Parser.dm

/*
 * n_Parser
 * An object that reads tokens and produces an AST (abstract syntax tree).
 */
/datum/n_Parser
	///The parser's current position in the token's list.
	var/index = 1
	///The token at <index> in <tokens>.
	var/datum/token/curToken
	var/datum/stack/blocks = new
	var/datum/node/BlockDefinition/GlobalBlock/global_block = new
	var/datum/node/BlockDefinition/curBlock
	///A list of tokens in the source code generated by a scanner.
	var/list/tokens = new
	///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.
	var/list/errors = new
	////A list of non-fatal problems in the script.
	var/list/warnings = new

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

///Sets <curToken> to the next token in the <tokens> list, or null if there are no more tokens.
/datum/n_Parser/proc/NextToken()
	if(index >= length(tokens))
		curToken = null
	else
		curToken = tokens[++index]
	return curToken

/*
 * nS_Parser
 * An implmentation of a parser for n_Script.
 */
/datum/n_Parser/nS_Parser
	var/datum/n_scriptOptions/options

/datum/n_Parser/nS_Parser/New(tokens[], datum/n_scriptOptions/options)
	src.tokens = tokens
	src.options = options
	src.curBlock = global_block
	return ..()

/datum/n_Parser/nS_Parser/Parse()
	ASSERT(tokens)
	for(,index <= length(tokens), index++)
		curToken = tokens[index]
		switch(curToken.type)
			if(/datum/token/keyword)
				var/datum/n_Keyword/kw = options.keywords[curToken.value]
				kw = new kw()
				if(kw)
					if(!kw.Parse(src))
						return
					continue
			if(/datum/token/symbol)
				if(curToken.value == "}")
					if(!EndBlock())
						errors += new /datum/scriptError/BadToken(curToken)
						continue
					continue
			if(/datum/token/end)
				continue
		curBlock.statements += ParseExpression()
		if(!istype(curToken, /datum/token/end))
			errors += new /datum/scriptError/ExpectedToken(";", curToken)
			continue

	return global_block

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

/datum/n_Parser/nS_Parser/proc/AddBlock(datum/node/BlockDefinition/B)
	blocks.Push(curBlock)
	curBlock = B

/datum/n_Parser/nS_Parser/proc/EndBlock()
	if(curBlock == global_block)
		return FALSE
	curBlock = blocks.Pop()
	return TRUE