from io import open

from os.path import isdir

import re

def filterLines(lines, regex):

	'''Filters each line of the given line iterator using the given regular

	expression string. For each match, a tuple containing the text matching

	each capture group from the regular expression is yielded.

	'''

	matcher = re.compile(regex)

	for line in lines:

		if line.endswith('\n'):

			line = line[ : -1]

		match = matcher.match(line)

		if match:

			yield match.groups()

def filterFile(filePath, regex):

	'''Filters each line of the given text file using the given regular

	expression string. For each match, a tuple containing the text matching

	each capture group from the regular expression is yielded.

	'''

	with open(filePath, 'r', encoding='utf-8') as inp:

		for groups in filterLines(inp, regex):

			yield groups

def joinContinuedLines(lines):

	'''Iterates through the given lines, replacing lines that are continued

	using a trailing backslash with a single line.

	'''

	buf = ''

	for line in lines:

		if line.endswith('\\\n'):

			buf += line[ : -2]

		elif line.endswith('\\'):

			buf += line[ : -1]

		else:

			yield buf + line

			buf = ''

	if buf:

		raise ValueError('Continuation on last line')

_reEval = re.compile(r'(\$\(|\))')

def evalMakeExpr(expr, makeVars):

	'''Evaluates variable references in an expression.

	Raises ValueError if there is a syntax error in the expression.

	Raises KeyError if the expression references a non-existing variable.

	'''

	stack = [ [] ]

	for part in _reEval.split(expr):

		if part == '$(':

			stack.append([])

		elif part == ')' and len(stack) != 1:

			name = ''.join(stack.pop())

			if name.startswith('addprefix '):

				prefix, args = name[len('addprefix') : ].split(',')

				prefix = prefix.strip()

				value = ' '.join(prefix + arg for arg in args.split())

			elif name.startswith('addsuffix '):

				suffix, args = name[len('addsuffix') : ].split(',')

				suffix = suffix.strip()

				value = ' '.join(arg + suffix for arg in args.split())

			elif name.startswith('shell '):

				# Unsupported; assume result is never used.

				value = '?'

			elif name.isdigit():

				# This is a function argument; assume the evaluated result is

				# never used.

				value = '?'

			else:

				value = makeVars[name]

			stack[-1].append(value)

		else:

			stack[-1].append(part)

	if len(stack) != 1:

		raise ValueError('Open without close in "%s"' % expr)

	return ''.join(stack.pop())

def extractMakeVariables(filePath, makeVars = None):

	'''Extract all variable definitions from the given Makefile.

	The optional makeVars argument is a dictionary containing the already

	defined variables. These variables will be included in the output; the

	given dictionary is not modified.

	Returns a dictionary that maps each variable name to its value.

	'''

	makeVars = {} if makeVars is None else dict(makeVars)

	with open(filePath, 'r', encoding='utf-8') as inp:

		for name, assign, value in filterLines(

			joinContinuedLines(inp),

			r'[ ]*([A-Za-z0-9_]+)[ ]*([+:]?=)(.*)'

			):

			if assign == '=':

				makeVars[name] = value.strip()

			elif assign == ':=':

				makeVars[name] = evalMakeExpr(value, makeVars).strip()

			elif assign == '+=':

				# Note: Make will or will not evaluate the added expression

				#       depending on how the variable was originally defined,

				#       but we don't store that information.

				makeVars[name] = makeVars[name] + ' ' + value.strip()

			else:

				assert False, assign

	return makeVars

def parseBool(valueStr):

	'''Parses a string containing a boolean value.

	Accepted values are "true" and "false"; anything else raises ValueError.

	'''

	if valueStr == 'true':

		return True

	elif valueStr == 'false':

		return False

	else:

		raise ValueError('Invalid boolean "%s"' % valueStr)