From 7d52374fc01cf9c29cd9fe7a59b0d101b535886a Mon Sep 17 00:00:00 2001
From: Kenzie Togami <ket1999@gmail.com>
Date: Sun, 13 Oct 2019 02:02:47 -0700
Subject: [PATCH] Add initial ANTLR setup + lex/parser

---
 worldedit-core/build.gradle.kts               |  27 +++
 .../com/sk89q/worldedit/antlr/Expression.g4   | 186 ++++++++++++++++++
 2 files changed, 213 insertions(+)
 create mode 100644 worldedit-core/src/main/antlr/com/sk89q/worldedit/antlr/Expression.g4

diff --git a/worldedit-core/build.gradle.kts b/worldedit-core/build.gradle.kts
index a20b254f8..19dcecc05 100644
--- a/worldedit-core/build.gradle.kts
+++ b/worldedit-core/build.gradle.kts
@@ -1,7 +1,10 @@
+import org.gradle.plugins.ide.idea.model.IdeaModel
+
 plugins {
     id("java-library")
     id("net.ltgt.apt-eclipse")
     id("net.ltgt.apt-idea")
+    id("antlr")
 }
 
 applyPlatformAndCoreConfiguration()
@@ -23,6 +26,10 @@ dependencies {
     "compile"("org.slf4j:slf4j-api:1.7.26")
     "compile"("it.unimi.dsi:fastutil:8.2.1")
 
+    val antlrVersion = "4.7.2"
+    "antlr"("org.antlr:antlr4:$antlrVersion")
+    "implementation"("org.antlr:antlr4-runtime:$antlrVersion")
+
     "compileOnly"(project(":worldedit-libs:core:ap"))
     "annotationProcessor"(project(":worldedit-libs:core:ap"))
     // ensure this is on the classpath for the AP
@@ -36,6 +43,26 @@ tasks.withType<JavaCompile>().configureEach {
     options.compilerArgs.add("-Aarg.name.key.prefix=")
 }
 
+tasks.named<AntlrTask>("generateGrammarSource").configure {
+    val pkg = "com.sk89q.worldedit.antlr"
+    outputDirectory = file("build/generated-src/antlr/main/${pkg.replace('.', '/')}")
+    arguments = listOf(
+        "-visitor", "-package", pkg,
+        "-Xexact-output-dir"
+    )
+}
+
+// Give intellij info about where ANTLR code comes from
+plugins.withId("idea") {
+    configure<IdeaModel> {
+        afterEvaluate {
+            module.sourceDirs.add(file("src/main/antlr"))
+            module.sourceDirs.add(file("build/generated-src/antlr/main"))
+            module.generatedSourceDirs.add(file("build/generated-src/antlr/main"))
+        }
+    }
+}
+
 sourceSets {
     main {
         java {
diff --git a/worldedit-core/src/main/antlr/com/sk89q/worldedit/antlr/Expression.g4 b/worldedit-core/src/main/antlr/com/sk89q/worldedit/antlr/Expression.g4
new file mode 100644
index 000000000..254e0bf46
--- /dev/null
+++ b/worldedit-core/src/main/antlr/com/sk89q/worldedit/antlr/Expression.g4
@@ -0,0 +1,186 @@
+grammar Expression;
+
+// Lexer tokens:
+
+PLUS : '+' ;
+MINUS : '-' ;
+TIMES : '*' ;
+DIVIDE : '/' ;
+MODULO : '%' ;
+POWER : '^' | '**' ;
+LEFT_SHIFT : '<<' ;
+RIGHT_SHIFT : '>>' ;
+ASSIGN : '=' ;
+COMPLEMENT : '~' ;
+
+PLUS_ASSIGN : '+=' ;
+MINUS_ASSIGN : '-=' ;
+TIMES_ASSIGN : '*=' ;
+DIVIDE_ASSIGN : '/=' ;
+MODULO_ASSIGN : '%=' ;
+POWER_ASSIGN : '^=' ;
+
+EQUAL : '==' ;
+NOT_EQUAL : '!=' ;
+NEAR : '~=' ;
+LESS_THAN : '<' ;
+LESS_THAN_OR_EQUAL : '<=' ;
+GREATER_THAN : '>' ;
+GREATER_THAN_OR_EQUAL : '>=' ;
+// SC = "Short Circuit"
+// Non-SC variants not currently implemented.
+AND_SC : '&&' ;
+OR_SC : '||' ;
+
+INCREMENT : '++' ;
+DECREMENT : '--' ;
+
+COMMA : ',' ;
+OPEN_PAREN : '(' ;
+CLOSE_PAREN : ')' ;
+OPEN_BRACKET : '{' ;
+CLOSE_BRACKET : '}' ;
+SEMI_COLON : ';' ;
+QUESTION_MARK : '?' ;
+COLON : ':' ;
+EXCLAMATION_MARK : '!' ;
+
+IF : 'if' ;
+ELSE : 'else' ;
+WHILE : 'while' ;
+DO : 'do' ;
+FOR : 'for' ;
+BREAK : 'break' ;
+CONTINUE : 'continue' ;
+RETURN : 'return' ;
+SWITCH : 'switch' ;
+CASE : 'case' ;
+DEFAULT : 'default' ;
+
+fragment DIGIT : [0-9] ;
+fragment SIGN : [+-] ;
+fragment EXP_CHAR : [eE] ;
+fragment DECIMAL : '.' DIGIT+ ( EXP_CHAR SIGN? DIGIT+ )? ;
+
+// All numbers are treated the same. No int/dec divide.
+NUMBER : SIGN? ( DIGIT+ DECIMAL? | DECIMAL ) ;
+
+ID : [A-Za-z] [0-9A-Za-z_]* ;
+
+WS  :  [ \t\r\n\u000C]+ -> skip ;
+
+// Parser rules:
+
+/**
+ * All statements parseable from the input. Forces consumption of EOF token.
+ */
+allStatements : statements EOF ;
+
+statements : statement+ ;
+
+statement
+    : block
+    | ifStatement
+    | whileStatement
+    | doStatement
+    | forStatement
+    | breakStatement
+    | continueStatement
+    | returnStatement
+    | switchStatement
+    | expressionStatement
+    | SEMI_COLON
+    ;
+
+block : '{' statements '}' ;
+
+ifStatement : IF '(' expression ')' statement ( ELSE statement ) ;
+
+whileStatement : WHILE '(' expression ')' statement ;
+
+doStatement : DO statement WHILE '(' expression ')' SEMI_COLON ;
+
+forStatement
+    : FOR '('
+        // C-style for loop
+        ( expression ';' expression ';' expression
+        // Range for loop
+        | ID ASSIGN ID ',' ID
+        )
+      ')' statement ;
+
+breakStatement : BREAK ;
+
+continueStatement : CONTINUE ;
+
+returnStatement : RETURN expression? ;
+
+switchStatement : SWITCH '(' expression ')' '{' (switchLabel ':' statements )+ '}' ;
+
+switchLabel
+    : CASE constantExpression
+    | DEFAULT
+    ;
+
+expressionStatement : expression SEMI_COLON ;
+
+expression
+    : constantExpression
+    | functionCall
+    | identifierExpression
+    | '(' expression ')'
+    | unaryOp expression
+    | identifierExpression binaryAssignOp expression
+    | expression binaryOp expression
+    | expression postUnaryOp
+    ;
+
+constantExpression : NUMBER ;
+
+functionCall : ID '(' (expression ( ',' expression )*)? ')' ;
+
+identifierExpression : ID ;
+
+unaryOp
+    : MINUS
+    | EXCLAMATION_MARK
+    | COMPLEMENT
+    | INCREMENT
+    | DECREMENT
+    ;
+
+postUnaryOp
+    : INCREMENT
+    | DECREMENT
+    | EXCLAMATION_MARK
+    ;
+
+binaryOp
+    : POWER
+    | TIMES
+    | DIVIDE
+    | MODULO
+    | PLUS
+    | MINUS
+    | LEFT_SHIFT
+    | RIGHT_SHIFT
+    | LESS_THAN
+    | GREATER_THAN
+    | LESS_THAN_OR_EQUAL
+    | GREATER_THAN_OR_EQUAL
+    | EQUAL
+    | NOT_EQUAL
+    | NEAR
+    | AND_SC
+    | OR_SC
+    ;
+
+binaryAssignOp
+    : ASSIGN
+    | PLUS_ASSIGN
+    | MINUS_ASSIGN
+    | TIMES_ASSIGN
+    | DIVIDE_ASSIGN
+    | MODULO_ASSIGN
+    | POWER_ASSIGN
+    ;