from drf_spectacular.utils import extend_schema_field
from rest_framework import serializers

from tasks.models import (
    TaskColumn,
    TaskColumnRow,
    TaskLabel,
)

from .common import validate_board_access


class TaskLabelSerializer(serializers.ModelSerializer):
    class Meta:
        model = TaskLabel
        fields = ["id", "name", "color"]
        read_only_fields = ["id"]

    def validate_name(self, value):
        name = value.strip()
        duplicate = TaskLabel.objects.only("id", "name")
        if self.instance:
            duplicate = duplicate.exclude(pk=self.instance.pk)
        normalized_name = name.casefold()
        if any(label.name.casefold() == normalized_name for label in duplicate):
            raise serializers.ValidationError("Метка с таким названием уже существует.")
        return name


class TaskColumnSerializer(serializers.ModelSerializer):
    tasks_count = serializers.IntegerField(read_only=True, default=0)
    subcolumns_count = serializers.SerializerMethodField()

    class Meta:
        model = TaskColumn
        validators = []
        fields = [
            "id",
            "board",
            "parent",
            "name",
            "position",
            "color",
            "is_done",
            "is_archived",
            "tasks_count",
            "subcolumns_count",
            "created_at",
            "updated_at",
        ]
        read_only_fields = [
            "id",
            "created_at",
            "updated_at",
            "tasks_count",
            "subcolumns_count",
        ]

    def validate_board(self, board):
        return validate_board_access(self, board)

    @extend_schema_field(serializers.IntegerField())
    def get_subcolumns_count(self, obj):
        annotated_count = getattr(obj, "subcolumns_count", None)
        if annotated_count is not None:
            return annotated_count
        return obj.subcolumns.filter(is_archived=False).count()

    def _validate_immutable_relations(self, attrs, board, parent) -> None:
        if self.instance and board and self.instance.board_id != board.id:
            raise serializers.ValidationError(
                {"board": "Доску существующей колонки изменить нельзя."}
            )
        if self.instance and "parent" in attrs:
            requested_parent_id = parent.id if parent else None
            if self.instance.parent_id != requested_parent_id:
                raise serializers.ValidationError(
                    {"parent": "Родителя существующей колонки изменить нельзя."}
                )

    @staticmethod
    def _validate_parent(attrs, board, parent) -> None:
        if not parent:
            return
        if board and parent.board_id != board.id:
            raise serializers.ValidationError(
                {"parent": "Подколонка должна принадлежать той же доске."}
            )
        if parent.parent_id:
            raise serializers.ValidationError(
                {"parent": "Допускается только один уровень подколонок."}
            )
        if parent.is_archived:
            raise serializers.ValidationError(
                {"parent": "Нельзя добавить подколонку в архивную колонку."}
            )
        attrs["is_done"] = parent.is_done

    def _validate_archive(self, attrs) -> None:
        archiving_parent = (
            self.instance
            and attrs.get("is_archived") is True
            and self.instance.subcolumns.exists()
        )
        if archiving_parent:
            raise serializers.ValidationError(
                {"is_archived": "Сначала удалите подколонки."}
            )

    def _validate_unique_name(self, attrs, board, parent) -> None:
        name = attrs.get("name", getattr(self.instance, "name", ""))
        if not board or not name:
            return
        duplicate_columns = TaskColumn.objects.filter(name=name)
        if parent:
            duplicate_columns = duplicate_columns.filter(parent=parent)
        else:
            duplicate_columns = duplicate_columns.filter(
                board=board,
                parent__isnull=True,
            )
        if self.instance:
            duplicate_columns = duplicate_columns.exclude(pk=self.instance.pk)
        if duplicate_columns.exists():
            raise serializers.ValidationError(
                {"name": "Колонка с таким названием уже существует здесь."}
            )

    def validate(self, attrs):
        board = attrs.get("board") or getattr(self.instance, "board", None)
        parent = attrs.get("parent", getattr(self.instance, "parent", None))
        self._validate_immutable_relations(attrs, board, parent)
        self._validate_parent(attrs, board, parent)
        self._validate_archive(attrs)
        self._validate_unique_name(attrs, board, parent)
        return attrs

    def create(self, validated_data):
        parent = validated_data.get("parent")
        if parent:
            validated_data.setdefault("color", parent.color)
            validated_data.setdefault("is_done", parent.is_done)
        return super().create(validated_data)


class TaskColumnRowSerializer(serializers.ModelSerializer):
    tasks_count = serializers.IntegerField(read_only=True, default=0)

    class Meta:
        model = TaskColumnRow
        fields = [
            "id",
            "column",
            "name",
            "position",
            "color",
            "tasks_count",
            "created_at",
            "updated_at",
        ]
        read_only_fields = ["id", "tasks_count", "created_at", "updated_at"]

    def validate_column(self, column):
        validate_board_access(self, column.board)
        if column.parent_id:
            raise serializers.ValidationError(
                "Дорожки можно создавать только в основной колонке."
            )
        if column.is_archived:
            raise serializers.ValidationError(
                "Нельзя создать дорожку в архивной колонке."
            )
        return column

    def validate(self, attrs):
        column = attrs.get("column") or getattr(self.instance, "column", None)
        if self.instance and column and self.instance.column_id != column.id:
            raise serializers.ValidationError(
                {"column": "Основную колонку дорожки изменить нельзя."}
            )
        name = attrs.get("name", getattr(self.instance, "name", "")).strip()
        if not name:
            raise serializers.ValidationError({"name": "Укажите название дорожки."})
        duplicate = TaskColumnRow.objects.filter(column=column, name__iexact=name)
        if self.instance:
            duplicate = duplicate.exclude(pk=self.instance.pk)
        if duplicate.exists():
            raise serializers.ValidationError(
                {"name": "Дорожка с таким названием уже существует в колонке."}
            )
        attrs["name"] = name
        return attrs