import os
import uuid
from django.conf import settings
from rest_framework import viewsets, status
from rest_framework.decorators import action
from rest_framework.parsers import MultiPartParser, FormParser
from rest_framework.response import Response

from apps.compliance.permissions import IsOpsOrAdmin

from .models import Document, CertificateOfAnalysis, RegulatoryCert
from .serializers import DocumentSerializer, DocumentUploadSerializer, CertificateOfAnalysisSerializer, RegulatoryCertSerializer


class DocumentViewSet(viewsets.ModelViewSet):
    queryset = Document.objects.all()
    serializer_class = DocumentSerializer
    # Documents and certificates are the evidence a buyer's auditor relies on.
    # The buyer portal serves the buyer-visible rows through the ORM
    # (apps/buyer/views.py), so this API needs no buyer access — read or write.
    permission_classes = [IsOpsOrAdmin]

    @action(detail=False, methods=["post"], parser_classes=[MultiPartParser, FormParser])
    def upload(self, request):
        serializer = DocumentUploadSerializer(data=request.data)
        serializer.is_valid(raise_exception=True)

        file = serializer.validated_data["file"]
        batch_id = serializer.validated_data.get("batch_id")
        doc_type = serializer.validated_data["doc_type"]
        visibility = serializer.validated_data.get("visibility", "buyer")

        file_ext = file.name.split(".")[-1].lower()
        allowed = ["pdf", "jpg", "jpeg", "png", "xlsx"]
        if file_ext not in allowed:
            return Response({"error": f"File type .{file_ext} not allowed"}, status=status.HTTP_400_BAD_REQUEST)

        if file.size > 50 * 1024 * 1024:
            return Response({"error": "File exceeds 50MB limit"}, status=status.HTTP_400_BAD_REQUEST)

        batch_dir = os.path.join(settings.MEDIA_ROOT, "ixg-documents", str(batch_id or "uncategorized"))
        os.makedirs(batch_dir, exist_ok=True)

        filename = f"{uuid.uuid4()}_{file.name}"
        filepath = os.path.join(batch_dir, filename)
        with open(filepath, "wb+") as dest:
            for chunk in file.chunks():
                dest.write(chunk)

        doc = Document.objects.create(
            batch_id=batch_id,
            doc_type=doc_type,
            file_url=f"/media/ixg-documents/{batch_id or 'uncategorized'}/{filename}",
            file_name=file.name,
            file_size_bytes=file.size,
            visibility=visibility,
            uploaded_by=request.user,
        )

        return Response(DocumentSerializer(doc).data, status=status.HTTP_201_CREATED)


class CertificateOfAnalysisViewSet(viewsets.ModelViewSet):
    queryset = CertificateOfAnalysis.objects.select_related("batch", "qc_result").all()
    serializer_class = CertificateOfAnalysisSerializer
    # A certificate is released to buyers through the ORM (apps/buyer/views.py),
    # not this API, so the API needs no buyer access. Only a published
    # certificate is buyer-visible at all, and only ops/admin may publish one.
    permission_classes = [IsOpsOrAdmin]

    @action(detail=True, methods=["post"])
    def approve(self, request, pk=None):
        """Commercial release approval: publishes the CoA and exposes it to buyers."""
        from apps.compliance.services import publish_coa

        coa = self.get_object()
        if coa.status != CertificateOfAnalysis.Status.PENDING_APPROVAL:
            return Response({"detail": "CoA is not pending approval"}, status=status.HTTP_400_BAD_REQUEST)
        publish_coa(coa, released_by=request.user)
        return Response(CertificateOfAnalysisSerializer(coa).data)

    @action(detail=True, methods=["post"])
    def supersede(self, request, pk=None):
        from django.utils import timezone

        coa = self.get_object()
        replacement_id = request.data.get("replacement_id")
        if not replacement_id:
            return Response({"detail": "replacement_id is required"}, status=status.HTTP_400_BAD_REQUEST)
        replacement = CertificateOfAnalysis.objects.filter(id=replacement_id).first()
        if not replacement:
            return Response({"detail": "Replacement CoA not found"}, status=status.HTTP_400_BAD_REQUEST)
        coa.status = CertificateOfAnalysis.Status.SUPERSEDED
        coa.superseded_at = timezone.now()
        coa.superseded_by = replacement
        coa.save()
        return Response(CertificateOfAnalysisSerializer(coa).data)


class RegulatoryCertViewSet(viewsets.ModelViewSet):
    queryset = RegulatoryCert.objects.all()
    serializer_class = RegulatoryCertSerializer
    # Regulatory certificates are an internal compliance record; the buyer portal
    # does not read them, so the API is ops/admin only.
    permission_classes = [IsOpsOrAdmin]