#! /usr/bin/env python
# -*- coding: utf-8 -*-
# vim:fenc=utf-8
#
# Copyright © 2019 pavle <pavle.portic@tilda.center>
#
# Distributed under terms of the BSD-3-Clause license.

import math
import operator

from constants import (
	NUMBER, EOF,
	PLUS, MINUS, MUL, DIV, IDIV, MOD, POW, SQRT,
	HEX, DEC, BIN,
	PI,
	SWAP, POP,
)


class Token():
	def __init__(self, type, value):
		self.type = type
		self.value = value

	def __repr__(self):
		return "<{} {}>".format(self.type, self.value)


class Lexer():
	def __init__(self, text):
		self.text = text
		self.pos = 0
		self.current_char = self.text[self.pos]

	def error(self, value=None):
		if value is None:
			raise Exception(f'Unexpected character {self.current_char}')
		else:
			raise Exception(f'Unexpected token {value}')

	def advance(self):
		self.pos += 1

		if self.pos > len(self.text) - 1:
			self.current_char = None
		else:
			self.current_char = self.text[self.pos]

	def number(self):
		number = ''
		while self.current_char is not None and (self.current_char.isdigit() or self.current_char == '.'):
			number += self.current_char
			self.advance()

		return float(number)

	def skip_whitespace(self):
		while(self.current_char is not None and self.current_char.isspace()):
			self.advance()

	def get_next_token(self):
		while self.current_char is not None:
			if self.current_char.isspace():
				self.skip_whitespace()
				continue

			elif self.current_char.isdigit():
				return Token(NUMBER, self.number())

			elif self.current_char == '+':
				self.advance()
				return Token(PLUS, operator.add)

			elif self.current_char == '-':
				self.advance()
				if self.current_char is not None and self.current_char.isdigit():
					return Token(NUMBER, -self.number())

				return Token(MINUS, operator.sub)

			elif self.current_char == '*':
				self.advance()
				return Token(MUL, operator.mul)

			elif self.current_char == '/':
				self.advance()
				if self.current_char == '/':
					self.advance()
					return Token(IDIV, operator.floordiv)
				return Token(DIV, operator.truediv)

			elif self.current_char == '%':
				self.advance()
				return Token(MOD, operator.mod)

			elif self.current_char == '^':
				self.advance()
				return Token(POW, operator.pow)

			elif self.current_char and self.current_char.isalpha():
				text = ''
				while self.current_char and (self.current_char.isalpha() or self.current_char.isdigit() or self.current_char == '_'):
					text += self.current_char
					self.advance()

				check = text.lower()
				if check.lower() == HEX.lower():
					return Token(HEX, hex)
				elif check.lower() == DEC.lower():
					return Token(DEC, float)
				elif check.lower() == BIN.lower():
					return Token(BIN, bin)
				elif check.lower() == SQRT.lower():
					return Token(SQRT, math.sqrt)
				elif check.lower() == PI.lower():
					return Token(NUMBER, math.pi)
				elif check.lower() == SWAP.lower():
					return Token(SWAP, text)
				elif check.lower() == POP.lower():
					return Token(POP, text)
				else:
					self.error(text)

			self.error()

		return Token(EOF, None)