#! /usr/bin/env python3
def read_file(path: str) -> "List of lines":
    #f = open(path, 'r')
    with open(path, 'r') as f: 
    # f.read(buflen) - binary read
    # f.readline() - 1 Textzeile lesen -> str
    # f.readlines - alle Textzeilen lesen ->str
    # f ist gleichzeitig Iterator
    # 1 möglichkeit
    #lines = list(map(lambda s : s.rstrip(), f))
    # 2 möflichkeit
        lines = list(map(str.rstrip, f))
    # 3 möglichkeit
    #lines = []
    #for line in f.readlines():
    #    lines.append(line.rstrip())
    #f.close()
    return lines

def parse_passwd_lines(line: str) -> "Dict of passwd details":
    parts = line.split(':')
    userdict = {
        "username" : parts[0],
        "uid" : parts[2],
        "gid" : parts[3],
        "gecos" : parts[4],
        "home" : parts[5],
        "shell": parts[6]
    }
    return userdict

def build_userlist(lines) -> "List of user dicts":
    result = []
    for line in lines:
        result.append(parse_passwd_lines(line))
    return result

def print_userlist_sorted_by_username(userlist):
    #ruft für jedes Element key(elem) also e im Lambda-Ausdruck ist ein Element der Liste user dict
    for user in sorted(userlist, key=lambda e: e['username'].lower()):
        print(
            user['username'], 
            user['uid'], 
            user['gecos'], 
            user['home'], 
            user['shell']
            )

def print_userlist_sorted_by_uid(userlist):
    pass

def main():
    output_functions = {
        'username': print_userlist_sorted_by_username,
        'uid': print_userlist_sorted_by_uid,
    }
    outfunc = output_functions['username']
    lines = read_file("/etc/passwd")
    userlist = build_userlist(lines)
    outfunc(userlist)


main()