/******************************************************************************\
  Expression 2 Pre-Processor for Garry's Mod
  Andreas "Syranide" Svensson, me@syranide.com
\******************************************************************************/

AddCSLuaFile("preprocessor.lua")

PreProcessor = {}
PreProcessor.__index = PreProcessor

function PreProcessor.Execute(...)
	-- instantiate PreProcessor
	local instance = setmetatable({}, PreProcessor)
	
	-- and pcall the new instance's Process method.
	return pcall(instance.Process, instance, ...)
end

function PreProcessor:Error(message, column)
	error(message .. " at line " .. self.readline .. ", char " .. (column or 1), 0)
end

local type_map = {
	v4 = "xv4",
	v2 = "xv2",
	m4 = "xm4",
	m2 = "xm2",
	rd = "xrd",
	wl = "xwl",
	number = "n",
}
local function gettype(tp)
	tp = tp:Trim():lower()
	local up = tp:upper()
	return type_map[tp] or (wire_expression_types[up] and wire_expression_types[up][1]) or tp
end

function PreProcessor:HandlePPCommand(comment)
	local command,args = comment:match("^([^ ]*) ?(.*)$")
	local handler = self["PP_"..command]
	if handler then return handler(self, args) end
end

function PreProcessor:FindComments( line )
	local ret, count, pos, found = {}, 0, 1
	repeat
		found = line:find( '[#"]', pos )
		if (found) then -- We found something
			local char = line:sub(found,found)
			if (char == "#") then -- We found a comment
				local before = line:sub( found-1, found-1 )
				if (before == "]") then -- We found an ending
					count = count + 1
					ret[count] = { type = "end", pos = found-1 }
					pos = found + 1
				else
					local after = line:sub( found+1, found+1 )
					if (after == "[") then -- We found a start
						count = count + 1
						ret[count] = { type = "start", pos = found }
						pos = found + 2
					else -- We found a normal comment
						count = count + 1
						ret[count] = { type = "normal", pos = found }
						pos = found + 1
					end
				end
			elseif (char == '"') then -- We found a string
				local before = line:sub( found-1, found-1 )
				if (before == "\\" and line:sub( found-2, found-2 ) != "\\") then -- It was an escaped character
					pos = found + 1 -- Skip it
				else -- It's a string
					count = count + 1
					ret[count] = { type = "string", pos = found }
					pos = found + 1
				end
			end
		end			
	until(!found)
	return ret, count
end

function PreProcessor:RemoveComments(line)

	local comments, num = self:FindComments( line ) -- Find all comments and strings on this line

	if (num == 0 and self.blockcomment) then
		return ""
	end
	
	local prev_disabled, ret, lastpos = self.disabled, "", 1
	
	for i=1, num do
		local type = comments[i].type
		if (type == "string" and !self.blockcomment) then -- Is it a string?
			self.multilinestring = !self.multilinestring
		elseif (!self.multilinestring) then -- Else it's a comment if we're not inside a multiline string
			if (self.blockcomment) then -- Time to look for a ]#
				if (type == "end") then -- We found one
					local pos = comments[i].pos
					ret = ret .. (" "):rep( pos - lastpos + 4 ) -- Replace the stuff in between with spaces
					lastpos = pos+2
					self.blockcomment = nil -- We're no longer in a block comment
				end
			else -- Time to look for a #[
				if (type == "start") then -- We found one
					local pos = comments[i].pos
					ret = ret .. line:sub( lastpos, pos-1 )
					lastpos = pos+2
					self.blockcomment = true -- We're now inside a block comment
				elseif (type == "normal") then -- We found a # instead
					local pos = comments[i].pos
					ret = ret .. line:sub( lastpos, pos-1 )
					lastpos = -1
					self:HandlePPCommand(line:sub(pos+1))
					break -- Don't care what comes after
				end
			end
		end
	end

	if (prev_disabled) then
		return ""
	elseif (lastpos != -1 and !self.blockcomment) then
		return ret .. line:sub( lastpos, -1 )
	else
		return ret
	end
end

function PreProcessor:ParseDirectives(line)
	if (self.multilinestring) then return line end
	
	-- parse directive
	local directive, value = line:match("^@([^ ]*) ?(.*)$")
	
	-- not a directive?
	if not directive then
		-- flag as "in code", if that is the case
		if string.Trim(line) ~= "" then
			self.incode = true
		end
		-- don't handle as a directive.
		return line
	end
	
	local col = directive:find("[A-Z]")
	if col then self:Error("Directive (@" .. E2Lib.limitString(directive, 10) .. ") must be lowercase", col+1) end
	if self.incode then self:Error("Directive (@" .. E2Lib.limitString(directive, 10) .. ") must appear before code") end
	
	-- evaluate directive
	if directive == "name" then
		if self.directives.name == nil then
			self.directives.name = value
		else
			self:Error("Directive (@name) must not be specified twice")
		end
	elseif directive == "model" then
		if self.directives.model == nil then
			self.directives.model = value
		else
			self:Error("Directive (@model) must not be specified twice")
		end
	elseif directive == "inputs" then
		local retval, columns = self:ParsePorts(value,#directive+2)
		
		for i,key in ipairs(retval[1]) do
			if self.directives.inputs[3][key] then
				self:Error("Directive (@input) contains multiple definitions of the same variable", columns[i])
			else
				local index = #self.directives.inputs[1] + 1
				self.directives.inputs[1][index] = key
				self.directives.inputs[2][index] = retval[2][i]
				self.directives.inputs[3][key] = retval[2][i]
			end
		end
	elseif directive == "outputs" then
		local retval, columns = self:ParsePorts(value,#directive+2)
		
		for i,key in ipairs(retval[1]) do
			if self.directives.outputs[3][key] then
				self:Error("Directive (@output) contains multiple definitions of the same variable", columns[i])
			else
				local index = #self.directives.outputs[1] + 1
				self.directives.outputs[1][index] = key
				self.directives.outputs[2][index] = retval[2][i]
				self.directives.outputs[3][key] = retval[2][i]
			end
		end
	elseif directive == "persist" then
		local retval, columns = self:ParsePorts(value,#directive+2)
		
		for i,key in ipairs(retval[1]) do
			if self.directives.persist[3][key] then
				self:Error("Directive (@persist) contains multiple definitions of the same variable", columns[i])
			else
				local index = #self.directives.persist[1] + 1
				self.directives.persist[1][index] = key
				self.directives.persist[2][index] = retval[2][i]
				self.directives.persist[3][key] = retval[2][i]
			end
		end
	elseif directive == "trigger" then
		local trimmed = string.Trim(value)
		if trimmed == "" then
		elseif trimmed == "all" then
			if self.directives.trigger[1] != nil then
				self:Error("Directive (@trigger) conflicts with previous directives")
			end
			self.directives.trigger[1] = true
		elseif trimmed == "none" then
			if self.directives.trigger[1] != nil then
				self:Error("Directive (@trigger) conflicts with previous directives")
			end
			self.directives.trigger[1] = false
		else
			if self.directives.trigger[1] != nil and #self.directives.trigger[2] == 0 then
				self:Error("Directive (@trigger) conflicts with previous directives")
			end
			
			self.directives.trigger[1] = false
			local retval, columns = self:ParsePorts(value,#directive+2)
			
			for i,key in ipairs(retval[1]) do
				if self.directives.trigger[key] then
					self:Error("Directive (@trigger) contains multiple definitions of the same variable", columns[i])
				else
					self.directives.trigger[2][key] = true
				end
			end
		end
	else
		self:Error("Unknown directive found (@" .. E2Lib.limitString(directive, 10) .. ")", 2)
	end
	
	-- remove line from output
	return ""
end

function PreProcessor:Process(buffer, params)
	local lines = string.Explode("\n", buffer)
	
	self.directives = {
		name = nil,
		model = nil,
		inputs = { {}, {}, {} },
		outputs = { {}, {}, {} },
		persist = { {}, {}, {} },
		delta = { {}, {}, {} },
		trigger = { nil, {} },
	}
	
	for i,line in ipairs(lines) do
		self.readline = i
		line = string.TrimRight(line)
		
		line = self:RemoveComments(line)
		line = self:ParseDirectives(line)
		
		lines[i] = line
	end
	
	if self.directives.trigger[1] == nil then self.directives.trigger[1] = true end
	if !self.directives.name then self.directives.name = "" end
	
	return self.directives, string.Implode("\n", lines)
end

function PreProcessor:ParsePorts(ports, startoffset)
	local names = {}
	local types = {}
	local columns = {}
	ports = ports:gsub("%[.-%]", function(s)
		return s:gsub(" ",",")
	end) -- preprocess multi-variable definitions.
	
	for column,key in ports:gmatch("()([^ ]+)") do
		column = startoffset+column
		key = key:Trim()
		
		-------------------------------- variable names --------------------------------
		
		-- single-variable definition?
		local _,i,namestring = key:find("^([A-Z][A-Za-z0-9_]*)")
		if i then 
			-- yes -> add the variable
			names[#names + 1] = namestring
		else
			-- no -> maybe a multi-variable definition?
			_,i,namestring = key:find("^%[([^]]+)%]")
			if not i then
				-- no -> malformed variable name
				self:Error("Variable name (" .. E2Lib.limitString(key, 10) .. ") must start with an uppercase letter", column)
			end
			-- yes -> add all variables.
			for column2,var in namestring:gmatch("()([^,]+)") do
				column2 = column+column2
				var = string.Trim(var)
				-- skip empty entries
				if var ~= "" then
					-- error on malformed variable names
					if not var:match("^[A-Z]") then self:Error("Variable name (" .. E2Lib.limitString(var, 10) .. ") must start with an uppercase letter", column2) end
					local errcol = var:find("[^A-Za-z0-9_]")
					if errcol then self:Error("Variable declaration (" .. E2Lib.limitString(var, 10) .. ") contains invalid characters", column2+errcol-1) end
					-- and finally add the variable.
					names[#names + 1] = var
				end
			end
		end
		
		-------------------------------- variable types --------------------------------
		
		local vtype
		local character = key:sub(i+1, i+1)
		if character == ":" then
			-- type is specified -> check for validity
			vtype = key:sub(i + 2)
			
			if vtype ~= vtype:lower() then
				self:Error("Variable type [" .. E2Lib.limitString(vtype, 10) .. "] must be lowercase", column+i+1)
			end
			
			if vtype == "number" then vtype = "normal" end
			
			if not wire_expression_types[vtype:upper()] then
				self:Error("Unknown variable type [" .. E2Lib.limitString(vtype, 10) .. "] specified for variable(s) (" .. E2Lib.limitString(namestring, 10) .. ")", column+i+1)
			end
		elseif character == "" then
			-- type is not specified -> default to NORMAL
			vtype = "NORMAL"
		else
			-- invalid -> raise an error
			self:Error("Variable declaration (" .. E2Lib.limitString(key, 10) .. ") contains invalid characters", column+i)
		end
		
		-- fill in the missing types
		for i = #types+1,#names do
			types[i] = vtype:upper()
			columns[i] = column
		end
	end
	
	return { names, types }, columns
end

function PreProcessor:PP_ifdef(args)
	if self.disabled ~= nil then self:Error("Found nested #ifdef") end
	local thistype,colon,name,argtypes = args:match("([^:]-)(:?)([^:(]+)%(([^)]*)%)")
	if not thistype or (thistype ~= "") ~= (colon ~= "") then self:Error("Malformed #ifdef argument "..args) end
	
	thistype = gettype(thistype)
	
	local tps = { thistype..colon }
	for i,argtype in ipairs(string.Explode(",", argtypes)) do
		argtype = gettype(argtype)
		table.insert(tps, argtype)
	end
	local pars = table.concat(tps)
	local a = wire_expression2_funcs[name .. "(" .. pars .. ")"]
	
	self.disabled = not a
end

function PreProcessor:PP_ifndef(args)
	local ret = self:PP_ifdef(args)
	self.disabled = not self.disabled
	return ret
end

function PreProcessor:PP_else(args)
	if self.disabled == nil then self:Error("Found #else outside #ifdef block") end
	if args:Trim() ~= "" then self:Error("Must not pass an argument to #else") end
	self.disabled = not self.disabled
end

function PreProcessor:PP_endif(args)
	if self.disabled == nil then self:Error("Found #endif outside #ifdef block") end
	if args:Trim() ~= "" then self:Error("Must not pass an argument to #endif") end
	self.disabled = nil
end