add calculator history class

engine/src/main/java/mscalc/engine/CalculatorHistory.java

@@ -0,0 +1,108 @@
+package mscalc.engine;
+
+import mscalc.engine.commands.IExpressionCommand;
+
+import java.util.ArrayList;
+import java.util.List;
+
+public class CalculatorHistory implements HistoryDisplay {
+    static class HISTORYITEMVECTOR
+    {
+        List<Pair<String, Integer>> spTokens = new ArrayList<>();
+        List<IExpressionCommand> spCommands = new ArrayList<>();
+        String expression = "";
+        String result = "";
+    }
+
+    static class HISTORYITEM
+    {
+        HISTORYITEMVECTOR historyItemVector = new HISTORYITEMVECTOR();
+    }
+
+    private final List<HISTORYITEM> m_historyItems = new ArrayList<>();
+    private final int m_maxHistorySize;
+
+    public CalculatorHistory(int maxSize) {
+        this.m_maxHistorySize = maxSize;
+    }
+
+    public int MaxHistorySize()
+    {
+        return m_maxHistorySize;
+    }
+
+    static String GetGeneratedExpression(List<Pair<String, Integer>> tokens)
+    {
+        StringBuilder expression = new StringBuilder();
+        boolean isFirst = true;
+
+        for (var token : tokens)
+        {
+            if (isFirst)
+            {
+                isFirst = false;
+            }
+            else
+            {
+                expression.append(' ');
+            }
+            expression.append(token.getKey());
+        }
+
+        return expression.toString();
+    }
+
+    @Override
+    public int addToHistory(List<Pair<String, Integer>> tokens, List<IExpressionCommand> commands, String result) {
+        HISTORYITEM spHistoryItem = new HISTORYITEM();
+
+        spHistoryItem.historyItemVector.spTokens = tokens;
+        spHistoryItem.historyItemVector.spCommands = commands;
+        spHistoryItem.historyItemVector.expression = GetGeneratedExpression(tokens);
+        spHistoryItem.historyItemVector.result = result;
+        return AddItem(spHistoryItem);
+    }
+
+    int AddItem(HISTORYITEM spHistoryItem)
+    {
+        if (m_historyItems.size() >= m_maxHistorySize)
+        {
+            m_historyItems.removeFirst();
+        }
+
+        m_historyItems.add(spHistoryItem);
+        return (m_historyItems.size() - 1);
+    }
+
+    boolean RemoveItem(int uIdx)
+    {
+        if (uIdx < m_historyItems.size())
+        {
+            m_historyItems.remove(uIdx);
+            return true;
+        }
+
+        return false;
+    }
+
+    List<HISTORYITEM> GetHistory()
+    {
+        return m_historyItems;
+    }
+
+    HISTORYITEM GetHistoryItem(int uIdx)
+    {
+        assert(uIdx < m_historyItems.size());
+        return m_historyItems.get(uIdx);
+    }
+
+    void ClearHistory()
+    {
+        m_historyItems.clear();
+    }
+
+    @Override
+    public void close() throws Exception {
+
+    }
+}