import json

from django.core.exceptions import ImproperlyConfigured
from django.core.serializers.json import DjangoJSONEncoder
from django.core.validators import MaxLengthValidator
from django.db import models
from django.db.models.fields.json import KeyTransform
from django.utils.encoding import force_str

from wagtail.blocks import Block, BlockField, StreamBlock, StreamValue
from wagtail.rich_text import (
    RichTextMaxLengthValidator,
    extract_references_from_rich_text,
    get_text_for_indexing,
)


class RichTextField(models.TextField):
    def __init__(self, *args, **kwargs):
        # 'editor' and 'features' are popped before super().__init__ has chance to capture them
        # for use in deconstruct(). This is intentional - they would not be useful in migrations
        # and retrospectively adding them would generate unwanted migration noise
        self.editor = kwargs.pop("editor", "default")
        self.features = kwargs.pop("features", None)

        super().__init__(*args, **kwargs)

    def clone(self):
        name, path, args, kwargs = self.deconstruct()
        # add back the 'features' and 'editor' kwargs that were not preserved by deconstruct()
        kwargs["features"] = self.features
        kwargs["editor"] = self.editor
        return self.__class__(*args, **kwargs)

    def formfield(self, **kwargs):
        from wagtail.admin.rich_text import get_rich_text_editor_widget

        defaults = {
            "widget": get_rich_text_editor_widget(self.editor, features=self.features)
        }
        defaults.update(kwargs)
        field = super().formfield(**defaults)

        # replace any MaxLengthValidators with RichTextMaxLengthValidators to ignore tags
        for (i, validator) in enumerate(field.validators):
            if isinstance(validator, MaxLengthValidator):
                field.validators[i] = RichTextMaxLengthValidator(
                    validator.limit_value, message=validator.message
                )

        return field

    def get_searchable_content(self, value):
        # Strip HTML tags to prevent search backend from indexing them
        source = force_str(value)
        return [get_text_for_indexing(source)]

    def extract_references(self, value):
        yield from extract_references_from_rich_text(force_str(value))


# https://github.com/django/django/blob/64200c14e0072ba0ffef86da46b2ea82fd1e019a/django/db/models/fields/subclassing.py#L31-L44
class Creator:
    """
    A placeholder class that provides a way to set the attribute on the model.
    """

    def __init__(self, field):
        self.field = field

    def __get__(self, obj, type=None):
        if obj is None:
            return self
        field_name = self.field.name

        if field_name not in obj.__dict__:
            # Field is deferred. Fetch it from db.
            obj.refresh_from_db(fields=[field_name])
        return obj.__dict__[field_name]

    def __set__(self, obj, value):
        obj.__dict__[self.field.name] = self.field.to_python(value)


class StreamField(models.Field):
    def __init__(self, block_types, use_json_field=None, **kwargs):
        # extract kwargs that are to be passed on to the block, not handled by super
        block_opts = {}
        for arg in ["min_num", "max_num", "block_counts", "collapsed"]:
            if arg in kwargs:
                block_opts[arg] = kwargs.pop(arg)

        # for a top-level block, the 'blank' kwarg (defaulting to False) always overrides the
        # block's own 'required' meta attribute, even if not passed explicitly; this ensures
        # that the field and block have consistent definitions
        block_opts["required"] = not kwargs.get("blank", False)

        super().__init__(**kwargs)

        self.use_json_field = use_json_field

        if isinstance(block_types, Block):
            # use the passed block as the top-level block
            self.stream_block = block_types
        elif isinstance(block_types, type):
            # block passed as a class - instantiate it
            self.stream_block = block_types()
        else:
            # construct a top-level StreamBlock from the list of block types
            self.stream_block = StreamBlock(block_types)

        self.stream_block.set_meta_options(block_opts)

    @property
    def json_field(self):
        return models.JSONField(encoder=DjangoJSONEncoder)

    def _check_json_field(self):
        if self.use_json_field is not True:
            # RemovedInWagtail60Warning - make use_json_field optional and default to True
            raise ImproperlyConfigured(
                "StreamField must explicitly set use_json_field=True"
            )

    def get_internal_type(self):
        return "JSONField"

    def get_lookup(self, lookup_name):
        return self.json_field.get_lookup(lookup_name)

    def get_transform(self, lookup_name):
        return self.json_field.get_transform(lookup_name)

    def deconstruct(self):
        name, path, _, kwargs = super().deconstruct()
        block_types = list(self.stream_block.child_blocks.items())
        args = [block_types]
        kwargs["use_json_field"] = self.use_json_field
        return name, path, args, kwargs

    def to_python(self, value):
        value = self._to_python(value)

        # The top-level StreamValue is passed a reference to the StreamField, to support
        # pickling. This is necessary because unpickling needs access to the StreamBlock
        # definition, which cannot itself be pickled; instead we store a pointer to the
        # field within the model, which gives us a path to retrieve the StreamBlock definition.

        value._stream_field = self
        return value

    def _to_python(self, value):
        if value is None or value == "":
            return StreamValue(self.stream_block, [])
        elif isinstance(value, StreamValue):
            return value
        elif isinstance(value, str):
            try:
                unpacked_value = json.loads(value)
            except ValueError:
                # value is not valid JSON; most likely, this field was previously a
                # rich text field before being migrated to StreamField, and the data
                # was left intact in the migration. Return an empty stream instead
                # (but keep the raw text available as an attribute, so that it can be
                # used to migrate that data to StreamField)
                return StreamValue(self.stream_block, [], raw_text=value)

            if unpacked_value is None:
                # we get here if value is the literal string 'null'. This should probably
                # never happen if the rest of the (de)serialization code is working properly,
                # but better to handle it just in case...
                return StreamValue(self.stream_block, [])

            return self.stream_block.to_python(unpacked_value)
        elif value and isinstance(value, list) and isinstance(value[0], dict):
            # The value is already unpacked since JSONField-based StreamField should
            # accept deserialised values (no need to call json.dumps() first).
            # In addition, the value is not a list of (block_name, value) tuples
            # handled in the `else` block.
            return self.stream_block.to_python(value)
        else:
            # See if it looks like the standard non-smart representation of a
            # StreamField value: a list of (block_name, value) tuples
            try:
                [None for (x, y) in value]
            except (TypeError, ValueError):
                # Give up trying to make sense of the value
                raise TypeError(
                    "Cannot handle %r (type %r) as a value of StreamField"
                    % (value, type(value))
                )

            # Test succeeded, so return as a StreamValue-ified version of that value
            return StreamValue(self.stream_block, value)

    def get_prep_value(self, value):
        if (
            isinstance(value, StreamValue)
            and not (value)
            and value.raw_text is not None
        ):
            # An empty StreamValue with a nonempty raw_text attribute should have that
            # raw_text attribute written back to the db. (This is probably only useful
            # for reverse migrations that convert StreamField data back into plain text
            # fields.)
            return value.raw_text
        elif isinstance(value, StreamValue):
            # StreamValue instances must be prepared first.
            return json.dumps(
                self.stream_block.get_prep_value(value), cls=DjangoJSONEncoder
            )
        else:
            # When querying with JSONField features, the rhs might not be a StreamValue.
            # Note: when Django 4.2 is the minimum supported version, this can be removed
            # as the serialisation is handled in get_db_prep_value instead.
            return self.json_field.get_prep_value(value)

    def get_db_prep_value(self, value, connection, prepared=False):
        if not isinstance(value, StreamValue):
            # When querying with JSONField features, the rhs might not be a StreamValue.
            # As of Django 4.2, JSONField value serialisation is handled in
            # get_db_prep_value instead of get_prep_value.
            return self.json_field.get_db_prep_value(value, connection, prepared)
        return super().get_db_prep_value(value, connection, prepared)

    def from_db_value(self, value, expression, connection):
        if isinstance(expression, KeyTransform):
            # This could happen when using JSONField key transforms,
            # e.g. Page.object.values('body__0').
            try:
                # We might be able to properly resolve to the appropriate StreamValue
                # based on `expression` and `self.stream_block`, but it might be too
                # complicated to do so. For now, just deserialise the value.
                return json.loads(value)
            except ValueError:
                # Just in case the extracted value is not valid JSON.
                return value

        return self.to_python(value)

    def formfield(self, **kwargs):
        """
        Override formfield to use a plain forms.Field so that we do no transformation on the value
        (as distinct from the usual fallback of forms.CharField, which transforms it into a string).
        """
        defaults = {"form_class": BlockField, "block": self.stream_block}
        defaults.update(kwargs)
        return super().formfield(**defaults)

    def value_to_string(self, obj):
        value = self.value_from_object(obj)
        return self.get_prep_value(value)

    def get_searchable_content(self, value):
        return self.stream_block.get_searchable_content(value)

    def extract_references(self, value):
        yield from self.stream_block.extract_references(value)

    def get_block_by_content_path(self, value, path_elements):
        """
        Given a list of elements from a content path, retrieve the block at that path
        as a BoundBlock object, or None if the path does not correspond to a valid block.
        """
        return self.stream_block.get_block_by_content_path(value, path_elements)

    def check(self, **kwargs):
        errors = super().check(**kwargs)
        errors.extend(self.stream_block.check(field=self, **kwargs))
        return errors

    def contribute_to_class(self, cls, name, **kwargs):
        super().contribute_to_class(cls, name, **kwargs)

        # Output error on missing use_json_field=True argument, unless this is a fake model
        # for a migration
        if cls.__module__ != "__fake__":
            self._check_json_field()

        # Add Creator descriptor to allow the field to be set from a list or a
        # JSON string.
        setattr(cls, self.name, Creator(self))
