from datetime import timedelta
from django.utils import timezone
from rest_framework import serializers

from notes.models import Note, User


class UserSerializer(serializers.ModelSerializer):
    username = serializers.CharField(max_length=150)
    class Meta:
        model = User
        fields = ["id", "username", "first_name", "last_name"]
        read_only_fields = ["id", "first_name", "last_name"]


class NoteSerializer(serializers.ModelSerializer):
    from_user = UserSerializer(read_only=True)
    to_user = UserSerializer()

    class Meta:
        model = Note
        fields = [
            "from_user",
            "to_user",
            "note",
            "expiry",
            "created_at",
        ]
        read_only_fields = [
            "from_user",
            "created_at",
            "expiry",
        ]

    def validate_to_user(self, value):
        try:
            user = User.objects.get(username=value['username'])
        except User.DoesNotExist:
            raise serializers.ValidationError("User not found")

        current_user = self.context['request'].user
        if not current_user.allowed_notes_to.filter(pk=user.pk).exists():
            raise serializers.ValidationError(f"User not allowed to post notes to {user!r}")
        return user

    def save(self, **kwargs):
        to_user = self.validated_data['to_user']
        return Note.objects.create(
            from_user=self.context['request'].user,
            to_user=to_user,
            note=self.validated_data['note'],
            expiry=timezone.now() + timedelta(seconds=to_user.expiry_seconds)
        )