# -*- coding: utf-8 -*-

# Copyright 2018 Telefonica S.A.
#
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
#
#    http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or
# implied.
# See the License for the specific language governing permissions and
# limitations under the License.

import yaml
import logging
from http import HTTPStatus
from copy import deepcopy
from Crypto.Cipher import AES
from base64 import b64decode, b64encode

__author__ = "Alfonso Tierno <alfonso.tiernosepulveda@telefonica.com>"


class DbException(Exception):

    def __init__(self, message, http_code=HTTPStatus.NOT_FOUND):
        self.http_code = http_code
        Exception.__init__(self, "database exception " + str(message))


class DbBase(object):

    def __init__(self, logger_name='db'):
        """
        Constructor od dbBase
        :param logger_name: logging name
        """
        self.logger = logging.getLogger(logger_name)
        self.master_password = None
        self.secret_key = None

    def db_connect(self, config, target_version=None):
        """
        Connect to database
        :param config: Configuration of database. Contains among others:
            host:   database hosst (mandatory)
            port:   database port (mandatory)
            name:   database name (mandatory)
            user:   database username
            password:   database password
            masterpassword: database password used for sensible information encryption
        :param target_version: if provided it checks if database contains required version, raising exception otherwise.
        :return: None or raises DbException on error
        """
        raise DbException("Method 'db_connect' not implemented")

    def db_disconnect(self):
        """
        Disconnect from database
        :return: None
        """
        pass

    def get_list(self, table, q_filter=None):
        """
        Obtain a list of entries matching q_filter
        :param table: collection or table
        :param q_filter: Filter
        :return: a list (can be empty) with the found entries. Raises DbException on error
        """
        raise DbException("Method 'get_list' not implemented")

    def get_one(self, table, q_filter=None, fail_on_empty=True, fail_on_more=True):
        """
        Obtain one entry matching q_filter
        :param table: collection or table
        :param q_filter: Filter
        :param fail_on_empty: If nothing matches filter it returns None unless this flag is set tu True, in which case
        it raises a DbException
        :param fail_on_more: If more than one matches filter it returns one of then unless this flag is set tu True, so
        that it raises a DbException
        :return: The requested element, or None
        """
        raise DbException("Method 'get_one' not implemented")

    def del_list(self, table, q_filter=None):
        """
        Deletes all entries that match q_filter
        :param table: collection or table
        :param q_filter: Filter
        :return: Dict with the number of entries deleted
        """
        raise DbException("Method 'del_list' not implemented")

    def del_one(self, table, q_filter=None, fail_on_empty=True):
        """
        Deletes one entry that matches q_filter
        :param table: collection or table
        :param q_filter: Filter
        :param fail_on_empty: If nothing matches filter it returns '0' deleted unless this flag is set tu True, in
        which case it raises a DbException
        :return: Dict with the number of entries deleted
        """
        raise DbException("Method 'del_one' not implemented")

    def create(self, table, indata):
        """
        Add a new entry at database
        :param table: collection or table
        :param indata: content to be added
        :return: database id of the inserted element. Raises a DbException on error
        """
        raise DbException("Method 'create' not implemented")

    def set_one(self, table, q_filter, update_dict, fail_on_empty=True):
        """
        Modifies an entry at database
        :param table: collection or table
        :param q_filter: Filter
        :param update_dict: Plain dictionary with the content to be updated. It is a dot separated keys and a value
        :param fail_on_empty: If nothing matches filter it returns None unless this flag is set tu True, in which case
        it raises a DbException
        :return: Dict with the number of entries modified. None if no matching is found.
        """
        raise DbException("Method 'set_one' not implemented")

    def set_list(self, table, q_filter, update_dict):
        """
        Modifies al matching entries at database
        :param table: collection or table
        :param q_filter: Filter
        :param update_dict: Plain dictionary with the content to be updated. It is a dot separated keys and a value
        :return: Dict with the number of entries modified
        """
        raise DbException("Method 'set_list' not implemented")

    def replace(self, table, _id, indata, fail_on_empty=True):
        """
        Replace the content of an entry
        :param table: collection or table
        :param _id: internal database id
        :param indata: content to replace
        :param fail_on_empty: If nothing matches filter it returns None unless this flag is set tu True, in which case
        it raises a DbException
        :return: Dict with the number of entries replaced
        """
        raise DbException("Method 'replace' not implemented")

    @staticmethod
    def _join_passwords(passwd_byte, passwd_str):
        """
        Modifies passwd_byte with the xor of passwd_str. Used for adding salt, join passwords, etc
        :param passwd_byte: original password in bytes, 32 byte length
        :param passwd_str: string salt to be added
        :return: modified password in bytes
        """
        if not passwd_str:
            return passwd_byte
        secret_key = bytearray(passwd_byte)
        for i, b in enumerate(passwd_str.encode()):
            secret_key[i % 32] ^= b
        return bytes(secret_key)

    def set_secret_key(self, secret_key):
        """
        Set internal secret key used for encryption
        :param secret_key: byte array length 32 with the secret_key
        :return: None
        """
        assert (len(secret_key) == 32)
        self.secret_key = self._join_passwords(secret_key, self.master_password)

    def encrypt(self, value, schema_version=None, salt=None):
        """
        Encrypt a value
        :param value: value to be encrypted. It is string/unicode
        :param schema_version: used for version control. If None or '1.0' no encryption is done.
               If '1.1' symmetric AES encryption is done
        :param salt: optional salt to be used. Must be str
        :return: Encrypted content of value
        """
        if not schema_version or schema_version == '1.0':
            return value
        else:
            if not self.secret_key:
                raise DbException("Cannot encrypt. Missing secret_key", http_code=HTTPStatus.INTERNAL_SERVER_ERROR)
            secret_key = self._join_passwords(self.secret_key, salt)
            cipher = AES.new(secret_key)
            padded_private_msg = value + ('\0' * ((16-len(value)) % 16))
            encrypted_msg = cipher.encrypt(padded_private_msg)
            encoded_encrypted_msg = b64encode(encrypted_msg)
            return encoded_encrypted_msg.decode("ascii")

    def decrypt(self, value, schema_version=None, salt=None):
        """
        Decrypt an encrypted value
        :param value: value to be decrypted. It is a base64 string
        :param schema_version: used for known encryption method used. If None or '1.0' no encryption has been done.
               If '1.1' symmetric AES encryption has been done
        :param salt: optional salt to be used
        :return: Plain content of value
        """
        if not schema_version or schema_version == '1.0':
            return value
        else:
            if not self.secret_key:
                raise DbException("Cannot decrypt. Missing secret_key", http_code=HTTPStatus.INTERNAL_SERVER_ERROR)
            secret_key = self._join_passwords(self.secret_key, salt)
            encrypted_msg = b64decode(value)
            cipher = AES.new(secret_key)
            decrypted_msg = cipher.decrypt(encrypted_msg)
            unpadded_private_msg = decrypted_msg.decode().rstrip('\0')
            return unpadded_private_msg


def deep_update_rfc7396(dict_to_change, dict_reference, key_list=None):
    """
    Modifies one dictionary with the information of the other following https://tools.ietf.org/html/rfc7396
    Basically is a recursive python 'dict_to_change.update(dict_reference)', but a value of None is used to delete.
    It implements an extra feature that allows modifying an array. RFC7396 only allows replacing the entire array.
    For that, dict_reference should contains a dict with keys starting by "$" with the following meaning:
        $[index]    <index> is an integer for targeting a concrete index from dict_to_change array. If the value is None
                    the element of the array is deleted, otherwise it is edited.
        $+[index]   The value is inserted at this <index>. A value of None has not sense and an exception is raised.
        $+          The value is appended at the end. A value of None has not sense and an exception is raised.
        $val        It looks for all the items in the array dict_to_change equal to <val>. <val> is evaluated as yaml,
                    that is, numbers are taken as type int, true/false as boolean, etc. Use quotes to force string.
                    Nothing happens if no match is found. If the value is None the matched elements are deleted.
        $key: val   In case a dictionary is passed in yaml format, if looks for all items in the array dict_to_change
                    that are dictionaries and contains this <key> equal to <val>. Several keys can be used by yaml
                    format '{key: val, key: val, ...}'; and all of them mast match. Nothing happens if no match is
                    found. If value is None the matched items are deleted, otherwise they are edited.
        $+val       If no match if found (see '$val'), the value is appended to the array. If any match is found nothing
                    is changed. A value of None has not sense.
        $+key: val  If no match if found (see '$key: val'), the value is appended to the array. If any match is found
                    nothing is changed. A value of None has not sense.
    If there are several editions, insertions and deletions; editions and deletions are done first in reverse index
        order; then insertions also in reverse index order; and finally appends in any order. So indexes used at
        insertions must take into account the deleted items.
    :param dict_to_change:  Target dictionary to be changed.
    :param dict_reference: Dictionary that contains changes to be applied.
    :param key_list: This is used internally for recursive calls. Do not fill this parameter.
    :return: none or raises and exception only at array modification when there is a bad format or conflict.
    """
    def _deep_update_array(array_to_change, _dict_reference, _key_list):
        to_append = {}
        to_insert_at_index = {}
        values_to_edit_delete = {}
        indexes_to_edit_delete = []
        array_edition = None
        _key_list.append("")
        for k in _dict_reference:
            _key_list[-1] = str(k)
            if not isinstance(k, str) or not k.startswith("$"):
                if array_edition is True:
                    raise DbException("Found array edition (keys starting with '$') and pure dictionary edition in the"
                                      " same dict at '{}'".format(":".join(_key_list[:-1])))
                array_edition = False
                continue
            else:
                if array_edition is False:
                    raise DbException("Found array edition (keys starting with '$') and pure dictionary edition in the"
                                      " same dict at '{}'".format(":".join(_key_list[:-1])))
                array_edition = True
            insert = False
            indexes = []  # indexes to edit or insert
            kitem = k[1:]
            if kitem.startswith('+'):
                insert = True
                kitem = kitem[1:]
                if _dict_reference[k] is None:
                    raise DbException("A value of None has not sense for insertions at '{}'".format(
                        ":".join(_key_list)))

            if kitem.startswith('[') and kitem.endswith(']'):
                try:
                    index = int(kitem[1:-1])
                    if index < 0:
                        index += len(array_to_change)
                    if index < 0:
                        index = 0  # skip outside index edition
                    indexes.append(index)
                except Exception:
                    raise DbException("Wrong format at '{}'. Expecting integer index inside quotes".format(
                        ":".join(_key_list)))
            elif kitem:
                # match_found_skip = False
                try:
                    filter_in = yaml.safe_load(kitem)
                except Exception:
                    raise DbException("Wrong format at '{}'. Expecting '$<yaml-format>'".format(":".join(_key_list)))
                if isinstance(filter_in, dict):
                    for index, item in enumerate(array_to_change):
                        for filter_k, filter_v in filter_in.items():
                            if not isinstance(item, dict) or filter_k not in item or item[filter_k] != filter_v:
                                break
                        else:  # match found
                            if insert:
                                # match_found_skip = True
                                insert = False
                                break
                            else:
                                indexes.append(index)
                else:
                    index = 0
                    try:
                        while True:  # if not match a ValueError exception will be raise
                            index = array_to_change.index(filter_in, index)
                            if insert:
                                # match_found_skip = True
                                insert = False
                                break
                            indexes.append(index)
                            index += 1
                    except ValueError:
                        pass

                # if match_found_skip:
                #     continue
            elif not insert:
                raise DbException("Wrong format at '{}'. Expecting '$+', '$[<index]' or '$[<filter>]'".format(
                    ":".join(_key_list)))
            for index in indexes:
                if insert:
                    if index in to_insert_at_index and to_insert_at_index[index] != _dict_reference[k]:
                        # Several different insertions on the same item of the array
                        raise DbException("Conflict at '{}'. Several insertions on same array index {}".format(
                            ":".join(_key_list), index))
                    to_insert_at_index[index] = _dict_reference[k]
                else:
                    if index in indexes_to_edit_delete and values_to_edit_delete[index] != _dict_reference[k]:
                        # Several different editions on the same item of the array
                        raise DbException("Conflict at '{}'. Several editions on array index {}".format(
                            ":".join(_key_list), index))
                    indexes_to_edit_delete.append(index)
                    values_to_edit_delete[index] = _dict_reference[k]
            if not indexes:
                if insert:
                    to_append[k] = _dict_reference[k]
                # elif _dict_reference[k] is not None:
                #     raise DbException("Not found any match to edit in the array, or wrong format at '{}'".format(
                #         ":".join(_key_list)))

        # edition/deletion is done before insertion
        indexes_to_edit_delete.sort(reverse=True)
        for index in indexes_to_edit_delete:
            _key_list[-1] = str(index)
            try:
                if values_to_edit_delete[index] is None:  # None->Anything
                    try:
                        del (array_to_change[index])
                    except IndexError:
                        pass  # it is not consider an error if this index does not exist
                elif not isinstance(values_to_edit_delete[index], dict):  # NotDict->Anything
                    array_to_change[index] = deepcopy(values_to_edit_delete[index])
                elif isinstance(array_to_change[index], dict):  # Dict->Dict
                    deep_update_rfc7396(array_to_change[index], values_to_edit_delete[index], _key_list)
                else:  # Dict->NotDict
                    if isinstance(array_to_change[index], list):  # Dict->List. Check extra array edition
                        if _deep_update_array(array_to_change[index], values_to_edit_delete[index], _key_list):
                            continue
                    array_to_change[index] = deepcopy(values_to_edit_delete[index])
                    # calling deep_update_rfc7396 to delete the None values
                    deep_update_rfc7396(array_to_change[index], values_to_edit_delete[index], _key_list)
            except IndexError:
                raise DbException("Array edition index out of range at '{}'".format(":".join(_key_list)))

        # insertion with indexes
        to_insert_indexes = list(to_insert_at_index.keys())
        to_insert_indexes.sort(reverse=True)
        for index in to_insert_indexes:
            array_to_change.insert(index, to_insert_at_index[index])

        # append
        for k, insert_value in to_append.items():
            _key_list[-1] = str(k)
            insert_value_copy = deepcopy(insert_value)
            if isinstance(insert_value_copy, dict):
                # calling deep_update_rfc7396 to delete the None values
                deep_update_rfc7396(insert_value_copy, insert_value, _key_list)
            array_to_change.append(insert_value_copy)

        _key_list.pop()
        if array_edition:
            return True
        return False

    if key_list is None:
        key_list = []
    key_list.append("")
    for k in dict_reference:
        key_list[-1] = str(k)
        if dict_reference[k] is None:   # None->Anything
            if k in dict_to_change:
                del dict_to_change[k]
        elif not isinstance(dict_reference[k], dict):  # NotDict->Anything
            dict_to_change[k] = deepcopy(dict_reference[k])
        elif k not in dict_to_change:  # Dict->Empty
            dict_to_change[k] = deepcopy(dict_reference[k])
            # calling deep_update_rfc7396 to delete the None values
            deep_update_rfc7396(dict_to_change[k], dict_reference[k], key_list)
        elif isinstance(dict_to_change[k], dict):  # Dict->Dict
            deep_update_rfc7396(dict_to_change[k], dict_reference[k], key_list)
        else:       # Dict->NotDict
            if isinstance(dict_to_change[k], list):  # Dict->List. Check extra array edition
                if _deep_update_array(dict_to_change[k], dict_reference[k], key_list):
                    continue
            dict_to_change[k] = deepcopy(dict_reference[k])
            # calling deep_update_rfc7396 to delete the None values
            deep_update_rfc7396(dict_to_change[k], dict_reference[k], key_list)
    key_list.pop()


def deep_update(dict_to_change, dict_reference):
    """ Maintained for backward compatibility. Use deep_update_rfc7396 instead"""
    return deep_update_rfc7396(dict_to_change, dict_reference)