public class MainActivity extends AppCompatActivity {

private SignInButton signIn;


private int RC_SIGN_IN=1;
private GoogleSignInClient mGoogleSignInClient;
private String TAG = "MainActivity";
private FirebaseAuth mAuth;

private Button registration;

private EditText email;
private EditText password;
private Button login;


private BottomNavigationView bottomNavigationItemView;



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

    signIn = (SignInButton)findViewById(R.id.sign_in_button);

    mAuth = FirebaseAuth.getInstance();

    registration = (Button) findViewById(R.id.registrate);
    email = (EditText)findViewById(R.id.email);
    password = (EditText)findViewById(R.id.password);
    login = (Button)findViewById(R.id.login);


    bottomNavigationItemView = (BottomNavigationView)findViewById(R.id.navB) ;
    bottomNavigationItemView.getMenu().getItem(0).setChecked(true);


    bottomNavigationItemView.setOnNavigationItemSelectedListener(new BottomNavigationView.OnNavigationItemSelectedListener() {
        @Override
        public boolean onNavigationItemSelected(@NonNull MenuItem menuItem) {
            switch (menuItem.getItemId()) {
                case R.id.register_menu: {

                    Intent intent = new Intent(MainActivity.this, RegistrationActivity.class);
                    startActivity(intent);
                    break;
                }
            }
            return true;
        }
    });



    GoogleSignInOptions gso = new GoogleSignInOptions.Builder(GoogleSignInOptions.DEFAULT_SIGN_IN)
            .requestIdToken(getString(R.string.default_web_client_id))
            .requestEmail()
            .build();

    mGoogleSignInClient = GoogleSignIn.getClient(this, gso);



    signIn.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View v) {
            signIn();
        }
    });


    registration.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View v) {
            Intent intent = new Intent(MainActivity.this, RegistrationActivity.class);
            startActivity(intent);
        }
    });



    login.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View v) {

            String email_text = email.getText().toString().trim();
            String password_text = password.getText().toString().trim();

            if(TextUtils.isEmpty(email_text) || TextUtils.isEmpty(password_text))
            {
                Toast.makeText(MainActivity.this, "One or more fields are empty", Toast.LENGTH_LONG).show();
            }
            else
            {
                mAuth.signInWithEmailAndPassword(email_text, password_text).addOnCompleteListener(new OnCompleteListener<AuthResult>() {
                    @Override
                    public void onComplete(@NonNull Task<AuthResult> task) {

                        if(!task.isSuccessful())
                        {
                            Toast.makeText(MainActivity.this, "Sign in problem", Toast.LENGTH_LONG).show();
                        }
                        else
                        {
                            Intent intent = new Intent(MainActivity.this, AccountActivity.class);
                            startActivity(intent);
                        }
                    }
                });
            }

        }
    });


}


private void signIn() {   /*Sign in to the app with Google Account*/
    Intent signInIntent = mGoogleSignInClient.getSignInIntent();
    startActivityForResult(signInIntent, RC_SIGN_IN);


}

@Override
public void onActivityResult(int requestCode, int resultCode, Intent data) {
    super.onActivityResult(requestCode, resultCode, data);

    // Result returned from launching the Intent from GoogleSignInClient.getSignInIntent(...);
    if (requestCode == RC_SIGN_IN) {
        // The Task returned from this call is always completed, no need to attach
        // a listener.
        Task<GoogleSignInAccount> task = GoogleSignIn.getSignedInAccountFromIntent(data);
        try{
            GoogleSignInAccount account = task.getResult(ApiException.class);
            firebaseAuthWithGoogle(account);
        }
        catch(ApiException e){

            Log.w(TAG, "Google Sin in Failed");
        }
    }
}

private void firebaseAuthWithGoogle(GoogleSignInAccount acct)
{
    Log.d(TAG, "firebaseAuthWithGoogle:" + acct.getId());
    AuthCredential credential = GoogleAuthProvider.getCredential(acct.getIdToken(), null);
    mAuth.signInWithCredential(credential)
            .addOnCompleteListener(this, new OnCompleteListener<AuthResult>()
            {
                @Override
                public void onComplete(@NonNull Task<AuthResult> task)
                {
                    if(task.isSuccessful())
                    {
                        Log.d(TAG, "signInWithCredential: success");
                        FirebaseUser user = mAuth.getCurrentUser();
                        updateUI(user);
                    }
                    else
                    {
                        Log.w(TAG, "signInWithCredential: failure", task.getException());  /*In case of unsuccessful login*/
                        Toast.makeText(MainActivity.this, "You are not able to log in to Google", Toast.LENGTH_LONG).show();
                        //updateUI(null);
                    }
                }
            });


}

private void updateUI(FirebaseUser user)   /*In case of successful registration*/
{

    GoogleSignInAccount acct = GoogleSignIn.getLastSignedInAccount(getApplicationContext());
    if (acct != null) {
        String personName = acct.getDisplayName();
        String personGivenName = acct.getGivenName();
        String personFamilyName = acct.getFamilyName();
        String personEmail = acct.getEmail();
        String personId = acct.getId();
        Uri personPhoto = acct.getPhotoUrl();
        Toast.makeText(this, "Name of User : " + personName + "UserId is : " + personId, Toast.LENGTH_LONG);


        Intent intent = new Intent(this, AccountActivity.class);
        intent.putExtra("personPhoto", personPhoto.toString());
        startActivity(intent);
    }
}

public class AccountActivity extends AppCompatActivity {

private GoogleSignInClient mGoogleSignInClient;


private FirebaseAuth mAuth;
private FirebaseAuth.AuthStateListener mAuthStateListener;


private CardView signOut;
private CardView ratingTable;
private CardView settings;
private CardView map;
private CardView favoritePlaces;

DatabaseReference databaseReference;
FirebaseDatabase database;
List<User> users;

CollapsingToolbarLayout collapsingToolbarLayout;


String photoString="No photo";


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


    mAuth = FirebaseAuth.getInstance();


    signOut = (CardView) findViewById(R.id.logout);
    ratingTable = (CardView) findViewById(R.id.rating);
    settings = (CardView)findViewById(R.id.settings);
    map = (CardView) findViewById(R.id.map);
    favoritePlaces = (CardView)findViewById(R.id.favorite);



    database = FirebaseDatabase.getInstance();
    databaseReference = database.getReference();
    users = new ArrayList<User>();

    collapsingToolbarLayout = (CollapsingToolbarLayout) findViewById(R.id.collaps);




    if(mAuth.getCurrentUser().getDisplayName()!=null)
    {
        Intent i = getIntent();
        photoString = i.getStringExtra("personPhoto");
    }



    databaseReference.child("user").addValueEventListener(new ValueEventListener() {   /*A new user is registered in the database*/
        @Override
        public void onDataChange(DataSnapshot dataSnapshot) {

            Iterable<DataSnapshot> children = dataSnapshot.getChildren();
            for (DataSnapshot child : children) {
                User user = child.getValue(User.class);
                users.add(user);
            }

            if (!findUser())   /*If the user is not found, this is a new user and must be registered*/
                addUser();
            showName();   /*A user-specific message*/
        }


        @Override
        public void onCancelled(DatabaseError databaseError) {

        }
    });


        GoogleSignInOptions gso = new GoogleSignInOptions.Builder(GoogleSignInOptions.DEFAULT_SIGN_IN)
                .requestIdToken(getString(R.string.default_web_client_id))
                .requestEmail()
                .build();
        mGoogleSignInClient = GoogleSignIn.getClient(this, gso);




    signOut.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View v) {

            if(mAuth.getCurrentUser().getDisplayName()!=null)
            {
                mGoogleSignInClient.signOut();
               //Intent intent = new Intent(AccountActivity.this, MainActivity.class);
               // startActivity(intent);
                Intent i = getBaseContext().getPackageManager().getLaunchIntentForPackage(getBaseContext().getPackageName());
                i.addFlags(Intent.FLAG_ACTIVITY_CLEAR_TOP);
                startActivity(i);


            }
            else
            {
                mAuth.signOut();
                Intent i = getBaseContext().getPackageManager().getLaunchIntentForPackage(getBaseContext().getPackageName());
                i.addFlags(Intent.FLAG_ACTIVITY_CLEAR_TOP);
                startActivity(i);
            }
        }
    });



    settings.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View v) {
            Intent intent = new Intent(AccountActivity.this, SettingsActivity.class);
            startActivity(intent);
        }
    });

    map.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View v) {
            Intent intent = new Intent(AccountActivity.this, MapsActivity.class);
            startActivity(intent);
        }
    });

    favoritePlaces.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View v) {
            Intent intent = new Intent(AccountActivity.this, favoritePlacesActivity.class);
            startActivity(intent);
        }
    });

    ratingTable.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View v) {
            Intent intent = new Intent(AccountActivity.this, RatingTableActivity.class);
            startActivity(intent);

        }
    });


}




private void showName()  /*A user-specific message*/
{
    String name = "";
    String userId = mAuth.getUid();
    for (User tmpUser : users) {
        if (userId.equals(tmpUser.getUserId()))
        {
            name = tmpUser.getUserName();
            break;
        }
    }
    collapsingToolbarLayout.setTitle("Hi " + name);
}



private boolean findUser()  /*Check if a logged-on user is already registered in the database*/
{

    FirebaseUser user = mAuth.getCurrentUser();
    String userId = mAuth.getUid();



    for (User tmpUser : users) {
        if (userId.equals(tmpUser.getUserId())) {
            return true;
        }
    }
    return false;

}

private void addUser()  /*In case of registration from Google Account*/
{
    String userId = mAuth.getUid();
    if(mAuth.getCurrentUser().getDisplayName()!=null)  /*In case of registration not from Google Account*/
    {
        databaseReference = FirebaseDatabase.getInstance().getReference("user");
        FirebaseUser user = mAuth.getCurrentUser();
        String userName = user.getDisplayName();
        User newUser = User.getInstance(userId, userName, photoString);
        databaseReference.child(userId).setValue(newUser);
    }

    else   /*If the user is not registered the function registers it in the database*/
    {
        databaseReference = FirebaseDatabase.getInstance().getReference("user");
        Intent i = getIntent();
        String firstName = i.getStringExtra("firstName");
        String lastName = i.getStringExtra("lastName");


        User newUser = User.getInstance(userId, firstName + " " + lastName, photoString);
        databaseReference.child(userId).setValue(newUser);
    }

}

public class RegistrationActivity extends AppCompatActivity {

EditText email_text;
EditText pass1;
EditText pass2;
EditText first;
EditText last;
Button registrate;

FirebaseAuth mAuth;
private ProgressDialog progressDialog;



private BottomNavigationView bottomNavigationItemView;

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

    mAuth = FirebaseAuth.getInstance();
    progressDialog = new ProgressDialog(this);

    email_text = (EditText)findViewById(R.id.email);
    pass1 = (EditText)findViewById(R.id.password1);
    pass2 = (EditText)findViewById(R.id.password2);
    first = (EditText)findViewById(R.id.first_name);
    last = (EditText)findViewById(R.id.last_name);
    registrate = (Button)findViewById(R.id.registrate);




    bottomNavigationItemView = (BottomNavigationView)findViewById(R.id.navB) ;

    bottomNavigationItemView.getMenu().getItem(1).setChecked(true);



    bottomNavigationItemView.setOnNavigationItemSelectedListener(new BottomNavigationView.OnNavigationItemSelectedListener() {
        @Override
        public boolean onNavigationItemSelected(@NonNull MenuItem menuItem) {
            switch (menuItem.getItemId()) {
                case R.id.Signin_menu: {

                    Intent intent = new Intent(RegistrationActivity.this, MainActivity.class);
                    startActivity(intent);
                    break;
                }
            }
            return true;
        }
    });


    registrate.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View v) {

            final String email = email_text.getText().toString().trim();
            String password1 = pass1.getText().toString().trim();
            String password2 = pass2.getText().toString().trim();
            final String first_name = first.getText().toString().trim();
            final String last_name = last.getText().toString().trim();
            boolean correctFlag=true;

            /*All tests for input integrity*/
            if(!password1.equals(password2))
            {
                Toast.makeText(RegistrationActivity.this, "The password does not match", Toast.LENGTH_LONG).show();
                correctFlag=false;
            }
            if(password1.equals("") && password2.equals(""))
            {
                Toast.makeText(RegistrationActivity.this, "No password entered", Toast.LENGTH_LONG).show();
                correctFlag=false;
            }
            if(email.equals("") || first_name.equals("") || last_name.equals(""))
            {
                Toast.makeText(RegistrationActivity.this, "One or more of the parameters are incorrect", Toast.LENGTH_LONG).show();
                correctFlag=false;
            }

            if(correctFlag)  /*There is no problem filling the fields*/
            {
                progressDialog.setMessage("Registrating user...");
                progressDialog.show();

                mAuth.createUserWithEmailAndPassword(email, password1).addOnCompleteListener(new OnCompleteListener<AuthResult>() {
                    @Override
                    public void onComplete(@NonNull Task<AuthResult> task) {

                        if(task.isSuccessful())
                        {
                            Toast.makeText(RegistrationActivity.this, "Registered Succesfully", Toast.LENGTH_SHORT).show();
                            progressDialog.cancel();
                            Intent intent = new Intent(RegistrationActivity.this, AccountActivity.class);
                            intent.putExtra("firstName", first_name);
                            intent.putExtra("lastName", last_name);
                            startActivity(intent);
                        }
                        else
                        {
                            Toast.makeText(RegistrationActivity.this, "could not register. please try again", Toast.LENGTH_SHORT).show();
                            progressDialog.cancel();
                        }
                    }
                });
            }
        }
    });
}