#  ----------------------------------------------------------------------------
#  "THE BEER-WARE LICENSE" (Revision 42):
#  dkratzert@gmx.de> wrote this file.  As long as you retain
#  this notice you can do whatever you want with this stuff. If we meet some day,
#  and you think this stuff is worth it, you can buy me a beer in return.
#  Dr. Daniel Kratzert
#  ----------------------------------------------------------------------------
import re
from collections import namedtuple
from pathlib import Path
from typing import Dict, List, Tuple, Union, Generator, Type

import gemmi
from gemmi.cif import as_string, Document, Loop
from shelxfile import Shelxfile

from finalcif.cif.cif_order import order, special_keys
from finalcif.cif.hkl import HKL, Limit
from finalcif.cif.text import utf8_to_str, quote, retranslate_delimiter
from finalcif.datafiles.utils import DSRFind
from finalcif.tools.misc import essential_keys, non_centrosymm_keys, isnumeric, grouper, strip_finalcif_of_name


class CifContainer():
    """
    This class holds the content of a cif file, independent of the file parser used.
    """

    def __init__(self, file: Union[Path, str], new_block: str = ''):
        if isinstance(file, str):
            self.fileobj = Path(file)
        elif isinstance(file, Path):
            self.fileobj = file
        else:
            raise TypeError('The file parameter must be string or Path object.')
        self.current_block = ''
        # I do this in small steps instead of gemmi.cif.read_file() in order to
        # leave out the check_for_missing_values. This was gemmi reads cif files
        # with missing values.
        if new_block:
            self.doc: Document = gemmi.cif.Document()
            self.doc.add_new_block(new_block)
        else:
            self.doc = self.read_file(str(self.fileobj.resolve(strict=True)))
        # Starting with first block, but can use others with subsequent self._onload():
        self.block = self.doc[0]
        self._on_load()

    @property
    def path_base(self) -> Path:
        """
        The absolute path of the current file without file name:
        /foo/bar/baz
        """
        return Path(self.doc.source).resolve().parent

    @property
    def filename(self) -> str:
        """
        The name of the current file without path:
        foo.cif
        """
        return Path(self.doc.source).name

    @property
    def finalcif_file(self) -> Path:
        """
        The full path of the file with '-finalcif' attached to the end:
        foo/bar/baz-finalcif.cif
        """
        filename = self.finalcif_file_prefixed(prefix='', suffix='-finalcif.cif')
        return filename

    def finalcif_file_prefixed(self, prefix: str, suffix: str = '-finalcif.cif') -> Path:
        """
        The full path of the file with a prefix and '-finalcif.cif' attached to the end.
        The suffix needs '-finalcif' in order to contain the finalcif ending.
        "foo/bar/baz-finalcif.cif"
        """
        file_witout_finalcif = strip_finalcif_of_name(Path(self.filename).stem)
        filename = self.path_base.joinpath(Path(prefix + file_witout_finalcif + suffix))
        return filename

    @property
    def is_multi_cif(self) -> bool:
        return True if len(self.doc) > 1 else False

    def load_this_block(self, index: int) -> None:
        self.block = self.doc[index]
        self.current_block = self.block.name
        self._on_load()

    def _on_load(self) -> None:
        # will not ok with non-ascii characters in the res file:
        self.chars_ok = True
        self.doc.check_for_duplicates()
        self.hkl_extra_info = self._abs_hkl_details()
        self.order = order
        self.dsr_used = DSRFind(self.res_file_data).dsr_used
        self.atomic_struct: gemmi.SmallStructure = gemmi.make_small_structure_from_block(self.block)
        # A dictionary to convert Atom names like 'C1_2' or 'Ga3' into Element names like 'C' or 'Ga'
        self._name2elements = dict(
            zip([x.upper() for x in self.block.find_loop('_atom_site_label')],
                [x.upper() for x in self.block.find_loop('_atom_site_type_symbol')]))
        self.check_hkl_min_max()

    def check_hkl_min_max(self) -> None:
        if not all([self['_diffrn_reflns_limit_h_min'], self['_diffrn_reflns_limit_h_max'],
                    self['_diffrn_reflns_limit_k_min'], self['_diffrn_reflns_limit_k_max'],
                    self['_diffrn_reflns_limit_l_min'], self['_diffrn_reflns_limit_l_max']]) and self.hkl_file:
            limits = self.min_max_diffrn_reflns_limit()
            self['_diffrn_reflns_limit_h_min'] = str(limits.h_min)
            self['_diffrn_reflns_limit_h_max'] = str(limits.h_max)
            self['_diffrn_reflns_limit_k_min'] = str(limits.k_min)
            self['_diffrn_reflns_limit_k_max'] = str(limits.k_max)
            self['_diffrn_reflns_limit_l_min'] = str(limits.l_min)
            self['_diffrn_reflns_limit_l_max'] = str(limits.l_max)

    def read_file(self, path: str) -> gemmi.cif.Document:
        """
        Reads a cif file and returns a gemmi document object.
        """
        doc = gemmi.cif.Document()
        # support for platon squeeze files:
        if path.endswith('.sqf'):
            txt = Path(path).read_text(encoding='ascii')
            txt = 'data_justrandomlkdsadflkmcn\n' + txt
            doc.parse_string(txt)
        else:
            doc.source = path
            doc.parse_file(path)
        return doc

    def read_string(self, cif_string: str) -> gemmi.cif.Document:
        """
        Reads a cif file from a string and returns a gemmi cif docment.
        :param cif_string: cif as string
        :return: gemmi document
        """
        doc = gemmi.cif.Document()
        doc.parse_string(cif_string)
        return doc

    def cif_as_string(self, without_hkl=False) -> str:
        if without_hkl:
            # return a copy, do not delete hkl from original:
            doc = gemmi.cif.Document()
            doc.parse_string(self.doc.as_string(style=gemmi.cif.Style.Indent35))
            for block in doc:
                if block.find_pair_item('_shelx_hkl_file'):
                    block.find_pair_item('_shelx_hkl_file').erase()
                if block.find_pair_item('_shelx_fcf_file'):
                    block.find_pair_item('_shelx_fcf_file').erase()
            return doc.as_string(style=gemmi.cif.Style.Indent35)
        else:
            return self.doc.as_string(style=gemmi.cif.Style.Indent35)

    def __getitem__(self, item: str) -> str:
        result = self.block.find_value(item)
        if result:
            # can I do this? No:
            # return retranslate_delimiter(result)
            return as_string(result)
        else:
            return ''

    def __setitem__(self, key: str, value: str) -> None:
        """Set a key value pair of the current block.
        Values are automatically encoded from utf-8 and delimited.
        """
        self.set_pair_delimited(key, value)

    def __delitem__(self, key: str):
        self.block.find_pair_item(key).erase()

    def __contains__(self, item):
        return bool(self.__getitem__(item))

    def __str__(self) -> str:
        return "CIF file: {0}\n" \
               "{1} Block(s): {2}\n" \
               "Contains SHELX res file: {3}\n" \
               "Contains hkl data: {4}\n" \
               "Has {5} atoms" \
               ", {6} bonds" \
               ", {7} angles" \
               "".format(str(self.fileobj.resolve()), len(c.doc), ', '.join([x.name for x in c.doc]),
                         True if self.res_file_data else False,
                         len(self.hkl_file) > 1,
                         self.natoms(), self.nbonds(), self.nangles())

    def set_pair_delimited(self, key: str, txt: str):
        """
        Converts special characters to their markup counterparts.
        """
        txt = utf8_to_str(txt)
        try:
            # bad hack to get the numbered values correct
            float(txt)
            self.block.set_pair(key, txt)
        except (TypeError, ValueError):
            # prevent _key '?' in cif:
            if txt == '?':
                self.block.set_pair(key, txt)
            else:
                self.block.set_pair(key, quote(txt))

    def save(self, filename: Path = None) -> None:
        """
        Saves the current cif file.
        :param filename:  Name to save cif file to.
        """
        if not filename:
            filename = self.finalcif_file
        self.order_cif_keys()
        print('Saving to', Path(filename).resolve())
        self.doc.write_file(str(filename), gemmi.cif.Style.Indent35)

    def order_cif_keys(self):
        """
        Brings the current CIF in the specific order of the order list.
        """
        for block in self.doc:
            for key in reversed(self.order):
                try:
                    block.move_item(block.get_index(key), 0)
                except (RuntimeError, ValueError):
                    pass
                    # print('Not in list:', key)
            # make sure hkl file and res file are at the end if the cif file:
            for key in special_keys:
                try:
                    block.move_item(block.get_index(key), -1)
                except (RuntimeError, ValueError):
                    continue

    @property
    def res_file_data(self) -> str:
        try:
            # Should i do this:
            if self['_shelx_res_file']:
                return self.block.find_value('_shelx_res_file')
            elif self['_iucr_refine_instructions_details']:
                return self.block.find_value('_iucr_refine_instructions_details')
            else:
                return ''
        except UnicodeDecodeError:
            # This is a fallback in case _shelx_res_file has non-ascii characters.
            print('File has non-ascii characters. Switching to compatible mode.')
            self.doc = self.read_string(self.fileobj.read_text(encoding='cp1250', errors='ignore'))
            self.block = self.doc.sole_block()
            self.chars_ok = False
            return self.block.find_value('_shelx_res_file')

    @property
    def hkl_file(self) -> str:
        hkl_loop: Loop = self.get_loop('_diffrn_refln_index_h')
        if hkl_loop and hkl_loop.width() > 4:
            return self._hkl_from_cif_format(hkl_loop)
        else:
            # returns an empty string if no cif hkl was found:
            return self._hkl_from_shelx()

    def _hkl_from_cif_format(self, hkl_loop: Loop) -> str:
        hkl_list = []
        format_string = '{:>4}{:>4}{:>4}{:>8}{:>8}'
        if hkl_loop.width() == 6:
            format_string = '{:>4}{:>4}{:>4}{:>8}{:>8}{:>4}'
        for line in grouper(hkl_loop.values, hkl_loop.width()):
            hkl_list.append(format_string.format(*line[:6]))
        return '\n'.join(hkl_list)

    def _hkl_from_shelx(self) -> str:
        try:
            if self['_shelx_hkl_file'].strip('\r\n'):
                return self['_shelx_hkl_file'].strip('\r\n')
            elif self['_iucr_refine_reflections_details']:
                return self['_iucr_refine_reflections_details']
            else:
                return ''
        except Exception as e:
            print('No hkl data found in CIF!, {}'.format(e))
            return ''

    @property
    def hkl_as_cif(self):
        return HKL(self.hkl_file, self.block.name, hklf_type=self.hklf_number).hkl_as_cif

    @property
    def hklf_number(self) -> int:
        hklf = 4
        if self.res_file_data:
            hklf = self._hklf_number_from_shelxl_file()
        return hklf

    def min_max_diffrn_reflns_limit(self) -> Limit:
        return HKL(self.hkl_file, self.block.name, hklf_type=self.hklf_number).get_hkl_min_max()

    def _hklf_number_from_shelxl_file(self) -> int:
        shx = Shelxfile()
        shx.read_string(self.res_file_data[1:-1])
        if shx.hklf:
            return shx.hklf.n if shx.hklf.n != 0 else 4
        else:
            return 4

    @property
    def hkl_file_without_foot(self) -> str:
        """Returns a hkl file with no content after the 0 0 0 reflection"""
        zero_reflection_position = self._find_line_of_000(self.hkl_file)
        if zero_reflection_position:
            return '\n'.join(self.hkl_file.splitlines(keepends=False)[:zero_reflection_position + 1])
        else:
            return self.hkl_file

    @staticmethod
    def _find_line_of_000(lines: str):
        pattern = re.compile(r'^\s+0\s+0\s+0\s+0.*')
        for num, line in enumerate(lines.splitlines(keepends=False)):
            found = pattern.match(line)
            if found and num > 0:
                return num
        return 0

    def _abs_hkl_details(self) -> Dict[str, str]:
        """
        This method tries to determine the information witten at the end of a cif hkl file by sadabs.
        """
        hkl = None
        all_sadabs_items = {'_exptl_absorpt_process_details' : '',
                            '_exptl_absorpt_correction_type' : '',
                            '_exptl_absorpt_correction_T_max': '',
                            '_exptl_absorpt_correction_T_min': '',
                            '_computing_structure_solution'  : '',
                            }
        try:
            hkl = self.hkl_file
        except Exception:
            pass
        if not hkl:
            return all_sadabs_items
        # zero_reflection_position = self.normal_search(hkl)
        hkl_splitted = hkl.splitlines(keepends=False)
        zero_reflection_position = self.reversed_search(hkl_splitted)
        if not zero_reflection_position:
            return all_sadabs_items
        hkl = hkl.splitlines(keepends=False)[zero_reflection_position:]
        # html-embedded cif has ')' instead of ';':
        hkl = [';' if x[:1] == ')' else x for x in hkl]
        # the keys have a blank char in front:
        hkl = [re.sub(r'^ _', '_', x) for x in hkl]
        hkl = 'data_hkldat\n' + '\n'.join(hkl)
        try:
            hkldoc = gemmi.cif.read_string(hkl)
            hklblock = hkldoc.sole_block()
        except Exception as e:
            print('Unable to get information from hkl foot.')
            print(e)
            return all_sadabs_items
        for key in all_sadabs_items:
            val = hklblock.find_value(key)
            if val:
                all_sadabs_items[key] = gemmi.cif.as_string(val).strip()
        return all_sadabs_items

    def normal_search(self, hkl):
        pattern = re.compile(r'\s+0\s+0\s+0\s+0')
        found = pattern.search(hkl)
        if found:
            zero_reflection_position = found.start()
        else:
            zero_reflection_position = 0
        return zero_reflection_position

    def reversed_search(self, hkl_splitted: List):
        pattern = re.compile(r'\s+0\s+0\s+0\s+0')
        zero_reflection_position = 0
        for num, line in enumerate(reversed(hkl_splitted)):
            found = pattern.search(line)
            if num > 500:
                # A longer footer is not realistic
                break
            if found:
                zero_reflection_position = len(hkl_splitted) - num
        return zero_reflection_position

    @property
    def loops(self) -> List[gemmi.cif.Loop]:
        """
        Returns a list of loops contained in the current block.
        """
        loops = []
        for b in self.block:
            if b.loop:
                loops.append(b.loop)
        return loops

    @property
    def n_loops(self):
        return len(self.loops)

    def get_loop(self, key_in_loop: str) -> gemmi.cif.Loop:
        return self.block.find_loop(key_in_loop).get_loop()

    def get_loop_column(self, key_in_loop: str) -> List:
        return [retranslate_delimiter(as_string(x)) for x in self.block.find_loop(key_in_loop)]

    def init_loop(self, loop_keywords: List) -> gemmi.cif.Loop:
        return self.block.init_loop('', loop_keywords)

    @property
    def z_value(self):
        return self.atomic_struct.cell.volume / self.atomic_struct.cell.volume_per_image()

    @property
    def solution_program_details(self) -> str:
        return self.hkl_extra_info['_computing_structure_solution']

    @property
    def absorpt_process_details(self) -> str:
        return self.hkl_extra_info['_exptl_absorpt_process_details']

    @property
    def absorpt_correction_type(self) -> str:
        return self.hkl_extra_info['_exptl_absorpt_correction_type']

    @property
    def absorpt_correction_t_max(self) -> str:
        return self.hkl_extra_info['_exptl_absorpt_correction_T_max']

    @property
    def absorpt_correction_t_min(self) -> str:
        return self.hkl_extra_info['_exptl_absorpt_correction_T_min']

    def _spgr(self) -> gemmi.SpaceGroup:
        if self.symmops and self.symmops != ['']:
            symm_ops = self.symmops
        else:
            symm_ops = self.symmops_from_spgr
        return gemmi.find_spacegroup_by_ops(gemmi.GroupOps([gemmi.Op(o) for o in symm_ops]))

    @property
    def space_group(self) -> str:
        """
        Returns the space group from the symmetry operators.
        spgr.short_name() gives the short name.
        """
        try:
            return self._spgr().xhm()
        except (AttributeError, RuntimeError, ValueError):
            if self['_space_group_name_H-M_alt']:
                return gemmi.cif.as_string(self['_space_group_name_H-M_alt'])
            elif self['_symmetry_space_group_name_H-M']:
                return gemmi.cif.as_string(self['_symmetry_space_group_name_H-M'])
            else:
                return ''

    @property
    def symmops_from_spgr(self) -> List[str]:
        # _symmetry_space_group_name_Hall
        space_group = None
        if self['_space_group_name_H-M_alt']:
            space_group = self['_space_group_name_H-M_alt']
        if self['_symmetry_space_group_name_H-M']:
            space_group = self['_symmetry_space_group_name_H-M']
        if not space_group:
            return []
        ops = [op.triplet() for op in
               gemmi.find_spacegroup_by_name(gemmi.cif.as_string(space_group)).operations()]
        return ops

    @property
    def spgr_number_from_symmops(self) -> int:
        return self._spgr().number

    @property
    def spgr_number(self) -> int:
        if self['_space_group_IT_number'] and isnumeric(self['_space_group_IT_number']):
            return int(self['_space_group_IT_number'])
        elif self['_symmetry_Int_Tables_number'] and isnumeric(self['_symmetry_Int_Tables_number']):
            return int(self['_symmetry_Int_Tables_number'])
        else:
            return self.spgr_number_from_symmops

    @property
    def crystal_system(self) -> str:
        if not self._spgr():
            return ''
        return self._spgr().crystal_system_str()

    @property
    def hall_symbol(self) -> str:
        return self._spgr().hall

    @property
    def hkl_checksum_calcd(self) -> int:
        """
        Calculates the shelx checksum for the hkl file content of a cif file.
        """
        if self.hkl_file:
            return self.calc_checksum(self.hkl_file)
        else:
            return 0

    @property
    def res_checksum_calcd(self) -> int:
        """
        Calculates the shelx checksum for the res file content of a cif file.
        """
        if self.res_file_data:
            return self.calc_checksum(self.res_file_data[1:-1])
        return 0

    @staticmethod
    def calc_checksum(input_str: str) -> int:
        """
        Calculates the shelx checksum of a cif file.
        The original algorithm was posted by Berthold Stöger on the Bruker Users Mailing list.
        """
        crc_sum = 0
        try:
            input_str = input_str.encode('cp1250', 'ignore')
        except Exception:
            input_str = input_str.encode('ascii', 'ignore')
        for char in input_str:
            # print(char)
            if char > 32:  # ascii 32 is space character
                crc_sum += char
        crc_sum %= 714025
        crc_sum = crc_sum * 1366 + 150889
        crc_sum %= 714025
        crc_sum %= 100000
        return crc_sum

    def rename_data_name(self, newname: str = ''):
        """
        Renames data_ tags to the newname. Also _vrf tags are renamed accordingly.
        http://journals.iucr.org/services/cif/checking/checkfaq.html
        """
        # Have to use ord(), because Python 3.6 has not str.isascii():
        newname = ''.join([i for i in newname if ord(i) < 127])
        self.block.name = newname
        for item in self.block:
            if item.pair is not None:
                key, value = item.pair
                if key.startswith('_vrf'):
                    newkey = '_' + '_'.join(key.split('_')[1:3]) + '_' + newname
                    self.block.find_pair_item(key).erase()
                    self.block.set_pair(newkey, value)

    @property
    def symmops(self) -> List[str]:
        """
        Reads the symmops from the cif file.
        """
        xyz1 = self.block.find(("_symmetry_equiv_pos_as_xyz",))  # deprecated
        xyz2 = self.block.find(("_space_group_symop_operation_xyz",))  # New definition
        if xyz1:
            return [i.str(0) for i in xyz1]
        elif xyz2:
            return [i.str(0) for i in xyz2]
        else:
            return self.symmops_from_spgr

    @property
    def is_centrosymm(self) -> bool:
        """
        Whether a structuere is centro symmetric or not.
        """
        if not self.symmops or self.symmops == ['']:
            # Do not crash without symmops
            return False
        ops = gemmi.GroupOps([gemmi.Op(o) for o in self.symmops])
        try:
            return ops.is_centric()
        except AttributeError:
            return ops.is_centrosymmetric()

    def atoms(self, without_h: bool = False) -> Generator:
        """
        Atoms from the CIF where values are returned as string like in the CIF with esds.
        """
        labels = self.block.find_loop('_atom_site_label')
        types = self.block.find_loop('_atom_site_type_symbol')
        x = self.block.find_loop('_atom_site_fract_x')
        y = self.block.find_loop('_atom_site_fract_y')
        z = self.block.find_loop('_atom_site_fract_z')
        part = self.block.find_loop('_atom_site_disorder_group')
        occ = self.block.find_loop('_atom_site_occupancy')
        u_eq = self.block.find_loop('_atom_site_U_iso_or_equiv')
        atom = namedtuple('Atom', ('label', 'type', 'x', 'y', 'z', 'part', 'occ', 'u_eq'))
        for label, type, x, y, z, part, occ, u_eq in zip(labels, types, x, y, z,
                                                         part if part else ('0',) * len(labels),
                                                         occ if occ else ('1.000000',) * len(labels),
                                                         u_eq):
            if without_h and self.ishydrogen(label):
                continue
            #         0    1   2  3  4   5   6     7
            # yield label, type, x, y, z, part, occ, ueq
            yield atom(label=label, type=type, x=x, y=y, z=z, part=part, occ=occ, u_eq=u_eq)

    @property
    def atoms_fract(self) -> Generator:
        """Atoms with numbers as float values without esd."""
        for at in self.atomic_struct.sites:
            yield [at.label, at.type_symbol, at.fract.x, at.fract.y, at.fract.z, at.disorder_group, at.occ, at.u_iso]

    @property
    def atoms_orth(self) -> Generator:
        atom = namedtuple('Atom', ('label', 'type', 'x', 'y', 'z', 'part', 'occ', 'u_eq'))
        cell = self.atomic_struct.cell
        for at in self.atomic_struct.sites:
            x, y, z = at.orth(cell)
            yield atom(label=at.label, type=at.type_symbol, x=x, y=y, z=z,
                       part=at.disorder_group, occ=at.occ, u_eq=at.u_iso)

    @property
    def hydrogen_atoms_present(self) -> bool:
        for at in self.atomic_struct.sites:
            if at.type_symbol in ('H', 'D'):
                return True
        return False

    @property
    def disorder_present(self) -> bool:
        for at in self.atomic_struct.sites:
            if at.disorder_group:
                return True
        return False

    @property
    def cell(self) -> Type['cell']:
        c = self.atomic_struct.cell
        nt = namedtuple('cell', 'a, b, c, alpha, beta, gamma, volume')
        return nt(c.a, c.b, c.c, c.alpha, c.beta, c.gamma, c.volume)

    def ishydrogen(self, label: str) -> bool:
        """
        Determines if an atom with the name 'label' is a hydrogen atom.
        """
        hydrogen = ('H', 'D')
        if self._iselement(label) in hydrogen:
            return True
        else:
            return False

    def checksymm(self, symm):
        """Add translation of 555 to symmetry elements without translation"""
        if len(symm) == 1 and not (symm == '.' or symm == '?'):
            symm = symm + '_555'
        return symm

    def bonds(self, without_h: bool = False) -> Generator:
        """
        Yields a list of bonds in the cif file.
        """
        label1 = self.block.find_loop('_geom_bond_atom_site_label_1')
        label2 = self.block.find_loop('_geom_bond_atom_site_label_2')
        dist = self.block.find_loop('_geom_bond_distance')
        symm = self.block.find_loop('_geom_bond_site_symmetry_2')
        bond = namedtuple('Bond', ('label1', 'label2', 'dist', 'symm'))
        for label1, label2, dist, symm in zip(label1, label2, dist, symm):
            if without_h and (self.ishydrogen(label1) or self.ishydrogen(label2)):
                continue
            else:
                yield bond(label1=label1, label2=label2, dist=dist, symm=self.checksymm(symm))

    def angles(self, without_H: bool = False) -> Generator:
        label1 = self.block.find_loop('_geom_angle_atom_site_label_1')
        label2 = self.block.find_loop('_geom_angle_atom_site_label_2')
        label3 = self.block.find_loop('_geom_angle_atom_site_label_3')
        angle_val = self.block.find_loop('_geom_angle')
        symm1 = self.block.find_loop('_geom_angle_site_symmetry_1')
        symm2 = self.block.find_loop('_geom_angle_site_symmetry_3')
        angle = namedtuple('Angle', ('label1', 'label2', 'label3', 'angle_val', 'symm1', 'symm2'))
        for label1, label2, label3, angle_val, symm1, symm2 in zip(label1, label2, label3, angle_val, symm1, symm2):
            if without_H and (self.ishydrogen(label1) or self.ishydrogen(label2) or self.ishydrogen(label3)):
                continue
            else:
                yield angle(label1=label1, label2=label2, label3=label3, angle_val=angle_val,
                            symm1=self.checksymm(symm1), symm2=self.checksymm(symm2))

    def _iselement(self, name: str) -> str:
        return self._name2elements[name.upper()]

    def natoms(self, without_h: bool = False) -> int:
        return len(tuple(self.atoms(without_h)))

    def nbonds(self, without_h: bool = False) -> int:
        """
        Number of bonds in the cif object, with and without hydrogen atoms.
        """
        return len(tuple(self.bonds(without_h)))

    def nangles(self, without_h: bool = False) -> int:
        """
        Number of bond angles in the cif object, with and without hydrogen atoms.
        """
        return len(tuple(self.angles(without_h)))

    def ntorsion_angles(self, without_h: bool = False) -> int:
        """
        Number of torsion angles in the cif object, with and without hydrogen atoms.
        """
        return len(tuple(self.torsion_angles(without_h)))

    def torsion_angles(self, without_h: bool = False) -> Generator:
        label1 = self.block.find_loop('_geom_torsion_atom_site_label_1')
        label2 = self.block.find_loop('_geom_torsion_atom_site_label_2')
        label3 = self.block.find_loop('_geom_torsion_atom_site_label_3')
        label4 = self.block.find_loop('_geom_torsion_atom_site_label_4')
        torsang = self.block.find_loop('_geom_torsion')
        symm1 = self.block.find_loop('_geom_torsion_site_symmetry_1')
        symm2 = self.block.find_loop('_geom_torsion_site_symmetry_2')
        symm3 = self.block.find_loop('_geom_torsion_site_symmetry_3')
        symm4 = self.block.find_loop('_geom_torsion_site_symmetry_4')
        tors = namedtuple('Torsion',
                          ('label1', 'label2', 'label3', 'label4', 'torsang', 'symm1', 'symm2', 'symm3', 'symm4'))
        for label1, label2, label3, label4, torsang, symm1, symm2, symm3, symm4 in zip(label1, label2, label3, label4,
                                                                                       torsang, symm1, symm2, symm3,
                                                                                       symm4):
            if without_h and (self.ishydrogen(label1) or self.ishydrogen(label2)
                              or self.ishydrogen(label3) or self.ishydrogen(label3)):
                continue
            yield tors(label1=label1, label2=label2, label3=label3, label4=label4, torsang=torsang,
                       symm1=self.checksymm(symm1),
                       symm2=self.checksymm(symm2),
                       symm3=self.checksymm(symm3),
                       symm4=self.checksymm(symm4))

    def hydrogen_bonds(self) -> Generator:
        label_d = self.block.find_loop('_geom_hbond_atom_site_label_D')
        label_h = self.block.find_loop('_geom_hbond_atom_site_label_H')
        label_a = self.block.find_loop('_geom_hbond_atom_site_label_A')
        dist_dh = self.block.find_loop('_geom_hbond_distance_DH')
        dist_ha = self.block.find_loop('_geom_hbond_distance_HA')
        dist_da = self.block.find_loop('_geom_hbond_distance_DA')
        angle_dha = self.block.find_loop('_geom_hbond_angle_DHA')
        symm = self.block.find_loop('_geom_hbond_site_symmetry_A')
        hydr = namedtuple('HydrogenBond', ('label_d', 'label_h', 'label_a', 'dist_dh', 'dist_ha', 'dist_da',
                                           'angle_dha', 'symm'))
        for label_d, label_h, label_a, dist_dh, dist_ha, dist_da, angle_dha, symm in \
            zip(label_d, label_h, label_a, dist_dh, dist_ha, dist_da, angle_dha, symm):
            yield hydr(label_d, label_h, label_a, dist_dh, dist_ha, dist_da, angle_dha, self.checksymm(symm))

    def key_value_pairs(self) -> List[Tuple[str, str]]:
        """
        Returns the key/value pairs of a cif file sorted by priority.
        """
        keys_without_values, keys_with_values = self.get_keys()
        return keys_without_values + [('These below are already in:', '---------------------')] + keys_with_values

    def _is_centrokey(self, key) -> bool:
        """
        Is True if the kurrent key is only valid 
        for non-centrosymmetric structures
        """
        return self.is_centrosymm and key in non_centrosymm_keys

    def get_keys(self) -> Tuple[List[Tuple[str, str]], List[Tuple[str, str]]]:
        """
        Returns the keys to be displayed in the main table as two separate lists.
        """
        questions = []
        # contains the answered keys:
        with_values = []
        for item in self.block:
            if item.pair is not None:
                key, value = item.pair
                if key.startswith('_shelx'):
                    # No-one should edit shelx values:
                    continue
                if self._is_centrokey(key):
                    continue
                if not value or value == '?' or value == "'?'":
                    questions.append((key, value))
                else:
                    with_values.append((key, value))
        all_keys = [x[0] for x in with_values] + [x[0] for x in questions]
        self.check_for_missing_essential_keys(all_keys, questions)
        return sorted(questions), sorted(with_values)

    def check_for_missing_essential_keys(self, all_keys: List[Tuple[str, str]],
                                         questions: List[Tuple[str, str]]) -> None:
        """
        Check if there are keys not in the cif but in essential_keys and append them if so.
        """
        for key in essential_keys:
            if key not in all_keys:
                if self._is_centrokey(key):
                    continue
                questions.append((key, '?'))
                self.block.set_pair(key, '?')

    def test_res_checksum(self) -> bool:
        """
        A method to check whether the checksums in the cif file fit to the content.
        """
        cif_res_ckecksum = 0
        res_checksum_calcd = self.res_checksum_calcd
        if res_checksum_calcd > 0:
            cif_res_ckecksum = self['_shelx_res_checksum'] or -1
            try:
                cif_res_ckecksum = int(cif_res_ckecksum)
            except ValueError:
                cif_res_ckecksum = -1
        if cif_res_ckecksum > 0 and cif_res_ckecksum != res_checksum_calcd:
            return False
        else:
            return True

    def test_hkl_checksum(self) -> bool:
        """
        A method to check whether the checksums in the cif file fit to the content.
        """
        cif_hkl_ckecksum = 0
        hkl_checksum_calcd = self.hkl_checksum_calcd
        if hkl_checksum_calcd > 0:
            cif_hkl_ckecksum = self['_shelx_hkl_checksum'] or -1
            try:
                cif_hkl_ckecksum = int(cif_hkl_ckecksum)
            except ValueError:
                cif_hkl_ckecksum = -1
        if cif_hkl_ckecksum > 0 and cif_hkl_ckecksum != hkl_checksum_calcd:
            return False
        else:
            return True


if __name__ == '__main__':
    # c = CifContainer('../41467_2015.cif')
    c = CifContainer('test-data/p21c.cif')
    c.load_this_block(len(c.doc) - 1)
    print(c)
    # print(c.hkl_file)
    # print(c.hkl_as_cif)
    # print(c.test_hkl_checksum())
    # s = Shelxfile()
    # print(c.res_file_data)
    # s.read_string(c.res_file_data)
    # print(s.hklf.n)

    # print(CifContainer('tests/examples/1979688.cif').hkl_as_cif[-250:])

    """
    import n#umpy as np
    mtz = gemmi.Mtz(with_base=True)
    data = [x.split() for x in c.hkl_file.splitlines()]
    mtz.add_column('I', 'I')
    mtz.add_column('SIGI', 'Q')
    mtz.set_data(data)
    mtz.set_cell_for_all(gemmi.UnitCell(c.cell.a, c.cell.b, c.cell.c, c.cell.alpha, c.cell.beta, c.cell.gamma))
    mtz.spacegroup = gemmi.find_spacegroup_by_name(c.space_group)
    mtz.update_reso()
    size = mtz.get_size_for_hkl()
    np.seterr(divide='ignore', invalid='ignore')
    ios =  intensity.array / sigma.array
    
    doc = gemmi.cif.read('tests/examples/1979688-finalcif.fcf')
    rblock = gemmi.hkl_cif_as_refln_block(doc[0])
    """
