Handle missing methods in one place

7 files changed, 27 insertions, 19 deletions

diff --git a/src/main/java/org/zwobble/couscous/interpreter/Evaluator.java b/src/main/java/org/zwobble/couscous/interpreter/Evaluator.java
index 7a57137..7aba54b 100644
--- a/src/main/java/org/zwobble/couscous/interpreter/Evaluator.java
+++ b/src/main/java/org/zwobble/couscous/interpreter/Evaluator.java
@@ -65,7 +65,8 @@ public class Evaluator implements ExpressionNodeVisitor<InterpreterValue> {
             .stream()
             .map(argument -> eval(argument))
             .collect(Collectors.toList());
-        // TODO: handle missing methods
-        return receiver.callMethod(methodCall.getMethodName(), arguments);
+        val method = receiver.getMethod(methodCall.getMethodName())
+            .orElseThrow(() -> new NoSuchMethod(methodCall.getMethodName()));
+        return method.call(arguments);
     }
 }
diff --git a/src/main/java/org/zwobble/couscous/values/BooleanValue.java b/src/main/java/org/zwobble/couscous/values/BooleanValue.java
index dd8cd39..0bcb256 100644
--- a/src/main/java/org/zwobble/couscous/values/BooleanValue.java
+++ b/src/main/java/org/zwobble/couscous/values/BooleanValue.java
@@ -1,6 +1,6 @@
 package org.zwobble.couscous.values;
 
-import java.util.List;
+import java.util.Optional;
 
 import lombok.AccessLevel;
 import lombok.Getter;
@@ -16,7 +16,7 @@ public class BooleanValue implements InterpreterValue {
     }
 
     @Override
-    public InterpreterValue callMethod(String methodName, List<InterpreterValue> arguments) {
+    public Optional<MethodValue> getMethod(String methodName) {
         throw new UnsupportedOperationException();
     }
 }
diff --git a/src/main/java/org/zwobble/couscous/values/IntegerValue.java b/src/main/java/org/zwobble/couscous/values/IntegerValue.java
index acc0c56..9b77b69 100644
--- a/src/main/java/org/zwobble/couscous/values/IntegerValue.java
+++ b/src/main/java/org/zwobble/couscous/values/IntegerValue.java
@@ -1,6 +1,6 @@
 package org.zwobble.couscous.values;
 
-import java.util.List;
+import java.util.Optional;
 
 import lombok.Value;
 
@@ -9,7 +9,7 @@ public class IntegerValue implements InterpreterValue {
     int value;
 
     @Override
-    public InterpreterValue callMethod(String methodName, List<InterpreterValue> arguments) {
+    public Optional<MethodValue> getMethod(String methodName) {
         throw new UnsupportedOperationException();
     }
 }
diff --git a/src/main/java/org/zwobble/couscous/values/InterpreterValue.java b/src/main/java/org/zwobble/couscous/values/InterpreterValue.java
index 6162aaa..17a3722 100644
--- a/src/main/java/org/zwobble/couscous/values/InterpreterValue.java
+++ b/src/main/java/org/zwobble/couscous/values/InterpreterValue.java
@@ -1,7 +1,7 @@
 package org.zwobble.couscous.values;
 
-import java.util.List;
+import java.util.Optional;
 
 public interface InterpreterValue {
-    InterpreterValue callMethod(String methodName, List<InterpreterValue> arguments);
+    Optional<MethodValue> getMethod(String methodName);
 }
diff --git a/src/main/java/org/zwobble/couscous/values/MethodValue.java b/src/main/java/org/zwobble/couscous/values/MethodValue.java
new file mode 100644
index 0000000..38ef1d5
--- /dev/null
+++ b/src/main/java/org/zwobble/couscous/values/MethodValue.java
@@ -0,0 +1,7 @@
+package org.zwobble.couscous.values;
+
+import java.util.List;
+
+public interface MethodValue {
+    InterpreterValue call(List<InterpreterValue> arguments);
+}
diff --git a/src/main/java/org/zwobble/couscous/values/StringValue.java b/src/main/java/org/zwobble/couscous/values/StringValue.java
index 9cf81ff..3f4b2b0 100644
--- a/src/main/java/org/zwobble/couscous/values/StringValue.java
+++ b/src/main/java/org/zwobble/couscous/values/StringValue.java
@@ -1,8 +1,6 @@
 package org.zwobble.couscous.values;
 
-import java.util.List;
-
-import org.zwobble.couscous.interpreter.NoSuchMethod;
+import java.util.Optional;
 
 import lombok.Value;
 import lombok.val;
@@ -12,15 +10,17 @@ public class StringValue implements InterpreterValue {
     String value;
 
     @Override
-    public InterpreterValue callMethod(String methodName, List<InterpreterValue> arguments) {
+    public Optional<MethodValue> getMethod(String methodName) {
         if (methodName == "length") {
-            return new IntegerValue(value.length());
+            return Optional.of(arguments -> new IntegerValue(value.length()));
         } else if (methodName == "substring") {
-            val startIndex = (IntegerValue)arguments.get(0);
-            val endIndex = (IntegerValue)arguments.get(1);
-            return new StringValue(value.substring(startIndex.getValue(), endIndex.getValue()));
+            return Optional.of(arguments -> {
+                val startIndex = (IntegerValue)arguments.get(0);
+                val endIndex = (IntegerValue)arguments.get(1);
+                return new StringValue(value.substring(startIndex.getValue(), endIndex.getValue()));
+            });
         } else {
-            throw new NoSuchMethod(methodName);
+            return Optional.empty();
         }
     }
 }
diff --git a/src/main/java/org/zwobble/couscous/values/UnitValue.java b/src/main/java/org/zwobble/couscous/values/UnitValue.java
index 030fb03..8d75529 100644
--- a/src/main/java/org/zwobble/couscous/values/UnitValue.java
+++ b/src/main/java/org/zwobble/couscous/values/UnitValue.java
@@ -1,6 +1,6 @@
 package org.zwobble.couscous.values;
 
-import java.util.List;
+import java.util.Optional;
 
 import lombok.ToString;
 
@@ -12,7 +12,7 @@ public class UnitValue implements InterpreterValue {
     }
 
     @Override
-    public InterpreterValue callMethod(String methodName, List<InterpreterValue> arguments) {
+    public Optional<MethodValue> getMethod(String methodName) {
         throw new UnsupportedOperationException();
     }
 }