From cf52b6e8a2ebf85b4be8b9065a755f3481eb43db Mon Sep 17 00:00:00 2001
From: Michael Williamson <mike@zwobble.org>
Date: Sat, 8 Jul 2023 21:42:45 +0100
Subject: Parse if expressions

---
 .../java/org/shedlang/compiler/parser/Parser.java  | 50 ++++++++++++++++++++++
 1 file changed, 50 insertions(+)

(limited to 'src/main/java/org/shedlang/compiler/parser')

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);
 
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