feat: add EventQL grammar file

grammar/EventQL.g4

@@ -0,0 +1,172 @@
+/*
+ * EventQL Grammar
+ * Version 1.2.0
+ *
+ * Copyright (c) the native web GmbH — https://www.thenativeweb.io
+ *
+ * This grammar file is provided by the native web GmbH. You are granted
+ * permission to read and to redistribute this file as part of the EventQL
+ * parser project. Modification of this file is not permitted.
+ *
+ * This file is provided "as is", without warranty of any kind, express or
+ * implied, including but not limited to the warranties of merchantability,
+ * fitness for a particular purpose, and non-infringement. In no event shall
+ * the native web GmbH be liable for any claim, damages, or other liability,
+ * whether in an action of contract, tort, or otherwise, arising from, out of,
+ * or in connection with this file or the use of this file.
+ *
+ * For questions, feedback, or any other inquiries, please contact:
+ * hello@thenativeweb.io
+ */
+
+grammar EventQL;
+ options { caseInsensitive = true; }
+
+entrypointQuery: query EOF;										// Main entrypoint
+entrypointExpression: expression EOF; 				// Primarily used for testing
+
+query: from+ where? orderBy? groupBy? skip? top? projectInto;
+
+from: FROM variableRef IN source;
+source: sourceName | LPAREN query RPAREN;
+where: WHERE condition;
+orderBy: ORDER BY expression (ASC | DESC)?;
+groupBy: GROUP BY expression having?;
+having: HAVING condition;
+top: TOP expression;
+skip: SKIP_KW expression;
+projectInto: PROJECT INTO DISTINCT? projectionStructure;
+
+condition: expression;
+projectionStructure: expression;
+
+equalityOperator: EQ | NEQ | CONTAINS;
+relationalOperator: GT | GTE | LT | LTE;
+additiveOperator: PLUS | MINUS;
+multiplicativeOperator: ASTERISK | SLASH | MOD;
+prefixOperator: NOT | MINUS;
+
+expression:
+	atom																						# AtomExpression					// Highest precedence
+	| arrayLiteral																	# ArrayExpression
+	| mapLiteral																		# MapExpression
+	| expression LBRACK expression RBRACK						# ArrayIndexExpression
+	| expression DOT unrestrictedIdentifier					# NestedIdentifier
+	| functionCall																	# FunctionCallExpression
+	| prefixOperator expression											# PrefixExpression
+	| LPAREN expression RPAREN											# ParenthesesExpression
+	| expression multiplicativeOperator expression	# MultiplicativeExpression
+	| expression additiveOperator expression				# AdditiveExpression
+	| expression AS IDENTIFIER											# CastExpression
+	| expression relationalOperator expression			# RelationalExpression
+	| expression equalityOperator expression				# EqualityExpression
+	| expression AND expression											# AndExpression
+	| expression XOR expression											# XorExpression
+	| expression OR expression											# OrExpression 						// Lowest precedence
+	;
+
+functionCall:
+	functionRef LPAREN (expression (COMMA expression)*)? RPAREN;
+mapPair:
+	unrestrictedIdentifier COLON expression;
+mapLiteral:
+	LBRACE (mapPair (COMMA mapPair)*)? RBRACE;
+arrayLiteral:
+	LBRACK (expression (COMMA expression)*)? RBRACK;
+
+atom: variableRef | INT | FLOAT | STRING | NULL | TRUE | FALSE;
+variableRef: IDENTIFIER;
+functionRef: IDENTIFIER;
+sourceName: IDENTIFIER;
+unrestrictedIdentifier: // This is a special case for identifiers that can be keywords (such in keys in a map)
+	IDENTIFIER
+	| AND
+	| ASC
+	| AS
+	| BY
+	| CONTAINS
+	| DESC
+	| DISTINCT
+	| FROM
+	| FALSE
+	| GROUP
+	| HAVING
+	| IN
+	| INTO
+	| TOP
+	| NOT
+	| NULL
+	| OR
+	| ORDER
+	| PROJECT
+	| SKIP_KW
+	| TRUE
+	| WHERE
+	| XOR
+	;
+
+// Operators
+ASTERISK: '*';
+EQ: '==';
+GT: '>';
+GTE: '>=';
+LT: '<';
+LTE: '<=';
+MINUS: '-';
+MOD: '%';
+NEQ: '!=';
+PLUS: '+';
+SLASH: '/';
+
+// Delimiters
+COMMA: ',';
+COLON: ':';
+DOT: '.';
+BLOCK_COMMENT_START: '/*';
+BLOCK_COMMENT_END: '*/';
+BLOCK_COMMENT: BLOCK_COMMENT_START .*? BLOCK_COMMENT_END -> channel(HIDDEN);
+LINE_COMMENT: '//' ~[\r\n]* -> channel(HIDDEN);
+WHITESPACE: [ \t] -> channel(HIDDEN);
+LINE_BREAK: [\r\n] -> channel(HIDDEN);
+
+// Brackets
+LBRACE: '{';
+LBRACK: '[';
+LPAREN: '(';
+RBRACE: '}';
+RBRACK: ']';
+RPAREN: ')';
+
+// Keywords
+AND: 'AND';
+ASC: 'ASC';
+AS: 'AS';
+BY: 'BY';
+CONTAINS: 'CONTAINS';
+DESC: 'DESC';
+DISTINCT: 'DISTINCT';
+FALSE: 'FALSE';
+FROM: 'FROM';
+GROUP: 'GROUP';
+HAVING: 'HAVING';
+IN: 'IN';
+INTO: 'INTO';
+NOT: 'NOT';
+NULL: 'NULL';
+OR: 'OR';
+ORDER: 'ORDER';
+PROJECT: 'PROJECT';
+SKIP_KW: 'SKIP'; 	// SKIP is a reserved keyword in ANTLR
+TOP: 'TOP';
+TRUE: 'TRUE';
+WHERE: 'WHERE';
+XOR: 'XOR';
+
+ESCAPE_CHARACTER : '\\' ('n' | 'r' | 't' | '"' | '\'' | '\\');
+
+// Identifiers + literals
+STRING: '"' (ESCAPE_CHARACTER | ~["\r\n])*? '"' | '\'' (ESCAPE_CHARACTER | ~['\r\n])*? '\'';
+FLOAT: [0-9]+ '.' [0-9]+;
+INT: [0-9]+;
+IDENTIFIER:
+	[a-z\u0080-\uFFFF_\p{Emoji}][a-z0-9\u0080-\uFFFF_\p{Emoji}]*;