#!/usr/bin/env python
from __future__ import print_function

from __future__ import absolute_import
import os
import sys
import subprocess
import re
from collections import defaultdict
import argparse
from six.moves import filter
from typing import Union, List, Dict

def get_ftype(fpath, use_shebang):
    # type: (str, bool) -> str
    ext = os.path.splitext(fpath)[1]
    if ext:
        return ext[1:]
    elif use_shebang:
        # opening a file may throw an OSError
        with open(fpath) as f:
            first_line = f.readline()
            if re.search(r'^#!.*\bpython', first_line):
                return 'py'
            elif re.search(r'^#!.*sh', first_line):
                return 'sh'
            elif re.search(r'^#!.*\bperl', first_line):
                return 'pl'
            elif re.search(r'^#!.*\bnode', first_line):
                return 'js'
            elif re.search(r'^#!.*\bruby', first_line):
                return 'rb'
            elif re.search(r'^#!', first_line):
                print('Error: Unknown shebang in file "%s":\n%s' % (fpath, first_line), file=sys.stderr)
                return ''
            else:
                return ''
    else:
        return ''

def list_files(targets=[], ftypes=[], use_shebang=True, modified_only=False,
               exclude=[], group_by_ftype=False):
    # type: (List[str], List[str], bool, bool, List[str], bool) -> Union[Dict[str, List[str]], List[str]]
    """
    List files tracked by git.
    Returns a list of files which are either in targets or in directories in targets.
    If targets is [], list of all tracked files in current directory is returned.

    Other arguments:
    ftypes - List of file types on which to filter the search.
        If ftypes is [], all files are included.
    use_shebang - Determine file type of extensionless files from their shebang.
    modified_only - Only include files which have been modified.
    exclude - List of paths to be excluded.
    group_by_ftype - If True, returns a dict of lists keyed by file type.
        If False, returns a flat list of files.
    """
    ftypes = [x.strip('.') for x in ftypes]
    ftypes_set = set(ftypes)

    cmdline = ['git', 'ls-files'] + targets
    if modified_only:
        cmdline.append('-m')

    files_gen = (x.strip() for x in subprocess.check_output(cmdline, universal_newlines=True).split('\n'))
    # throw away empty lines and non-files (like symlinks)
    files = list(filter(os.path.isfile, files_gen))

    result_dict = defaultdict(list) # type: Dict[str, List[str]]
    result_list = [] # type: List[str]

    for fpath in files:
        # this will take a long time if exclude is very large
        in_exclude = False
        for expath in exclude:
            expath = expath.rstrip('/')
            if fpath == expath or fpath.startswith(expath + '/'):
                in_exclude = True
        if in_exclude:
            continue

        if ftypes or group_by_ftype:
            try:
                filetype = get_ftype(fpath, use_shebang)
            except (OSError, UnicodeDecodeError) as e:
                etype = e.__class__.__name__
                print('Error: %s while determining type of file "%s":' % (etype, fpath), file=sys.stderr)
                print(e, file=sys.stderr)
                filetype = ''
            if ftypes and filetype not in ftypes_set:
                continue

        if group_by_ftype:
            result_dict[filetype].append(fpath)
        else:
            result_list.append(fpath)

    if group_by_ftype:
        return result_dict
    else:
        return result_list

if __name__=="__main__":
    parser = argparse.ArgumentParser(description="List files tracked by git and optionally filter by type")
    parser.add_argument('targets', nargs='*', default=[],
                        help='''files and directories to include in the result.
                        If this is not specified, the current directory is used''')
    parser.add_argument('-m', '--modified', action='store_true', default=False, help='list only modified files')
    parser.add_argument('-f', '--ftypes', nargs='+', default=[],
                        help="list of file types to filter on. All files are included if this option is absent")
    parser.add_argument('--ext-only', dest='extonly', action='store_true', default=False,
                        help='only use extension to determine file type')
    parser.add_argument('--exclude', nargs='+', default=[],
                        help='list of files and directories to exclude from listing')
    args = parser.parse_args()
    listing = list_files(targets=args.targets, ftypes=args.ftypes, use_shebang=not args.extonly,
                         modified_only=args.modified, exclude=args.exclude)
    for l in listing:
        print(l)
