''' Models: RSForms for conceptual schemas. '''
import re
from typing import Iterable, Optional, cast

from django.db import transaction
from django.db.models import (
    CASCADE, SET_NULL, ForeignKey, Model, PositiveIntegerField, QuerySet,
    TextChoices, TextField, BooleanField, CharField, DateTimeField, JSONField
)
from django.core.validators import MinValueValidator
from django.core.exceptions import ValidationError
from django.urls import reverse

from apps.users.models import User
from cctext import Resolver, Entity, extract_entities, split_grams, TermForm
from .graph import Graph
from .utils import apply_pattern
from . import messages as msg


_REF_ENTITY_PATTERN = re.compile(r'@{([^0-9\-].*?)\|.*?}')
_GLOBAL_ID_PATTERN = re.compile(r'([XCSADFPT][0-9]+)') # cspell:disable-line


class LibraryItemType(TextChoices):
    ''' Type of library items '''
    RSFORM = 'rsform'
    OPERATIONS_SCHEMA = 'oss'


class CstType(TextChoices):
    ''' Type of constituenta '''
    BASE = 'basic'
    CONSTANT = 'constant'
    STRUCTURED = 'structure'
    AXIOM = 'axiom'
    TERM = 'term'
    FUNCTION = 'function'
    PREDICATE = 'predicate'
    THEOREM = 'theorem'


class Syntax(TextChoices):
    ''' Syntax types '''
    UNDEF = 'undefined'
    ASCII = 'ascii'
    MATH = 'math'


def _empty_forms():
    return []

def _get_type_prefix(cst_type: CstType) -> str:
    ''' Get alias prefix. '''
    if cst_type == CstType.BASE:
        return 'X'
    if cst_type == CstType.CONSTANT:
        return 'C'
    if cst_type == CstType.STRUCTURED:
        return 'S'
    if cst_type == CstType.AXIOM:
        return 'A'
    if cst_type == CstType.TERM:
        return 'D'
    if cst_type == CstType.FUNCTION:
        return 'F'
    if cst_type == CstType.PREDICATE:
        return 'P'
    if cst_type == CstType.THEOREM:
        return 'T'
    return 'X'


class LibraryItem(Model):
    ''' Abstract library item.'''
    item_type: CharField = CharField(
        verbose_name='Тип',
        max_length=50,
        choices=LibraryItemType.choices
    )
    owner: ForeignKey = ForeignKey(
        verbose_name='Владелец',
        to=User,
        on_delete=SET_NULL,
        null=True
    )
    title: TextField = TextField(
        verbose_name='Название'
    )
    alias: CharField = CharField(
        verbose_name='Шифр',
        max_length=255,
        blank=True
    )
    comment: TextField = TextField(
        verbose_name='Комментарий',
        blank=True
    )
    is_common: BooleanField = BooleanField(
        verbose_name='Общая',
        default=False
    )
    is_canonical: BooleanField = BooleanField(
        verbose_name='Каноничная',
        default=False
    )
    time_create: DateTimeField = DateTimeField(
        verbose_name='Дата создания',
        auto_now_add=True
    )
    time_update: DateTimeField = DateTimeField(
        verbose_name='Дата изменения',
        auto_now=True
    )

    class Meta:
        ''' Model metadata. '''
        verbose_name = 'Схема'
        verbose_name_plural = 'Схемы'

    def __str__(self) -> str:
        return f'{self.title}'

    def get_absolute_url(self):
        return f'/api/library/{self.pk}'

    def subscribers(self) -> list[User]:
        ''' Get all subscribers for this item . '''
        return [subscription.user for subscription in Subscription.objects.filter(item=self.pk)]

    @transaction.atomic
    def save(self, *args, **kwargs):
        subscribe = not self.pk and self.owner
        super().save(*args, **kwargs)
        if subscribe:
            Subscription.subscribe(user=self.owner, item=self)


class LibraryTemplate(Model):
    ''' Template for library items and constituents. '''
    lib_source: ForeignKey = ForeignKey(
        verbose_name='Источник',
        to=LibraryItem,
        on_delete=CASCADE,
        null=True
    )

    class Meta:
        ''' Model metadata. '''
        verbose_name = 'Шаблон'
        verbose_name_plural = 'Шаблоны'


class Subscription(Model):
    ''' User subscription to library item. '''
    user: ForeignKey = ForeignKey(
        verbose_name='Пользователь',
        to=User,
        on_delete=CASCADE
    )
    item: ForeignKey = ForeignKey(
        verbose_name='Элемент',
        to=LibraryItem,
        on_delete=CASCADE
    )

    class Meta:
        ''' Model metadata. '''
        verbose_name = 'Подписки'
        verbose_name_plural = 'Подписка'
        unique_together = [['user', 'item']]

    def __str__(self) -> str:
        return f'{self.user} -> {self.item}'

    @staticmethod
    def subscribe(user: User, item: LibraryItem) -> bool:
        ''' Add subscription. '''
        if Subscription.objects.filter(user=user, item=item).exists():
            return False
        Subscription.objects.create(user=user, item=item)
        return True

    @staticmethod
    def unsubscribe(user: User, item: LibraryItem) -> bool:
        ''' Remove subscription. '''
        sub = Subscription.objects.filter(user=user, item=item)
        if not sub.exists():
            return False
        sub.delete()
        return True


class Constituenta(Model):
    ''' Constituenta is the base unit for every conceptual schema '''
    schema: ForeignKey = ForeignKey(
        verbose_name='Концептуальная схема',
        to=LibraryItem,
        on_delete=CASCADE
    )
    order: PositiveIntegerField = PositiveIntegerField(
        verbose_name='Позиция',
        validators=[MinValueValidator(1)],
        default=-1,
    )
    alias: CharField = CharField(
        verbose_name='Имя',
        max_length=8,
        default='undefined'
    )
    cst_type: CharField = CharField(
        verbose_name='Тип',
        max_length=10,
        choices=CstType.choices,
        default=CstType.BASE
    )
    convention: TextField = TextField(
        verbose_name='Комментарий/Конвенция',
        default='',
        blank=True
    )
    term_raw: TextField = TextField(
        verbose_name='Термин (с отсылками)',
        default='',
        blank=True
    )
    term_resolved: TextField = TextField(
        verbose_name='Термин',
        default='',
        blank=True
    )
    term_forms: JSONField = JSONField(
        verbose_name='Словоформы',
        default=_empty_forms
    )
    definition_formal: TextField = TextField(
        verbose_name='Родоструктурное определение',
        default='',
        blank=True
    )
    definition_raw: TextField = TextField(
        verbose_name='Текстовое определение (с отсылками)',
        default='',
        blank=True
    )
    definition_resolved: TextField = TextField(
        verbose_name='Текстовое определение',
        default='',
        blank=True
    )

    class Meta:
        ''' Model metadata. '''
        verbose_name = 'Конституента'
        verbose_name_plural = 'Конституенты'

    def get_absolute_url(self):
        ''' URL access. '''
        return reverse('constituenta-detail', kwargs={'pk': self.pk})

    def __str__(self) -> str:
        return f'{self.alias}'

    def set_term_resolved(self, new_term: str):
        ''' Set term and reset forms if needed. '''
        if new_term == self.term_resolved:
            return
        self.term_resolved = new_term
        self.term_forms = []


class RSForm:
    ''' RSForm is a math form of capturing conceptual schema. '''
    def __init__(self, item: LibraryItem):
        if item.item_type != LibraryItemType.RSFORM:
            raise ValueError(msg.libraryTypeUnexpected())
        self.item = item

    @staticmethod
    def create(**kwargs) -> 'RSForm':
        return RSForm(LibraryItem.objects.create(item_type=LibraryItemType.RSFORM, **kwargs))

    def constituents(self) -> QuerySet['Constituenta']:
        ''' Get QuerySet containing all constituents of current RSForm. '''
        return Constituenta.objects.filter(schema=self.item)

    def resolver(self) -> Resolver:
        ''' Create resolver for text references based on schema terms. '''
        result = Resolver({})
        for cst in self.constituents():
            entity = Entity(
                alias=cst.alias,
                nominal=cst.term_resolved,
                manual_forms=[
                    TermForm(text=form['text'], grams=split_grams(form['tags']))
                    for form in cst.term_forms
                ]
            )
            result.context[cst.alias] = entity
        return result

    @transaction.atomic
    def on_term_change(self, changed: Iterable[str]):
        ''' Trigger cascade resolutions when term changes. '''
        graph_terms = self._term_graph()
        expansion = graph_terms.expand_outputs(changed)
        resolver = self.resolver()
        if len(expansion) > 0:
            for alias in graph_terms.topological_order():
                if alias not in expansion:
                    continue
                cst = self.constituents().get(alias=alias)
                resolved = resolver.resolve(cst.term_raw)
                if resolved == cst.term_resolved:
                    continue
                cst.set_term_resolved(resolved)
                cst.save()
                resolver.context[cst.alias] = Entity(cst.alias, resolved)

        graph_defs = self._definition_graph()
        update_defs = set(expansion + graph_defs.expand_outputs(expansion)).union(changed)
        if len(update_defs) == 0:
            return
        for alias in update_defs:
            cst = self.constituents().get(alias=alias)
            resolved = resolver.resolve(cst.definition_raw)
            if resolved == cst.definition_resolved:
                continue
            cst.definition_resolved = resolved
            cst.save()

    @transaction.atomic
    def insert_at(self, position: int, alias: str, insert_type: CstType) -> 'Constituenta':
        ''' Insert new constituenta at given position.
            All following constituents order is shifted by 1 position. '''
        if position <= 0:
            raise ValidationError(msg.positionNegative())
        if self.constituents().filter(alias=alias).exists():
            raise ValidationError(msg.renameTaken(alias))
        currentSize = self.constituents().count()
        position =  max(1, min(position, currentSize + 1))
        update_list = \
            Constituenta.objects \
                .only('id', 'order', 'schema') \
                .filter(schema=self.item, order__gte=position)
        for cst in update_list:
            cst.order += 1
        Constituenta.objects.bulk_update(update_list, ['order'])

        result = Constituenta.objects.create(
            schema=self.item,
            order=position,
            alias=alias,
            cst_type=insert_type
        )
        self.item.save()
        result.refresh_from_db()
        return result

    @transaction.atomic
    def insert_last(self, alias: str, insert_type: CstType) -> 'Constituenta':
        ''' Insert new constituenta at last position. '''
        if self.constituents().filter(alias=alias).exists():
            raise ValidationError(msg.renameTaken(alias))
        position = 1
        if self.constituents().exists():
            position += self.constituents().count()
        result = Constituenta.objects.create(
            schema=self.item,
            order=position,
            alias=alias,
            cst_type=insert_type
        )
        self.item.save()
        result.refresh_from_db()
        return result

    @transaction.atomic
    def move_cst(self, listCst: list['Constituenta'], target: int):
        ''' Move list of constituents to specific position '''
        count_moved = 0
        count_top = 0
        count_bot = 0
        size = len(listCst)
        update_list = []
        for cst in self.constituents().only('id', 'order').order_by('order'):
            if cst not in listCst:
                if count_top + 1 < target:
                    cst.order = count_top + 1
                    count_top += 1
                else:
                    cst.order = target + size + count_bot
                    count_bot += 1
            else:
                cst.order = target + count_moved
                count_moved += 1
            update_list.append(cst)
        Constituenta.objects.bulk_update(update_list, ['order'])
        self.item.save()

    @transaction.atomic
    def delete_cst(self, listCst):
        ''' Delete multiple constituents. Do not check if listCst are from this schema. '''
        for cst in listCst:
            cst.delete()
        self._reset_order()
        self.resolve_all_text()
        self.item.save()

    @transaction.atomic
    def create_cst(self, data: dict, insert_after: Optional[str]=None) -> 'Constituenta':
        ''' Create new cst from data. '''
        resolver = self.resolver()
        cst = self._insert_new(data, insert_after)
        cst.convention = data.get('convention', '')
        cst.definition_formal = data.get('definition_formal', '')
        cst.term_forms = data.get('term_forms', [])
        cst.term_raw = data.get('term_raw', '')
        if cst.term_raw != '':
            resolved = resolver.resolve(cst.term_raw)
            cst.term_resolved = resolved
            resolver.context[cst.alias] = Entity(cst.alias, resolved)
        cst.definition_raw = data.get('definition_raw', '')
        if cst.definition_raw != '':
            cst.definition_resolved = resolver.resolve(cst.definition_raw)
        cst.save()
        self.on_term_change([cst.alias])
        cst.refresh_from_db()
        return cst

    @transaction.atomic
    def substitute(
        self,
        original: 'Constituenta',
        substitution: 'Constituenta',
        transfer_term: bool
    ):
        ''' Execute constituenta substitution. '''
        assert original.pk != substitution.pk
        mapping = { original.alias: substitution.alias }
        self.apply_mapping(mapping)
        if transfer_term:
            substitution.term_raw = original.term_raw
            substitution.term_forms = original.term_forms
            substitution.save()
        original.delete()
        self.on_term_change([substitution.alias])

    def reset_aliases(self):
        ''' Recreate all aliases based on constituents order. '''
        mapping = self._create_reset_mapping()
        self.apply_mapping(mapping, change_aliases=True)

    def _create_reset_mapping(self) -> dict[str, str]:
        bases = cast(dict[str, int], {})
        mapping = cast(dict[str, str], {})
        for cst_type in CstType.values:
            bases[cst_type] = 1
        cst_list = self.constituents().order_by('order')
        for cst in cst_list:
            alias = f'{_get_type_prefix(cst.cst_type)}{bases[cst.cst_type]}'
            bases[cst.cst_type] += 1
            if cst.alias != alias:
                mapping[cst.alias] = alias
        return mapping

    @transaction.atomic
    def apply_mapping(self, mapping: dict[str, str], change_aliases: bool = False):
        ''' Apply rename mapping. '''
        cst_list = self.constituents().order_by('order')
        for cst in cst_list:
            modified = False
            if change_aliases and cst.alias in mapping:
                modified = True
                cst.alias = mapping[cst.alias]
            expression = apply_pattern(cst.definition_formal, mapping, _GLOBAL_ID_PATTERN)
            if expression != cst.definition_formal:
                modified = True
                cst.definition_formal = expression
            convention = apply_pattern(cst.convention, mapping, _GLOBAL_ID_PATTERN)
            if convention != cst.convention:
                modified = True
                cst.convention = convention
            term = apply_pattern(cst.term_raw, mapping, _REF_ENTITY_PATTERN)
            if term != cst.term_raw:
                modified = True
                cst.term_raw = term
            definition = apply_pattern(cst.definition_raw, mapping, _REF_ENTITY_PATTERN)
            if definition != cst.definition_raw:
                modified = True
                cst.definition_raw = definition
            if modified:
                cst.save()

    @transaction.atomic
    def resolve_all_text(self):
        ''' Trigger reference resolution for all texts. '''
        graph_terms = self._term_graph()
        resolver = Resolver({})
        for alias in graph_terms.topological_order():
            cst = self.constituents().get(alias=alias)
            resolved = resolver.resolve(cst.term_raw)
            resolver.context[cst.alias] = Entity(cst.alias, resolved)
            if resolved != cst.term_resolved:
                cst.term_resolved = resolved
                cst.save()
        for cst in self.constituents():
            resolved = resolver.resolve(cst.definition_raw)
            if resolved != cst.definition_resolved:
                cst.definition_resolved = resolved
                cst.save()

    @transaction.atomic
    def _reset_order(self):
        order = 1
        for cst in self.constituents().only('id', 'order').order_by('order'):
            if cst.order != order:
                cst.order = order
                cst.save()
            order += 1

    def _insert_new(self, data: dict, insert_after: Optional[str]=None) -> 'Constituenta':
        if insert_after is not None:
            cst_after = Constituenta.objects.get(pk=insert_after)
            return self.insert_at(cst_after.order + 1, data['alias'], data['cst_type'])
        else:
            return self.insert_last(data['alias'], data['cst_type'])

    def _term_graph(self) -> Graph:
        result = Graph()
        cst_list = \
            self.constituents() \
                .only('order', 'alias', 'term_raw') \
                .order_by('order')
        for cst in cst_list:
            result.add_node(cst.alias)
        for cst in cst_list:
            for alias in extract_entities(cst.term_raw):
                if result.contains(alias):
                    result.add_edge(id_from=alias, id_to=cst.alias)
        return result

    def _definition_graph(self) -> Graph:
        result = Graph()
        cst_list = \
            self.constituents() \
                .only('order', 'alias', 'definition_raw') \
                .order_by('order')
        for cst in cst_list:
            result.add_node(cst.alias)
        for cst in cst_list:
            for alias in extract_entities(cst.definition_raw):
                if result.contains(alias):
                    result.add_edge(id_from=alias, id_to=cst.alias)
        return result