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import os

import re

def escape(pattern):

'''Escape special characters'''

ESCAPE = "(){}[].^$+\\?|"

def escape_char(char):

if char in ESCAPE:

return "\\" + char

else:

return char

return ''.join(escape_char(c) for c in pattern)

SEP = escape(os.sep)

STAR_STAR_REGEX = "([^%s]*%s)*" % (SEP, SEP)

STAR_REGEX = "[^%s]*" % SEP

def validate_pattern(pattern):

'''Validate that an include/exclude pattern is of the correct syntax.'''

kind, glob = pattern.split(":")

if not kind in ("include", "exclude"):

raise SyntaxError("Illegal type: '%s'" % kind)

parts = glob.split("/")

for p in parts:

if "**" in p and p != "**":

raise SyntaxError("Illegal path element: '%s'" % p)

def glob_part_to_regex(glob, add_sep):

'''Convert glob part to regex pattern'''

if glob == "**":

return STAR_STAR_REGEX

if '*' in glob:

pattern = glob.replace('*', STAR_REGEX)

else:

pattern = glob

if add_sep:

return pattern + SEP

else:

return pattern

def glob_to_regex(glob, prefix=""):

'''Convert entire glob to a compiled regex'''

# When the glob ends in `/`, we need to remember this so that we don't accidentally add an

# extra separator to the final regex.

end_sep = "" if glob.endswith("/") else SEP

glob = glob.strip().strip("/")

parts = glob.split("/")

#Trailing '**' is redundant, so strip it off.

if parts[-1] == "**":

parts = parts[:-1]

if not parts:

return ".*"

# The `glob.strip("/")` call above will have removed all trailing slashes, but if there was at

# least one trailing slash, we want there to be an extra part, so we add it explicitly here in

# that case, using the emptyness of `end_sep` as a proxy.

if end_sep == "":

parts += [""]

parts = [ glob_part_to_regex(escape(p), True) for p in parts[:-1] ] + [ glob_part_to_regex(escape(parts[-1]), False) ]

# we need to escape the prefix, specifically because on windows the prefix will be

# something like `C:\\folder\\subfolder\\` and without escaping the

# backslash-path-separators will get interpreted as regex escapes (which might be

# invalid sequences, causing the extractor to crash)

full_pattern = escape(prefix) + ''.join(parts) + "(?:" + end_sep + ".*|$)"

return re.compile(full_pattern)

def filter_from_pattern(pattern, prev_filter, prefix):

'''Create a filter function from a pattern and the previous filter.

The pattern takes precedence over the previous filter

'''

validate_pattern(pattern)

kind, glob = pattern.strip().split(":")

result = kind == "include"

regex = glob_to_regex(glob, prefix)

def filter(path):

if regex.match(path):

return result

return prev_filter(path)

return filter