Initial commit

22 files changed, 348 insertions, 0 deletions

diff --git a/src/main/java/org/zwobble/couscous/Project.java b/src/main/java/org/zwobble/couscous/Project.java
new file mode 100644
index 0000000..6afac6e
--- /dev/null
+++ b/src/main/java/org/zwobble/couscous/Project.java
@@ -0,0 +1,7 @@
+package org.zwobble.couscous;
+
+import org.zwobble.couscous.ast.ClassNode;
+
+public interface Project {
+    ClassNode findClass(String name);
+}
diff --git a/src/main/java/org/zwobble/couscous/ast/Assignment.java b/src/main/java/org/zwobble/couscous/ast/Assignment.java
new file mode 100644
index 0000000..aa7f89b
--- /dev/null
+++ b/src/main/java/org/zwobble/couscous/ast/Assignment.java
@@ -0,0 +1,16 @@
+package org.zwobble.couscous.ast;
+
+import org.zwobble.couscous.ast.visitors.ExpressionNodeVisitor;
+
+import lombok.Value;
+
+@Value
+public class Assignment implements ExpressionNode {
+    VariableReferenceNode target;
+    ExpressionNode value;
+    
+    @Override
+    public <T> T accept(ExpressionNodeVisitor<T> visitor) {
+        return visitor.visit(this);
+    }
+}
diff --git a/src/main/java/org/zwobble/couscous/ast/CallNode.java b/src/main/java/org/zwobble/couscous/ast/CallNode.java
new file mode 100644
index 0000000..d71c891
--- /dev/null
+++ b/src/main/java/org/zwobble/couscous/ast/CallNode.java
@@ -0,0 +1,5 @@
+package org.zwobble.couscous.ast;
+
+public class CallNode {
+
+}
diff --git a/src/main/java/org/zwobble/couscous/ast/ClassNode.java b/src/main/java/org/zwobble/couscous/ast/ClassNode.java
new file mode 100644
index 0000000..ffa5165
--- /dev/null
+++ b/src/main/java/org/zwobble/couscous/ast/ClassNode.java
@@ -0,0 +1,14 @@
+package org.zwobble.couscous.ast;
+
+import java.util.List;
+
+import lombok.Builder;
+import lombok.Singular;
+import lombok.Value;
+
+@Builder
+@Value
+public class ClassNode {
+    @Singular
+    List<MethodNode> methods;
+}
diff --git a/src/main/java/org/zwobble/couscous/ast/ExpressionNode.java b/src/main/java/org/zwobble/couscous/ast/ExpressionNode.java
new file mode 100644
index 0000000..097377a
--- /dev/null
+++ b/src/main/java/org/zwobble/couscous/ast/ExpressionNode.java
@@ -0,0 +1,7 @@
+package org.zwobble.couscous.ast;
+
+import org.zwobble.couscous.ast.visitors.ExpressionNodeVisitor;
+
+public interface ExpressionNode {
+    <T> T accept(ExpressionNodeVisitor<T> visitor);
+}
diff --git a/src/main/java/org/zwobble/couscous/ast/ExpressionStatementNode.java b/src/main/java/org/zwobble/couscous/ast/ExpressionStatementNode.java
new file mode 100644
index 0000000..ec04663
--- /dev/null
+++ b/src/main/java/org/zwobble/couscous/ast/ExpressionStatementNode.java
@@ -0,0 +1,15 @@
+package org.zwobble.couscous.ast;
+
+import org.zwobble.couscous.ast.visitors.StatementNodeVisitor;
+
+import lombok.Value;
+
+@Value
+public class ExpressionStatementNode implements StatementNode {
+    ExpressionNode expression;
+
+    @Override
+    public <T> T accept(StatementNodeVisitor<T> visitor) {
+        return visitor.visit(this);
+    }
+}
diff --git a/src/main/java/org/zwobble/couscous/ast/FormalArgumentNode.java b/src/main/java/org/zwobble/couscous/ast/FormalArgumentNode.java
new file mode 100644
index 0000000..da3a838
--- /dev/null
+++ b/src/main/java/org/zwobble/couscous/ast/FormalArgumentNode.java
@@ -0,0 +1,9 @@
+package org.zwobble.couscous.ast;
+
+import lombok.Value;
+
+@Value
+public class FormalArgumentNode implements VariableNode {
+    int id;
+    String name;
+}
diff --git a/src/main/java/org/zwobble/couscous/ast/LiteralNode.java b/src/main/java/org/zwobble/couscous/ast/LiteralNode.java
new file mode 100644
index 0000000..38688d8
--- /dev/null
+++ b/src/main/java/org/zwobble/couscous/ast/LiteralNode.java
@@ -0,0 +1,26 @@
+package org.zwobble.couscous.ast;
+
+import org.zwobble.couscous.ast.visitors.ExpressionNodeVisitor;
+import org.zwobble.couscous.values.IntegerValue;
+import org.zwobble.couscous.values.InterpreterValue;
+import org.zwobble.couscous.values.StringValue;
+
+import lombok.Value;
+
+@Value
+public class LiteralNode implements ExpressionNode {
+    public static LiteralNode of(String value) {
+        return new LiteralNode(new StringValue(value));
+    }
+    
+    public static LiteralNode of(int value) {
+        return new LiteralNode(new IntegerValue(value));
+    }
+    
+    InterpreterValue value;
+
+    @Override
+    public <T> T accept(ExpressionNodeVisitor<T> visitor) {
+        return visitor.visit(this);
+    }
+}
diff --git a/src/main/java/org/zwobble/couscous/ast/MethodNode.java b/src/main/java/org/zwobble/couscous/ast/MethodNode.java
new file mode 100644
index 0000000..91acbd5
--- /dev/null
+++ b/src/main/java/org/zwobble/couscous/ast/MethodNode.java
@@ -0,0 +1,22 @@
+package org.zwobble.couscous.ast;
+
+import java.util.List;
+
+import lombok.Builder;
+import lombok.Singular;
+import lombok.Value;
+
+@Builder
+@Value
+public class MethodNode {
+    public static MethodNodeBuilder staticMethod(String name) {
+        return builder().isStatic(true).name(name);
+    }
+    
+    boolean isStatic;
+    String name;
+    @Singular
+    List<FormalArgumentNode> arguments; 
+    @Singular("statement")
+    List<StatementNode> body;
+}
diff --git a/src/main/java/org/zwobble/couscous/ast/ReturnNode.java b/src/main/java/org/zwobble/couscous/ast/ReturnNode.java
new file mode 100644
index 0000000..529dbb5
--- /dev/null
+++ b/src/main/java/org/zwobble/couscous/ast/ReturnNode.java
@@ -0,0 +1,15 @@
+package org.zwobble.couscous.ast;
+
+import org.zwobble.couscous.ast.visitors.StatementNodeVisitor;
+
+import lombok.Value;
+
+@Value
+public class ReturnNode implements StatementNode {
+    ExpressionNode value;
+
+    @Override
+    public <T> T accept(StatementNodeVisitor<T> visitor) {
+        return visitor.visit(this);
+    }
+}
diff --git a/src/main/java/org/zwobble/couscous/ast/StatementNode.java b/src/main/java/org/zwobble/couscous/ast/StatementNode.java
new file mode 100644
index 0000000..773420e
--- /dev/null
+++ b/src/main/java/org/zwobble/couscous/ast/StatementNode.java
@@ -0,0 +1,7 @@
+package org.zwobble.couscous.ast;
+
+import org.zwobble.couscous.ast.visitors.StatementNodeVisitor;
+
+public interface StatementNode {
+    <T> T accept(StatementNodeVisitor<T> visitor); 
+}
diff --git a/src/main/java/org/zwobble/couscous/ast/VariableNode.java b/src/main/java/org/zwobble/couscous/ast/VariableNode.java
new file mode 100644
index 0000000..4c689c5
--- /dev/null
+++ b/src/main/java/org/zwobble/couscous/ast/VariableNode.java
@@ -0,0 +1,5 @@
+package org.zwobble.couscous.ast;
+
+public interface VariableNode {
+    int getId();
+}
diff --git a/src/main/java/org/zwobble/couscous/ast/VariableReferenceNode.java b/src/main/java/org/zwobble/couscous/ast/VariableReferenceNode.java
new file mode 100644
index 0000000..536a7c3
--- /dev/null
+++ b/src/main/java/org/zwobble/couscous/ast/VariableReferenceNode.java
@@ -0,0 +1,19 @@
+package org.zwobble.couscous.ast;
+
+import org.zwobble.couscous.ast.visitors.ExpressionNodeVisitor;
+
+import lombok.Value;
+
+@Value
+public class VariableReferenceNode implements ExpressionNode {
+    public static VariableReferenceNode reference(VariableNode variable) {
+        return new VariableReferenceNode(variable.getId());
+    }
+    
+    int referentId;
+
+    @Override
+    public <T> T accept(ExpressionNodeVisitor<T> visitor) {
+        return visitor.visit(this);
+    }
+}
diff --git a/src/main/java/org/zwobble/couscous/ast/visitors/ExpressionNodeVisitor.java b/src/main/java/org/zwobble/couscous/ast/visitors/ExpressionNodeVisitor.java
new file mode 100644
index 0000000..0167abc
--- /dev/null
+++ b/src/main/java/org/zwobble/couscous/ast/visitors/ExpressionNodeVisitor.java
@@ -0,0 +1,11 @@
+package org.zwobble.couscous.ast.visitors;
+
+import org.zwobble.couscous.ast.Assignment;
+import org.zwobble.couscous.ast.LiteralNode;
+import org.zwobble.couscous.ast.VariableReferenceNode;
+
+public interface ExpressionNodeVisitor<T> {
+    T visit(LiteralNode literal);
+    T visit(VariableReferenceNode variableReference);
+    T visit(Assignment assignment);
+}
diff --git a/src/main/java/org/zwobble/couscous/ast/visitors/StatementNodeVisitor.java b/src/main/java/org/zwobble/couscous/ast/visitors/StatementNodeVisitor.java
new file mode 100644
index 0000000..6cec404
--- /dev/null
+++ b/src/main/java/org/zwobble/couscous/ast/visitors/StatementNodeVisitor.java
@@ -0,0 +1,9 @@
+package org.zwobble.couscous.ast.visitors;
+
+import org.zwobble.couscous.ast.ExpressionStatementNode;
+import org.zwobble.couscous.ast.ReturnNode;
+
+public interface StatementNodeVisitor<T> {
+    T visit(ReturnNode returnNode);
+    T visit(ExpressionStatementNode expressionStatement);
+}
diff --git a/src/main/java/org/zwobble/couscous/interpreter/Interpreter.java b/src/main/java/org/zwobble/couscous/interpreter/Interpreter.java
new file mode 100644
index 0000000..49c651b
--- /dev/null
+++ b/src/main/java/org/zwobble/couscous/interpreter/Interpreter.java
@@ -0,0 +1,110 @@
+package org.zwobble.couscous.interpreter;
+
+import java.util.List;
+import java.util.Map;
+import java.util.Optional;
+import java.util.stream.IntStream;
+
+import org.zwobble.couscous.Project;
+import org.zwobble.couscous.ast.Assignment;
+import org.zwobble.couscous.ast.ExpressionNode;
+import org.zwobble.couscous.ast.ExpressionStatementNode;
+import org.zwobble.couscous.ast.LiteralNode;
+import org.zwobble.couscous.ast.MethodNode;
+import org.zwobble.couscous.ast.ReturnNode;
+import org.zwobble.couscous.ast.VariableReferenceNode;
+import org.zwobble.couscous.ast.visitors.ExpressionNodeVisitor;
+import org.zwobble.couscous.ast.visitors.StatementNodeVisitor;
+import org.zwobble.couscous.values.InterpreterValue;
+
+import static com.google.common.collect.Iterables.find;
+import static java.util.stream.Collectors.toMap;
+import static org.zwobble.couscous.values.UnitValue.UNIT;
+
+import lombok.val;
+
+public class Interpreter {
+    private Project project;
+
+    public Interpreter(Project project) {
+        this.project = project;
+    }
+    
+    public InterpreterValue run(String className, String methodName, List<InterpreterValue> arguments) {
+        val clazz = project.findClass(className);
+        val method = find(clazz.getMethods(),
+            method -> method.getName().equals(methodName));
+        val stackFrame = buildStackFrame(method, arguments);
+        
+        for (val statement : method.getBody()) {
+            val result = statement.accept(new Executor(new Evaluator(stackFrame)));
+            if (result.isPresent()) {
+                return result.get();
+            }
+        }
+        return UNIT;
+    }
+
+    private Map<Integer, InterpreterValue> buildStackFrame(
+        final MethodNode method,
+        List<InterpreterValue> arguments) {
+        
+        if (method.getArguments().size() != arguments.size()) {
+            throw new WrongNumberOfArguments(method.getArguments().size(), arguments.size());
+        }
+        
+        return IntStream.range(0, method.getArguments().size())
+            .boxed()
+            .collect(toMap(
+                index -> method.getArguments().get(index).getId(),
+                index -> arguments.get(index)));
+    }
+    
+    private class Executor implements StatementNodeVisitor<Optional<InterpreterValue>> {
+        private Evaluator evaluator;
+
+        public Executor(Evaluator evaluator) {
+            this.evaluator = evaluator;
+        }
+        
+        @Override
+        public Optional<InterpreterValue> visit(ReturnNode returnNode) {
+            return Optional.of(evaluator.eval(returnNode.getValue()));
+        }
+
+        @Override
+        public Optional<InterpreterValue> visit(ExpressionStatementNode expressionStatement) {
+            evaluator.eval(expressionStatement.getExpression());
+            return Optional.empty();
+        }
+    }
+    
+    private class Evaluator implements ExpressionNodeVisitor<InterpreterValue> {
+        private final Map<Integer, InterpreterValue> stackFrame;
+
+        public Evaluator(Map<Integer, InterpreterValue> stackFrame) {
+            this.stackFrame = stackFrame;
+        }
+        
+        public InterpreterValue eval(ExpressionNode expression) {
+            return expression.accept(this);
+        }
+
+        @Override
+        public InterpreterValue visit(LiteralNode literal) {
+            return literal.getValue();
+        }
+
+        @Override
+        public InterpreterValue visit(VariableReferenceNode variableReference) {
+            return stackFrame.get(variableReference.getReferentId());
+        }
+
+        @Override
+        public InterpreterValue visit(Assignment assignment) {
+            val value = eval(assignment.getValue());
+            stackFrame.put(assignment.getTarget().getReferentId(), value);
+            return value;
+        }
+    }
+}
diff --git a/src/main/java/org/zwobble/couscous/interpreter/InterpreterException.java b/src/main/java/org/zwobble/couscous/interpreter/InterpreterException.java
new file mode 100644
index 0000000..d6d7020
--- /dev/null
+++ b/src/main/java/org/zwobble/couscous/interpreter/InterpreterException.java
@@ -0,0 +1,6 @@
+package org.zwobble.couscous.interpreter;
+
+public class InterpreterException extends RuntimeException {
+    private static final long serialVersionUID = 1L;
+
+}
diff --git a/src/main/java/org/zwobble/couscous/interpreter/WrongNumberOfArguments.java b/src/main/java/org/zwobble/couscous/interpreter/WrongNumberOfArguments.java
new file mode 100644
index 0000000..06d8079
--- /dev/null
+++ b/src/main/java/org/zwobble/couscous/interpreter/WrongNumberOfArguments.java
@@ -0,0 +1,13 @@
+package org.zwobble.couscous.interpreter;
+
+import lombok.EqualsAndHashCode;
+import lombok.Value;
+
+@Value
+@EqualsAndHashCode(callSuper=false)
+public class WrongNumberOfArguments extends InterpreterException {
+    private static final long serialVersionUID = 1L;
+    
+    int expected;
+    int actual;
+}
diff --git a/src/main/java/org/zwobble/couscous/values/IntegerValue.java b/src/main/java/org/zwobble/couscous/values/IntegerValue.java
new file mode 100644
index 0000000..062d137
--- /dev/null
+++ b/src/main/java/org/zwobble/couscous/values/IntegerValue.java
@@ -0,0 +1,8 @@
+package org.zwobble.couscous.values;
+
+import lombok.Value;
+
+@Value
+public class IntegerValue implements InterpreterValue {
+    int value;
+}
diff --git a/src/main/java/org/zwobble/couscous/values/InterpreterValue.java b/src/main/java/org/zwobble/couscous/values/InterpreterValue.java
new file mode 100644
index 0000000..64b0e91
--- /dev/null
+++ b/src/main/java/org/zwobble/couscous/values/InterpreterValue.java
@@ -0,0 +1,5 @@
+package org.zwobble.couscous.values;
+
+public interface InterpreterValue {
+
+}
diff --git a/src/main/java/org/zwobble/couscous/values/StringValue.java b/src/main/java/org/zwobble/couscous/values/StringValue.java
new file mode 100644
index 0000000..1478d41
--- /dev/null
+++ b/src/main/java/org/zwobble/couscous/values/StringValue.java
@@ -0,0 +1,8 @@
+package org.zwobble.couscous.values;
+
+import lombok.Value;
+
+@Value
+public class StringValue implements InterpreterValue {
+    String value;
+}
diff --git a/src/main/java/org/zwobble/couscous/values/UnitValue.java b/src/main/java/org/zwobble/couscous/values/UnitValue.java
new file mode 100644
index 0000000..1cf9dc7
--- /dev/null
+++ b/src/main/java/org/zwobble/couscous/values/UnitValue.java
@@ -0,0 +1,11 @@
+package org.zwobble.couscous.values;
+
+import lombok.ToString;
+
+@ToString
+public class UnitValue implements InterpreterValue {
+    public static final UnitValue UNIT = new UnitValue(); 
+    
+    private UnitValue() {
+    }
+}