"""Utilities for comparing files and directories.

Classes:
 dircmp

Functions:
 cmp(f1, f2, shallow=True) -> int
 cmpfiles(a, b, common) -> ([], [], [])
 clear_cache()

"""

import os
import stat
from itertools import filterfalse

__all__ = ['clear_cache', 'cmp', 'dircmp', 'cmpfiles', 'DEFAULT_IGNORES']

_cache = {}
BUFSIZE = 8*1024

DEFAULT_IGNORES = [
 'RCS', 'CVS', 'tags', '.git', '.hg', '.bzr', '_darcs', '__pycache__']

def clear_cache():
 """Clear the filecmp cache."""
 _cache.clear()

def cmp(f1, f2, shallow=True):
 """Compare two files.

 Arguments:

 f1 -- First file name

 f2 -- Second file name

 shallow -- Just check stat signature (do not read the files).
 defaults to True.

 Return value:

 True if the files are the same, False otherwise.

 This function uses a cache for past comparisons and the results,
 with cache entries invalidated if their stat information
 changes. The cache may be cleared by calling clear_cache().

 """

 s1 = _sig(os.stat(f1))
 s2 = _sig(os.stat(f2))
 if s1[0] != stat.S_IFREG or s2[0] != stat.S_IFREG:
 return False
 if shallow and s1 == s2:
 return True
 if s1[1] != s2[1]:
 return False

 outcome = _cache.get((f1, f2, s1, s2))
 if outcome is None:
 outcome = _do_cmp(f1, f2)
 if len(_cache) > 100: # limit the maximum size of the cache
 clear_cache()
 _cache[f1, f2, s1, s2] = outcome
 return outcome

def _sig(st):
 return (stat.S_IFMT(st.st_mode),
 st.st_size,
 st.st_mtime)

def _do_cmp(f1, f2):
 bufsize = BUFSIZE
 with open(f1, 'rb') as fp1, open(f2, 'rb') as fp2:
 while True:
 b1 = fp1.read(bufsize)
 b2 = fp2.read(bufsize)
 if b1 != b2:
 return False
 if not b1:
 return True

# Directory comparison class.
#
class dircmp:
 """A class that manages the comparison of 2 directories.

 dircmp(a, b, ignore=None, hide=None)
 A and B are directories.
 IGNORE is a list of names to ignore,
 defaults to DEFAULT_IGNORES.
 HIDE is a list of names to hide,
 defaults to [os.curdir, os.pardir].

 High level usage:
 x = dircmp(dir1, dir2)
 x.report() -> prints a report on the differences between dir1 and dir2
 or
 x.report_partial_closure() -> prints report on differences between dir1
 and dir2, and reports on common immediate subdirectories.
 x.report_full_closure() -> like report_partial_closure,
 but fully recursive.

 Attributes:
 left_list, right_list: The files in dir1 and dir2,
 filtered by hide and ignore.
 common: a list of names in both dir1 and dir2.
 left_only, right_only: names only in dir1, dir2.
 common_dirs: subdirectories in both dir1 and dir2.
 common_files: files in both dir1 and dir2.
 common_funny: names in both dir1 and dir2 where the type differs between
 dir1 and dir2, or the name is not stat-able.
 same_files: list of identical files.
 diff_files: list of filenames which differ.
 funny_files: list of files which could not be compared.
 subdirs: a dictionary of dircmp objects, keyed by names in common_dirs.
 """

 def __init__(self, a, b, ignore=None, hide=None): # Initialize
 self.left = a
 self.right = b
 if hide is None:
 self.hide = [os.curdir, os.pardir] # Names never to be shown
 else:
 self.hide = hide
 if ignore is None:
 self.ignore = DEFAULT_IGNORES
 else:
 self.ignore = ignore

 def phase0(self): # Compare everything except common subdirectories
 self.left_list = _filter(os.listdir(self.left),
 self.hide+self.ignore)
 self.right_list = _filter(os.listdir(self.right),
 self.hide+self.ignore)
 self.left_list.sort()
 self.right_list.sort()

 def phase1(self): # Compute common names
 a = dict(zip(map(os.path.normcase, self.left_list), self.left_list))
 b = dict(zip(map(os.path.normcase, self.right_list), self.right_list))
 self.common = list(map(a.__getitem__, filter(b.__contains__, a)))
 self.left_only = list(map(a.__getitem__, filterfalse(b.__contains__, a)))
 self.right_only = list(map(b.__getitem__, filterfalse(a.__contains__, b)))

 def phase2(self): # Distinguish files, directories, funnies
 self.common_dirs = []
 self.common_files = []
 self.common_funny = []

 for x in self.common:
 a_path = os.path.join(self.left, x)
 b_path = os.path.join(self.right, x)

 ok = 1
 try:
 a_stat = os.stat(a_path)
 except OSError as why:
 # print('Can\'t stat', a_path, ':', why.args[1])
 ok = 0
 try:
 b_stat = os.stat(b_path)
 except OSError as why:
 # print('Can\'t stat', b_path, ':', why.args[1])
 ok = 0

 if ok:
 a_type = stat.S_IFMT(a_stat.st_mode)
 b_type = stat.S_IFMT(b_stat.st_mode)
 if a_type != b_type:
 self.common_funny.append(x)
 elif stat.S_ISDIR(a_type):
 self.common_dirs.append(x)
 elif stat.S_ISREG(a_type):
 self.common_files.append(x)
 else:
 self.common_funny.append(x)
 else:
 self.common_funny.append(x)

 def phase3(self): # Find out differences between common files
 xx = cmpfiles(self.left, self.right, self.common_files)
 self.same_files, self.diff_files, self.funny_files = xx

 def phase4(self): # Find out differences between common subdirectories
 # A new dircmp object is created for each common subdirectory,
 # these are stored in a dictionary indexed by filename.
 # The hide and ignore properties are inherited from the parent
 self.subdirs = {}
 for x in self.common_dirs:
 a_x = os.path.join(self.left, x)
 b_x = os.path.join(self.right, x)
 self.subdirs[x] = dircmp(a_x, b_x, self.ignore, self.hide)

 def phase4_closure(self): # Recursively call phase4() on subdirectories
 self.phase4()
 for sd in self.subdirs.values():
 sd.phase4_closure()

 def report(self): # Print a report on the differences between a and b
 # Output format is purposely lousy
 print('diff', self.left, self.right)
 if self.left_only:
 self.left_only.sort()
 print('Only in', self.left, ':', self.left_only)
 if self.right_only:
 self.right_only.sort()
 print('Only in', self.right, ':', self.right_only)
 if self.same_files:
 self.same_files.sort()
 print('Identical files :', self.same_files)
 if self.diff_files:
 self.diff_files.sort()
 print('Differing files :', self.diff_files)
 if self.funny_files:
 self.funny_files.sort()
 print('Trouble with common files :', self.funny_files)
 if self.common_dirs:
 self.common_dirs.sort()
 print('Common subdirectories :', self.common_dirs)
 if self.common_funny:
 self.common_funny.sort()
 print('Common funny cases :', self.common_funny)

 def report_partial_closure(self): # Print reports on self and on subdirs
 self.report()
 for sd in self.subdirs.values():
 print()
 sd.report()

 def report_full_closure(self): # Report on self and subdirs recursively
 self.report()
 for sd in self.subdirs.values():
 print()
 sd.report_full_closure()

 methodmap = dict(subdirs=phase4,
 same_files=phase3, diff_files=phase3, funny_files=phase3,
 common_dirs = phase2, common_files=phase2, common_funny=phase2,
 common=phase1, left_only=phase1, right_only=phase1,
 left_list=phase0, right_list=phase0)

 def __getattr__(self, attr):
 if attr not in self.methodmap:
 raise AttributeError(attr)
 self.methodmap[attr](self)
 return getattr(self, attr)

def cmpfiles(a, b, common, shallow=True):
 """Compare common files in two directories.

 a, b -- directory names
 common -- list of file names found in both directories
 shallow -- if true, do comparison based solely on stat() information

 Returns a tuple of three lists:
 files that compare equal
 files that are different
 filenames that aren't regular files.

 """
 res = ([], [], [])
 for x in common:
 ax = os.path.join(a, x)
 bx = os.path.join(b, x)
 res[_cmp(ax, bx, shallow)].append(x)
 return res


# Compare two files.
# Return:
# 0 for equal
# 1 for different
# 2 for funny cases (can't stat, etc.)
#
def _cmp(a, b, sh, abs=abs, cmp=cmp):
 try:
 return not abs(cmp(a, b, sh))
 except OSError:
 return 2


# Return a copy with items that occur in skip removed.
#
def _filter(flist, skip):
 return list(filterfalse(skip.__contains__, flist))


# Demonstration and testing.
#
def demo():
 import sys
 import getopt
 options, args = getopt.getopt(sys.argv[1:], 'r')
 if len(args) != 2:
 raise getopt.GetoptError('need exactly two args', None)
 dd = dircmp(args[0], args[1])
 if ('-r', '') in options:
 dd.report_full_closure()
 else:
 dd.report()

if __name__ == '__main__':
 demo()