From 8b97d74e0a4e59c81b04532605aa157b9b4fc6d4 Mon Sep 17 00:00:00 2001
From: dfsek <dfsek@protonmail.com>
Date: Sun, 20 Dec 2020 01:50:41 -0700
Subject: [PATCH] allow constant expressions in if statements

---
 .../terra/api/structures/parser/Parser.java   | 12 ++++++++--
 .../parser/lang/ConstantExpression.java       | 22 +++++++++++++++++++
 .../terra/api/structures/tokenizer/Token.java |  4 ++++
 common/src/test/resources/test.tesf           |  2 +-
 4 files changed, 37 insertions(+), 3 deletions(-)
 create mode 100644 common/src/main/java/com/dfsek/terra/api/structures/parser/lang/ConstantExpression.java

diff --git a/common/src/main/java/com/dfsek/terra/api/structures/parser/Parser.java b/common/src/main/java/com/dfsek/terra/api/structures/parser/Parser.java
index d7f0700f2..a971995c6 100644
--- a/common/src/main/java/com/dfsek/terra/api/structures/parser/Parser.java
+++ b/common/src/main/java/com/dfsek/terra/api/structures/parser/Parser.java
@@ -2,6 +2,8 @@ package com.dfsek.terra.api.structures.parser;
 
 import com.dfsek.terra.api.structures.parser.exceptions.ParseException;
 import com.dfsek.terra.api.structures.parser.lang.Block;
+import com.dfsek.terra.api.structures.parser.lang.ConstantExpression;
+import com.dfsek.terra.api.structures.parser.lang.Expression;
 import com.dfsek.terra.api.structures.parser.lang.Function;
 import com.dfsek.terra.api.structures.parser.lang.Item;
 import com.dfsek.terra.api.structures.parser.lang.Keyword;
@@ -70,13 +72,13 @@ public class Parser {
 
             checkType(functionAndArguments.remove(0), Token.Type.BODY_BEGIN);
 
-            Function<?> left = parseFunction(functionAndArguments, false);
+            Expression<?> left = parseExpression(functionAndArguments);
 
             Statement statement = null;
             Token comparator = functionAndArguments.remove(0);
             checkType(comparator, Token.Type.BOOLEAN_OPERATOR);
 
-            Function<?> right = parseFunction(functionAndArguments, false);
+            Expression<?> right = parseExpression(functionAndArguments);
 
             checkType(functionAndArguments.remove(0), Token.Type.BODY_END);
             if(comparator.getContent().equals("==")) {
@@ -89,6 +91,12 @@ public class Parser {
         return k;
     }
 
+    private Expression<?> parseExpression(List<Token> tokens) throws ParseException {
+        if(tokens.get(0).isConstant()) {
+            return new ConstantExpression(tokens.remove(0));
+        } else return parseFunction(tokens, false);
+    }
+
     private Block parseBlock(List<Token> tokens) throws ParseException {
         List<Item<?>> parsedItems = new GlueList<>();
         List<Token> functionArgs = new GlueList<>();
diff --git a/common/src/main/java/com/dfsek/terra/api/structures/parser/lang/ConstantExpression.java b/common/src/main/java/com/dfsek/terra/api/structures/parser/lang/ConstantExpression.java
new file mode 100644
index 000000000..bf82fe7af
--- /dev/null
+++ b/common/src/main/java/com/dfsek/terra/api/structures/parser/lang/ConstantExpression.java
@@ -0,0 +1,22 @@
+package com.dfsek.terra.api.structures.parser.lang;
+
+import com.dfsek.terra.api.math.vector.Location;
+import com.dfsek.terra.api.platform.world.Chunk;
+
+public class ConstantExpression implements Expression<Object> {
+    private final Object constant;
+
+    public ConstantExpression(Object constant) {
+        this.constant = constant;
+    }
+
+    @Override
+    public Object apply(Location location) {
+        return constant;
+    }
+
+    @Override
+    public Object apply(Location location, Chunk chunk) {
+        return constant;
+    }
+}
diff --git a/common/src/main/java/com/dfsek/terra/api/structures/tokenizer/Token.java b/common/src/main/java/com/dfsek/terra/api/structures/tokenizer/Token.java
index 34f5f9eb1..9696943bf 100644
--- a/common/src/main/java/com/dfsek/terra/api/structures/tokenizer/Token.java
+++ b/common/src/main/java/com/dfsek/terra/api/structures/tokenizer/Token.java
@@ -28,6 +28,10 @@ public class Token {
         return type + ": '" + content + "'";
     }
 
+    public boolean isConstant() {
+        return this.type.equals(Type.NUMBER) || this.type.equals(Type.STRING) || this.type.equals(Type.BOOLEAN);
+    }
+
     public enum Type {
         /**
          * Function identifier or language keyword
diff --git a/common/src/test/resources/test.tesf b/common/src/test/resources/test.tesf
index 916c3537c..8fe2f603a 100644
--- a/common/src/test/resources/test.tesf
+++ b/common/src/test/resources/test.tesf
@@ -1,7 +1,7 @@
 test("hello", 1);
 test("ghgj{}()\"\\hgjhgj", 3.4);
 
-if(test("hello", 1) == test("hello", 1)) {
+if(test("hello", 1) == "a string literal") {
     test("hello", 1);
 }