=========================
Part I - First Component
=========================

First Step – Adding login
=========================

The first step on this tutorial will be to add a login component to learn how to interact with the Bexstream backend API.


1 – Creating the login component
--------------------------------

``ng generate component login``

This command creates 3 files:

login.component.ts
login.component.html
login.component.less

2 – Adding the login form
--------------------------

.. highlight:: ts

Add to the *login.component.ts* file the following code:

.. code-block::
    :linenos:
    :caption: login.component.ts

    import { Component, OnInit } from '@angular/core';
    import { FormBuilder } from '@angular/forms';

    @Component({
        selector: 'app-login',
        templateUrl: './login.component.html',
        styleUrls: ['./login.component.less']
    })
    export class LoginComponent implements OnInit {

        user = { username: '', password: '' }; // see body on OpenAPI definition for POST /api/v1/auth/user

        loginForm = this.formBuilder.group({
            username: '',
            password: ''
        });

        constructor(private formBuilder: FormBuilder) { }

        ngOnInit(): void {
            this.user = { username: '', password: '' };
        }

        /**
        * User authentication method
        */
        public authenticate(): void {
        }


    }



Since we will be using ReactiveForms we need to add this module to our app module, located in *app.module.ts*.

.. code-block::
    :linenos:
    :caption: app.module.ts
    :emphasize-lines: 3, 17

    import { BrowserModule } from '@angular/platform-browser';
    import { NgModule } from '@angular/core';
    import { ReactiveFormsModule } from '@angular/forms';

    import { AppRoutingModule } from './app-routing.module';
    import { AppComponent } from './app.component';
    import { LoginComponent } from './login/login.component';

    @NgModule({
        declarations: [
            AppComponent,
            LoginComponent
        ],
        imports: [
            BrowserModule,
            AppRoutingModule,
            ReactiveFormsModule,
        ],
        providers: [],
        bootstrap: [AppComponent]
    })
    export class AppModule { }


.. ATTENTION::
   After adding a new module, we must restart our angular app. Stop the running ng serve and run it again.


Edit login.component.html with the following code:

.. code-block:: html+ng2
    :linenos:
    :caption: login.component.html

    <h3>Login Form</h3>

    <form [formGroup]="loginForm" (ngSubmit)="authenticate()">

    <div>
        <label for="username">
            Username
        </label>
        <input id="username" type="text" formControlName="username">
    </div>

    <div>
        <label for="password">
            Password
        </label>
        <input id="password" type="password" formControlName="password">
    </div>

    <button class="button" type="submit">Login</button>

    </form>






3 – Adding the component to the app
-----------------------------------

First, clear *app.component.html* file and add the following line:

.. code-block:: html
    :linenos:
    :caption: app.component.html

    <router-outlet id="parent-router-outlet"></router-outlet>


The router-outlet  turns our application into a single page application where to a certain route (ex. http://localhost:4200/drones) matches with a Component (ex. DroneListComponent).

Second, lets add a route and the corresponding component to the “routes” variable:

.. code-block:: TS
    :linenos:
    :caption: app-routing.module.ts
    :emphasize-lines: 3, 6

    import { NgModule } from '@angular/core';
    import { Routes, RouterModule } from '@angular/router';
    import { LoginComponent } from './login/login.component';
    
    const routes: Routes = [
        { path: '', component: LoginComponent },
    ];

    @NgModule({
        imports: [RouterModule.forRoot(routes)],
        exports: [RouterModule]
    })
    export class AppRoutingModule { }


In our case the root url (“/”) will show our LoginComponent. 





4 – Invoking bexstream backend API
----------------------------------

We will use HTTP, to communicate with the bexstream API. So the first step is to import it to our App module in *app.module.ts*:

.. code-block::
    :linenos:
    :caption: app.module.ts
    :emphasize-lines: 4, 18, 19

    import { BrowserModule } from '@angular/platform-browser';
    import { NgModule } from '@angular/core';
    import { ReactiveFormsModule } from '@angular/forms';
    import { HttpClientModule } from '@angular/common/http';

    import { AppRoutingModule } from './app-routing.module';
    import { AppComponent } from './app.component';
    import { LoginComponent } from './login/login.component';

    @NgModule({
        declarations: [
            AppComponent,
            LoginComponent
        ],
        imports: [
            BrowserModule,
            AppRoutingModule,
            ReactiveFormsModule,
            HttpClientModule
        ],
        providers: [],
        bootstrap: [AppComponent]
    })
    export class AppModule { }

Restart your angular app.

Afterwards, we will add the communication code to the authenticate method on *login.component.ts*:

.. code-block::
    :linenos:
    :caption: login.component.ts
    :emphasize-lines: 3, 30-48

    import { Component, OnInit } from '@angular/core';
    import { FormBuilder } from '@angular/forms';
    import { HttpClient } from '@angular/common/http';
    import { User } from './models/user';

    @Component({
        selector: 'app-login',
        templateUrl: './login.component.html',
        styleUrls: ['./login.component.less']
    })
    export class LoginComponent implements OnInit {

        user = { username: '', password: '' }; // see body on OpenAPI definition for POST /api/v1/auth/user

        loginForm = this.formBuilder.group({
            username: '',
            password: ''
        });

        constructor(private formBuilder: FormBuilder,
                    private http: HttpClient) { }

        ngOnInit(): void {
            this.user = { username: '', password: '' };
        }

        /**
        * User authentication method
        */
        public authenticate(): void {
            const loginFormValues = this.loginForm.value
            this.user.username = loginFormValues.username;
            this.user.password = loginFormValues.password;

            this.http.post<any>('https://bexstream-preprod.beyond-vision.com/api/v1/auth/user', this.user)
                .subscribe({
                    next: (result) => {
                        if (result.token) {
                            alert(`${this.user.username} has been successfully logged in!`);
                        } else {
                            alert(`Unexpected response from the server for /api/v1/auth/user. Check the network request/response for details!`);
                        }
                    },
                    error: (err) => {
                        alert(`Error on login. Please check the username and the password!.`);
                    }
                });
        }

    }

Finally, to test that you've complete the PART I, try to login with:

``user: drone-pilot-tutorial``

``pass: drone-pilot-tutorial``

If everything was done correctly, you should have an alert pop-up with the login result.

.. image:: ../../_static/images/bexstream/tutorial/login.webp
    :align: center