Implement error handling for the create qualification form (#19)

Co-authored-by: Phan Huy Tran <p.tran@neusta.de>
Reviewed-on: #19
Reviewed-by: Constantin Simonis <constantin@simonis.lol>

src/app/create-qualification/create-qualification.component.ts

@@ -1,41 +1,76 @@
 import {Component, inject} from '@angular/core';
-import {FormBuilder, ReactiveFormsModule} from "@angular/forms";
-import EmployeeApiService from "../services/employee-api.service";
+import {FormBuilder, ReactiveFormsModule, Validators} from "@angular/forms";
 import QualificationService from "../services/qualification.service";
-import {Router} from "@angular/router";
-import {MatDialogRef} from "@angular/material/dialog";
+import {MatDialogActions, MatDialogContent, MatDialogRef, MatDialogTitle} from "@angular/material/dialog";
+import {NgIf} from "@angular/common";
+import {MatError, MatFormField, MatLabel} from "@angular/material/form-field";
+import {MatButton} from "@angular/material/button";
+import {MatInput} from "@angular/material/input";
+import {filter} from "rxjs";
 
 @Component({
-  selector: 'app-create-qualification',
-  imports: [
-    ReactiveFormsModule
-  ],
-  templateUrl: './create-qualification.component.html',
-  styleUrl: './create-qualification.component.css'
+    selector: 'app-create-qualification',
+    imports: [
+        ReactiveFormsModule,
+        MatError,
+        NgIf,
+        MatLabel,
+        MatDialogTitle,
+        MatDialogContent,
+        MatFormField,
+        MatDialogActions,
+        MatButton,
+        MatInput
+    ],
+    templateUrl: './create-qualification.component.html',
+    styleUrl: './create-qualification.component.css'
 })
 export class CreateQualificationComponent {
-  private formBuilder: FormBuilder = inject(FormBuilder);
-  private qualificationService: QualificationService = inject(QualificationService);
-  private dialogRef: MatDialogRef<CreateQualificationComponent> = inject(MatDialogRef);
+    private formBuilder: FormBuilder = inject(FormBuilder);
+    private qualificationService: QualificationService = inject(QualificationService);
+    private dialogRef: MatDialogRef<CreateQualificationComponent> = inject(MatDialogRef);
 
-  qualificationForm = this.formBuilder.group({
-    'skill': [''],
-  });
+    public apiErrorMessage: string = '';
 
-  create() {
-    if (this.qualificationForm.valid) {
-      this.qualificationService.create(this.qualificationForm.value).subscribe({
-        next: (createdQualification) => {
-          this.dialogRef.close(createdQualification);
-        },
-        error: (error) => {
-          console.error('Error creating qualification:', error);
+    qualificationForm = this.formBuilder.group({
+        'skill': ['', Validators.required],
+    });
+
+    isFieldInvalid(fieldName: string): boolean {
+        const field = this.qualificationForm.get(fieldName);
+
+        if (!field) {
+            throw new Error('Form field does not exist: ' + fieldName)
         }
-      });
-    }
-  }
 
-  cancel() {
-    this.dialogRef.close();
-  }
+        return field.invalid && (field.dirty || field.touched);
+    }
+
+    getErrorMessage(fieldName: string): string {
+        const field = this.qualificationForm.get(fieldName);
+
+        if (field?.errors?.['required']) {
+            return 'This field is required';
+        }
+
+        return '';
+    }
+
+    create() {
+        if (!this.qualificationForm.valid) {
+            console.error('Validation failed');
+            return;
+        }
+
+        this.qualificationService.create(this.qualificationForm.value).subscribe({
+            next: (createdQualification) => {
+                this.dialogRef.close(createdQualification);
+            },
+            error: (error) => {
+                console.error('Error creating qualification:', error);
+
+                this.apiErrorMessage = 'API Error';
+            }
+        });
+    }
 }