# coding: utf-8

# FIXME python2
from __future__ import absolute_import, print_function, unicode_literals
from future.utils import python_2_unicode_compatible

import base64
import logging
import os
import re
import uuid
import zlib
from copy import deepcopy

from construct import Container, ChecksumError
from lxml import etree
from lxml.builder import E

from pykeepass.attachment import Attachment
from pykeepass.entry import Entry
from pykeepass.exceptions import *
from pykeepass.group import Group
from pykeepass.kdbx_parsing.kdbx import KDBX
from pykeepass.kdbx_parsing.kdbx4 import kdf_uuids
from pykeepass.xpath import attachment_xp, entry_xp, group_xp, path_xp

logger = logging.getLogger(__name__)


BLANK_DATABASE_FILENAME = "blank_database.kdbx"
BLANK_DATABASE_LOCATION = os.path.join(os.path.dirname(os.path.realpath(__file__)), BLANK_DATABASE_FILENAME)
BLANK_DATABASE_PASSWORD = "password"


# FIXME python2
@python_2_unicode_compatible
class PyKeePass(object):
    """Open a KeePass database

    Args:
        filename (:obj:`str`, optional): path to database or stream object.
            If None, the path given when the database was opened is used.
        password (:obj:`str`, optional): database password.  If None,
            database is assumed to have no password
        keyfile (:obj:`str`, optional): path to keyfile.  If None,
            database is assumed to have no keyfile
        transformed_key (:obj:`bytes`, optional): precomputed transformed
            key.

    Raises:
        CredentialsError: raised when password/keyfile or transformed key
            are wrong
        HeaderChecksumError: raised when checksum in database header is
            is wrong.  e.g. database tampering or file corruption
        PayloadChecksumError: raised when payload blocks checksum is wrong,
            e.g. corruption during database saving

    Todo:
        - raise, no filename provided, database not open
    """

    def __init__(self, filename, password=None, keyfile=None,
                 transformed_key=None):

        self.read(
            filename=filename,
            password=password,
            keyfile=keyfile,
            transformed_key=transformed_key
        )

    def __enter__(self):
        return self

    def __exit__(self, typ, value, tb):
        # see issue 137
        pass

    def read(self, filename=None, password=None, keyfile=None,
             transformed_key=None):
        """
        See class docstring.

        Todo:
            - raise, no filename provided, database not open
        """
        self.password = password
        self.keyfile = keyfile
        if filename:
            self.filename = filename
        else:
            filename = self.filename

        try:
            if hasattr(filename, "read"):
                self.kdbx = KDBX.parse_stream(
                    filename,
                    password=password,
                    keyfile=keyfile,
                    transformed_key=transformed_key
                )
            else:
                self.kdbx = KDBX.parse_file(
                    filename,
                    password=password,
                    keyfile=keyfile,
                    transformed_key=transformed_key
                )

        except ChecksumError as e:
            if e.path in (
                    '(parsing) -> body -> cred_check', # KDBX4
                    '(parsing) -> cred_check' # KDBX3
                    ):
                raise CredentialsError
            elif e.path == '(parsing) -> body -> sha256':
                raise HeaderChecksumError
            elif e.path in (
                    '(parsing) -> body -> payload -> hmac_hash', # KDBX4
                    '(parsing) -> xml -> block_hash' # KDBX3
                    ):
                raise PayloadChecksumError
            else:
                raise

    def reload(self):
        """Reload current database using previous credentials """

        self.read(self.filename, self.password, self.keyfile)

    def save(self, filename=None, transformed_key=None):
        """Save current database object to disk.

        Args:
            filename (:obj:`str`, optional): path to database or stream object.
                If None, the path given when the database was opened is used.
                PyKeePass.filename is unchanged.
            transformed_key (:obj:`bytes`, optional): precomputed transformed
                key.
        """
        output = None
        if not filename:
            filename = self.filename

        if hasattr(filename, "write"):
            output = KDBX.build_stream(
                self.kdbx,
                filename,
                password=self.password,
                keyfile=self.keyfile,
                transformed_key=transformed_key
            )
        else:
            output = KDBX.build_file(
                self.kdbx,
                filename,
                password=self.password,
                keyfile=self.keyfile,
                transformed_key=transformed_key
            )
        return output

    @property
    def version(self):
        """tuple: Length 2 tuple of ints containing major and minor versions.
        Generally (3, 1) or (4, 0)."""
        return (
            self.kdbx.header.value.major_version,
            self.kdbx.header.value.minor_version
        )

    @property
    def encryption_algorithm(self):
        """str: encryption algorithm used by database during decryption.
        Can be one of 'aes256', 'chacha20', or 'twofish'."""
        return self.kdbx.header.value.dynamic_header.cipher_id.data

    @property
    def kdf_algorithm(self):
        """str: key derivation algorithm used by database during decryption.
        Can be one of 'aeskdf', 'argon2', or 'aeskdf'"""
        if self.version == (3, 1):
            return 'aeskdf'
        elif self.version == (4, 0):
            kdf_parameters = self.kdbx.header.value.dynamic_header.kdf_parameters.data.dict
            if kdf_parameters['$UUID'].value == kdf_uuids['argon2']:
                return 'argon2'
            elif kdf_parameters['$UUID'].value == kdf_uuids['aeskdf']:
                return 'aeskdf'

    @property
    def transformed_key(self):
        """bytes: transformed key used in database decryption.  May be cached
        and passed to `open` for faster database opening"""
        return self.kdbx.body.transformed_key

    @property
    def tree(self):
        """lxml.etree._ElementTree: database XML payload"""
        return self.kdbx.body.payload.xml

    @property
    def root_group(self):
        """Group: root Group of database"""
        return self.find_groups(path='', first=True)

    @property
    def recyclebin_group(self):
        """Group: RecycleBin Group of database"""
        elem = self._xpath('/KeePassFile/Meta/RecycleBinUUID', first=True)
        recyclebin_uuid = uuid.UUID( bytes = base64.b64decode(elem.text) )
        return self.find_groups(uuid=recyclebin_uuid, first=True)

    @property
    def groups(self):
        """:obj:`list` of :obj:`Group`: list of all Group objects in database
        """
        return self._xpath('//Group', cast=True)

    @property
    def entries(self):
        """:obj:`list` of :obj:`Entry`: list of all Entry objects in database,
        excluding history"""
        return self._xpath('//Entry', cast=True)

    def xml(self):
        """Get XML part of database as string

        Returns:
            str: XML payload section of database.
        """
        return etree.tostring(
            self.tree,
            pretty_print=True,
            standalone=True,
            encoding='unicode'
        )

    def dump_xml(self, filename):
        """ Dump the contents of the database to file as XML

        Args:
            filename (str): path to output file
        """
        with open(filename, 'wb') as f:
            f.write(
                etree.tostring(
                    self.tree,
                    pretty_print=True,
                    standalone=True,
                    encoding='utf-8'
                )
            )

    def _xpath(self, xpath_str, tree=None, first=False, history=False,
               cast=False, **kwargs):
        """Look up elements in the XML payload and return corresponding object.

        Internal function which searches the payload lxml ElementTree for
        elements via XPath.  Matched entry, group, and attachment elements are
        automatically cast to their corresponding objects, otherwise an error
        is raised.

        Args:
            xpath_str (str): XPath query for finding element(s)
            tree (:obj:`_ElementTree`, :obj:`Element`, optional): use this
                element as root node when searching
            first (bool): If True, function returns first result or None.  If
                False, function returns list of matches or empty list.  Default
                is False.
            history (bool): If True, history entries are included in results.
                Default is False.
            cast (bool): If True, matches are instead instantiated as
                pykeepass Group, Entry, or Attachment objects.  An exception
                is raised if a match cannot be cast.  Default is False.
        """

        if tree is None:
            tree = self.tree
        logger.debug('xpath query: ' + xpath_str)
        elements = tree.xpath(
            xpath_str, namespaces={'re': 'http://exslt.org/regular-expressions'}
        )

        res = []
        for e in elements:
            if history or e.getparent().tag != 'History':
                if cast:
                    if e.tag == 'Entry':
                        res.append(Entry(element=e, kp=self))
                    elif e.tag == 'Group':
                        res.append(Group(element=e, kp=self))
                    elif e.tag == 'Binary' and e.getparent().tag == 'Entry':
                        res.append(Attachment(element=e, kp=self))
                    else:
                        raise Exception('Could not cast element {}'.format(e))
                else:
                    res.append(e)

        # return first object in list or None
        if first:
            res = res[0] if res else None

        return res

    def _find(self, prefix, keys_xp, path=None, tree=None, first=False,
              history=False, regex=False, flags=None, **kwargs):

        xp = ''

        if path is not None:

            first = True

            xp += '/KeePassFile/Root/Group'
            # split provided path into group and element
            group_path = path[:-1]
            element = path[-1] if len(path) > 0 else ''
            # build xpath from group_path and element
            for group in group_path:
                xp += path_xp[regex]['group'].format(group, flags=flags)
            if 'Entry' in prefix:
                xp += path_xp[regex]['entry'].format(element, flags=flags)
            elif element and 'Group' in prefix:
                xp += path_xp[regex]['group'].format(element, flags=flags)

        else:
            if tree is not None:
                xp += '.'

            if kwargs.keys():
                xp += prefix

            # handle searching custom string fields
            if 'string' in kwargs.keys():
                for key, value in kwargs['string'].items():
                    xp += keys_xp[regex]['string'].format(key, value, flags=flags)

                kwargs.pop('string')

            # convert uuid to base64 form before building xpath
            if 'uuid' in kwargs.keys():
                kwargs['uuid'] = base64.b64encode(kwargs['uuid'].bytes).decode('utf-8')

            # convert tags to semicolon separated string before building xpath
            if 'tags' in kwargs.keys():
                kwargs['tags'] = ';'.join(kwargs['tags'])

            # build xpath to filter results with specified attributes
            for key, value in kwargs.items():
                if key not in keys_xp[regex].keys():
                    raise TypeError('Invalid keyword argument "{}"'.format(key))

                xp += keys_xp[regex][key].format(value, flags=flags)

        res = self._xpath(
            xp,
            tree=tree._element if tree else None,
            first=first,
            history=history,
            cast=True,
            **kwargs
        )

        return res

    def _can_be_moved_to_recyclebin(self, entry_or_group):
        if entry_or_group == self.root_group:
            return False
        recyclebin_group = self.recyclebin_group
        if recyclebin_group is None:
            return True
        uuid_str = base64.b64encode( entry_or_group.uuid.bytes).decode('utf-8')
        elem = self._xpath('./UUID[text()="{}"]/..'.format(uuid_str), tree=recyclebin_group._element, first=True, history=False, cast=False)
        return elem is None


    # ---------- Groups ----------

    def find_groups(self, recursive=True, path=None, group=None, **kwargs):

        prefix = '//Group' if recursive else '/Group'
        res = self._find(prefix, group_xp, path=path, tree=group, **kwargs)
        return res

    def find_groups_by_name(self, group_name, regex=False, flags=None,
                            group=None, first=False):
        return self.find_groups(
            name=group_name,
            regex=regex,
            flags=flags,
            group=group,
            first=first
        )

    def find_groups_by_path(self, group_path_str=None, regex=False, flags=None,
                            group=None, first=False):
        return self.find_groups(
            path=group_path_str,
            regex=regex,
            flags=flags,
            group=group,
            first=first
        )

    def find_groups_by_uuid(self, uuid, regex=False, flags=None,
                            group=None, history=False, first=False):
        return self.find_groups(
            uuid=uuid,
            regex=regex,
            flags=flags,
            group=group,
            history=history,
            first=first
        )

    def find_groups_by_notes(self, notes, regex=False, flags=None,
                             group=None, history=False, first=False):
        return self.find_groups(
            notes=notes,
            regex=regex,
            flags=flags,
            group=group,
            history=history,
            first=first
        )

    # creates a new group and all parent groups, if necessary
    def add_group(self, destination_group, group_name, icon=None, notes=None):
        logger.debug('Creating group {}'.format(group_name))

        if icon:
            group = Group(name=group_name, icon=icon, notes=notes, kp=self)
        else:
            group = Group(name=group_name, notes=notes, kp=self)
        destination_group.append(group)

        return group

    def delete_group(self, group):
        group.delete()

    def deref(self, value):
        if not value:
            return value
        references = set(re.findall(r'({REF:([TUPANI])@([TUPANI]):([^}]+)})', value))
        if not references:
            return value
        field_to_attribute = {
            'T': 'title',
            'U': 'username',
            'P': 'password',
            'A': 'url',
            'N': 'notes',
            'I': 'uuid',
        }
        for ref, wanted_field, search_in, search_value in references:
            wanted_field = field_to_attribute[wanted_field]
            search_in = field_to_attribute[search_in]
            if search_in == 'uuid':
                search_value = uuid.UUID(search_value)
            ref_entry = self.find_entries(first=True, **{search_in: search_value})
            value = value.replace(ref, getattr(ref_entry, wanted_field))
        return self.deref(value)

    def move_group(self, group, destination_group):
        destination_group.append(group)

    def _create_or_get_recyclebin_group(self, **kwargs):
        existing_group = self.recyclebin_group
        if existing_group is not None:
            return existing_group
        kwargs.setdefault('group_name', 'Recycle Bin')
        group = self.add_group( self.root_group, **kwargs)
        elem = self._xpath('/KeePassFile/Meta/RecycleBinUUID', first=True)
        elem.text = base64.b64encode(group.uuid.bytes).decode('utf-8')
        return group

    def trash_group(self, group):
        """Move a group to the RecycleBin

        Args:
            group (:obj:`Group`): Group to send to the RecycleBin
        """
        if not self._can_be_moved_to_recyclebin(group):
            raise UnableToSendToRecycleBin
        recyclebin_group = self._create_or_get_recyclebin_group()
        self.move_group( group, recyclebin_group)

    def empty_group(self, group):
        """Delete the content of a group.

        This does not delete the group itself

        Args:
            group (:obj:`Group`): Group to empty
        """
        while len(group.subgroups):
            self.delete_group(group.subgroups[0])
        while len(group.entries):
            self.delete_entry(group.entries[0])

    # ---------- Entries ----------

    def find_entries(self, recursive=True, path=None, group=None, **kwargs):

        prefix = '//Entry' if recursive else '/Entry'
        res = self._find(prefix, entry_xp, path=path, tree=group, **kwargs)

        return res

    def find_entries_by_title(self, title, regex=False, flags=None,
                              group=None, history=False, first=False):
        return self.find_entries(
            title=title,
            regex=regex,
            flags=flags,
            group=group,
            history=history,
            first=first
        )

    def find_entries_by_username(self, username, regex=False, flags=None,
                                 group=None, history=False, first=False):
        return self.find_entries(
            username=username,
            regex=regex,
            flags=flags,
            group=group,
            history=history,
            first=first
        )

    def find_entries_by_password(self, password, regex=False, flags=None,
                                 group=None, history=False, first=False):
        return self.find_entries(
            password=password,
            regex=regex,
            flags=flags,
            group=group,
            history=history,
            first=first
        )

    def find_entries_by_url(self, url, regex=False, flags=None,
                            group=None, history=False, first=False):
        return self.find_entries(
            url=url,
            regex=regex,
            flags=flags,
            group=group,
            history=history,
            first=first
        )

    def find_entries_by_notes(self, notes, regex=False, flags=None,
                              group=None, history=False, first=False):
        return self.find_entries(
            notes=notes,
            regex=regex,
            flags=flags,
            group=group,
            history=history,
            first=first
        )

    def find_entries_by_path(self, path, regex=False, flags=None,
                             group=None, history=False, first=False):
        return self.find_entries(
            path=path,
            regex=regex,
            flags=flags,
            group=group,
            history=history,
            first=first
        )

    def find_entries_by_uuid(self, uuid, regex=False, flags=None,
                             group=None, history=False, first=False):
        return self.find_entries(
            uuid=uuid,
            regex=regex,
            flags=flags,
            group=group,
            history=history,
            first=first
        )

    def find_entries_by_string(self, string, regex=False, flags=None,
                               group=None, history=False, first=False):
        return self.find_entries(
            string=string,
            regex=regex,
            flags=flags,
            group=group,
            history=history,
            first=first
        )

    def add_entry(self, destination_group, title, username,
                  password, url=None, notes=None, expiry_time=None,
                  tags=None, icon=None, force_creation=False):

        entries = self.find_entries(
            title=title,
            username=username,
            first=True,
            group=destination_group,
            recursive=False
        )

        if entries and not force_creation:
            raise Exception(
                'An entry "{}" already exists in "{}"'.format(
                    title, destination_group
                )
            )
        else:
            logger.debug('Creating a new entry')
            entry = Entry(
                title=title,
                username=username,
                password=password,
                notes=notes,
                url=url,
                tags=tags,
                expires=True if expiry_time else False,
                expiry_time=expiry_time,
                icon=icon,
                kp=self
            )
            destination_group.append(entry)

        return entry

    def delete_entry(self, entry):
        entry.delete()

    def move_entry(self, entry, destination_group):
        destination_group.append(entry)

    def trash_entry(self, entry):
        """Move an entry to the RecycleBin

        Args:
            entry (:obj:`Entry`): Entry to send to the RecycleBin
        """
        if not self._can_be_moved_to_recyclebin(entry):
            raise UnableToSendToRecycleBin
        recyclebin_group = self._create_or_get_recyclebin_group()
        self.move_entry( entry, recyclebin_group)

    # ---------- Attachments ----------

    def find_attachments(self, recursive=True, path=None, element=None, **kwargs):

        prefix = '//Binary' if recursive else '/Binary'
        res = self._find(prefix, attachment_xp, path=path, tree=element, **kwargs)

        return res

    @property
    def attachments(self):
        return self.find_attachments(filename='.*', regex=True)

    @property
    def binaries(self):
        if self.version >= (4, 0):
            # first byte is a prepended flag
            binaries = [a.data[1:] for a in self.kdbx.body.payload.inner_header.binary]
        else:
            binaries = []
            for elem in self._xpath('/KeePassFile/Meta/Binaries/Binary'):
                if elem.get('Compressed') == 'True':
                    data = zlib.decompress(
                        base64.b64decode(elem.text),
                        zlib.MAX_WBITS | 32
                    )
                else:
                    data = base64.b64decode(elem.text)
                binaries.insert(int(elem.attrib['ID']), data)

        return binaries

    def add_binary(self, data, compressed=True, protected=True):
        if self.version >= (4, 0):
            # add protected flag byte
            if protected:
                data = b'\x01' + data
            else:
                data = b'\x00' + data
            # add binary element to inner header
            c = Container(type='binary', data=data)
            self.kdbx.body.payload.inner_header.binary.append(c)
        else:
            binaries = self._xpath(
                '/KeePassFile/Meta/Binaries',
                first=True
            )
            if compressed:
                # gzip compression
                compressor = zlib.compressobj(
                    zlib.Z_DEFAULT_COMPRESSION,
                    zlib.DEFLATED,
                    zlib.MAX_WBITS | 16
                )
                data = compressor.compress(data)
                data += compressor.flush()
            data = base64.b64encode(data).decode()

            # set ID for Binary Element
            binary_id = len(self.binaries)

            # add binary element to XML
            binaries.append(
                E.Binary(data, ID=str(binary_id), Compressed=str(compressed))
            )

        # return binary id
        return len(self.binaries) - 1

    def delete_binary(self, id):
        try:
            if self.version >= (4, 0):
                # remove binary element from inner header
                self.kdbx.body.payload.inner_header.binary.pop(id)
            else:
                # remove binary element from XML
                binaries = self._xpath('/KeePassFile/Meta/Binaries', first=True)
                binaries.remove(binaries.getchildren()[id])
        except IndexError:
            raise BinaryError('No such binary with id {}'.format(id))

        # remove all entry references to this attachment
        for reference in self.find_attachments(id=id):
            reference.delete()

        # decrement references greater than this id
        binaries_gt = self._xpath(
            '//Binary/Value[@Ref > "{}"]/..'.format(id),
            cast=True
        )
        for reference in binaries_gt:
            reference.id = reference.id - 1


def create_database(
        filename, password=None, keyfile=None, transformed_key=None
):
    keepass_instance = PyKeePass(
        BLANK_DATABASE_LOCATION, BLANK_DATABASE_PASSWORD
    )

    keepass_instance.filename = filename
    keepass_instance.password = password
    keepass_instance.keyfile = keyfile

    keepass_instance.save(transformed_key)
    return keepass_instance
