lexer.lua

-- MIT License
-- 
-- Copyright (c) 2018 LoganDark
-- 
-- Permission is hereby granted, free of charge, to any person obtaining a copy
-- of this software and associated documentation files (the "Software"), to deal
-- in the Software without restriction, including without limitation the rights
-- to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
-- copies of the Software, and to permit persons to whom the Software is
-- furnished to do so, subject to the following conditions:
-- 
-- The above copyright notice and this permission notice shall be included in all
-- copies or substantial portions of the Software.
-- 
-- THE SOFTWARE 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 NONINFRINGEMENT. IN NO EVENT SHALL THE
-- AUTHORS OR COPYRIGHT HOLDERS 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 THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
-- SOFTWARE.

local function lookupify(src, list)
	list = list or {}

	if type(src) == 'string' then
		for i = 1, src:len() do
			list[src:sub(i, i)] = true
		end
	elseif type(src) == 'table' then
		for i = 1, #src do
			list[src[i]] = true
		end
	end

	return list
end

local base_ident = 'abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ_'
local base_digits = '0123456789'
local base_operators = '+-*/^%#'

local chars = {
	whitespace = lookupify(' \n\t\r'),
	validEscapes = lookupify('abfnrtv"\'\\'),
	ident = lookupify(
		base_ident .. base_digits,
		{
			start = lookupify(base_ident),
		}
	),

	digits = lookupify(
		base_digits,
		{
			hex = lookupify(base_digits .. 'abcdefABCDEF')
		}
	),

	symbols = lookupify(
		base_operators .. ',{}[]();.:', {
			equality = lookupify('~=><'),
			operators = lookupify(base_operators)
		}
	)
}

local keywords = {
	structure = lookupify({
		'and', 'break', 'do', 'else', 'elseif', 'end', 'for', 'function',
		'goto', 'if', 'in', 'local', 'not', 'or', 'repeat', 'return', 'then',
		'until', 'while'
	}),

	values = lookupify({
		'true', 'false', 'nil'
	})
}

return function(text)
	local pos = 1
	local start = 1
	local buffer = {}
	local lines = {}

	local function look(delta)
		delta = pos + (delta or 0)

		return text:sub(delta, delta)
	end

	local function get()
		pos = pos + 1

		return look(-1)
	end

	local function getDataLevel()
		local num = 0

		while look(num) == '=' do
			num = num + 1
		end

		if look(num) == '[' then
			pos = pos + num + 1

			return num
		end
	end

	local function getCurrentTokenText()
		return text:sub(start, pos - 1)
	end

	local currentLineLength = 0
	local lineoffset = 0

	local function pushToken(type, text)
		text = text or getCurrentTokenText()

		local tk = buffer[#buffer]

		if not tk or tk.type ~= type then
			tk = {
				type = type,
				data = text,
				posFirst = start - lineoffset,
				posLast = pos - 1 - lineoffset
			}

			if tk.data ~= '' then
				buffer[#buffer + 1] = tk
			end
		else
			tk.data = tk.data .. text
			tk.posLast = tk.posLast + text:len()
		end

		currentLineLength = currentLineLength + text:len()
		start = pos

		return tk
	end

	local function newline()
		lines[#lines + 1] = buffer
		buffer = {}

		get()
		pushToken('newline')
		buffer[1] = nil

		lineoffset = lineoffset + currentLineLength
		currentLineLength = 0
	end

	local function getData(level, type)
		while true do
			local char = get()

			if char == '' then
				return
			elseif char == '\n' then
				pos = pos - 1
				pushToken(type)
				newline()
			elseif char == ']' then
				local valid = true

				for i = 1, level do
					if look() == '=' then
						pos = pos + 1
					else
						valid = false
						break
					end
				end

				if valid and look() == ']' then
					pos = pos - level - 1

					return
				end
			end
		end
	end

	local function chompWhitespace()
		while true do
			local char = look()

			if char == '\n' then
				pushToken('whitespace')
				newline()
			elseif chars.whitespace[char] then
				pos = pos + 1
			else
				break
			end
		end

		pushToken('whitespace')
	end

	while true do
		chompWhitespace()

		local char = get()

		if char == '' then
			break
		elseif char == '-' and look() == '-' then
			pos = pos + 1

			if look() == '[' then
				pos = pos + 1

				local level = getDataLevel()

				if level then
					getData(level, 'comment')

					pos = pos + level + 2
					pushToken('comment')
				else
					while true do
						local char2 = get()

						if char2 == '' or char2 == '\n' then
							pos = pos - 1
							pushToken('comment')

							if char2 == '\n' then
								newline()
							end

							break
						end
					end
				end
			else
				while true do
					local char2 = get()

					if char2 == '' or char2 == '\n' then
						pos = pos - 1
						pushToken('comment')

						if char2 == '\n' then
							newline()
						end

						break
					end
				end
			end

			pushToken('comment')
		elseif char == '\'' or char == '"' then
			pushToken('string_start')

			while true do
				local char2 = get()

				if char2 == '\\' then
					pos = pos - 1
					pushToken('string')
					get()

					local char3 = get()

					if chars.digits[char3] then
						for i = 1, 2 do
							if chars.digits[look()] then
								pos = pos + 1
							end
						end
					elseif char3 == 'x' then
						if chars.digits.hex[look()] and chars.digits.hex[look(1)] then
							pos = pos + 2
						else
							pushToken('unidentified')
						end
					elseif char3 == '\n' then
						pos = pos - 1
						pushToken('escape')
						newline()
					elseif not chars.validEscapes[char3] then
						pushToken('unidentified')
					end

					pushToken('escape')
				elseif char2 == '\n' then
					pos = pos - 1
					pushToken('string')
					newline()

					break
				elseif char2 == char or char2 == '' then
					pos = pos - 1
					pushToken('string')
					get()

					break
				end
			end

			pushToken('string_end')
		elseif chars.ident.start[char] then
			while chars.ident[look()] do
				pos = pos + 1
			end

			local word = getCurrentTokenText()

			if keywords.structure[word] then
				pushToken('keyword')
			elseif keywords.values[word] then
				pushToken('value')
			else
				pushToken('ident')
			end
		elseif chars.digits[char] or (char == '.' and chars.digits[look()]) then
			if char == '0' and look() == 'x' then
				pos = pos + 1

				while chars.digits.hex[look()] do
					pos = pos + 1
				end
			else
				while chars.digits[look()] do
					pos = pos + 1
				end

				if look() == '.' then
					pos = pos + 1

					while chars.digits[look()] do
						pos = pos + 1
					end
				end

				if look():lower() == 'e' then
					pos = pos + 1

					if look() == '-' then
						pos = pos + 1
					end

					while chars.digits[look()] do
						pos = pos + 1
					end
				end
			end

			pushToken('number')
		elseif char == '[' then
			local level = getDataLevel()

			if level then
				pushToken('string_start')

				getData(level, 'string')
				pushToken('string')

				pos = pos + level + 2
				pushToken('string_end')
			else
				pushToken('symbol')
			end
		elseif char == '.' then
			if look() == '.' then
				pos = pos + 1

				if look() == '.' then
					pos = pos + 1
				end
			end

			if getCurrentTokenText():len() == 3 then
				pushToken('vararg')
			else
				pushToken('symbol')
			end
		elseif char == ':' and look() == ':' then
			get()

			pushToken('label_start')

			chompWhitespace()

			if chars.ident.start[look()] then
				get()

				while chars.ident[look()] do
					get()
				end

				pushToken('label')

				chompWhitespace()

				if look() == ':' and look(1) == ':' then
					get()
					get()

					pushToken('label_end')
				end
			end
		elseif chars.symbols.equality[char] then
			if look() == '=' then
				pos = pos + 1
			end

			pushToken('operator')
		elseif chars.symbols[char] then
			if chars.symbols.operators[char] then
				pushToken('operator')
			else
				pushToken('symbol')
			end
		else
			pushToken('unidentified')
		end
	end

	lines[#lines + 1] = buffer

	return lines
end