from collections import deque

from .context import FileContext
from .tokenize import Tokenizer, WHITESPACE
from .opcodes import make_opcodes
from .util import can_be_mark, can_convert_to_int, autoint, int16_2_bytes
from .directives import SetDirective

class ParsingError(Exception): 
	pass

class Assembler(object):
	"""
	This class is used for generating bytecode from a file containing assembly.

	Also required is the memory definition of the interpreter given as a dict::

		{
			"registers": <register_count>,
			"memory": <number of memory words>,
			"program_memory": <number of words available for the program>
		}

	And the definition of the commands. This is a list of dicts::
		
		[
			{
				"mnemonic": <mnemonic>,
				"args": [
						("register"|"memory"|"program_memory"|"direct_input"), ...
					]
			}
		]
	
	The method ``parse`` will parse the input file and ``bindump`` will dump the binary
	bytecode into a file.
	"""
	def __init__(self, file_, memory_definition, command_definition, custom_directives):
		self._file_context = FileContext(file_)
		self._code_objects = deque()
		self._memory_definition = memory_definition
		self._command_definition = command_definition
		self._word_count = 0
		self._marks = {}

		self._opcodes = make_opcodes([cmd["mnemonic"] for cmd in command_definition])
		self._commands_by_mnemonic = {cmd["mnemonic"]: cmd for cmd in command_definition}
		self._tokenizer = Tokenizer(self._file_context)

		self._directives = {"set": SetDirective()}
		self._directives.update(custom_directives)

	def parse(self):
		try:
			for token in self._tokenizer:

				# Comments
				if(token == ";"):
					while(token != "\n"):
						token = next(self._tokenizer)
					continue

				# Commands
				if(token in self._commands_by_mnemonic):
					self.parse_command(token)
					continue

				# Directives
				if(token == "."):
					self.parse_directive()
					continue

				# The default is trying to parse a mark
				if(not can_be_mark(token)):
					self.raise_unexpected_token(token
						, "comment, command, directive or mark"
						, token)
				self.parse_mark(token)
		except StopIteration:
			raise ParsingError("Unexpected EOF while parsing.")
			
		for mark, mark_data in self._marks.items():
			if(mark_data["target"] < 0):
				raise ParsingError("Mark {} undefined. Referenced in lines: {}".format(
						mark
						, mark_data["references"]))

		self._code_objects = [self._marks[c]["target"] if c in self._marks else c 
							for c in self._code_objects ]

	def bindump(self, file_):
		# FIXME:
		# Make this work for tons of data.
		# Or is that necessary?
		# TODO:
		# Figure out whether/what improovements are necessary here
		length = int16_2_bytes(len(self._code_objects))
		if(len(self._code_objects).bit_length() > 16):
			raise ValueError("Program size excceeds 2^16.")
		file_.write(length)
		for word in self._code_objects:
			file_.write(int16_2_bytes(word))


	def parse_mark(self, token):
		should_be_colon = next(self._tokenizer)

		if(should_be_colon != ":"):
			self.raise_unexpected_token(token, "':'", should_be_colon)

		should_be_newline = next(self._tokenizer)
		if(should_be_newline != "\n"):
			self.raise_unexpected_token(token + ":", "'\\n'", should_be_newline)

		if(token in self._marks):
			if(self._marks[token]["target"] != -1):
				raise ParsingError("Error in line {} column {} mark already defined: '{}'. Previous was in line {}.".format(
						self._file_context._line
						, self._column
						, token
						, self._marks[token]["target_line"]))
			self._marks[token]["target"] = self._word_count
			self._marks[token]["target_line"] = self._file_context._line

		else:
			self._marks[token] = {
				"target": self._word_count
				, "target_line": self._file_context._line
				, "references": []
			}


	def parse_directive(self):
		should_be_name = next(self._tokenizer)
		
		if(not should_be_name in self._directives):
			self.raise_unexpected_token(".", "directive name", should_be_name)

		should_be_whitespace = next(self._tokenizer)
		if(not should_be_whitespace in WHITESPACE):
			self.raise_unexpected_token(should_be_name, "' '", should_be_whitespace)

		words = self._directives[should_be_name].parse(self, self._tokenizer)
		
		self._word_count += len(words)
		self._code_objects.extend(words)

		should_be_newline = next(self._tokenizer)
		if(should_be_newline != "\n"):
			self.raise_unexpected_token(".", "newline", should_be_newline)




	def parse_command(self, cmd):
		# We have no arguments
		if(not self._commands_by_mnemonic[cmd]["args"]):
			self._code_objects.append(self._opcodes[cmd])
			self._word_count += 1
			token = next(self._tokenizer)
			if(token != "\n"):
				self.raise_unexpected_token(cmd, "newline", token)
			return 

		# Small argument must be treated separately
		should_be_whitespace = next(self._tokenizer)
		if(should_be_whitespace not in WHITESPACE 
				or should_be_whitespace == "\n"):
			self.raise_unexpected_token(cmd, "' '", should_be_whitespace)

		should_be_an_argument = next(self._tokenizer)
		argument = self.check_and_convert_argument(cmd
				, should_be_an_argument
				, self._commands_by_mnemonic[cmd]["args"][0])
		self._word_count += 1
		# NOTE:
		# The Small Argument is stored within the first word (!)
		self._code_objects.append(self._opcodes[cmd] | (argument & 0xffff))
		

		# All the 16bit arguments
		for argument in self._commands_by_mnemonic[cmd]["args"][1:]:
			should_be_comma = next(self._tokenizer)
			if(should_be_comma != ","):
				self.raise_unexpected_token(cmd, "','", should_be_comma)

			self._word_count += 1
			self._code_objects.append(
					self.check_and_convert_argument(
						cmd
						, next(self._tokenizer)
						, argument))

		should_be_newline = next(self._tokenizer)
		if(should_be_newline != "\n"):
			self.raise_unexpected_token(cmd, "newline", should_be_newline)
			
			
	def raise_unexpected_token(self, after, expected, got):
		raise ParsingError("Error in line {} column {} after '{}': expected {}, got '{}'".format(
					self._file_context._line
					, self._file_context._column
					, after
					, expected
					, got))

	def raise_invalid_address(self, after, memtype, maxval, got):
		raise ParsingError("Error in line {} column {} after '{}': value {} is invalid for {} (max is {})".format(
					self._file_context._line
					, self._file_context._column
					, after
					, got
					, memtype
					, maxval))

	def check_and_convert_argument(self, cmd, argument, argument_definition):
		if(argument_definition == "register"):
			if(not argument.startswith("r")):
				self.raise_unexpected_token(cmd, "register name", argument)
			register_offset = argument[1:]
			raise_could_not_convert_register_offset = False
			try:
				register_offset = int(register_offset)
			except:
				raise_could_not_convert_register_offset = True

			if(raise_could_not_convert_register_offset):
				self.raise_unexpected_token(cmd, "register name", argument)

			if(register_offset > self._memory_definition["registers"] 
					or register_offset < 0):
				self.raise_invalid_address(cmd
						, "register"
						, self._memory_definition["registers"]
						, register_offset)

			return register_offset

		if(argument_definition == "memory"):
			if(not can_convert_to_int(argument)):
				self.raise_unexpected_token(cmd, "integer address", argument)
			argument = autoint(argument)

			if(argument < 0 or argument > self._memory_definition["memory"]):
				self.raise_invalid_address(cmd
						, "memory"
						, self._memory_definition["memory"]
						, argument)
			return argument

		if(argument_definition == "program_memory"):
			# Non-integer Argument.
			if(not can_convert_to_int(argument)):
				# Just nonsense.
				if(not can_be_mark(argument)):
					self.raise_unexpected_token(cmd, "integer address or mark", argument)
				# The Mark has appeared before.
				if(argument in self._marks):
					# Add this line to the references.
					self._marks[argument]["references"].append(self._file_context._line)
					# The target is already known. Insert it now.
					if(self._marks[argument]["target"] != -1):
						return self._marks[argument]["target"]
					# The target is unknown.
					return argument
				# The Mark has not appeared before.
				self._marks[argument] = {
					"target": -1
					, "target_line": 0
					, "references": [self._file_context._line]
				}
				# Target is obviously unknown.
				return argument


			# Integer argument.
			argument = autoint(argument)

			if(argument < 0 or argument > self._memory_definition["program_memory"]):
				self.raise_invalid_address(cmd
						, "program_memory"
						, self._memory_definition["program_memory"]
						, argument)
			return argument

		# This is direct input (default).

		# Integer
		if(can_convert_to_int(argument)):
			return autoint(argument)

		# This is nonsense.
		if(not can_be_mark(argument)):
			self.raise_unexpected_token(cmd, "integer, char or mark", argument)

		# It is a Mark.
		if(argument in self._marks):
			if(self._marks[argument]["target"] >= 0):
				self._marks[argument]["references"].append(self._file_context._line)
				return self._marks[argument]["target"]
			self._marks[argument]["references"].append(self._file_context._line)
			return argument
			
		self._marks[argument] = {
			"target": -1
			, "target_line": 0
			, "references": [self._file_context._line]
		}

		return argument