from drf_spectacular.types import OpenApiTypes
from drf_spectacular.utils import OpenApiResponse, extend_schema, inline_serializer
from rest_framework import generics, permissions, serializers, status
from rest_framework.exceptions import ValidationError
from rest_framework.response import Response
from rest_framework.throttling import ScopedRateThrottle
from rest_framework.views import APIView
from rest_framework_simplejwt.exceptions import TokenError
from rest_framework_simplejwt.tokens import RefreshToken
from django.contrib.auth import get_user_model
from django.db import transaction, IntegrityError

from apps.skills.models import Skill, UserSkill
from apps.skills.utils import proficiency_to_level

from .models import UserProfile
from .serializers import (
    LoginSerializer,
    ProfileWithSkillsSerializer,
    RegisterSerializer,
    UserProfileSerializer,
    UserSerializer,
)

User = get_user_model()


# Shape for endpoints that issue JWTs (register, login).
_AUTH_RESPONSE = inline_serializer(
    name='AuthTokenResponse',
    fields={
        'access': serializers.CharField(),
        'refresh': serializers.CharField(),
        'user': UserSerializer(),
    },
)


@extend_schema(
    responses={
        201: _AUTH_RESPONSE,
        400: OpenApiResponse(
            description='Validation error — duplicate email, weak/mismatched '
            'password, or missing fields (body is {"<field>": [...]}).',
        ),
    },
)
class RegisterView(generics.CreateAPIView):
    queryset = User.objects.all()
    permission_classes = [permissions.AllowAny]
    throttle_classes = [ScopedRateThrottle]
    throttle_scope = 'register'
    serializer_class = RegisterSerializer

    def create(self, request, *args, **kwargs):
        serializer = self.get_serializer(data=request.data)
        serializer.is_valid(raise_exception=True)
        try:
            user = serializer.save()
        except IntegrityError:
            # Concurrent-registration race: two simultaneous case-variant emails
            # can both pass the case-insensitive validate_email check; both then
            # insert the SAME app-lowercased value, and the plain `unique=True`
            # constraint on email/username rejects the loser. Surface a clean 400
            # keyed on `email` (matching validate_email) instead of a 500.
            return Response(
                {'email': ['A user with this email already exists.']},
                status=status.HTTP_400_BAD_REQUEST,
            )

        refresh = RefreshToken.for_user(user)
        return Response({
            'access': str(refresh.access_token),
            'refresh': str(refresh),
            'user': UserSerializer(user).data
        }, status=status.HTTP_201_CREATED)


@extend_schema(
    request=LoginSerializer,
    responses={200: _AUTH_RESPONSE},
)
class LoginView(APIView):
    serializer_class = LoginSerializer
    permission_classes = [permissions.AllowAny]
    throttle_classes = [ScopedRateThrottle]
    throttle_scope = 'login'

    def post(self, request):
        serializer = LoginSerializer(data=request.data, context={'request': request})
        serializer.is_valid(raise_exception=True)
        user = serializer.validated_data

        refresh = RefreshToken.for_user(user)

        return Response({
            'access': str(refresh.access_token),
            'refresh': str(refresh),
            'user': UserSerializer(user).data
        }, status=status.HTTP_200_OK)


@extend_schema(
    request=inline_serializer(
        name='LogoutRequest',
        fields={'refresh_token': serializers.CharField()},
    ),
    responses={
        204: OpenApiResponse(description='Token blacklisted.'),
        400: OpenApiResponse(description='Missing or invalid refresh token.'),
    },
)
class LogoutView(APIView):
    permission_classes = [permissions.IsAuthenticated]

    def post(self, request):
        try:
            refresh_token = request.data.get('refresh_token')
            if not refresh_token:
                return Response(
                    {'detail': 'refresh_token is required'},
                    status=status.HTTP_400_BAD_REQUEST
                )
            token = RefreshToken(refresh_token)
            token.blacklist()
            return Response(status=status.HTTP_204_NO_CONTENT)
        except TokenError:
            return Response(
                {'detail': 'Invalid or expired token'},
                status=status.HTTP_400_BAD_REQUEST
            )


class UserMeView(generics.RetrieveAPIView):
    serializer_class = UserSerializer
    permission_classes = [permissions.IsAuthenticated]

    def get_object(self):
        return self.request.user


@extend_schema(
    request={
        'multipart/form-data': inline_serializer(
            name='ResumeUpload',
            fields={'resume': serializers.FileField()},
        ),
    },
    responses={
        200: inline_serializer(
            name='ParseResumeResponse',
            fields={
                'skills': serializers.ListField(child=serializers.DictField()),
                'parser_version': serializers.ListField(child=serializers.CharField()),
                'note': serializers.CharField(),
            },
        ),
        400: OpenApiResponse(description='Empty / missing file or parse error.'),
    },
)
class ParseResumeStubView(APIView):
    """Resume parsing — Module 8 MVP.

    Accepts a multipart PDF upload and returns pre-fill predictions scored
    against the Skill catalog. This is the "degraded fallback" layer in the
    research/06-dataset-sourcing.md §5 fallback chain — pdfplumber + lexical
    match. Higher NER layers can be plugged in behind
    `apps.accounts.resume_parser.extract_skills_from_pdf` when the ML
    env-setup track (SpaCy/BERT wheels + pgvector) lands.

    Class name kept as-is (`ParseResumeStubView`) so URLConf + existing routes
    don't churn — the view is no longer a stub but the URL name is stable.
    """
    permission_classes = [permissions.IsAuthenticated]
    throttle_classes = [ScopedRateThrottle]
    throttle_scope = 'resume_parse'

    def post(self, request):
        upload = (
            request.FILES.get('resume')
            or request.FILES.get('file')
            or next(iter(request.FILES.values()), None)
        )
        if upload is None:
            return Response(
                {"detail": "Upload a PDF file under the 'resume' form field."},
                status=status.HTTP_400_BAD_REQUEST,
            )
        if upload.size == 0:
            return Response(
                {"detail": "Uploaded file is empty."},
                status=status.HTTP_400_BAD_REQUEST,
            )

        from .resume_parser import ResumeParseError, parse_resume_envelope

        try:
            envelope = parse_resume_envelope(upload.read())
        except ResumeParseError as exc:
            return Response(
                {"detail": str(exc)},
                status=status.HTTP_400_BAD_REQUEST,
            )

        return Response(
            {
                "skills": envelope["skills"],
                "parser_version": envelope["parser_version"],
                "note": (
                    "Predictions are merged across the layers listed above. "
                    "Review the proficiency values — they are heuristics from "
                    "the surrounding context, not assertions."
                ),
            },
            status=status.HTTP_200_OK,
        )


class ProfileView(APIView):
    serializer_class = ProfileWithSkillsSerializer
    permission_classes = [permissions.IsAuthenticated]

    @extend_schema(responses=ProfileWithSkillsSerializer)
    def get(self, request):
        user = request.user
        UserProfile.objects.get_or_create(user=user)
        serializer = ProfileWithSkillsSerializer(user)
        return Response(serializer.data, status=status.HTTP_200_OK)

    @extend_schema(
        request=inline_serializer(
            name='ProfileUpdateRequest',
            fields={
                'degree': serializers.CharField(required=False, allow_blank=True),
                'semester': serializers.IntegerField(required=False, allow_null=True),
                'interests': serializers.CharField(required=False, allow_blank=True),
                'bio': serializers.CharField(required=False, allow_blank=True),
                'skills': serializers.ListField(
                    child=inline_serializer(
                        name='ProfileSkillItem',
                        fields={
                            'skill_id': serializers.IntegerField(),
                            'proficiency': serializers.IntegerField(min_value=0, max_value=100),
                        },
                    ),
                    required=False,
                ),
            },
        ),
        responses=ProfileWithSkillsSerializer,
    )
    @transaction.atomic
    def put(self, request):
        user = request.user
        profile, _ = UserProfile.objects.get_or_create(user=user)

        profile_serializer = UserProfileSerializer(
            profile, data=request.data, partial=True
        )
        profile_serializer.is_valid(raise_exception=True)
        profile_serializer.save()

        # Upsert skills (transactional — any error rolls back all changes)
        skills_data = request.data.get('skills', []) or []
        requested_ids = {
            int(item['skill_id']) for item in skills_data
            if item.get('skill_id') is not None and item.get('proficiency') is not None
        }
        known_ids = set(
            Skill.objects.filter(id__in=requested_ids).values_list('id', flat=True)
        ) if requested_ids else set()

        for item in skills_data:
            skill_id = item.get('skill_id')
            proficiency = item.get('proficiency')
            if skill_id is None or proficiency is None:
                continue
            skill_id = int(skill_id)
            proficiency = int(proficiency)
            if not (0 <= proficiency <= 100):
                raise ValidationError(f"Proficiency must be 0-100 for skill_id {skill_id}")
            if skill_id not in known_ids:
                raise ValidationError(f"Skill with id={skill_id} does not exist")
            UserSkill.objects.update_or_create(
                user=user, skill_id=skill_id,
                defaults={
                    'proficiency': proficiency,
                    'user_level': proficiency_to_level(proficiency)
                }
            )

        serializer = ProfileWithSkillsSerializer(user)
        return Response(serializer.data, status=status.HTTP_200_OK)