from decimal import Decimal, InvalidOperation

from django.http import HttpResponse
from django.template.loader import render_to_string
from rest_framework import viewsets, status
from rest_framework.decorators import action
from rest_framework.exceptions import ValidationError
from rest_framework.permissions import IsAuthenticated
from rest_framework.response import Response
from rest_framework.views import APIView
from weasyprint import HTML

from apps.fields.models import Field
from apps.materials.stock_service import (
    confirm_spreading as confirm_spreading_service,
    create_reserves_for_plan,
    delete_reserves_for_plan,
    unconfirm_spreading,
)
from apps.plans.models import Plan, Variety
from .models import (
    Fertilizer, FertilizationPlan, FertilizationEntry,
    DeliveryPlan, DeliveryGroup, DeliveryGroupField, DeliveryTrip, DeliveryTripItem,
)
from .serializers import (
    FertilizerSerializer,
    FertilizationPlanSerializer,
    FertilizationPlanWriteSerializer,
    DeliveryPlanListSerializer,
    DeliveryPlanReadSerializer,
    DeliveryPlanWriteSerializer,
)


class FertilizerViewSet(viewsets.ModelViewSet):
    permission_classes = [IsAuthenticated]
    queryset = Fertilizer.objects.all()
    serializer_class = FertilizerSerializer


class FertilizationPlanViewSet(viewsets.ModelViewSet):
    permission_classes = [IsAuthenticated]

    def get_queryset(self):
        qs = FertilizationPlan.objects.select_related('variety', 'variety__crop').prefetch_related(
            'entries', 'entries__field', 'entries__fertilizer', 'entries__fertilizer__material'
        )
        year = self.request.query_params.get('year')
        if year:
            qs = qs.filter(year=year)
        return qs

    def get_serializer_class(self):
        if self.action in ['create', 'update', 'partial_update']:
            return FertilizationPlanWriteSerializer
        return FertilizationPlanSerializer

    def perform_create(self, serializer):
        instance = serializer.save()
        create_reserves_for_plan(instance)

    def perform_update(self, serializer):
        if serializer.instance.is_confirmed:
            raise ValidationError({'detail': '確定済みの施肥計画は編集できません。'})
        instance = serializer.save()
        create_reserves_for_plan(instance)

    def perform_destroy(self, instance):
        delete_reserves_for_plan(instance)
        instance.delete()

    @action(detail=True, methods=['get'])
    def pdf(self, request, pk=None):
        plan = self.get_object()
        entries = plan.entries.select_related('field', 'fertilizer').order_by(
            'field__display_order', 'field__id', 'fertilizer__name'
        )

        # 圃場・肥料の一覧を整理
        fields_map = {}
        fertilizers_map = {}
        for entry in entries:
            fields_map[entry.field_id] = entry.field
            fertilizers_map[entry.fertilizer_id] = entry.fertilizer

        fields = sorted(fields_map.values(), key=lambda f: (f.display_order, f.id))
        fertilizers = sorted(fertilizers_map.values(), key=lambda f: f.name)

        # マトリクスデータ生成
        matrix = {}
        for entry in entries:
            matrix[(entry.field_id, entry.fertilizer_id)] = entry.bags

        rows = []
        for field in fields:
            cells = [matrix.get((field.id, fert.id), '') for fert in fertilizers]
            total = sum(v for v in cells if v != '')
            rows.append({
                'field': field,
                'cells': cells,
                'total': total,
            })

        # 肥料ごとの合計
        fert_totals = []
        for fert in fertilizers:
            total = sum(
                matrix.get((field.id, fert.id), Decimal('0'))
                for field in fields
            )
            fert_totals.append(total)

        context = {
            'plan': plan,
            'fertilizers': fertilizers,
            'rows': rows,
            'fert_totals': fert_totals,
            'grand_total': sum(fert_totals),
        }
        html_string = render_to_string('fertilizer/pdf.html', context)
        pdf_file = HTML(string=html_string).write_pdf()
        response = HttpResponse(pdf_file, content_type='application/pdf')
        response['Content-Disposition'] = f'attachment; filename="fertilization_{plan.year}_{plan.id}.pdf"'
        return response

    @action(detail=True, methods=['post'], url_path='confirm_spreading')
    def confirm_spreading(self, request, pk=None):
        plan = self.get_object()

        if plan.is_confirmed:
            return Response(
                {'detail': 'この計画は既に散布確定済みです。'},
                status=status.HTTP_400_BAD_REQUEST,
            )

        entries_data = request.data.get('entries', [])
        if not entries_data:
            return Response(
                {'detail': '実績データが空です。'},
                status=status.HTTP_400_BAD_REQUEST,
            )

        actual_entries = []
        for entry in entries_data:
            field_id = entry.get('field_id')
            fertilizer_id = entry.get('fertilizer_id')
            if not field_id or not fertilizer_id:
                return Response(
                    {'detail': 'field_id と fertilizer_id が必要です。'},
                    status=status.HTTP_400_BAD_REQUEST,
                )
            try:
                actual_bags = Decimal(str(entry.get('actual_bags', 0)))
            except InvalidOperation:
                return Response(
                    {'detail': 'actual_bags は数値で指定してください。'},
                    status=status.HTTP_400_BAD_REQUEST,
                )
            actual_entries.append(
                {
                    'field_id': field_id,
                    'fertilizer_id': fertilizer_id,
                    'actual_bags': actual_bags,
                }
            )

        confirm_spreading_service(plan, actual_entries)
        plan.refresh_from_db()
        serializer = self.get_serializer(plan)
        return Response(serializer.data)

    @action(detail=True, methods=['post'], url_path='unconfirm')
    def unconfirm(self, request, pk=None):
        plan = self.get_object()

        if not plan.is_confirmed:
            return Response(
                {'detail': 'この計画はまだ確定されていません。'},
                status=status.HTTP_400_BAD_REQUEST,
            )

        unconfirm_spreading(plan)
        plan.refresh_from_db()
        serializer = self.get_serializer(plan)
        return Response(serializer.data)


class CandidateFieldsView(APIView):
    """作付け計画から圃場候補を返す"""
    permission_classes = [IsAuthenticated]

    def get(self, request):
        year = request.query_params.get('year')
        variety_id = request.query_params.get('variety_id')
        if not year or not variety_id:
            return Response({'error': 'year と variety_id が必要です'}, status=status.HTTP_400_BAD_REQUEST)

        field_ids = Plan.objects.filter(
            year=year, variety_id=variety_id
        ).values_list('field_id', flat=True)

        fields = Field.objects.filter(id__in=field_ids).order_by('display_order', 'id')
        data = [
            {
                'id': f.id,
                'name': f.name,
                'area_tan': str(f.area_tan),
                'area_m2': f.area_m2,
                'group_name': f.group_name,
            }
            for f in fields
        ]
        return Response(data)


class CalculateView(APIView):
    """自動計算（保存しない）"""
    permission_classes = [IsAuthenticated]

    def post(self, request):
        method = request.data.get('method')   # 'nitrogen' | 'even' | 'per_tan'
        param = request.data.get('param')     # 数値パラメータ
        fertilizer_id = request.data.get('fertilizer_id')
        field_ids = request.data.get('field_ids', [])

        if not method or param is None or not field_ids:
            return Response({'error': 'method, param, field_ids が必要です'}, status=status.HTTP_400_BAD_REQUEST)

        try:
            param = Decimal(str(param))
        except InvalidOperation:
            return Response({'error': 'param は数値で指定してください'}, status=status.HTTP_400_BAD_REQUEST)

        fields = Field.objects.filter(id__in=field_ids)
        if not fields.exists():
            return Response({'error': '圃場が見つかりません'}, status=status.HTTP_400_BAD_REQUEST)

        results = []

        if method == 'per_tan':
            # 反当袋数配分: S = Sa × A
            for field in fields:
                area = Decimal(str(field.area_tan))
                bags = (param * area).quantize(Decimal('0.01'))
                results.append({'field_id': field.id, 'bags': float(bags)})

        elif method == 'even':
            # 在庫/指定数量均等配分: S = (SS / Sum(A)) × A
            total_area = sum(Decimal(str(f.area_tan)) for f in fields)
            if total_area == 0:
                return Response({'error': '圃場の面積が0です'}, status=status.HTTP_400_BAD_REQUEST)
            for field in fields:
                area = Decimal(str(field.area_tan))
                bags = (param * area / total_area).quantize(Decimal('0.01'))
                results.append({'field_id': field.id, 'bags': float(bags)})

        elif method == 'nitrogen':
            # 反当チッソ成分量配分: S = (Nr / (C × Nd/100)) × A
            if not fertilizer_id:
                return Response({'error': 'nitrogen 方式には fertilizer_id が必要です'}, status=status.HTTP_400_BAD_REQUEST)
            try:
                fertilizer = Fertilizer.objects.get(id=fertilizer_id)
            except Fertilizer.DoesNotExist:
                return Response({'error': '肥料が見つかりません'}, status=status.HTTP_404_NOT_FOUND)
            if not fertilizer.capacity_kg or not fertilizer.nitrogen_pct:
                return Response(
                    {'error': 'この肥料には1袋重量(kg)と窒素含有率(%)の登録が必要です'},
                    status=status.HTTP_400_BAD_REQUEST
                )
            c = Decimal(str(fertilizer.capacity_kg))
            nd = Decimal(str(fertilizer.nitrogen_pct))
            # 1袋あたりの窒素量 (kg)
            nc = c * nd / Decimal('100')
            if nc == 0:
                return Response({'error': '窒素含有量が0のため計算できません'}, status=status.HTTP_400_BAD_REQUEST)
            for field in fields:
                area = Decimal(str(field.area_tan))
                bags = (param / nc * area).quantize(Decimal('0.01'))
                results.append({'field_id': field.id, 'bags': float(bags)})

        else:
            return Response({'error': 'method は nitrogen / even / per_tan のいずれかです'}, status=status.HTTP_400_BAD_REQUEST)

        return Response(results)


class DeliveryPlanViewSet(viewsets.ModelViewSet):
    permission_classes = [IsAuthenticated]

    def get_queryset(self):
        qs = DeliveryPlan.objects.prefetch_related(
            'groups', 'groups__field_assignments', 'groups__field_assignments__field',
            'trips', 'trips__items', 'trips__items__field', 'trips__items__fertilizer',
        )
        year = self.request.query_params.get('year')
        if year:
            qs = qs.filter(year=year)
        return qs

    def get_serializer_class(self):
        if self.action in ['create', 'update', 'partial_update']:
            return DeliveryPlanWriteSerializer
        if self.action == 'list':
            return DeliveryPlanListSerializer
        return DeliveryPlanReadSerializer

    @action(detail=True, methods=['get'])
    def pdf(self, request, pk=None):
        plan = self.get_object()

        # 全tripのitemから使用肥料を収集
        all_items = DeliveryTripItem.objects.filter(
            trip__delivery_plan=plan
        ).select_related('field', 'fertilizer')

        fert_ids = all_items.values_list('fertilizer_id', flat=True).distinct()
        fertilizers = sorted(
            Fertilizer.objects.filter(id__in=fert_ids),
            key=lambda f: f.name
        )

        # グループ情報: field_id → group_name
        field_group_map = {}
        for gf in DeliveryGroupField.objects.filter(
            delivery_plan=plan
        ).select_related('group', 'field'):
            field_group_map[gf.field_id] = gf.group

        # 回ごとにページを構築
        trip_pages = []
        for trip in plan.trips.prefetch_related('items__field', 'items__fertilizer').all():
            items = trip.items.all()
            if not items:
                continue

            # この回の肥料一覧
            trip_fert_ids = set(item.fertilizer_id for item in items)
            trip_fertilizers = [f for f in fertilizers if f.id in trip_fert_ids]

            # items を (field_id, fertilizer_id) → bags のマトリクスに変換
            item_map = {}
            for item in items:
                item_map[(item.field_id, item.fertilizer_id)] = item.bags

            # グループごとにまとめる
            groups_dict = {}  # group_name → {'group': group, 'fields': [field, ...]}
            ungrouped_fields = []
            for item in items:
                group = field_group_map.get(item.field_id)
                if group:
                    if group.name not in groups_dict:
                        groups_dict[group.name] = {'group': group, 'fields': []}
                    if item.field not in groups_dict[group.name]['fields']:
                        groups_dict[group.name]['fields'].append(item.field)
                else:
                    if item.field not in ungrouped_fields:
                        ungrouped_fields.append(item.field)

            # グループを order 順にソート
            sorted_groups = sorted(groups_dict.values(), key=lambda g: (g['group'].order, g['group'].id))

            group_rows = []
            for g_data in sorted_groups:
                fields_in_group = sorted(g_data['fields'], key=lambda f: (f.display_order, f.id))
                group_totals = []
                for fert in trip_fertilizers:
                    total = sum(
                        item_map.get((f.id, fert.id), Decimal('0'))
                        for f in fields_in_group
                    )
                    group_totals.append(total)

                field_rows = []
                for field in fields_in_group:
                    cells = [item_map.get((field.id, fert.id), '') for fert in trip_fertilizers]
                    field_rows.append({'field': field, 'cells': cells})

                group_rows.append({
                    'name': g_data['group'].name,
                    'totals': group_totals,
                    'field_rows': field_rows,
                })

            # 未グループ圃場
            if ungrouped_fields:
                ungrouped_fields = sorted(ungrouped_fields, key=lambda f: (f.display_order, f.id))
                ua_totals = [
                    sum(item_map.get((f.id, fert.id), Decimal('0')) for f in ungrouped_fields)
                    for fert in trip_fertilizers
                ]
                field_rows = []
                for field in ungrouped_fields:
                    cells = [item_map.get((field.id, fert.id), '') for fert in trip_fertilizers]
                    field_rows.append({'field': field, 'cells': cells})
                group_rows.append({
                    'name': '未グループ',
                    'totals': ua_totals,
                    'field_rows': field_rows,
                })

            fert_totals = [
                sum(r['totals'][i] for r in group_rows)
                for i in range(len(trip_fertilizers))
            ]

            trip_pages.append({
                'trip': trip,
                'fertilizers': trip_fertilizers,
                'group_rows': group_rows,
                'fert_totals': fert_totals,
            })

        context = {
            'plan': plan,
            'trip_pages': trip_pages,
        }
        html_string = render_to_string('fertilizer/delivery_pdf.html', context)
        pdf_file = HTML(string=html_string).write_pdf()
        response = HttpResponse(pdf_file, content_type='application/pdf')
        response['Content-Disposition'] = (
            f'attachment; filename="delivery_{plan.year}_{plan.id}.pdf"'
        )
        return response