Nexus/parser/rulebook.py

from constants import *
import expression

def parse(input_):
	rulebook_length = len(input_)

	# Main parsing loop
	idx = 0
	tab_count = 0
	current_level = 0
	current_rule = {}
	target_rule = None
	statement_cache = None
	new_line = True
	multiple_statements = False
	buff = ""
	bins = {}

	while idx < rulebook_length:
		char = input_[idx]
		
		if char == "\t":
			if buff == "":
				new_line = True
				tab_count += 1
			else:
				buff += char
		else:
			if new_line == True:
				if tab_count > current_level + 1:
					raise RulebookIndentationError("Incorrect indentation encountered.")
				
				if input_[idx:idx+2] == "=>":
					# Skip over this, it's optional at the start of a line
					idx += 2
					continue
					
				new_line = False
			
			if char == "\r":
				idx += 1
				continue # Ignore, we don't want carriage returns
			elif char == "\n":
				# Process
				if buff.strip() == "":
					# Skip empty lines, we don't care about them
					idx += 1
					tab_count = 0
					continue
					
				current_level = tab_count
				tab_count = 0
				
				if current_level == 0:
					bin_name = buff.strip()
					new_bin = Bin(bin_name)
					current_rule[current_level] = new_bin
					bins[bin_name] = new_bin
				else:
					if multiple_statements == True:
						new_rule = create_rule(buff, statement_cache)
					else:
						new_rule = create_rule(buff, current_rule[current_level - 1])
						
					current_rule[current_level] = new_rule
					
				buff = ""
				new_line = True
				multiple_statements = False
			elif char == "=" and input_[idx + 1] == ">":
				# Next rule, same line!
				if multiple_statements == True:
					statement_cache = create_rule(buff, statement_cache)
				else:
					multiple_statements = True
					statement_cache = create_rule(buff, current_rule[tab_count - 1])
				
				buff = ""
				idx += 1 # We read one extra character ahead
			else:
				# TODO: add entire chunks at once for speed
				buff += char
				
		idx += 1
		
	return bins

def create_rule(buff, input_):
	buff = buff.strip()
	if buff[0] == "*":
		# Node reference
		new_obj = NodeReference(input_, buff[1:])
	elif buff[0] == "@":
		# Method call
		new_obj = MethodReference(input_, buff[1:])
	elif buff[0] == "#":
		# Bin reference
		new_obj = BinReference(input_, buff[1:])
	elif buff[0] == ":":
		# Distributor
		if "(" in buff and buff[-1:] == ")":
			name, arglist = buff[1:-1].split("(", 1)
			args = [x.strip() for x in arglist.split(",")]
		else:
			name = buff[1:]
			args = []
		new_obj = DistributorReference(input_, name, args)
	else:
		# Filter
		new_obj = Filter(input_, buff)
		
	input_.outputs.append(new_obj)
	return new_obj

class Element(object):
	def __init__(self):
		self.outputs = []
		
	def display(self, indent):
		print ("\t" * indent) + self.get_description()
		for output in self.outputs:
			output.display(indent + 1)
	
class Bin(Element):
	def __init__(self, name):
		Element.__init__(self)
		self.name = name
		
	def get_description(self):
		return "[Bin] %s" % self.name
		
	def process(self, message):
		self.forward(message)
		
	def forward(self, message):
		for output in self.outputs:
			output.process(message)
	
class Rule(Element):
	def __init__(self, input_):
		Element.__init__(self)
		self.input_ = input_
		
	def process(self, message):
		self.forward(message)
		
	def forward(self, message):
		for output in self.outputs:
			output.process(message)
	
class Filter(Rule):
	def __init__(self, input_, rule):
		Rule.__init__(self, input_)
		self.rule = rule
		self.root = expression.parse(rule)
		
	def get_description(self):
		return "[Filter] %s" % self.rule
		
	def evaluate(self, message):
		return self.root.evaluate(message)
		
	def process(self, message):
		if self.evaluate(message):
			self.forward(message)
			
class BinReference(Rule):
	def __init__(self, input_, name):
		Rule.__init__(self, input_)
		self.bin_name = name
		
	def get(self):
		try:
			return bins[self.bin_name]
		except KeyError, e:
			new_bin = Bin(self.bin_name)
			bins[self.bin_name] = new_bin
			return new_bin
			
	def get_description(self):
		return "[BinRef] %s" % self.bin_name
		
	def process(self, message):
		# TODO: Actually deposit into bin
		print "DEPOSITED INTO BIN %s" % self.name

class NodeReference(Rule):
	def __init__(self, input_, name):
		Rule.__init__(self, input_)
		self.node_name = name
		
	def get_description(self):
		return "[NodeRef] %s" % self.node_name
		
	def process(self, message):
		# TODO: Actually forward to node
		print "FORWARDED TO NODE %s" % self.node_name
		
class MethodReference(Rule):
	def __init__(self, input_, name):
		Rule.__init__(self, input_)
		# TODO: Support arguments?
		self.method_name = name
		
	def get_description(self):
		return "[MethodRef] %s" % self.method_name
		
	def process(self, message):
		# TODO: Actually pass to method
		print "PASSED TO METHOD %s" % self.method_name
		
class DistributorReference(Rule):
	def __init__(self, input_, name, args):
		Rule.__init__(self, input_)
		self.distributor_name = name
		self.args = args
		# TODO: Parse outputs
		# Perhaps have special syntax for counting group as one entity?
		
	def get_description(self):
		return "[DistRef] %s (%s)" % (self.distributor_name, ", ".join(self.args))
		
	def process(self, message):
		# TODO: Actually distribute
		# TODO: Parse args
		print "DISTRIBUTED TO %s" % self.get_description()