"""Index entries adapters for sphinx.environment."""

from __future__ import annotations

import re
import unicodedata
from itertools import groupby
from typing import Any, Literal

from sphinx.builders import Builder
from sphinx.environment import BuildEnvironment
from sphinx.errors import NoUri
from sphinx.locale import _, __
from sphinx.util import logging, split_into

logger = logging.getLogger(__name__)


class IndexEntries:
    def __init__(self, env: BuildEnvironment) -> None:
        self.env = env
        self.builder: Builder

    def create_index(self, builder: Builder, group_entries: bool = True,
                     _fixre: re.Pattern = re.compile(r'(.*) ([(][^()]*[)])'),
                     ) -> list[tuple[str, list[tuple[str, Any]]]]:
        """Create the real index from the collected index entries."""
        new: dict[str, list] = {}

        rel_uri: str | Literal[False]
        index_domain = self.env.domains['index']
        for docname, entries in index_domain.entries.items():
            try:
                rel_uri = builder.get_relative_uri('genindex', docname)
            except NoUri:
                rel_uri = False

            # new entry types must be listed in directives/other.py!
            for entry_type, value, target_id, main, category_key in entries:
                uri = rel_uri is not False and f'{rel_uri}#{target_id}'
                try:
                    if entry_type == 'single':
                        try:
                            entry, sub_entry = split_into(2, 'single', value)
                        except ValueError:
                            entry, = split_into(1, 'single', value)
                            sub_entry = ''
                        _add_entry(entry, sub_entry, main,
                                   dic=new, link=uri, key=category_key)
                    elif entry_type == 'pair':
                        first, second = split_into(2, 'pair', value)
                        _add_entry(first, second, main,
                                   dic=new, link=uri, key=category_key)
                        _add_entry(second, first, main,
                                   dic=new, link=uri, key=category_key)
                    elif entry_type == 'triple':
                        first, second, third = split_into(3, 'triple', value)
                        _add_entry(first, second + ' ' + third, main,
                                   dic=new, link=uri, key=category_key)
                        _add_entry(second, third + ', ' + first, main,
                                   dic=new, link=uri, key=category_key)
                        _add_entry(third, first + ' ' + second, main,
                                   dic=new, link=uri, key=category_key)
                    elif entry_type == 'see':
                        first, second = split_into(2, 'see', value)
                        _add_entry(first, _('see %s') % second, None,
                                   dic=new, link=False, key=category_key)
                    elif entry_type == 'seealso':
                        first, second = split_into(2, 'see', value)
                        _add_entry(first, _('see also %s') % second, None,
                                   dic=new, link=False, key=category_key)
                    else:
                        logger.warning(__('unknown index entry type %r'), entry_type,
                                       location=docname)
                except ValueError as err:
                    logger.warning(str(err), location=docname)

        for (targets, sub_items, _category_key) in new.values():
            targets.sort(key=_key_func_0)
            for (sub_targets, _0, _sub_category_key) in sub_items.values():
                sub_targets.sort(key=_key_func_0)

        new_list = sorted(new.items(), key=_key_func_1)

        if group_entries:
            # fixup entries: transform
            #   func() (in module foo)
            #   func() (in module bar)
            # into
            #   func()
            #     (in module foo)
            #     (in module bar)
            old_key = ''
            old_sub_items: dict[str, list] = {}
            i = 0
            while i < len(new_list):
                key, (targets, sub_items, category_key) = new_list[i]
                # cannot move if it has sub_items; structure gets too complex
                if not sub_items:
                    m = _fixre.match(key)
                    if m:
                        if old_key == m.group(1):
                            # prefixes match: add entry as subitem of the
                            # previous entry
                            old_sub_items.setdefault(
                                m.group(2), [[], {}, category_key])[0].extend(targets)
                            del new_list[i]
                            continue
                        old_key = m.group(1)
                    else:
                        old_key = key
                old_sub_items = sub_items
                i += 1

        return [(key_, list(group))
                for (key_, group) in groupby(new_list, _key_func_3)]


def _add_entry(word: str, subword: str, main: str | None, *,
               dic: dict[str, list], link: str | Literal[False], key: str | None) -> None:
    entry = dic.setdefault(word, [[], {}, key])
    if subword:
        entry = entry[1].setdefault(subword, [[], {}, key])
    if link:
        entry[0].append((main, link))


def _key_func_0(entry: tuple[str, str]) -> tuple[bool, str]:
    """sort the index entries for same keyword."""
    main, uri = entry
    return not main, uri  # show main entries at first


def _key_func_1(entry: tuple[str, list]) -> tuple[tuple[int, str], str]:
    """Sort the index entries"""
    key, (_targets, _sub_items, category_key) = entry
    if category_key:
        # using the specified category key to sort
        key = category_key
    lc_key = unicodedata.normalize('NFD', key.lower())
    if lc_key.startswith('\N{RIGHT-TO-LEFT MARK}'):
        lc_key = lc_key[1:]

    if not lc_key[0:1].isalpha() and not lc_key.startswith('_'):
        # put symbols at the front of the index (0)
        group = 0
    else:
        # put non-symbol characters at the following group (1)
        group = 1
    # ensure a deterministic order *within* letters by also sorting on
    # the entry itself
    return (group, lc_key), entry[0]


def _key_func_2(entry: tuple[str, list]) -> str:
    """sort the sub-index entries"""
    key = unicodedata.normalize('NFD', entry[0].lower())
    if key.startswith('\N{RIGHT-TO-LEFT MARK}'):
        key = key[1:]
    if key[0:1].isalpha() or key.startswith('_'):
        key = chr(127) + key
    return key


def _key_func_3(entry: tuple[str, list]) -> str:
    """Group the entries by letter"""
    key, (targets, sub_items, category_key) = entry
    # hack: mutating the sub_items dicts to a list in the key_func
    entry[1][1] = sorted(((sub_key, sub_targets)
                          for (sub_key, (sub_targets, _0, _sub_category_key))
                          in sub_items.items()), key=_key_func_2)

    if category_key is not None:
        return category_key

    # now calculate the key
    if key.startswith('\N{RIGHT-TO-LEFT MARK}'):
        key = key[1:]
    letter = unicodedata.normalize('NFD', key[0])[0].upper()
    if letter.isalpha() or letter == '_':
        return letter

    # get all other symbols under one heading
    return _('Symbols')