Implement a table as a history tracker.

src/org/nwapw/abacus/window/HistoryTableModel.java

@@ -0,0 +1,97 @@
+package org.nwapw.abacus.window;
+
+import org.nwapw.abacus.tree.TreeNode;
+
+import javax.swing.event.TableModelListener;
+import javax.swing.table.AbstractTableModel;
+import javax.swing.table.TableModel;
+import java.util.ArrayList;
+
+public class HistoryTableModel extends AbstractTableModel {
+
+    public static final String[] COLUMN_NAMES = {
+            "Input",
+            "Parsed Input",
+            "Output"
+    };
+
+    public static final Class[] CLASS_TYPES = {
+            String.class,
+            TreeNode.class,
+            String.class
+    };
+
+    public static class HistoryEntry {
+        public String input;
+        public TreeNode parsedInput;
+        public String output;
+
+        public HistoryEntry(String input, TreeNode parsedInput, String output){
+            this.input = input;
+            this.parsedInput = parsedInput;
+            this.output = output;
+        }
+
+        Object nthValue(int n){
+            if(n == 0) return input;
+            if(n == 1) return parsedInput;
+            if(n == 2) return output;
+            return null;
+        }
+    }
+
+    ArrayList<HistoryEntry> entries;
+
+    public HistoryTableModel() {
+        entries = new ArrayList<>();
+    }
+
+    public void addEntry(HistoryEntry entry){
+        entries.add(entry);
+    }
+
+        @Override
+    public int getRowCount() {
+        return entries.size();
+    }
+
+    @Override
+    public int getColumnCount() {
+        return 3;
+    }
+
+    @Override
+    public String getColumnName(int columnIndex) {
+        return COLUMN_NAMES[columnIndex];
+    }
+
+    @Override
+    public Class<?> getColumnClass(int columnIndex) {
+        return CLASS_TYPES[columnIndex];
+    }
+
+    @Override
+    public boolean isCellEditable(int rowIndex, int columnIndex) {
+        return false;
+    }
+
+    @Override
+    public Object getValueAt(int rowIndex, int columnIndex) {
+        return entries.get(rowIndex).nthValue(columnIndex);
+    }
+
+    @Override
+    public void setValueAt(Object aValue, int rowIndex, int columnIndex) {
+        return;
+    }
+
+    @Override
+    public void addTableModelListener(TableModelListener l) {
+
+    }
+
+    @Override
+    public void removeTableModelListener(TableModelListener l) {
+
+    }
+}

src/org/nwapw/abacus/window/Window.java

@@ -45,13 +45,17 @@ public class Window extends JFrame {
      */
     private JTextArea lastOutputArea;
     /**
-     * The text area used for all history output.
+     * The table used for storing history results.
      */
-    private JTextArea historyArea;
+    private JTable historyTable;
+    /**
+     * The table model used for managing history.
+     */
+    private HistoryTableModel historyModel;
     /**
      * The scroll pane for the history area.
      */
-    private JScrollPane historyAreaScroll;
+    private JScrollPane historyScroll;
 
     /**
      * The panel where the input occurs.
@@ -109,7 +113,6 @@ public class Window extends JFrame {
     private Window() {
         super();
 
-
         history = "";
         lastOutput = "";
 
@@ -123,15 +126,15 @@ public class Window extends JFrame {
         inputPanel.add(inputField, BorderLayout.CENTER);
         inputPanel.add(inputEnterButton, BorderLayout.EAST);
 
-        historyArea = new JTextArea(history);
+        historyModel = new HistoryTableModel();
-        historyAreaScroll = new JScrollPane(historyArea);
+        historyTable = new JTable(historyModel);
+        historyScroll = new JScrollPane(historyTable);
         lastOutputArea = new JTextArea(lastOutput);
         lastOutputArea.setEditable(false);
-        lastOutputArea.setText(":)");
 
         outputPanel = new JPanel();
         outputPanel.setLayout(new BorderLayout());
-        outputPanel.add(historyAreaScroll, BorderLayout.CENTER);
+        outputPanel.add(historyScroll, BorderLayout.CENTER);
         outputPanel.add(lastOutputArea, BorderLayout.SOUTH);
 
         numberSystemList = new JComboBox<>();
@@ -158,5 +161,21 @@ public class Window extends JFrame {
         add(outputPanel, BorderLayout.CENTER);
         add(sidePanel, BorderLayout.EAST);
         add(inputPanel, BorderLayout.SOUTH);
+
+        inputEnterButton.addActionListener((event) -> {
+            TreeNode parsedExpression = TreeNode.fromString(inputField.getText());
+            if(parsedExpression == null){
+                lastOutputArea.setText(SYNTAX_ERR_STRING);
+                return;
+            }
+            lastOutput = parsedExpression.reduce(reducer).toString();
+            history += (history.length() == 0) ? "" : "\n\n";
+            history += lastOutput;
+
+            historyModel.addEntry(new HistoryTableModel.HistoryEntry(inputField.getText(), parsedExpression, lastOutput));
+            historyTable.invalidate();
+            lastOutputArea.setText(lastOutput);
+            inputField.setText(lastOutput);
+        });
     }
 }