"""Общие (shared) сериализаторы: Skill, Position, EmployeeAction."""

from drf_spectacular.utils import extend_schema_field
from django.contrib.auth.models import Group
from employees.constants import ACTION_CHOICES, TEMPORARY_START_ACTIONS
from employees.models import EmployeeAction, Position, Skill
from rest_framework import serializers


class GroupVerboseSerializer(serializers.Serializer):
    id = serializers.IntegerField()
    name = serializers.CharField()


class EmployeeActionHistorySerializer(serializers.Serializer):
    history_id = serializers.IntegerField()
    history_type = serializers.CharField()
    history_type_display = serializers.CharField(allow_null=True)
    history_date = serializers.DateTimeField()
    history_date_display = serializers.CharField()
    history_user = serializers.CharField(allow_null=True)
    action = serializers.CharField(allow_null=True)
    action_display = serializers.CharField(allow_null=True)
    changes = serializers.DictField()


class SkillSerializer(serializers.ModelSerializer):
    class Meta:
        model = Skill
        fields = ["id", "name"]


class PositionBriefSerializer(serializers.ModelSerializer):
    class Meta:
        model = Position
        fields = ("id", "name")


class PositionSerializer(serializers.ModelSerializer):
    groups = serializers.PrimaryKeyRelatedField(
        queryset=Group.objects.all(), many=True, required=False
    )
    groups_verbose = serializers.SerializerMethodField(read_only=True)

    class Meta:
        model = Position
        fields = ["id", "name", "description", "groups", "groups_verbose"]

    @extend_schema_field(GroupVerboseSerializer(many=True))
    def get_groups_verbose(self, obj):
        return [{"id": g.id, "name": g.name} for g in obj.groups.all()]


class EmployeeActionSerializer(serializers.ModelSerializer):
    action_display = serializers.SerializerMethodField()
    date_display = serializers.SerializerMethodField()
    history = serializers.SerializerMethodField()

    class Meta:
        model = EmployeeAction
        fields = [
            "id",
            "employee",
            "action",
            "action_display",
            "date",
            "date_to",
            "date_display",
            "comment",
            "extra",
            "history",
        ]

    def validate(self, attrs):
        action = attrs.get(
            "action",
            getattr(self.instance, "action", None),
        )
        date = attrs.get("date", getattr(self.instance, "date", None))
        date_to = attrs.get("date_to", getattr(self.instance, "date_to", None))

        if date_to is not None and action not in TEMPORARY_START_ACTIONS:
            raise serializers.ValidationError(
                {
                    "date_to": (
                        "Дата окончания доступна только для временных "
                        "кадровых событий."
                    )
                }
            )

        if (
            action in TEMPORARY_START_ACTIONS
            and date_to is None
            and (
                self.instance is None
                or "action" in attrs
                or "date" in attrs
                or "date_to" in attrs
            )
        ):
            raise serializers.ValidationError(
                {
                    "date_to": (
                        "Дата окончания обязательна для временных "
                        "кадровых событий."
                    )
                }
            )

        if date and date_to and date_to < date.date():
            raise serializers.ValidationError(
                {"date_to": "Дата окончания не может быть раньше даты начала."}
            )

        return attrs

    @extend_schema_field(serializers.CharField())
    def get_action_display(self, obj):
        return obj.get_action_display()

    @extend_schema_field(serializers.CharField(allow_null=True))
    def get_date_display(self, obj):
        return obj.date.strftime("%d.%m.%Y %H:%M") if obj.date else None

    @extend_schema_field(EmployeeActionHistorySerializer(many=True))
    def get_history(self, obj):
        if not self.context.get("include_action_history", False):
            return []

        items = list(
            obj.history.select_related("history_user").order_by(
                "-history_date", "-history_id"
            )
        )

        action_labels = dict(ACTION_CHOICES)
        history_type_labels = {"+": "Создано", "~": "Изменено", "-": "Удалено"}
        diff_fields = ["action", "date", "date_to", "comment", "extra"]

        out = []
        for i, cur in enumerate(items):
            prev = items[i + 1] if i + 1 < len(items) else None
            changes = {}

            for name in diff_fields:
                new = getattr(cur, name, None)
                old = getattr(prev, name, None) if prev else None

                if name in {"date", "date_to"}:
                    new_fmt = new.isoformat() if new else None
                    old_fmt = old.isoformat() if old else None
                    if new_fmt != old_fmt:
                        changes[name] = {"old": old_fmt, "new": new_fmt}
                elif name == "action":
                    if old != new:
                        changes[name] = {
                            "old": old,
                            "old_display": action_labels.get(old),
                            "new": new,
                            "new_display": action_labels.get(new),
                        }
                else:
                    if old != new:
                        changes[name] = {"old": old, "new": new}

            out.append(
                {
                    "history_id": cur.history_id,
                    "history_type": cur.history_type,
                    "history_type_display": history_type_labels.get(
                        cur.history_type
                    ),
                    "history_date": cur.history_date.isoformat(),
                    "history_date_display": cur.history_date.strftime(
                        "%d.%m.%Y %H:%M"
                    ),
                    "history_user": getattr(cur.history_user, "email", None),
                    "action": getattr(cur, "action", None),
                    "action_display": action_labels.get(
                        getattr(cur, "action", None)
                    ),
                    "changes": changes,
                }
            )
        return out