#!/usr/bin/env python3

"""\
List python source files.

There are three functions to check whether a file is a Python source, listed
here with increasing complexity:

- has_python_ext() checks whether a file name ends in '.py[w]'.
- look_like_python() checks whether the file is not binary and either has
 the '.py[w]' extension or the first line contains the word 'python'.
- can_be_compiled() checks whether the file can be compiled by compile().

The file also must be of appropriate size - not bigger than a megabyte.

walk_python_files() recursively lists all Python files under the given directories.
"""
__author__ = "Oleg Broytmann, Georg Brandl"

__all__ = ["has_python_ext", "looks_like_python", "can_be_compiled", "walk_python_files"]


import os, re

binary_re = re.compile(br'[\x00-\x08\x0E-\x1F\x7F]')

debug = False

def print_debug(msg):
 if debug: print(msg)


def _open(fullpath):
 try:
 size = os.stat(fullpath).st_size
 except OSError as err: # Permission denied - ignore the file
 print_debug("%s: permission denied: %s" % (fullpath, err))
 return None

 if size > 1024*1024: # too big
 print_debug("%s: the file is too big: %d bytes" % (fullpath, size))
 return None

 try:
 return open(fullpath, "rb")
 except IOError as err: # Access denied, or a special file - ignore it
 print_debug("%s: access denied: %s" % (fullpath, err))
 return None

def has_python_ext(fullpath):
 return fullpath.endswith(".py") or fullpath.endswith(".pyw")

def looks_like_python(fullpath):
 infile = _open(fullpath)
 if infile is None:
 return False

 with infile:
 line = infile.readline()

 if binary_re.search(line):
 # file appears to be binary
 print_debug("%s: appears to be binary" % fullpath)
 return False

 if fullpath.endswith(".py") or fullpath.endswith(".pyw"):
 return True
 elif b"python" in line:
 # disguised Python script (e.g. CGI)
 return True

 return False

def can_be_compiled(fullpath):
 infile = _open(fullpath)
 if infile is None:
 return False

 with infile:
 code = infile.read()

 try:
 compile(code, fullpath, "exec")
 except Exception as err:
 print_debug("%s: cannot compile: %s" % (fullpath, err))
 return False

 return True


def walk_python_files(paths, is_python=looks_like_python, exclude_dirs=None):
 """\
 Recursively yield all Python source files below the given paths.

 paths: a list of files and/or directories to be checked.
 is_python: a function that takes a file name and checks whether it is a
 Python source file
 exclude_dirs: a list of directory base names that should be excluded in
 the search
 """
 if exclude_dirs is None:
 exclude_dirs=[]

 for path in paths:
 print_debug("testing: %s" % path)
 if os.path.isfile(path):
 if is_python(path):
 yield path
 elif os.path.isdir(path):
 print_debug(" it is a directory")
 for dirpath, dirnames, filenames in os.walk(path):
 for exclude in exclude_dirs:
 if exclude in dirnames:
 dirnames.remove(exclude)
 for filename in filenames:
 fullpath = os.path.join(dirpath, filename)
 print_debug("testing: %s" % fullpath)
 if is_python(fullpath):
 yield fullpath
 else:
 print_debug(" unknown type")


if __name__ == "__main__":
 # Two simple examples/tests
 for fullpath in walk_python_files(['.']):
 print(fullpath)
 print("----------")
 for fullpath in walk_python_files(['.'], is_python=can_be_compiled):
 print(fullpath)