import re
import configparser

from .users import ElabUser
from .constants import (
    USERS,
    ADMINS,
    ALUMNI,
    READ_ACL,
    WRITE_ACL,
    RESTRICTED,
    SVN_SUFFIX,
    GROUP_DEFAULTS,
)

RE_LIST_SEPARATORS = re.compile("[\t ,;]+")


def format_ini_option(key, value):
    """formats a key value pair for writing an ini file"""
    return " = ".join((key, str(value).replace("\n", "\n\t")))


class AuthzConfigParser(configparser.ConfigParser):
    """custom functions for parsing the "authz" file as used at cpi

    there is a dict of users defined, the journals themselves can be accessed
    via the sections functionality of the ConfigParser base class
    """

    def __init__(self):
        """initialization of the class"""
        self.elab_users = {}
        self.original_path = None
        super().__init__()

    def optionxform(self, value):
        """reset the method to use cases sensitive names"""
        return str(value)

    def read(self, path):
        """set up the acl defaults after reading the file"""
        super().read(path)
        self.original_path = path
        self._extract_user_info_from_config()

    @classmethod
    def from_file(cls, path):
        instance = cls()
        instance.read(path)
        return instance

    def write_to_file(self, path=None):
        path = path or self.original_path
        if not path:
            raise IOError("No path specified")
        with open(path, "w") as filehandle:
            self.write(filehandle)

    def write(self, fp):
        """Write an .ini-format representation of the configuration state.

        this is adapted from the original library file. changes:
            - no default section
            - group-section at top
            - rest of section sorted by name
        """
        sorted_keys = sorted(self._sections.keys())
        sorting = ["groups"]
        sorting.extend([k for k in sorted_keys if k != "groups"])
        for section in sorting:
            fp.write("[%s]\n" % section)
            acls = {
                k: v
                for k, v in self._sections[section].items()
                if k != "__name__"
            }
            if section != "groups":
                for group in (ADMINS, USERS, RESTRICTED, ALUMNI):
                    group_id = "@" + group
                    acl_value = acls.pop(group_id, GROUP_DEFAULTS[group])
                    key = format_ini_option(group_id, acl_value)
                    fp.write("%s\n" % (key))
            for (key, value) in acls.items():
                if (value is not None) or (self._optcre == self.OPTCRE):
                    key = format_ini_option(key, value)
                fp.write("%s\n" % (key))
            fp.write("\n")

    def _extract_user_info_from_config(self):
        """extracts the user information from the config file

        the information of the journals can be accessed via get_journal_info
        """
        # first parse the group definitions
        self._extract_group_definitions()
        # walk through the sections to get individual acl information
        self._extract_individual_acls()

    def _extract_group_definitions(self):
        """extracts the group information from the config file"""
        # first parse the group definitions
        for group, userlist in self.items("groups"):
            if group not in GROUP_DEFAULTS:
                raise KeyError(f"Undefined group {group} in authz file")
            for username in RE_LIST_SEPARATORS.split(userlist):
                if username in self.elab_users:
                    raise Exception(
                        (
                            f"Found duplicate entry for user "
                            f"{username} in authz file"
                        )
                    )
                self.elab_users[username] = ElabUser(username, group)

    def _extract_individual_acls(self):
        """extracts the acl information from the elab section"""
        elabs = (item for item in self.sections() if item.endswith(SVN_SUFFIX))
        for elab in elabs:
            for (user_or_group, acl) in self.items(elab):
                if user_or_group in self.elab_users:
                    # a nicer name for the lab journal
                    belongs_to = elab[: -len(SVN_SUFFIX)]
                    # a acl entry for a user
                    if acl.lower() == WRITE_ACL:
                        self.elab_users[user_or_group].write_acl.add(
                            belongs_to
                        )
                    elif acl.lower() == READ_ACL:
                        self.elab_users[user_or_group].read_acl.add(belongs_to)

    def group_users(self):
        """uses the list of users to group them by their group name"""
        groups = {key: [] for key in GROUP_DEFAULTS.keys()}
        for user in self.elab_users.values():
            if user.group not in groups:
                raise KeyError(
                    f"found unknown group {user.group} for user {user.name}"
                )
            groups[user.group].append(user.name)
        return groups

    def add_journal_acl_for(self, username, group):
        """sets the acls for a new user an the corresponding journal"""
        self.elab_users[username] = ElabUser(username, group)
        journal_path = username + SVN_SUFFIX
        self.add_section(journal_path)
        self.set(journal_path, username, WRITE_ACL)
        for group, acl in GROUP_DEFAULTS.items():
            self.set(journal_path, f"@{group}", acl)
        self._update_user_group_config()
        return self.elab_users[username]

    def move_user_to_alumni(self, name):
        """moves a user to the alumni group and removes the acl privileges"""
        user = self.elab_users[name]
        user.group = ALUMNI
        for access_to in user.write_acl:
            self.remove_option(access_to + SVN_SUFFIX, user.name)
        for access_to in user.read_acl:
            self.remove_option(access_to + SVN_SUFFIX, user.name)
        user.write_acl = set()
        user.read_acl = set()
        self._update_user_group_config()
        return user

    def _update_user_group_config(self):
        """updates the config settings of the groups section"""
        groups = self.group_users()
        for group, userlist in groups.items():
            self.set("groups", group, ", ".join(sorted(userlist)))

    def get_journal_info(self, elab):
        """returns read and write access info of an lab journal"""
        if not elab.endswith(SVN_SUFFIX):
            elab = elab + SVN_SUFFIX
        if not self.has_section(elab):
            return None
        info = {WRITE_ACL: [], READ_ACL: []}
        for (user_or_group, acl) in self.items(elab):
            if acl in (WRITE_ACL, READ_ACL):
                info[acl].append(user_or_group)
        return info