From 5450d67497aea8a74db431665174526e1287cb01 Mon Sep 17 00:00:00 2001
From: Riccardo Azzolini <riccardo4096@gmail.com>
Date: Sat, 6 Oct 2018 11:51:33 +0200
Subject: [PATCH] Implement SumPattern

---
 .../math/rules/dsl/patterns/SumPattern.java   | 39 ++++++++++++++
 .../warppi/math/rules/dsl/PatternTest.java    | 51 +++++++++++++++++++
 2 files changed, 90 insertions(+)
 create mode 100644 core/src/main/java/it/cavallium/warppi/math/rules/dsl/patterns/SumPattern.java

diff --git a/core/src/main/java/it/cavallium/warppi/math/rules/dsl/patterns/SumPattern.java b/core/src/main/java/it/cavallium/warppi/math/rules/dsl/patterns/SumPattern.java
new file mode 100644
index 00000000..951bd4ce
--- /dev/null
+++ b/core/src/main/java/it/cavallium/warppi/math/rules/dsl/patterns/SumPattern.java
@@ -0,0 +1,39 @@
+package it.cavallium.warppi.math.rules.dsl.patterns;
+
+import it.cavallium.warppi.math.Function;
+import it.cavallium.warppi.math.functions.Sum;
+import it.cavallium.warppi.math.rules.dsl.Pattern;
+import it.cavallium.warppi.math.rules.dsl.VisitorPattern;
+
+import java.util.Map;
+import java.util.Optional;
+
+/**
+ * Matches and generates a sum of two other patterns.
+ */
+public class SumPattern extends VisitorPattern {
+    private final Pattern left;
+    private final Pattern right;
+
+    public SumPattern(Pattern left, Pattern right) {
+        this.left = left;
+        this.right = right;
+    }
+
+    @Override
+    public Optional<Map<String, Function>> visit(Sum sum) {
+        return left.match(sum.getParameter1())
+                .flatMap(leftMatch -> right.match(sum.getParameter2())
+                        .flatMap(rightMatch -> mergeMatches(leftMatch, rightMatch))
+                );
+    }
+
+    @Override
+    public Function replace(Map<String, Function> subFunctions) {
+        return new Sum(
+                null,
+                left.replace(subFunctions),
+                right.replace(subFunctions)
+        );
+    }
+}
diff --git a/core/src/test/java/it/cavallium/warppi/math/rules/dsl/PatternTest.java b/core/src/test/java/it/cavallium/warppi/math/rules/dsl/PatternTest.java
index 0f7c1651..448154ca 100644
--- a/core/src/test/java/it/cavallium/warppi/math/rules/dsl/PatternTest.java
+++ b/core/src/test/java/it/cavallium/warppi/math/rules/dsl/PatternTest.java
@@ -2,8 +2,11 @@ package it.cavallium.warppi.math.rules.dsl;
 
 import it.cavallium.warppi.math.Function;
 import it.cavallium.warppi.math.functions.Number;
+import it.cavallium.warppi.math.functions.Subtraction;
 import it.cavallium.warppi.math.functions.Sum;
+import it.cavallium.warppi.math.functions.Variable;
 import it.cavallium.warppi.math.rules.dsl.patterns.SubFunctionPattern;
+import it.cavallium.warppi.math.rules.dsl.patterns.SumPattern;
 import org.junit.Test;
 
 import java.util.Map;
@@ -27,4 +30,52 @@ public class PatternTest {
 
         assertEquals(func, pattern.replace(subFunctions.get()));
     }
+
+    @Test
+    public void sumPattern() {
+        final Pattern pattern = new SumPattern(
+                new SubFunctionPattern("x"),
+                new SubFunctionPattern("y")
+        );
+
+        final Function shouldNotMatch = new Subtraction(
+                null,
+                new Number(null, 1),
+                new Number(null, 2)
+        );
+        assertFalse(pattern.match(shouldNotMatch).isPresent());
+
+        final Function shouldMatch = new Sum(
+                null,
+                new Number(null, 1),
+                new Number(null, 2)
+        );
+        final Optional<Map<String, Function>> subFunctions = pattern.match(shouldMatch);
+        assertTrue(subFunctions.isPresent());
+        assertEquals(shouldMatch, pattern.replace(subFunctions.get()));
+    }
+
+    @Test
+    public void repeatedSubFunction() {
+        final Pattern pattern = new SumPattern(
+                new SubFunctionPattern("x"),
+                new SubFunctionPattern("x")
+        );
+
+        final Function shouldMatch = new Sum(
+                null,
+                new Number(null, 1),
+                new Number(null, 1)
+        );
+        final Optional<Map<String, Function>> subFunctions = pattern.match(shouldMatch);
+        assertTrue(subFunctions.isPresent());
+        assertEquals(shouldMatch, pattern.replace(subFunctions.get()));
+
+        final Function shouldNotMatch = new Sum(
+                null,
+                new Number(null, 1),
+                new Number(null, 2)
+        );
+        assertFalse(pattern.match(shouldNotMatch).isPresent());
+    }
 }
\ No newline at end of file