transition-all duration-200 hover:scale-[1.02] hover:-translate-y-0.5 hover:shadow-[0_10px_20px_rgba(79,172,254,0.3)] active:scale-[0.98] disabled:opacity-70 disabled:cursor-not-allowed disabled:transform-none disabled:shadow-none"
-      [disabled]="registerForm.invalid"
     >
       Sign Up
     </button>

frontend/src/app/auth/register/register.ts

@@ -1,20 +1,28 @@
-import { Component, inject} from '@angular/core';
+import { Component, inject, signal } from '@angular/core';
 import { CommonModule } from '@angular/common';
 import { FormBuilder, FormGroup, ReactiveFormsModule, Validators } from '@angular/forms';
 import { RouterLink } from '@angular/router';
-import {environment} from '../../../environments/environment';
+import { environment } from '../../../environments/environment';
-import {AuthStore} from '../auth.store';
+import { AuthStore } from '../auth.store';
+import { getFormValidationErrors, getMergedValidationErrors } from '../../core/helpers/forms';
+import { ValidationErrors } from '../../shared/validation-errors/validation-errors';
 
 @Component({
   selector: 'app-register',
   standalone: true,
-  imports: [CommonModule, ReactiveFormsModule, RouterLink],
+  imports: [CommonModule, ReactiveFormsModule, RouterLink, ValidationErrors],
   templateUrl: './register.html',
   styleUrl: './register.css',
 })
 export class Register {
   registerForm: FormGroup;
-  private readonly authStore = inject(AuthStore);
+  protected readonly authStore = inject(AuthStore);
+  private formErrors = signal(<Record<string, string[]>>{});
+
+  protected readonly allErrors = getMergedValidationErrors(
+    this.formErrors,
+    this.authStore.validationErrors,
+  );
 
   constructor(private fb: FormBuilder) {
     this.registerForm = this.fb.group({
@@ -26,9 +34,14 @@ export class Register {
   }
 
   register() {
-    if (this.registerForm.valid) {
+    if (this.registerForm.touched && !this.registerForm.valid) {
-      if(!environment.production) console.log('Register submitted:', this.registerForm.value);
+      this.registerForm.markAllAsTouched();
+      this.formErrors.set(getFormValidationErrors(this.registerForm));
+      return;
+    }
+
+    if (!environment.production) console.log('Registration started:', this.registerForm.value);
+    this.formErrors.set({});
     this.authStore.register(this.registerForm.value);
   }
-  }
 }

frontend/src/app/core/helpers/forms.ts

@@ -0,0 +1,52 @@
+import { FormGroup, ValidationErrors } from '@angular/forms';
+import { computed, Signal } from '@angular/core';
+
+export type FormErrors = Record<string, string[]> | null | undefined;
+
+export function getFormValidationErrors(form: FormGroup): Record<string, string[]> {
+  const result: Record<string, string[]> = {};
+
+  Object.keys(form.controls).forEach((key) => {
+    const controlErrors: ValidationErrors | null | undefined = form.get(key)?.errors;
+
+    if (controlErrors) {
+      result[key] = [];
+
+      Object.keys(controlErrors).forEach((keyError) => {
+        let errorMessage = keyError;
+
+        // Translate Angular's built-in errors into readable sentences. add other validation errors here
+        switch (keyError) {
+          case 'required':
+            errorMessage = `The ${key} field is required.`;
+            break;
+          case 'email':
+            errorMessage = `The ${key} must be a valid email address.`;
+            break;
+          case 'minlength':
+            errorMessage = `The ${key} must be at least ${controlErrors[keyError].requiredLength} characters.`;
+            break;
+          case 'maxlength':
+            errorMessage = `The ${key} must not be greater than ${controlErrors[keyError].requiredLength} characters.`;
+            break;
+          case 'pattern':
+            errorMessage = `The ${key} format is invalid.`;
+            break;
+        }
+
+        result[key].push(errorMessage);
+      });
+    }
+  });
+
+  return result;
+}
+
+export function getMergedValidationErrors(
+  formErrors: Signal<FormErrors>,
+  serverErrors: Signal<FormErrors>,
+): Signal<FormErrors> {
+  return computed(() => {
+    return { ...formErrors(), ...serverErrors() };
+  });
+}