Parse if expressions

7 files changed, 202 insertions, 1 deletions

diff --git a/src/main/java/org/shedlang/compiler/ast/untyped/UntypedConditionalBranchNode.java b/src/main/java/org/shedlang/compiler/ast/untyped/UntypedConditionalBranchNode.java
new file mode 100644
index 00000000..7f9e96aa
--- /dev/null
+++ b/src/main/java/org/shedlang/compiler/ast/untyped/UntypedConditionalBranchNode.java
@@ -0,0 +1,12 @@
+package org.shedlang.compiler.ast.untyped;
+
+import org.shedlang.compiler.sources.Source;
+
+import java.util.List;
+
+public record UntypedConditionalBranchNode(
+    UntypedExpressionNode condition,
+    List<UntypedFunctionStatementNode> body,
+    Source source
+) implements UntypedNode {
+}
diff --git a/src/main/java/org/shedlang/compiler/ast/untyped/UntypedExpressionNode.java b/src/main/java/org/shedlang/compiler/ast/untyped/UntypedExpressionNode.java
index cabf5876..729d8279 100644
--- a/src/main/java/org/shedlang/compiler/ast/untyped/UntypedExpressionNode.java
+++ b/src/main/java/org/shedlang/compiler/ast/untyped/UntypedExpressionNode.java
@@ -1,5 +1,5 @@
 package org.shedlang.compiler.ast.untyped;
 
 public sealed interface UntypedExpressionNode extends UntypedNode
-    permits UntypedBinaryOperationNode, UntypedBoolLiteralNode, UntypedCallNode, UntypedIntLiteralNode, UntypedReferenceNode, UntypedStringLiteralNode {
+    permits UntypedBinaryOperationNode, UntypedBoolLiteralNode, UntypedCallNode, UntypedIfNode, UntypedIntLiteralNode, UntypedReferenceNode, UntypedStringLiteralNode {
 }
diff --git a/src/main/java/org/shedlang/compiler/ast/untyped/UntypedIfNode.java b/src/main/java/org/shedlang/compiler/ast/untyped/UntypedIfNode.java
new file mode 100644
index 00000000..6baff19c
--- /dev/null
+++ b/src/main/java/org/shedlang/compiler/ast/untyped/UntypedIfNode.java
@@ -0,0 +1,12 @@
+package org.shedlang.compiler.ast.untyped;
+
+import org.shedlang.compiler.sources.Source;
+
+import java.util.List;
+
+public record UntypedIfNode(
+    List<UntypedConditionalBranchNode> conditionalBranches,
+    List<UntypedFunctionStatementNode> elseBody,
+    Source source
+) implements UntypedExpressionNode {
+}
diff --git a/src/main/java/org/shedlang/compiler/parser/Parser.java b/src/main/java/org/shedlang/compiler/parser/Parser.java
index bfb756db..4dd59eb4 100644
--- a/src/main/java/org/shedlang/compiler/parser/Parser.java
+++ b/src/main/java/org/shedlang/compiler/parser/Parser.java
@@ -248,6 +248,54 @@ public class Parser {
         };
     }
 
+    private static UntypedExpressionNode parseIf(TokenIterator<TokenType> tokens) {
+        var start = tokens.position();
+
+        var conditionalBranches = new ArrayList<UntypedConditionalBranchNode>();
+        var elseBody = List.<UntypedFunctionStatementNode>of();
+
+        while (true) {
+            var conditionalBranch = parseConditionalBranch(tokens);
+            conditionalBranches.add(conditionalBranch);
+
+            if (!tokens.trySkip(TokenType.KEYWORD_ELSE)) {
+                break;
+            }
+
+            if (!tokens.isNext(TokenType.KEYWORD_IF)) {
+                elseBody = parseBlock(tokens);
+                break;
+            }
+
+        }
+
+        var end = tokens.position();
+        var source = start.to(end);
+
+        return new UntypedIfNode(
+            conditionalBranches,
+            elseBody,
+            source
+        );
+    }
+
+    private static UntypedConditionalBranchNode parseConditionalBranch(TokenIterator<TokenType> tokens) {
+        var start = tokens.position();
+
+        tokens.skip(TokenType.KEYWORD_IF);
+
+        tokens.skip(TokenType.SYMBOL_PAREN_OPEN);
+        var condition = parseTopLevelExpression(tokens);
+        tokens.skip(TokenType.SYMBOL_PAREN_CLOSE);
+
+        var body = parseBlock(tokens);
+
+        var end = tokens.position();
+        var source = start.to(end);
+
+        return new UntypedConditionalBranchNode(condition, body, source);
+    }
+
     private static UntypedExpressionNode parseInt(TokenIterator<TokenType> tokens) {
         var start = tokens.position();
 
@@ -333,6 +381,8 @@ public class Parser {
             case IDENTIFIER -> parseReference(tokens);
             
             case INT -> parseInt(tokens);
+            
+            case KEYWORD_IF -> parseIf(tokens);
 
             case STRING -> parseStringLiteral(tokens);
 
diff --git a/src/main/java/org/shedlang/compiler/typechecker/TypeChecker.java b/src/main/java/org/shedlang/compiler/typechecker/TypeChecker.java
index 273f1898..afe7f565 100644
--- a/src/main/java/org/shedlang/compiler/typechecker/TypeChecker.java
+++ b/src/main/java/org/shedlang/compiler/typechecker/TypeChecker.java
@@ -276,6 +276,9 @@ public class TypeChecker {
             case UntypedCallNode untypedCall ->
                 typeCheckCall(untypedCall, context);
 
+            case UntypedIfNode untypedIf ->
+                throw new UnsupportedOperationException("TODO");
+
             case UntypedIntLiteralNode untypedIntLiteral ->
                 typeCheckIntLiteral(untypedIntLiteral, context);
 
diff --git a/src/test/java/org/shedlang/compiler/ast/untyped/UntypedNodeMatchers.java b/src/test/java/org/shedlang/compiler/ast/untyped/UntypedNodeMatchers.java
index bc237a00..17675e35 100644
--- a/src/test/java/org/shedlang/compiler/ast/untyped/UntypedNodeMatchers.java
+++ b/src/test/java/org/shedlang/compiler/ast/untyped/UntypedNodeMatchers.java
@@ -38,6 +38,17 @@ public class UntypedNodeMatchers {
         return UntypedCallNodeMatcher.empty();
     }
 
+    public static Matcher<UntypedConditionalBranchNode> isUntypedConditionalBranchNode(
+        Matcher<UntypedExpressionNode> condition,
+        Matcher<Iterable<? extends UntypedFunctionStatementNode>> body
+    ) {
+        return instanceOf(
+            UntypedConditionalBranchNode.class,
+            has("condition", x -> x.condition(), condition),
+            has("body", x -> x.body(), body)
+        );
+    }
+
     public static Matcher<UntypedExpressionNode> isUntypedEqualsNode(
         Matcher<UntypedExpressionNode> left,
         Matcher<UntypedExpressionNode> right
@@ -58,6 +69,17 @@ public class UntypedNodeMatchers {
         return UntypedFunctionDefinitionNodeMatcher.empty();
     }
 
+    public static Matcher<UntypedExpressionNode> isUntypedIfNode(
+        Matcher<Iterable<? extends UntypedConditionalBranchNode>> conditionalBranches,
+        Matcher<Iterable<? extends UntypedFunctionStatementNode>> elseBody
+    ) {
+        return instanceOf(
+            UntypedIfNode.class,
+            has("conditionalBranches", x -> x.conditionalBranches(), conditionalBranches),
+            has("elseBody", x -> x.elseBody(), elseBody)
+        );
+    }
+
     public static Matcher<UntypedExpressionNode> isUntypedIntLiteralNode(int value) {
         return isUntypedIntLiteralNode(BigInteger.valueOf(value));
     }
diff --git a/src/test/java/org/shedlang/compiler/parser/ParserIfTests.java b/src/test/java/org/shedlang/compiler/parser/ParserIfTests.java
new file mode 100644
index 00000000..5de0988d
--- /dev/null
+++ b/src/test/java/org/shedlang/compiler/parser/ParserIfTests.java
@@ -0,0 +1,102 @@
+package org.shedlang.compiler.parser;
+
+import org.junit.jupiter.api.Test;
+
+import static org.shedlang.compiler.ast.untyped.UntypedNodeMatchers.*;
+import static org.shedlang.compiler.parser.ParserTesting.parseString;
+import static org.zwobble.precisely.AssertThat.assertThat;
+import static org.zwobble.precisely.Matchers.isSequence;
+
+public class ParserIfTests {
+    @Test
+    public void canParseIfWithSingleConditionalBranchAndNoElse() {
+        var source = "if (a) { 1; }";
+
+        var node = parseString(source, Parser::parseTopLevelExpression);
+
+        assertThat(node, isUntypedIfNode(
+            isSequence(
+                isUntypedConditionalBranchNode(
+                    isUntypedReferenceNode("a"),
+                    isSequence(
+                        isUntypedExpressionStatementNode(isUntypedIntLiteralNode(1))
+                    )
+                )
+            ),
+            isSequence()
+        ));
+    }
+
+    @Test
+    public void canParseIfWithSingleConditionalBranchAndElse() {
+        var source = "if (a) { 1; } else { 2; }";
+
+        var node = parseString(source, Parser::parseTopLevelExpression);
+
+        assertThat(node, isUntypedIfNode(
+            isSequence(
+                isUntypedConditionalBranchNode(
+                    isUntypedReferenceNode("a"),
+                    isSequence(
+                        isUntypedExpressionStatementNode(isUntypedIntLiteralNode(1))
+                    )
+                )
+            ),
+            isSequence(
+                isUntypedExpressionStatementNode(isUntypedIntLiteralNode(2))
+            )
+        ));
+    }
+
+    @Test
+    public void canParseIfWithManyConditionalBranchesAndNoElse() {
+        var source = "if (a) { 1; } else if (b) { 2; }";
+
+        var node = parseString(source, Parser::parseTopLevelExpression);
+
+        assertThat(node, isUntypedIfNode(
+            isSequence(
+                isUntypedConditionalBranchNode(
+                    isUntypedReferenceNode("a"),
+                    isSequence(
+                        isUntypedExpressionStatementNode(isUntypedIntLiteralNode(1))
+                    )
+                ),
+                isUntypedConditionalBranchNode(
+                    isUntypedReferenceNode("b"),
+                    isSequence(
+                        isUntypedExpressionStatementNode(isUntypedIntLiteralNode(2))
+                    )
+                )
+            ),
+            isSequence()
+        ));
+    }
+
+    @Test
+    public void canParseIfWithManyConditionalBranchesAndElse() {
+        var source = "if (a) { 1; } else if (b) { 2; } else { 3; }";
+
+        var node = parseString(source, Parser::parseTopLevelExpression);
+
+        assertThat(node, isUntypedIfNode(
+            isSequence(
+                isUntypedConditionalBranchNode(
+                    isUntypedReferenceNode("a"),
+                    isSequence(
+                        isUntypedExpressionStatementNode(isUntypedIntLiteralNode(1))
+                    )
+                ),
+                isUntypedConditionalBranchNode(
+                    isUntypedReferenceNode("b"),
+                    isSequence(
+                        isUntypedExpressionStatementNode(isUntypedIntLiteralNode(2))
+                    )
+                )
+            ),
+            isSequence(
+                isUntypedExpressionStatementNode(isUntypedIntLiteralNode(3))
+            )
+        ));
+    }
+}