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

import os
from os.path import abspath
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, relative to repository root.
    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)

    # Really this is all bytes -- it's a file path -- but we get paths in
    # sys.argv as str, so that battle is already lost.  Settle for hoping
    # everything is UTF-8.
    repository_root = subprocess.check_output(['git', 'rev-parse', '--show-toplevel']).strip().decode('utf-8')
    exclude_abspaths = [os.path.join(repository_root, fpath).rstrip('/') for fpath in exclude]

    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
        absfpath = abspath(fpath)
        if any(absfpath == expath or absfpath.startswith(expath + '/')
               for expath in exclude_abspaths):
            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 results, relative to repo root')
    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)