vgstation13/code/modules/scripting/Parser/Keywords.dm

/*
	File: Keywords
*/
var/const
	KW_FAIL = 0 //Fatal error; stop parsing entire script.
	KW_PASS = 1 //OK
	KW_ERR  = 2 //Non-fatal error, keyword couldn't be handled properly. Ignore keyword but continue on.
	KW_WARN = 3 //Warning

/*
	Class: n_Keyword
	Represents a special statement in the code triggered by a keyword.
*/
/n_Keyword
	New(inline=0)
		src.inline=inline
		return ..()

	var
/*
	Var: inline
	1 if the keyword is in an expression (e.g. the new keyword in many languages), 0 otherwise (such as the if and else keywords).
*/
		inline

/*
	Proc: Parse
	Called when the parser finds a keyword in the code.

	Parameters:
	parser - The parser that created this object. You can use the parameter to manipulate the parser in order to add statements and blocks
	to its AST.
*/
	proc/Parse(n_Parser/parser)

/*
	Class: nS_Keyword
	A keyword in n_Script. By default these include return, if, else, while, and def. To enable or disable a keyword, change the
	<nS_Options.keywords> list.

	Behavior:
	When a parser is expecting a new statement, and a keyword listed in <nS_Options.keywords> is found, it will call the keyword's
	<n_Keyword.Parse()> proc.
*/
//
	nS_Keyword
		New(inline=0)
			if(inline)
				del src

		kwReturn
			Parse(n_Parser/nS_Parser/parser)
				.=KW_PASS
				if(istype(parser.curBlock, /node/BlockDefinition/GlobalBlock))
					parser.errors+=new/scriptError/BadReturn(parser.curToken)
					. = KW_WARN
				var/node/statement/ReturnStatement/stmt=new
				parser.NextToken()   //skip 'return' token
				stmt.value=parser.ParseExpression()
				parser.curBlock.statements+=stmt

		kwIf
			Parse(n_Parser/nS_Parser/parser)
				.=KW_PASS
				var/node/statement/IfStatement/stmt=new
				parser.NextToken()  //skip 'if' token
				stmt.cond=parser.ParseParenExpression()
				if(!parser.CheckToken(")", /token/symbol))
					return KW_FAIL
				if(!parser.CheckToken("{", /token/symbol, skip=0)) //Token needs to be preserved for parse loop, so skip=0
					return KW_ERR
				parser.curBlock.statements+=stmt
				stmt.block=new
				parser.AddBlock(stmt.block)

		kwElse
			Parse(n_Parser/nS_Parser/parser)
				.=KW_PASS
				var/list/L=parser.curBlock.statements
				var/node/statement/IfStatement/stmt
				if(L&&L.len) stmt=L[L.len] //Get the last statement in the current block
				if(!stmt || !istype(stmt) || stmt.else_block) //Ensure that it is an if statement
					parser.errors+=new/scriptError/ExpectedToken("if statement",parser.curToken)
					return KW_FAIL
				parser.NextToken()         //skip 'else' token
				if(!parser.CheckToken("{", /token/symbol, skip=0))
					return KW_ERR
				stmt.else_block=new()
				parser.AddBlock(stmt.else_block)

		kwWhile
			Parse(n_Parser/nS_Parser/parser)
				.=KW_PASS
				var/node/statement/WhileLoop/stmt=new
				parser.NextToken()  //skip 'while' token
				stmt.cond=parser.ParseParenExpression()
				if(!parser.CheckToken(")", /token/symbol))
					return KW_FAIL
				if(!parser.CheckToken("{", /token/symbol, skip=0))
					return KW_ERR
				parser.curBlock.statements+=stmt
				stmt.block=new
				parser.AddBlock(stmt.block)

		kwBreak
			Parse(n_Parser/nS_Parser/parser)
				.=KW_PASS
				if(istype(parser.curBlock, /node/BlockDefinition/GlobalBlock))
					parser.errors+=new/scriptError/BadToken(parser.curToken)
					. = KW_WARN
				var/node/statement/BreakStatement/stmt=new
				parser.NextToken()   //skip 'break' token
				parser.curBlock.statements+=stmt

		kwContinue
			Parse(n_Parser/nS_Parser/parser)
				.=KW_PASS
				if(istype(parser.curBlock, /node/BlockDefinition/GlobalBlock))
					parser.errors+=new/scriptError/BadToken(parser.curToken)
					. = KW_WARN
				var/node/statement/ContinueStatement/stmt=new
				parser.NextToken()   //skip 'break' token
				parser.curBlock.statements+=stmt

		kwDef
			Parse(n_Parser/nS_Parser/parser)
				.=KW_PASS
				var/node/statement/FunctionDefinition/def=new
				parser.NextToken() //skip 'def' token
				if(!parser.options.IsValidID(parser.curToken.value))
					parser.errors+=new/scriptError/InvalidID(parser.curToken)
					return KW_FAIL
				def.func_name=parser.curToken.value
				parser.NextToken()
				if(!parser.CheckToken("(", /token/symbol))
					return KW_FAIL
				for() //for now parameters can be separated by whitespace - they don't need a comma in between
					if(istype(parser.curToken, /token/symbol))
						switch(parser.curToken.value)
							if(",")
								parser.NextToken()
							if(")")
								break
							else
								parser.errors+=new/scriptError/BadToken(parser.curToken)
								return KW_ERR

					else if(istype(parser.curToken, /token/word))
						def.parameters+=parser.curToken.value
						parser.NextToken()
					else
						parser.errors+=new/scriptError/InvalidID(parser.curToken)
						return KW_ERR
				if(!parser.CheckToken(")", /token/symbol))
					return KW_FAIL

				if(istype(parser.curToken, /token/end)) //Function prototype
					parser.curBlock.statements+=def
				else if(parser.curToken.value=="{" && istype(parser.curToken, /token/symbol))
					def.block = new
					parser.curBlock.statements+=def
					parser.curBlock.functions[def.func_name]=def
					parser.AddBlock(def.block)
				else
					parser.errors+=new/scriptError/BadToken(parser.curToken)
					return KW_FAIL