/*
 [The "BSD licence"] Copyright (c) 2017 Sasa Coh, Michał Błotniak Copyright (c) 2019 Ivan Kochurkin,
 kvanttt@gmail.com, Positive Technologies Copyright (c) 2019 Dmitry Rassadin,
 flipparassa@gmail.com,Positive Technologies All rights reserved. Copyright (c) 2021 Martin Mirchev,
 mirchevmartin2203@gmail.com

 Redistribution and use in source and binary forms, with or without modification, are permitted
 provided that the following conditions are met: 1. Redistributions of source code must retain the
 above copyright notice, this list of conditions and the following disclaimer. 2. Redistributions in
 binary form must reproduce the above copyright notice, this list of conditions and the following
 disclaimer in the documentation and/or other materials provided with the distribution. 3. The name
 of the author may not be used to endorse or promote products derived from this software without
 specific prior written permission.

 THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING,
 BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
 SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
 SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
 CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
 NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
 POSSIBILITY OF SUCH DAMAGE.
 */

/*
 * A Go grammar for ANTLR 4 derived from the Go Language Specification https://golang.org/ref/spec
 */

parser grammar GoParser;

// @header{
// 	package antlr;
// }

options {
	tokenVocab = GoLexer; // https://github.com/antlr/antlr4/blob/master/doc/options.md
	// tokenVocab ANTLR assigns token type numbers to the tokens as it encounters them in a file. 
	// To use different token type values, such as with a separate lexer, 
	// use this option to have ANTLR pull in the tokens file.
	// ANTLR generates a tokens file from each grammar.
	superClass = GoParserBase;
	
}

// TODO:
sourceFile:
	packageClause eos (importDecl eos)* (
		(functionDecl | methodDecl | declaration) eos
	)* EOF;

packageClause: PACKAGE packageName = IDENTIFIER;
// package packageName(this name is an IDENTIFIER)

importDecl:
	IMPORT (importSpec | L_PAREN (importSpec eos)* R_PAREN);
// import 

importSpec: alias = importPath;

importPath: string_;

declaration: constDecl | typeDecl | varDecl;

constDecl: CONST (constSpec | L_PAREN (constSpec eos)* R_PAREN);	// TODO: 

constSpec: identifierList (type_? ASSIGN expressionList)?;

identifierList: IDENTIFIER (COMMA IDENTIFIER)*;

expressionList: expression (COMMA expression)*;

typeDecl: TYPE (typeSpec | L_PAREN (typeSpec eos)* R_PAREN);

typeSpec: IDENTIFIER ASSIGN? type_;

// Function declarations
functionDecl: FUNC IDENTIFIER (signature block?);	// TODO:
/*
funcName:
xxxxxxxxxxx
*/

methodDecl: FUNC receiver IDENTIFIER ( signature block?);

receiver: parameters;

varDecl: VAR (varSpec | L_PAREN (varSpec eos)* R_PAREN);

varSpec:
	identifierList (
		type_ (ASSIGN expressionList)?
		| ASSIGN expressionList
	);

block: L_CURLY statementList? R_CURLY;

statementList: (eos? statement eos)+;

statement:
	declaration
	| labeledStmt
	| simpleStmt
	| goStmt
	| returnStmt
	| breakStmt
	| continueStmt
	| gotoStmt
	| fallthroughStmt
	| block
	| ifStmt
	| switchStmt
	| selectStmt
	| forStmt
	| deferStmt;

simpleStmt:
	sendStmt
	| incDecStmt
	| assignment
	| expressionStmt
	| shortVarDecl;

expressionStmt: expression;

sendStmt: channel = expression RECEIVE expression;

incDecStmt: expression (PLUS_PLUS | MINUS_MINUS);

assignment: expressionList assign_op expressionList;

assign_op: (
		PLUS
		| MINUS
		| OR
		| CARET
		| STAR
		| DIV
		| MOD
		| LSHIFT
		| RSHIFT
		| AMPERSAND
		| BIT_CLEAR
	)? ASSIGN;

shortVarDecl: identifierList DECLARE_ASSIGN expressionList;

emptyStmt: EOS | SEMI;

labeledStmt: IDENTIFIER COLON statement?;

returnStmt: RETURN expressionList?;

breakStmt: BREAK IDENTIFIER?;

continueStmt: CONTINUE IDENTIFIER?;

gotoStmt: GOTO IDENTIFIER;

fallthroughStmt: FALLTHROUGH;

deferStmt: DEFER expression;

ifStmt:
	IF ( expression
			| eos expression
			| simpleStmt eos expression
			) block (
		ELSE (ifStmt | block)
	)?;

switchStmt: exprSwitchStmt | typeSwitchStmt;

exprSwitchStmt:
	SWITCH (expression?
					| simpleStmt? eos expression? // TODO: switch
					) L_CURLY exprCaseClause* R_CURLY;

exprCaseClause: exprSwitchCase COLON statementList?;

exprSwitchCase: CASE expressionList | DEFAULT;

typeSwitchStmt:
	SWITCH ( typeSwitchGuard
					| eos typeSwitchGuard
					| simpleStmt eos typeSwitchGuard) // TODO:
					 L_CURLY typeCaseClause* R_CURLY;

typeSwitchGuard: (IDENTIFIER DECLARE_ASSIGN)? primaryExpr DOT L_PAREN TYPE R_PAREN;

typeCaseClause: typeSwitchCase COLON statementList?;

typeSwitchCase: CASE typeList | DEFAULT;

typeList: (type_ | NIL_LIT) (COMMA (type_ | NIL_LIT))*;

selectStmt: SELECT L_CURLY commClause* R_CURLY;

commClause: commCase COLON statementList?;

commCase: CASE (sendStmt | recvStmt) | DEFAULT;

recvStmt: (expressionList ASSIGN | identifierList DECLARE_ASSIGN)? recvExpr = expression;

forStmt: FOR (expression | forClause | rangeClause)? block;

forClause:
	initStmt = simpleStmt? eos expression? eos postStmt = simpleStmt?;

rangeClause: (
		expressionList ASSIGN
		| identifierList DECLARE_ASSIGN
	)? RANGE expression;

goStmt: GO expression;

type_: typeName | typeLit | L_PAREN type_ R_PAREN;

typeName: qualifiedIdent | IDENTIFIER;

typeLit:
	arrayType
	| structType
	| pointerType
	| functionType
	| interfaceType
	| sliceType
	| mapType
	| channelType;

arrayType: L_BRACKET arrayLength R_BRACKET elementType;

arrayLength: expression;

elementType: type_;

pointerType: STAR type_;

interfaceType:
	INTERFACE L_CURLY ((methodSpec | typeName) eos)* R_CURLY;

sliceType: L_BRACKET R_BRACKET elementType;

// It's possible to replace `type` with more restricted typeLit list and also pay attention to nil maps
mapType: MAP L_BRACKET type_ R_BRACKET elementType;

channelType: (CHAN | CHAN RECEIVE | RECEIVE CHAN) elementType;

methodSpec:
	IDENTIFIER parameters result
	| IDENTIFIER parameters;

functionType: FUNC signature;

signature:
	parameters result
	| parameters;

result: parameters | type_;

parameters:
	L_PAREN (parameterDecl (COMMA parameterDecl)* COMMA?)? R_PAREN;

parameterDecl: identifierList? ELLIPSIS? type_;  // 同一个类型参数的定义 x,y float64

expression:
	primaryExpr
	| unary_op = (
		PLUS
		| MINUS
		| EXCLAMATION
		| CARET
		| STAR
		| AMPERSAND
		| RECEIVE
	) expression
	| expression mul_op = (
		STAR
		| DIV
		| MOD
		| LSHIFT
		| RSHIFT
		| AMPERSAND
		| BIT_CLEAR
	) expression
	| expression add_op = (PLUS | MINUS | OR | CARET) expression
	| expression rel_op = (
		EQUALS	
		| NOT_EQUALS
		| LESS
		| LESS_OR_EQUALS
		| GREATER
		| GREATER_OR_EQUALS
	) expression
	| expression LOGICAL_AND expression
	| expression LOGICAL_OR expression;

primaryExpr:
	operand
	| conversion
	| methodExpr
	| primaryExpr (
		(DOT IDENTIFIER) // 调用 math.Sqrt
		| index
		| slice_
		| typeAssertion
		| arguments
	);


conversion: nonNamedType L_PAREN expression COMMA? R_PAREN;

nonNamedType: typeLit | L_PAREN nonNamedType R_PAREN;

operand: literal | operandName | L_PAREN expression R_PAREN;

literal: basicLit | compositeLit | functionLit;

basicLit:
	NIL_LIT
	| integer
	| string_
	| FLOAT_LIT;

integer:
	DECIMAL_LIT
	| BINARY_LIT
	| OCTAL_LIT
	| HEX_LIT
	| IMAGINARY_LIT
	| RUNE_LIT;

operandName: IDENTIFIER;

qualifiedIdent: IDENTIFIER DOT IDENTIFIER;

compositeLit: literalType literalValue;

literalType:
	structType
	| arrayType
	| L_BRACKET ELLIPSIS R_BRACKET elementType
	| sliceType
	| mapType
	| typeName;

literalValue: L_CURLY (elementList COMMA?)? R_CURLY;

elementList: keyedElement (COMMA keyedElement)*;

keyedElement: (key COLON)? element;

key: expression | literalValue;

element: expression | literalValue;

structType: STRUCT L_CURLY (fieldDecl eos)* R_CURLY;

fieldDecl: (
		identifierList type_
		| embeddedField // TODO:
	) tag = string_?;
	

string_: RAW_STRING_LIT | INTERPRETED_STRING_LIT;

embeddedField: STAR? typeName;

functionLit: FUNC signature block; // function

index: L_BRACKET expression R_BRACKET;

slice_:
	L_BRACKET (
		expression? COLON expression?
		| expression? COLON expression COLON expression
	) R_BRACKET;

typeAssertion: DOT L_PAREN type_ R_PAREN;

arguments:
	L_PAREN (
		(expressionList | nonNamedType (COMMA expressionList)?) ELLIPSIS? COMMA?
	)? R_PAREN;

methodExpr: nonNamedType DOT IDENTIFIER;

//receiverType: typeName | '(' ('*' typeName | receiverType) ')';

receiverType: type_;

eos:
	SEMI
	| EOF
	| EOS
	| {closingBracket()}? // TODO: closingBracket()
	;