from datetime import date

from django.core.exceptions import ValidationError as DjangoValidationError
from django.db import transaction
from django.utils import timezone
from rest_framework import serializers

from locations.models import Atoll, Island

from .mobile import normalize_mobile
from .models import RegistrationTicket, User

MAX_AGE_YEARS = 120


class MobileField(serializers.CharField):
    """Accepts 7712345 / 9607712345 / +960 771 2345 and stores +9607712345."""

    def to_internal_value(self, data):
        value = super().to_internal_value(data)
        try:
            return normalize_mobile(value)
        except DjangoValidationError as exc:
            raise serializers.ValidationError(exc.messages) from exc


class AuthStartSerializer(serializers.Serializer):
    mobile = MobileField()


class PasswordLoginSerializer(serializers.Serializer):
    mobile = MobileField()
    password = serializers.CharField(trim_whitespace=False, write_only=True)


class OtpVerifySerializer(serializers.Serializer):
    mobile = MobileField()
    code = serializers.RegexField(r"^\d{6}$", write_only=True)


class UserSerializer(serializers.ModelSerializer):
    is_admin = serializers.BooleanField(source="is_admin_user", read_only=True)
    has_password = serializers.SerializerMethodField()
    atoll_name = serializers.CharField(source="atoll.name", default=None, read_only=True)
    island_name = serializers.CharField(
        source="island.name", default=None, read_only=True
    )

    class Meta:
        model = User
        fields = [
            "id",
            "mobile",
            "full_name",
            "email",
            "idnumber",
            "date_of_birth",
            "atoll",
            "atoll_name",
            "island",
            "island_name",
            "auth_method",
            "status",
            "rejection_reason",
            "mobile_verified",
            "is_admin",
            "has_password",
            "date_joined",
        ]
        read_only_fields = fields

    def get_has_password(self, obj) -> bool:
        return obj.has_usable_password()


class RegistrationSerializer(serializers.Serializer):
    """The registration form.

    The mobile number is not accepted from the client: it comes from the
    `registration_token`, which is only issued after that number confirmed an
    SMS code. So the number on the account is always one the applicant proved
    they control, and the form's prefilled field can't be tampered with.
    """

    registration_token = serializers.CharField(write_only=True)
    full_name = serializers.CharField(max_length=255)
    idnumber = serializers.CharField(max_length=32)
    date_of_birth = serializers.DateField()
    atoll = serializers.PrimaryKeyRelatedField(
        queryset=Atoll.objects.filter(is_active=True)
    )
    island = serializers.PrimaryKeyRelatedField(
        queryset=Island.objects.filter(is_active=True)
    )
    terms_accepted = serializers.BooleanField()
    policy_accepted = serializers.BooleanField()

    def validate_registration_token(self, value):
        ticket = RegistrationTicket.objects.active().filter(key=value).first()
        if ticket is None:
            raise serializers.ValidationError(
                "Your number needs to be verified again."
            )
        return ticket

    def validate_full_name(self, value):
        name = " ".join(value.split())
        if len(name) < 3:
            raise serializers.ValidationError("Enter your full name.")
        return name

    def validate_idnumber(self, value):
        return value.strip().upper()

    def validate_date_of_birth(self, value):
        today = date.today()
        if value > today:
            raise serializers.ValidationError("Date of birth can't be in the future.")
        if value.year < today.year - MAX_AGE_YEARS:
            raise serializers.ValidationError("Enter a valid date of birth.")
        return value

    def validate_terms_accepted(self, value):
        if not value:
            raise serializers.ValidationError(
                "You must agree to the terms and conditions."
            )
        return value

    def validate_policy_accepted(self, value):
        if not value:
            raise serializers.ValidationError(
                "You must confirm you understand the privacy policy."
            )
        return value

    def validate(self, attrs):
        island = attrs["island"]
        if island.atoll_id != attrs["atoll"].pk:
            raise serializers.ValidationError(
                {"island": "That island isn't in the selected atoll."}
            )

        ticket = attrs["registration_token"]
        if User.objects.filter(mobile=ticket.mobile).exists():
            raise serializers.ValidationError(
                {"mobile": "An account already exists for this number."}
            )
        return attrs

    @transaction.atomic
    def create(self, validated_data):
        ticket = validated_data["registration_token"]
        now = timezone.now()

        user = User.objects.create_user(
            mobile=ticket.mobile,
            full_name=validated_data["full_name"],
            idnumber=validated_data["idnumber"],
            date_of_birth=validated_data["date_of_birth"],
            atoll=validated_data["atoll"],
            island=validated_data["island"],
            auth_method=User.AuthMethod.OTP,
            status=User.Status.PENDING,
            mobile_verified=True,
            terms_accepted_at=now,
            policy_accepted_at=now,
        )
        ticket.consume()
        return user