Make candlestick calc configurable

src/main/java/ats/plugin/CandlestickCalc.java

@@ -5,6 +5,7 @@ package ats.plugin;
  * values.  For example, OHLC or Heikin-Ashi.
  */
 interface CandlestickCalc {
+    public enum Type { OHLC, HeikinAshi };
 
     /**
      * Reset the calculation for the beginning of an interval.

src/main/java/ats/plugin/HeikinAshiCandlestickCalc.java

@@ -0,0 +1,57 @@
+package ats.plugin;
+
+/**
+ * HeikinAshiCandlestickCalc calculates values using the Heikin-Ashi
+ * technique.
+ */
+class HeikinAshiCandlestickCalc implements CandlestickCalc {
+    private Double open;
+    private Double close;
+    private Double high;
+    private Double low;
+
+    
+    /**
+     * Reset the calculation for the beginning of an interval.
+     */
+    @Override
+    public void reset() {
+        open = null;
+        close = null;
+        high = null;
+        low = null;
+    }
+
+    /**
+     * Accept a current tick value to apply to the current
+     * calculations.
+     */
+    @Override
+    public void applyValue(double value) {
+        if (open == null) {
+            open = value;
+        }
+
+        close = value;
+
+        if (low == null) {
+            low = value;
+        } else if (low.compareTo(value) > 0) {
+            low = value;
+        }
+
+        if (high == null) {
+            high = value;
+        } else if (high.compareTo(value) < 0) {
+            high = value;
+        }
+    }
+
+    /**
+     * Return our calculated values up to now.
+     */
+    @Override
+    public OHLCValues getValues() {
+         return new OHLCValues(open, high, low, close);
+    }
+}

src/main/java/ats/plugin/OHLCPlugInView.java

@@ -27,6 +27,9 @@ public class OHLCPlugInView extends ViewSupport {
     private EventBean[] lastData;
 
 
+    /**
+     * Create a new plugin.
+     */
     public OHLCPlugInView(AgentInstanceViewFactoryChainContext context,
                           ExprNode calcTypeExpression,
                           ExprNode timeTypeExpression,
@@ -39,8 +42,32 @@ public class OHLCPlugInView extends ViewSupport {
         this.valueExpression = valueExpression;
         service = context.getStatementContext().getEventAdapterService();
 
-        CandlestickCalc calc = new OHLCCandlestickCalc();
         window = new DurationWindow(this, calc, context, intervalExpression);
+        CandlestickCalc calc = chooseCalc(calcTypeExpression);
+    }
+
+    /**
+     * Return the proper CandlestickCalc according to the value of the
+     * calc type parameter.
+     */
+    private CandlestickCalc chooseCalc(ExprNode calcTypeExpression) {
+        String calcType = exprNodeValue(calcTypeExpression);
+
+        if (CandlestickCalc.Type.valueOf(calcType) == CandlestickCalc.Type.HeikinAshi) {
+            log.info("Using Heikin-Ashi calc type");
+            return new HeikinAshiCandlestickCalc();
+        }
+
+        log.info("Using OHLC calc type");
+        return new OHLCCandlestickCalc();
+    }
+
+    /**
+     * Return the string value of a node.
+     */
+    private String exprNodeValue(ExprNode node) {
+        ExprEvaluator evaluator = node.getForge().getExprEvaluator();
+        return (String)evaluator.evaluate(null, true, context);
     }
 
     /**