Implement base connection to PrograMaker API.

- Login and check of the login token.

app/build.gradle

@@ -19,6 +19,10 @@ android {
             proguardFiles getDefaultProguardFile('proguard-android.txt'), 'proguard-rules.pro'
         }
     }
+    compileOptions {
+        sourceCompatibility = 1.8
+        targetCompatibility = 1.8
+    }
 }
 
 dependencies {

app/src/main/java/com/codigoparallevar/minicards/CanvasView.java

@@ -17,8 +17,8 @@ import com.codigoparallevar.minicards.types.PartConnection;
 import com.codigoparallevar.minicards.types.PartGrid;
 import com.codigoparallevar.minicards.types.Position;
 import com.codigoparallevar.minicards.types.Selectable;
-import com.codigoparallevar.minicards.types.Tuple2;
+import com.codigoparallevar.minicards.types.functional.Tuple2;
-import com.codigoparallevar.minicards.types.Tuple4;
+import com.codigoparallevar.minicards.types.functional.Tuple4;
 import com.codigoparallevar.minicards.types.connectors.input.AnyInputConnector;
 import com.codigoparallevar.minicards.types.connectors.input.BooleanInputConnector;
 import com.codigoparallevar.minicards.types.connectors.input.InputConnector;

app/src/main/java/com/codigoparallevar/minicards/CardFile.java

@@ -16,7 +16,7 @@ import com.codigoparallevar.minicards.parts.strings.ConvertToString;
 import com.codigoparallevar.minicards.types.Part;
 import com.codigoparallevar.minicards.types.PartConnection;
 import com.codigoparallevar.minicards.types.PartGrid;
-import com.codigoparallevar.minicards.types.Tuple2;
+import com.codigoparallevar.minicards.types.functional.Tuple2;
 
 import org.json.JSONArray;
 import org.json.JSONException;

app/src/main/java/com/codigoparallevar/minicards/CardPreviewArrayAdapter.java

@@ -50,7 +50,7 @@ class CardPreviewArrayAdapter extends ArrayAdapter<PreviewCard> {
             }
         });
 
-        final ImageView settingsButton = (ImageView) row.findViewById(R.id.card_preview_settings_button);
+        final ImageView settingsButton = row.findViewById(R.id.card_preview_settings_button);
         settingsButton.setOnClickListener(new View.OnClickListener() {
             @Override
             public void onClick(View v) {
@@ -58,19 +58,10 @@ class CardPreviewArrayAdapter extends ArrayAdapter<PreviewCard> {
             }
         });
 
-        CardView cardView = (CardView) row.findViewById(R.id.card_preview_card);
+        CardView cardView = row.findViewById(R.id.card_preview_card);
-        TextView nameView = (TextView) row.findViewById(R.id.card_preview_name);
+        TextView nameView = row.findViewById(R.id.card_preview_name);
 
-        int backgroundColor = card.getColor();
-        cardView.setBackgroundColor(backgroundColor);
         nameView.setText(card.getName());
-        if (backgroundColor == CardFile.DEFAULT_BACKGROUND_COLOR){
-            nameView.setTextColor(0xFFF0F0F0);
-        }
-        else {
-            nameView.setTextColor(0xFFFFFF ^ backgroundColor);
-        }
-
         return row;
     }
 
@@ -80,7 +71,7 @@ class CardPreviewArrayAdapter extends ArrayAdapter<PreviewCard> {
         final View openCardOptions = (LayoutInflater.from(getContext())
                 .inflate(R.layout.card_settings_dialog, null));
 
-        final EditText cardNameEditText = (EditText) openCardOptions.findViewById(R.id.card_setting_name_edit_text);
+        final EditText cardNameEditText = openCardOptions.findViewById(R.id.card_setting_name_edit_text);
         cardNameEditText.setText(card.getName());
 
         builder.setTitle("Card settings")
@@ -115,7 +106,7 @@ class CardPreviewArrayAdapter extends ArrayAdapter<PreviewCard> {
 
         final Dialog dialog = builder.create();
 
-        final TextView deleteCardLink = (TextView) openCardOptions.findViewById(R.id.card_setting_delete_card);
+        final TextView deleteCardLink = openCardOptions.findViewById(R.id.card_setting_delete_card);
         deleteCardLink.setOnClickListener(new View.OnClickListener() {
             @Override
             public void onClick(View v) {

app/src/main/java/com/codigoparallevar/minicards/DeckPreviewActivity.java

@@ -2,8 +2,13 @@ package com.codigoparallevar.minicards;
 
 import android.app.Dialog;
 import android.content.DialogInterface;
+import android.content.SharedPreferences;
 import android.os.AsyncTask;
 import android.os.Bundle;
+
+import com.codigoparallevar.minicards.types.functional.Function;
+import com.codigoparallevar.minicards.types.functional.Tuple2;
+import com.codigoparallevar.minicards.types.functional.Tuple3;
 import com.google.android.material.floatingactionbutton.FloatingActionButton;
 import androidx.appcompat.app.AlertDialog;
 import androidx.appcompat.widget.Toolbar;
@@ -27,6 +32,8 @@ import java.util.Vector;
 import com.programaker.api.ProgramakerApi;
 
 public class DeckPreviewActivity extends ReloadableAppCompatActivity {
+    private static final String TOKEN_KEY = "PROGRAMAKER_API_TOKEN";
+    private static final String PREFERENCES_NAME = "MINICARDS_PREFERENCES";
 
     public static final String INTENT = "com.codigoparallevar.minicards.DECK";
     private ListView listView;
@@ -39,11 +46,11 @@ public class DeckPreviewActivity extends ReloadableAppCompatActivity {
         final View loginDialog = (LayoutInflater.from(this)
                 .inflate(R.layout.login_dialog_view, null));
 
-        final EditText loginUsernameText = (EditText) loginDialog.findViewById(R.id.login_username_text);
+        final EditText loginUsernameText = loginDialog.findViewById(R.id.login_username_text);
-        final EditText loginPasswordText = (EditText) loginDialog.findViewById(R.id.login_password_text);
+        final EditText loginPasswordText = loginDialog.findViewById(R.id.login_password_text);
-        final Button loginButton = (Button) loginDialog.findViewById(R.id.login_dialog_login_button);
+        final Button loginButton = loginDialog.findViewById(R.id.login_dialog_login_button);
-        final Button cancelButton = (Button) loginDialog.findViewById(R.id.login_dialog_cancel_button);
+        final Button cancelButton = loginDialog.findViewById(R.id.login_dialog_cancel_button);
-        final TextView messageLabel = (TextView) loginDialog.findViewById(R.id.login_message_label);
+        final TextView messageLabel = loginDialog.findViewById(R.id.login_message_label);
 
         builder.setTitle("Login").setView(loginDialog);
         final Dialog dialog = builder.create();
@@ -84,19 +91,95 @@ public class DeckPreviewActivity extends ReloadableAppCompatActivity {
             public void onClick(View v) {
                 messageLabel.setVisibility(View.VISIBLE);
                 messageLabel.setText(R.string.loading);
-                watcher.afterTextChanged(null);
+                new CheckLogin().executeOnExecutor(AsyncTask.THREAD_POOL_EXECUTOR,
+                        new Tuple3<>(
+                                loginUsernameText.getText().toString(),
+                                loginPasswordText.getText().toString(),
+                                new Function<String>() {
+                                    public void apply(String token) {
+                                        if (token == null) {
+                                            messageLabel.setText(R.string.invalid_user_pass);
+                                        } else {
+                                            DeckPreviewActivity.this.setToken(token);
+                                            final Button loginToProgramakerButton = findViewById(R.id.login_in_programaker_button);
+
+                                            loginToProgramakerButton.setVisibility(View.GONE);
+                                            // Re-check... just in case
+                                            new CheckNeededLoginButton().executeOnExecutor(AsyncTask.THREAD_POOL_EXECUTOR,
+                                                    new Tuple2<>(DeckPreviewActivity.this.ProgramakerApi,
+                                                            loginToProgramakerButton));
+                                            dialog.cancel();
+                                        }
+                                    }
+                                }));
             }
         });
     }
 
+    private void setToken(String token) {
+        SharedPreferences preferences = getSharedPreferences(PREFERENCES_NAME, MODE_PRIVATE);
+        SharedPreferences.Editor edit = preferences.edit();
+
+        edit.putString(TOKEN_KEY, token);
+        edit.commit();
+
+        this.ProgramakerApi.setToken(token);
+    }
+
+    private String getToken() {
+        SharedPreferences preferences = getSharedPreferences(PREFERENCES_NAME, MODE_PRIVATE);
+        if (!preferences.contains(TOKEN_KEY)) {
+            return null;
+        }
+        else {
+            return preferences.getString(TOKEN_KEY, null);
+        }
+    }
+
+    static class CheckLogin extends  AsyncTask<Tuple3<String, String, Function<String>>,
+            Void, Tuple2<String, Function<String>>>{
+        @Override
+        protected Tuple2<String, Function<String>> doInBackground(Tuple3<String, String, Function<String>>... tuples) {
+            ProgramakerApi api = new ProgramakerApi();
+            boolean logged = false;
+            String token = null;
+            try {
+                token = api.login(tuples[0]._x, tuples[0]._y);
+            }
+            catch (Exception e) {
+                Log.e("Login to PrograMaker", e.toString());
+            }
+            return new Tuple2<String, Function<String>>(token, tuples[0]._z);
+        }
+
+        @Override
+        protected void onPostExecute(Tuple2<String, Function<String>> result) {
+            result.item2.apply(result.item1);
+        }
+    }
+
+    static class CheckNeededLoginButton extends  AsyncTask<Tuple2<ProgramakerApi, Button>, Void, Tuple2<Boolean, Button>>{
+        @Override
+        protected Tuple2<Boolean, Button> doInBackground(Tuple2<ProgramakerApi, Button>... tuples) {
+            return new Tuple2<>(tuples[0].item1.check(), tuples[0].item2);
+        }
+
+        @Override
+        protected void onPostExecute(Tuple2<Boolean, Button> result) {
+            if (!result.item1) {
+                result.item2.setVisibility(View.VISIBLE);
+            }
+        }
+    }
+
     @Override
     protected void onCreate(Bundle savedInstanceState) {
         super.onCreate(savedInstanceState);
         setContentView(R.layout.activity_deck_preview);
-        Toolbar toolbar = (Toolbar) findViewById(R.id.toolbar);
+        Toolbar toolbar = findViewById(R.id.toolbar);
         setSupportActionBar(toolbar);
 
-        FloatingActionButton fab = (FloatingActionButton) findViewById(R.id.create_new_card_fab);
+        FloatingActionButton fab = findViewById(R.id.create_new_card_fab);
         fab.setOnClickListener(new View.OnClickListener() {
             @Override
             public void onClick(View view) {
@@ -104,7 +187,7 @@ public class DeckPreviewActivity extends ReloadableAppCompatActivity {
             }
         });
 
-        Button loginButton = (Button) findViewById(R.id.login_in_programaker_button);
+        final Button loginButton = findViewById(R.id.login_in_programaker_button);
         loginButton.setOnClickListener(new View.OnClickListener() {
             @Override
             public void onClick(View v) {
@@ -112,18 +195,19 @@ public class DeckPreviewActivity extends ReloadableAppCompatActivity {
             }
        });
 
-        listView = (ListView) findViewById(R.id.card_deck_list);
+        listView = findViewById(R.id.card_deck_list);
 
-
+        String token = getToken();
-        new AsyncTask<ProgramakerApi, Void, Boolean>() {
+        if (token == null) {
-            protected Boolean doInBackground(ProgramakerApi... api) {
+            loginButton.setVisibility(View.VISIBLE);
-                return api[0].Check();
+        }
-            }
+        else {
-
+            loginButton.setVisibility(View.GONE);
-            protected void onPostExecute(Boolean result) {
+            this.ProgramakerApi.setToken(token);
-                Log.d("MiniCards",  "check result: " + result);
+            // Double check that is not needed
-            }
+            new CheckNeededLoginButton().executeOnExecutor(AsyncTask.THREAD_POOL_EXECUTOR,
-        }.executeOnExecutor(AsyncTask.THREAD_POOL_EXECUTOR, this.ProgramakerApi);
+                new Tuple2<>(this.ProgramakerApi, loginButton));
+        }
     }
 
     @Override
@@ -145,7 +229,7 @@ public class DeckPreviewActivity extends ReloadableAppCompatActivity {
         final View openCardOptions = (LayoutInflater.from(this)
                 .inflate(R.layout.create_new_card_view, null));
 
-        final EditText cardNameEditText = (EditText) openCardOptions.findViewById(R.id.card_name_edit_text);
+        final EditText cardNameEditText = openCardOptions.findViewById(R.id.card_name_edit_text);
 
         builder.setTitle("Create a new card")
                 .setView(openCardOptions)

app/src/main/java/com/codigoparallevar/minicards/PartInstantiator.java

@@ -2,7 +2,7 @@ package com.codigoparallevar.minicards;
 
 import com.codigoparallevar.minicards.types.Part;
 import com.codigoparallevar.minicards.types.PartGrid;
-import com.codigoparallevar.minicards.types.Tuple2;
+import com.codigoparallevar.minicards.types.functional.Tuple2;
 
 public abstract class PartInstantiator {
     protected abstract Part instantiate(PartGrid grid, Tuple2<Integer, Integer> center);

app/src/main/java/com/codigoparallevar/minicards/PartsHolder.java

@@ -12,7 +12,7 @@ import com.codigoparallevar.minicards.parts.logic.Toggle;
 import com.codigoparallevar.minicards.parts.samples.ColorBox;
 import com.codigoparallevar.minicards.parts.strings.ConvertToString;
 import com.codigoparallevar.minicards.types.Part;
-import com.codigoparallevar.minicards.types.Tuple2;
+import com.codigoparallevar.minicards.types.functional.Tuple2;
 
 import java.util.List;
 import java.util.Vector;

app/src/main/java/com/codigoparallevar/minicards/ScrolledCanvas.java

@@ -6,7 +6,7 @@ import android.graphics.Path;
 import android.graphics.Rect;
 import androidx.annotation.NonNull;
 
-import com.codigoparallevar.minicards.types.Tuple2;
+import com.codigoparallevar.minicards.types.functional.Tuple2;
 
 public class ScrolledCanvas {
     private final Canvas canvas;

app/src/main/java/com/codigoparallevar/minicards/StubPartGrid.java

@@ -2,7 +2,7 @@ package com.codigoparallevar.minicards;
 
 import com.codigoparallevar.minicards.types.PartGrid;
 import com.codigoparallevar.minicards.types.Selectable;
-import com.codigoparallevar.minicards.types.Tuple2;
+import com.codigoparallevar.minicards.types.functional.Tuple2;
 import com.codigoparallevar.minicards.types.connectors.input.BooleanInputConnector;
 import com.codigoparallevar.minicards.types.connectors.input.SignalInputConnector;
 import com.codigoparallevar.minicards.types.connectors.input.StringInputConnector;

app/src/main/java/com/codigoparallevar/minicards/parts/buttons/RoundButton.java

@@ -11,7 +11,7 @@ import com.codigoparallevar.minicards.types.Moveable;
 import com.codigoparallevar.minicards.types.Part;
 import com.codigoparallevar.minicards.types.PartConnection;
 import com.codigoparallevar.minicards.types.PartGrid;
-import com.codigoparallevar.minicards.types.Tuple2;
+import com.codigoparallevar.minicards.types.functional.Tuple2;
 import com.codigoparallevar.minicards.types.connectors.input.InputConnector;
 import com.codigoparallevar.minicards.types.connectors.output.OutputConnector;
 import com.codigoparallevar.minicards.types.wireData.Signal;

app/src/main/java/com/codigoparallevar/minicards/parts/connectors/BooleanRoundOutputConnector.java

@@ -7,7 +7,7 @@ import com.codigoparallevar.minicards.types.Drawable;
 import com.codigoparallevar.minicards.types.Moveable;
 import com.codigoparallevar.minicards.types.Part;
 import com.codigoparallevar.minicards.types.PartGrid;
-import com.codigoparallevar.minicards.types.Tuple2;
+import com.codigoparallevar.minicards.types.functional.Tuple2;
 import com.codigoparallevar.minicards.types.connectors.Wiring.BooleanWire;
 import com.codigoparallevar.minicards.types.connectors.input.BooleanInputConnector;
 import com.codigoparallevar.minicards.types.connectors.input.InputConnector;

app/src/main/java/com/codigoparallevar/minicards/parts/connectors/RoundOutputConnector.java

@@ -7,7 +7,7 @@ import com.codigoparallevar.minicards.types.Drawable;
 import com.codigoparallevar.minicards.types.Moveable;
 import com.codigoparallevar.minicards.types.Part;
 import com.codigoparallevar.minicards.types.PartGrid;
-import com.codigoparallevar.minicards.types.Tuple2;
+import com.codigoparallevar.minicards.types.functional.Tuple2;
 import com.codigoparallevar.minicards.types.connectors.Wiring.SignalWire;
 import com.codigoparallevar.minicards.types.connectors.input.InputConnector;
 import com.codigoparallevar.minicards.types.connectors.input.SignalInputConnector;

app/src/main/java/com/codigoparallevar/minicards/parts/connectors/StringRoundOutputConnector.java

@@ -7,7 +7,7 @@ import com.codigoparallevar.minicards.types.Drawable;
 import com.codigoparallevar.minicards.types.Moveable;
 import com.codigoparallevar.minicards.types.Part;
 import com.codigoparallevar.minicards.types.PartGrid;
-import com.codigoparallevar.minicards.types.Tuple2;
+import com.codigoparallevar.minicards.types.functional.Tuple2;
 import com.codigoparallevar.minicards.types.connectors.Wiring.StringWire;
 import com.codigoparallevar.minicards.types.connectors.input.InputConnector;
 import com.codigoparallevar.minicards.types.connectors.input.StringInputConnector;

app/src/main/java/com/codigoparallevar/minicards/parts/logic/Ticker.java

@@ -12,7 +12,7 @@ import com.codigoparallevar.minicards.types.Moveable;
 import com.codigoparallevar.minicards.types.Part;
 import com.codigoparallevar.minicards.types.PartConnection;
 import com.codigoparallevar.minicards.types.PartGrid;
-import com.codigoparallevar.minicards.types.Tuple2;
+import com.codigoparallevar.minicards.types.functional.Tuple2;
 import com.codigoparallevar.minicards.types.connectors.input.InputConnector;
 import com.codigoparallevar.minicards.types.connectors.output.OutputConnector;
 import com.codigoparallevar.minicards.types.wireData.Signal;

app/src/main/java/com/codigoparallevar/minicards/parts/logic/Toggle.java

@@ -13,7 +13,7 @@ import com.codigoparallevar.minicards.types.Moveable;
 import com.codigoparallevar.minicards.types.Part;
 import com.codigoparallevar.minicards.types.PartConnection;
 import com.codigoparallevar.minicards.types.PartGrid;
-import com.codigoparallevar.minicards.types.Tuple2;
+import com.codigoparallevar.minicards.types.functional.Tuple2;
 import com.codigoparallevar.minicards.types.connectors.input.InputConnector;
 import com.codigoparallevar.minicards.types.connectors.input.SignalInputConnector;
 import com.codigoparallevar.minicards.types.connectors.output.OutputConnector;

app/src/main/java/com/codigoparallevar/minicards/parts/samples/ColorBox.java

@@ -11,7 +11,7 @@ import com.codigoparallevar.minicards.parts.connectors.BooleanRoundInputConnecto
 import com.codigoparallevar.minicards.types.Moveable;
 import com.codigoparallevar.minicards.types.Part;
 import com.codigoparallevar.minicards.types.PartGrid;
-import com.codigoparallevar.minicards.types.Tuple2;
+import com.codigoparallevar.minicards.types.functional.Tuple2;
 import com.codigoparallevar.minicards.types.connectors.input.BooleanInputConnector;
 import com.codigoparallevar.minicards.types.connectors.input.InputConnector;
 import com.codigoparallevar.minicards.types.connectors.output.OutputConnector;

app/src/main/java/com/codigoparallevar/minicards/parts/strings/ConvertToString.java

@@ -14,7 +14,7 @@ import com.codigoparallevar.minicards.types.Moveable;
 import com.codigoparallevar.minicards.types.Part;
 import com.codigoparallevar.minicards.types.PartConnection;
 import com.codigoparallevar.minicards.types.PartGrid;
-import com.codigoparallevar.minicards.types.Tuple2;
+import com.codigoparallevar.minicards.types.functional.Tuple2;
 import com.codigoparallevar.minicards.types.connectors.input.AnyInputConnector;
 import com.codigoparallevar.minicards.types.connectors.input.InputConnector;
 import com.codigoparallevar.minicards.types.connectors.output.OutputConnector;

app/src/main/java/com/codigoparallevar/minicards/types/PartGrid.java

@@ -3,6 +3,7 @@ package com.codigoparallevar.minicards.types;
 import com.codigoparallevar.minicards.types.connectors.input.BooleanInputConnector;
 import com.codigoparallevar.minicards.types.connectors.input.SignalInputConnector;
 import com.codigoparallevar.minicards.types.connectors.input.StringInputConnector;
+import com.codigoparallevar.minicards.types.functional.Tuple2;
 
 public interface PartGrid {
     Selectable getPartOn(int x, int y);

app/src/main/java/com/codigoparallevar/minicards/types/connectors/output/OutputConnector.java

@@ -3,7 +3,7 @@ package com.codigoparallevar.minicards.types.connectors.output;
 import com.codigoparallevar.minicards.ScrolledCanvas;
 import com.codigoparallevar.minicards.types.Dropper;
 import com.codigoparallevar.minicards.types.Selectable;
-import com.codigoparallevar.minicards.types.Tuple2;
+import com.codigoparallevar.minicards.types.functional.Tuple2;
 import com.codigoparallevar.minicards.types.connectors.Wiring.Wire;
 import com.codigoparallevar.minicards.types.connectors.input.InputConnector;
 import com.codigoparallevar.minicards.types.wireData.WireDataType;

app/src/main/java/com/codigoparallevar/minicards/types/functional/Function.java

@@ -0,0 +1,5 @@
+package com.codigoparallevar.minicards.types.functional;
+
+public abstract class Function<T> {
+    public abstract void apply(T param);
+}

app/src/main/java/com/codigoparallevar/minicards/types/functional/Tuple2.java

@@ -1,4 +1,4 @@
-package com.codigoparallevar.minicards.types;
+package com.codigoparallevar.minicards.types.functional;
 
 public class Tuple2<T1, T2> {
     public final T1 item1;

app/src/main/java/com/codigoparallevar/minicards/types/functional/Tuple3.java

@@ -0,0 +1,19 @@
+package com.codigoparallevar.minicards.types.functional;
+
+public class Tuple3<T, T1, T2> {
+
+    public final T _x;
+    public final T1 _y;
+    public final T2 _z;
+
+    public Tuple3(T x, T1 y, T2 z) {
+        _x = x;
+        _y = y;
+        _z = z;
+    }
+
+    @Override
+    public String toString(){
+        return "(" + _x + " - " + _y + ", " + _z + ")";
+    }
+}

app/src/main/java/com/codigoparallevar/minicards/types/functional/Tuple4.java

@@ -1,4 +1,4 @@
-package com.codigoparallevar.minicards.types;
+package com.codigoparallevar.minicards.types.functional;
 
 public class Tuple4<T, T1, T2, T3> {
 

app/src/main/java/com/programaker/api/ProgramakerApi.kt

@@ -1,24 +1,25 @@
 package com.programaker.api
 
 import android.os.Build
-import android.util.JsonReader
 import android.util.Log
 import com.google.gson.Gson
-import com.google.gson.GsonBuilder
+import org.json.JSONObject
-import java.io.*
+import java.io.DataOutputStream
+import java.io.FileNotFoundException
+import java.io.InputStream
+import java.io.InputStreamReader
 import java.lang.reflect.Type
 import java.net.HttpURLConnection
 import java.net.URL
 import java.net.URLConnection
-import javax.net.ssl.HttpsURLConnection
 
 
 class ProgramakerApi(private val ApiRoot: String="https://programaker.com/api") {
     private val LogTag: String = "ProgramakerApi"
-    private val TokenEntry: String = "ProgramakerAuthToken"
+    var token: String? = null
 
     // API
-    fun Check(): Boolean {
+    fun check(): Boolean {
         val conn = URL(getCheckUrl()).openConnection() as HttpURLConnection
         if (conn == null){
             Log.e(LogTag, "URL Connection not established, set to NULL")
@@ -36,10 +37,34 @@ class ProgramakerApi(private val ApiRoot: String="https://programaker.com/api")
         } catch(ex: JsonParseException) {
             ex.logError(LogTag)
             return false
+        } catch (ex: FileNotFoundException) {
+            ex.logError(LogTag)
+            return false
         }
         return result.success
     }
 
+    fun login(user: String, password: String): String {
+        val conn = URL(getLoginUrl()).openConnection() as HttpURLConnection
+        conn.setRequestProperty("Content-Type", "application/json")
+
+        conn.requestMethod = "POST";
+        conn.doOutput = true;
+
+        val postData = JSONObject()
+        postData.put("username", user)
+        postData.put("password", password)
+
+        val wr = DataOutputStream(conn.outputStream)
+        wr.writeBytes(postData.toString());
+        wr.flush();
+        wr.close();
+
+        val result: ProgramakerLoginResult
+        result = parseJson(conn.inputStream, ProgramakerLoginResult::class.java)
+        return result.token
+    }
+
     // Initialization
     init {
         // Disable connection reuse if necessary
@@ -51,11 +76,20 @@ class ProgramakerApi(private val ApiRoot: String="https://programaker.com/api")
 
     // Private functions
     private fun getCheckUrl(): String {
-        return "$ApiRoot/v0/ping"
+        return "$ApiRoot/v0/sessions/check"
+    }
+
+    private fun getLoginUrl(): String {
+        return "$ApiRoot/v0/sessions/login"
     }
 
     private fun addAuthHeader(conn: URLConnection) {
-        // TODO("not implemented") //To change body of created functions use File | Settings | File Templates.
+        if (token != null) {
+            conn.setRequestProperty("Authorization", token)
+        }
+        else {
+            throw TokenNotFoundException()
+        }
     }
 
     private fun <T>parseJson(content: InputStream, resultClass: Type): T {
@@ -65,6 +99,10 @@ class ProgramakerApi(private val ApiRoot: String="https://programaker.com/api")
     }
 }
 
+private fun FileNotFoundException.logError(tag: String) {
+    Log.e(tag, "Cannot open: ${this.message}")
+}
+
 class JsonParseException(private val content: String, private val cls: Type) : Exception() {
     fun logError(tag: String) {
         Log.e(tag, "Cannot JSON parse: ${this.content} as ${this.cls}")

app/src/main/java/com/programaker/api/ProgramakerLoginResult.kt

@@ -0,0 +1,5 @@
+package com.programaker.api
+
+class ProgramakerLoginResult(val user_id: String, val token: String, val success: Boolean) {
+
+}

app/src/main/java/com/programaker/api/ProgramakerNetworkException.kt

@@ -0,0 +1,5 @@
+package com.programaker.api
+
+class ProgramakerNetworkException : Throwable() {
+
+}

app/src/main/res/values/strings.xml

@@ -14,4 +14,5 @@
     <string name="login_username_label">Username</string>
     <string name="action_login_short">Login</string>
     <string name="loading">Loading...</string>
+    <string name="invalid_user_pass">Invalid username/password</string>
 </resources>