/*
	File: Parser
*/
/*
	Class: n_Parser
	An object that reads tokens and produces an AST (abstract syntax tree).
*/
/n_Parser
	var
/*
	Var: index
	The parser's current position in the token's list.
*/
		index = 1
		list
/*
	Var: tokens
	A list of tokens in the source code generated by a scanner.
*/
			tokens   = new
/*
	Var: errors
	A list of fatal errors found by the parser. If there are any items in this list, then it is not safe to run the returned AST.

	See Also:
	- <scriptError>
*/
			errors   = new
/*
	Var: warnings
	A list of non-fatal problems in the script.
*/
			warnings = new
		token
/*
	Var: curToken
	The token at <index> in <tokens>.
*/
			curToken
		stack
			blocks=new
		node/BlockDefinition
			GlobalBlock/global_block=new
			curBlock

	proc
/*
	Proc: Parse
	Reads the tokens and returns the AST's <GlobalBlock> node. Be sure to populate the tokens list before calling this procedure.
*/
		Parse()

/*
	Proc: NextToken
	Sets <curToken> to the next token in the <tokens> list, or null if there are no more tokens.
*/
		NextToken()
			if(index>=tokens.len)
				curToken=null
			else
				curToken=tokens[++index]
			return curToken

/*
	Class: nS_Parser
	An implmentation of a parser for n_Script.
*/
/n_Parser/nS_Parser
	var/n_scriptOptions/nS_Options/options
/*
	Constructor: New

	Parameters:
	tokens  - A list of tokens to parse.
	options - An object used for configuration.
*/
	New(tokens[], n_scriptOptions/options)
		src.tokens=tokens
		src.options=options
		curBlock=global_block
		return ..()

	Parse()
		ASSERT(tokens)
		for(,src.index<=src.tokens.len, src.index++)
			curToken=tokens[index]
			switch(curToken.type)
				if(/token/keyword)
					var/n_Keyword/kw=options.keywords[curToken.value]
					kw=new kw()
					if(kw)
						if(!kw.Parse(src))
							return
				if(/token/word)
					var/token/ntok
					if(index+1>tokens.len)
						errors+=new/scriptError/BadToken(curToken)
						continue
					ntok=tokens[index+1]
					if(!istype(ntok, /token/symbol))
						errors+=new/scriptError/BadToken(ntok)
						continue
					if(ntok.value=="(")
						ParseFunctionStatement()
					else if(options.assign_operators.Find(ntok.value))
						ParseAssignment()
					else
						errors+=new/scriptError/BadToken(ntok)
						continue
					if(!istype(curToken, /token/end))
						errors+=new/scriptError/ExpectedToken(";", curToken)
						continue
				if(/token/symbol)
					if(curToken.value=="}")
						if(!EndBlock())
							errors+=new/scriptError/BadToken(curToken)
							continue
					else
						errors+=new/scriptError/BadToken(curToken)
						continue
				if(/token/end)
					warnings+=new/scriptError/BadToken(curToken)
					continue
				else
					errors+=new/scriptError/BadToken(curToken)
					return
		return global_block

	proc
		CheckToken(val, type, err=1, skip=1)
			if(curToken.value!=val || !istype(curToken,type))
				if(err)
					errors+=new/scriptError/ExpectedToken(val, curToken)
				return 0
			if(skip)NextToken()
			return 1

		AddBlock(node/BlockDefinition/B)
			blocks.Push(curBlock)
			curBlock=B

		EndBlock()
			if(curBlock==global_block) return 0
			curBlock=blocks.Pop()
			return 1

		ParseAssignment()
			var/name=curToken.value
			if(!options.IsValidID(name))
				errors+=new/scriptError/InvalidID(curToken)
				return
			NextToken()
			var/t=options.binary_operators[options.assign_operators[curToken.value]]
			var/node/statement/VariableAssignment/stmt=new()
			stmt.var_name=new(name)
			NextToken()
			if(t)
				stmt.value=new t()
				stmt.value:exp=new/node/expression/value/variable(stmt.var_name)
				stmt.value:exp2=ParseExpression()
			else
				stmt.value=ParseExpression()
			curBlock.statements+=stmt

		ParseFunctionStatement()
			if(!istype(curToken, /token/word))
				errors+=new/scriptError("Bad identifier in function call.")
				return
			var/node/statement/FunctionCall/stmt=new
			stmt.func_name=curToken.value
			NextToken() //skip function name
			if(!CheckToken("(", /token/symbol)) //Check for and skip open parenthesis
				return
			var/loops = 0
			for()
				loops++
				if(loops>=6000)
					CRASH("Something TERRIBLE has gone wrong in ParseFunctionStatement ;__;")

				if(!curToken)
					errors+=new/scriptError/EndOfFile()
					return
				if(istype(curToken, /token/symbol) && curToken.value==")")
					curBlock.statements+=stmt
					NextToken() //Skip close parenthesis
					return
				var/node/expression/P=ParseParamExpression()
				stmt.parameters+=P
				if(istype(curToken, /token/symbol) && curToken.value==",") NextToken()