package login.hfad.com;

import android.content.Intent;
import android.support.v7.app.AlertDialog;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.view.View;
import android.widget.Button;
import android.widget.EditText;
import android.widget.TextView;

import com.android.volley.RequestQueue;
import com.android.volley.Response;
import com.android.volley.toolbox.Volley;

import org.json.JSONException;
import org.json.JSONObject;

/**
 * Created by dipak on 24/03/2017.
 * This class is responsible for handling the login functionality of my application.
 * It contains implementation for the "Login" button's event handler that sends users login details
 * to my web server to be verified. It also contains error handling to ensure that all required fields
 * contain a value before attempting to log in to my system. It makes use of Volley library
 * functions to send and receive data to and from my web server.
 */
public class LoginActivity extends AppCompatActivity {

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_login);

         /* Declaration and initialisation of final variables that are
            assigned a View from my activity_login XML layout file. */
        final EditText etUsername = (EditText) findViewById(R.id.etUsername);
        final EditText etPassword = (EditText) findViewById(R.id.etPassword);
        final Button btnSignIn = (Button) findViewById(R.id.bLogin);
        final TextView registerLink = (TextView) findViewById(R.id.tvRegisterHere);

        //create a setOnClickListener for the "register" text link
        registerLink.setOnClickListener(new View.OnClickListener(){

            //implementation for setOnClickListeners , onClick method
            @Override
            public void onClick(View v) {

                //On click "register" text link, displays my Registration page to the user
                Intent registerIntent = new Intent(LoginActivity.this, RegisterActivity.class);
                LoginActivity.this.startActivity(registerIntent);
            }
        });

        //create a setOnClickListener for the "sign in" button
        btnSignIn.setOnClickListener(new View.OnClickListener() {

            //implementation for setOnClickListeners , onClick method
            //on click ("sign in") button stores username and password values from my View into variables
            //these values are sent to my server to be verified to gain access to my application
            @Override
            public void onClick(View v) {

                //declare and initialise username and password variables to store user input
                final String username = etUsername.getText().toString();
                final String password = etPassword.getText().toString();

                //declare and initialise a responseListener to store the response received from my web server
                Response.Listener<String> responseListener = new Response.Listener<String>() {

                    //implement onResponse() from Volley Library to handle servers response
                    @Override
                    //@param String response is the value received from my Login.php script sent by my web server
                    public void onResponse(String response) {

                        //Try Catch block used to prevent app crashes if my Login.php script does not respond with a JSON String
                        try {

                            //Login.php script responds to my application using JSON so my String response parameter
                            //above must be converted into a JSONObject to process my web servers response.
                            JSONObject serverJSONResponse = new JSONObject(response);

                            //declare and initialise variable of type Boolean to verify if the response received
                            //from my web server was successful.
                            boolean loginSuccessful = serverJSONResponse.getBoolean("success");

                            //if login was successful display UserAreaActivity page
                            //the name of the user is passed to the UserAreaActivity page to be displayed
                            if (loginSuccessful) {
                                //get and store the users profile name returned from the web server
                                String name = serverJSONResponse.getString("name");

                                //create an intent to display the UserAreaActivity page
                                Intent intent = new Intent(LoginActivity.this, UserAreaActivity.class);

                                //send the users profile name to UserAreaActivity page
                                intent.putExtra("name", name);

                                //display the UserAreaActivity page
                                LoginActivity.this.startActivity(intent);
                            }
                            else
                            //if login unsuccessful, display dialog box with retry button asking user to try logging in again
                            {
                                AlertDialog.Builder builder = new AlertDialog.Builder(LoginActivity.this);
                                builder.setMessage("Login Error \n\n" + "Please try logging in again" )
                                        .setNegativeButton("Retry", null)
                                        .create()
                                        .show();
                            }
                        //print exception error message to identify error
                        } catch (JSONException e) {
                            e.printStackTrace();
                        }
                    }
                };


                //declare and initialise a new request for user to login to their user account.
                //user must provide username and password to attempt to login as they are passed to the webserver
                //responseListener is required here to receive the servers response i.e. pass / fail.
                LoginRequest loginRequest = new LoginRequest(username, password, responseListener);

                //declare and initialise a login queue to handle simultaneous login requests
                RequestQueue queue = Volley.newRequestQueue(LoginActivity.this);

                //add a login request to the queue to be processed
                queue.add(loginRequest);
            }
        });
    }
}