from collections import Counter
from django.contrib import messages
from django.contrib.admin.models import LogEntry
from django.contrib.auth import get_user_model
from django.contrib.auth.decorators import login_required
from django.contrib.contenttypes.models import ContentType
from django.db.models import Count
from django.db.models.functions import TruncMonth
from django.http import HttpResponseForbidden
from django.shortcuts import get_object_or_404, redirect, render
from django.utils.translation import gettext_lazy as _
from rest_framework import viewsets
from rest_framework.permissions import IsAuthenticated

from .forms import RiskStatusForm, ControlStatusForm, IncidentStatusForm, ResidualReviewForm
from .models import AuditLog, Risk, Control, ResidualRisk, AuditLog, Incident, Notification
from .serializers import (
    ControlSerializer, RiskSerializer, ResidualRiskSerializer,
    UserSerializer, AuditSerializer, IncidentSerializer,
)

User = get_user_model()


# ---------------------------------------------------------------------------
# Helpers
# ---------------------------------------------------------------------------
def _can_edit_risk(user, risk: Risk) -> bool:
    return bool(user.is_staff or (risk.owner_id and risk.owner_id == user.id))


def _can_edit_control(user, control: Control) -> bool:
    return bool(user.is_staff or (control.responsible_id and control.responsible_id == user.id))


def _can_edit_incident(user, incident: Incident) -> bool:
    return bool(user.is_staff or (incident.reported_by_id and incident.reported_by_id == user.id))


# ---------------------------------------------------------------------------
# API ViewSets
# ---------------------------------------------------------------------------
class _ChangedByMixin:
    """Mixin to track user who changed an object."""
    def perform_create(self, serializer):
        instance = serializer.save()
        instance._changed_by = self.request.user

    def perform_update(self, serializer):
        instance = serializer.save()
        instance._changed_by = self.request.user


class RiskViewSet(_ChangedByMixin, viewsets.ModelViewSet):
    """API endpoint for managing Risks."""
    queryset = Risk.objects.all()
    serializer_class = RiskSerializer
    permission_classes = [IsAuthenticated]

    def perform_create(self, serializer):
        instance = serializer.save()
        instance._changed_by = self.request.user
        instance.save(update_fields=[])

    def perform_update(self, serializer):
        instance = serializer.save()
        instance._changed_by = self.request.user
        instance.save(update_fields=[])

class ControlViewSet(_ChangedByMixin, viewsets.ModelViewSet):
    """API endpoint for managing Controls."""
    queryset = Control.objects.all()
    serializer_class = ControlSerializer
    permission_classes = [IsAuthenticated]

    def perform_create(self, serializer):
        instance = serializer.save()
        instance._changed_by = self.request.user
        instance.save(update_fields=[])

    def perform_update(self, serializer):
        instance = serializer.save()
        instance._changed_by = self.request.user
        instance.save(update_fields=[])

class ResidualRiskViewSet(viewsets.ModelViewSet):
    """API endpoint for Residual Risks."""
    queryset = ResidualRisk.objects.all()
    serializer_class = ResidualRiskSerializer
    permission_classes = [IsAuthenticated]

    def perform_create(self, serializer):
        instance = serializer.save()
        instance._changed_by = self.request.user
        instance.save(update_fields=[])

    def perform_update(self, serializer):
        instance = serializer.save()
        instance._changed_by = self.request.user
        instance.save(update_fields=[])

class UserViewSet(_ChangedByMixin, viewsets.ReadOnlyModelViewSet):
    """API endpoint for listing users and their responsibilities."""
    queryset = User.objects.all()
    serializer_class = UserSerializer
    permission_classes = [IsAuthenticated]

    def perform_create(self, serializer):
        instance = serializer.save()
        instance._changed_by = self.request.user
        instance.save(update_fields=[])

    def perform_update(self, serializer):
        instance = serializer.save()
        instance._changed_by = self.request.user
        instance.save(update_fields=[])

class AuditViewSet(viewsets.ReadOnlyModelViewSet):
    """API endpoint for viewing audit logs."""
    queryset = AuditLog.objects.all()
    serializer_class = AuditSerializer
    permission_classes = [IsAuthenticated]


class IncidentViewSet(_ChangedByMixin, viewsets.ModelViewSet):
    """API endpoint for listing incidents and their related risks."""
    queryset = Incident.objects.all()
    serializer_class = IncidentSerializer
    permission_classes = [IsAuthenticated]

    def perform_create(self, serializer):
        instance = serializer.save(reported_by=self.request.user)
        instance._changed_by = self.request.user

    def perform_create(self, serializer):
        instance = serializer.save()
        instance._changed_by = self.request.user
        instance.save(update_fields=[])

    def perform_update(self, serializer):
        instance = serializer.save()
        instance._changed_by = self.request.user
        instance.save(update_fields=[])

# ---------------------------------------------------------------------------
# Web Views: Risks
# ---------------------------------------------------------------------------
@login_required
def list_risks(request):
    """List all risks with filters and sorting."""
    qs = Risk.objects.all().select_related("owner", "residual_risk")

    # Filters
    filters = {
        "id": request.GET.get("risk"),
        "controls__id": request.GET.get("control"),
        "owner_id": request.GET.get("owner"),
        "category": request.GET.get("category"),
        "asset": request.GET.get("asset"),
        "process": request.GET.get("process"),
    }
    qs = qs.filter(**{k: v for k, v in filters.items() if v})

    # Sorting
    sort = request.GET.get("sort") or "title"
    direction = request.GET.get("dir") or "asc"
    qs = qs.order_by(f"-{sort}" if direction == "desc" else sort)

    risks = qs.distinct()

    return render(request, "risks/list_risks.html", {
        "risks": risks,
        "risk_choices": Risk.objects.all().order_by("title"),
        "control_choices": Control.objects.all().order_by("title"),
        "owner_choices": User.objects.filter(owned_risks__isnull=False).distinct().order_by("username"),
        "category_choices": (Risk.objects.exclude(category__isnull=True).exclude(category__exact="")
                             .values_list("category", flat=True).distinct().order_by("category")),
        "asset_choices": (Risk.objects.exclude(asset__isnull=True).exclude(asset__exact="")
                          .values_list("asset", flat=True).distinct().order_by("asset")),
        "process_choices": (Risk.objects.exclude(process__isnull=True).exclude(process__exact="")
                            .values_list("process", flat=True).distinct().order_by("process")),
        "current_sort": sort,
        "current_dir": direction,
    })


@login_required
def show_risk(request, id):
    """Show single risk details + logs."""
    risk = get_object_or_404(
        Risk.objects.select_related("residual_risk", "owner").prefetch_related("controls"),
        pk=id,
    )
    ct = ContentType.objects.get_for_model(Risk)
    logs = LogEntry.objects.filter(content_type=ct, object_id=risk.pk).order_by("-action_time")
    return render(request, "risks/item_risk.html", {"risk": risk, "logs": logs})

@login_required
def mark_risk_reviewed(request, pk):
    """Mark a risk as reviewed and close if all controls are completed."""
    risk = get_object_or_404(Risk, pk=pk)
    all_done = all(c.status in ("completed", "verified") for c in risk.controls.all())

    if all_done:
        risk.status = "closed"
        risk._changed_by = request.user
        risk.save(update_fields=["status", "updated_at"])

        # ➜ AuditLog schreiben
        AuditLog.objects.create(
            user=request.user,
            action="reviewed",
            model="Risk",
            object_id=risk.pk,
            changes={"status": {"old": "review_required", "new": "closed"}},
        )

        messages.success(request, _("Risk has been marked as reviewed and closed."))
    else:
        messages.error(request, _("Not all controls are completed. Risk cannot be closed yet."))

    return redirect("risks:show_risk", id=risk.pk)

# ---------------------------------------------------------------------------
# Web Views: Controls
# ---------------------------------------------------------------------------
@login_required
def list_controls(request):
    """List all controls with filters."""
    qs = Control.objects.all().select_related("responsible")

    filters = {
        "id": request.GET.get("control"),
        "risks__id": request.GET.get("risk"),
        "status": request.GET.get("status"),
        "responsible_id": request.GET.get("responsible"),
    }
    qs = qs.filter(**{k: v for k, v in filters.items() if v})

    controls = qs.order_by("title").distinct()

    return render(request, "risks/list_controls.html", {
        "controls": controls,
        "control_choices": Control.objects.all().order_by("title"),
        "risk_choices": Risk.objects.all().order_by("title"),
        "responsible_choices": User.objects.filter(responsible_controls__isnull=False).distinct().order_by("username"),
        "status_choices": Control.STATUS_CHOICES,
    })


@login_required
def show_control(request, id):
    """Show single control details + logs."""
    control = get_object_or_404(Control, pk=id)
    ct = ContentType.objects.get_for_model(Control)
    logs = LogEntry.objects.filter(content_type=ct, object_id=control.pk).order_by("-action_time")
    return render(request, "risks/item_control.html", {"control": control, "logs": logs})


# ---------------------------------------------------------------------------
# Web Views: Incidents
# ---------------------------------------------------------------------------
@login_required
def list_incidents(request):
    """List all incidents with filters."""
    qs = Incident.objects.all().select_related("reported_by").prefetch_related("related_risks")

    filters = {
        "related_risks__id": request.GET.get("risk"),
        "status": request.GET.get("status"),
        "reported_by": request.GET.get("reported_by"),
    }
    qs = qs.filter(**{k: v for k, v in filters.items() if v})

    incidents = qs.order_by("title").distinct()

    return render(request, "risks/list_incidents.html", {
        "incidents": incidents,
        "incident_choices": incidents,
        "risk_choices": Risk.objects.all().order_by("title"),
        "user_choices": User.objects.filter(incidents__isnull=False).distinct().order_by("username"),
        "status_choices": Incident.STATUS_CHOICES,
    })


@login_required
def show_incident(request, id):
    """Show single incident details + logs."""
    incident = get_object_or_404(Incident, pk=id)
    ct = ContentType.objects.get_for_model(Incident)
    logs = LogEntry.objects.filter(content_type=ct, object_id=incident.pk).order_by("-action_time")
    return render(request, "risks/item_incident.html", {"incident": incident, "logs": logs})


# ---------------------------------------------------------------------------
# Dashboard
# ---------------------------------------------------------------------------
@login_required
def dashboard(request):
    # Bestehende KPIs
    risks_total = Risk.objects.count()
    risks_by_level = Risk.objects.values("level").annotate(count=Count("id"))

    # CIA Counter
    risks_cia = Risk.objects.values_list("cia", flat=True)
    cia_counter = Counter()
    for cia_list in risks_cia:
        if isinstance(cia_list, list):
            for c in cia_list:
                cia_counter[c] += 1
        elif cia_list:
            cia_counter[cia_list] += 1

    # Residual Risks
    residual_review_required = ResidualRisk.objects.filter(review_required=True).count()

    # Controls & Incidents
    controls_by_status = Control.objects.values("status").annotate(count=Count("id"))
    incidents_status = Incident.objects.values("status").annotate(count=Count("id"))

    # Notifications
    notifications_unread = Notification.objects.filter(user=request.user, read=False).count()

    # Risks by Level per Month (Trend)
    risks_trend_qs = (
        Risk.objects.annotate(month=TruncMonth("created_at"))
        .values("month", "level")
        .annotate(count=Count("id"))
        .order_by("month")
    )

    # Daten für ChartJS vorbereiten
    months = sorted(set(r["month"].strftime("%Y-%m") for r in risks_trend_qs if r["month"]))
    levels = {r["level"] for r in risks_trend_qs}

    trend_data = {lvl: [0] * len(months) for lvl in levels}
    for r in risks_trend_qs:
        if r["month"]:
            idx = months.index(r["month"].strftime("%Y-%m"))
            trend_data[r["level"]][idx] = r["count"]

    context = {
        "risks_total": risks_total,
        "risks_by_level": risks_by_level,
        "risks_by_cia": dict(cia_counter),
        "residual_review_required": residual_review_required,
        "controls_by_status": controls_by_status,
        "incidents_status": incidents_status,
        "notifications_unread": notifications_unread,
        # Trend-Daten
        "months": months,
        "trend_data": trend_data,
    }
    return render(request, "risks/dashboard.html", context)


# ---------------------------------------------------------------------------
# Notifications
# ---------------------------------------------------------------------------
@login_required
def notifications(request):
    """View own notifications with optional filter."""
    flt = request.GET.get("filter", "unread")
    qs = Notification.objects.filter(user=request.user).order_by("-created_at")
    if flt == "unread":
        qs = qs.filter(read=False)
    return render(request, "risks/notifications.html", {"notifications": qs, "filter": flt})


@login_required
def notification_mark_read(request, pk):
    """Mark single notification as read."""
    if request.method != "POST":
        return HttpResponseForbidden()
    notif = get_object_or_404(Notification, pk=pk, user=request.user)
    notif.read = True
    notif.save(update_fields=["read"])
    #messages.success(request, _("Notification marked as read."))
    return redirect(request.META.get("HTTP_REFERER") or "risks:notifications")


@login_required
def notification_mark_all_read(request):
    """Mark all notifications as read."""
    if request.method != "POST":
        return HttpResponseForbidden()
    Notification.objects.filter(user=request.user, read=False).update(read=True)
    #messages.success(request, _("All notifications marked as read."))
    return redirect("risks:notifications")


# ---------------------------------------------------------------------------
# Status Updates
# ---------------------------------------------------------------------------
@login_required
def update_risk_status(request, id):
    """Update risk status."""
    risk = get_object_or_404(Risk, pk=id)
    if not _can_edit_risk(request.user, risk):
        return HttpResponseForbidden()
    if request.method == "POST":
        form = RiskStatusForm(request.POST, instance=risk)
        if form.is_valid():
            obj = form.save(commit=False)
            obj._changed_by = request.user
            obj.save(update_fields=["status", "updated_at"])
            messages.success(request, _("Risk status updated."))
    return redirect("risks:show_risk", id=risk.pk)


@login_required
def update_control_status(request, id):
    """Update control status."""
    control = get_object_or_404(Control, pk=id)
    if not _can_edit_control(request.user, control):
        return HttpResponseForbidden()
    if request.method == "POST":
        form = ControlStatusForm(request.POST, instance=control)
        if form.is_valid():
            obj = form.save(commit=False)
            obj._changed_by = request.user
            obj.save(update_fields=["status", "updated_at"])
            messages.success(request, _("Control status updated."))
    return redirect("risks:show_control", id=control.pk)


@login_required
def update_incident_status(request, id):
    """Update incident status."""
    incident = get_object_or_404(Incident, pk=id)
    if not _can_edit_incident(request.user, incident):
        return HttpResponseForbidden()
    if request.method == "POST":
        form = IncidentStatusForm(request.POST, instance=incident)
        if form.is_valid():
            obj = form.save(commit=False)
            obj._changed_by = request.user
            obj.save(update_fields=["status", "updated_at"])
            messages.success(request, _("Incident status updated."))
    return redirect("risks:show_incident", id=incident.pk)


@login_required
def update_residual_review(request, risk_id):
    """Toggle residual risk review flag."""
    risk = get_object_or_404(Risk, pk=risk_id)
    if not _can_edit_risk(request.user, risk):
        return HttpResponseForbidden()
    residual, _ = ResidualRisk.objects.get_or_create(risk=risk)
    if request.method == "POST":
        form = ResidualReviewForm(request.POST, instance=residual)
        if form.is_valid():
            obj = form.save(commit=False)
            obj._changed_by = request.user
            obj.save(update_fields=["review_required", "updated_at"])
            messages.success(request, _("Residual review flag updated."))
    return redirect("risks:show_risk", id=risk.pk)


# ---------------------------------------------------------------------------
# Risk Matrix
# ---------------------------------------------------------------------------
def risk_matrix(request):
    """Show gross/net risk matrix."""
    risks = Risk.objects.select_related("owner", "residual_risk").all()
    impacts = sorted(Risk.IMPACT_CHOICES, key=lambda x: x[0])
    likelihoods = sorted(Risk.LIKELIHOOD_CHOICES, key=lambda x: x[0])

    gross_matrix = {i: {l: [] for l, _ in likelihoods} for i, _ in impacts}
    net_matrix = {i: {l: [] for l, _ in likelihoods} for i, _ in impacts}

    for r in risks:
        gross_matrix[r.impact][r.likelihood].append(r)
        rr = getattr(r, "residual_risk", None)
        if rr:
            net_matrix[rr.impact][rr.likelihood].append(r)

    return render(request, "risks/risk_matrix.html", {
        "impacts": impacts,
        "likelihoods": likelihoods,
        "gross_matrix": gross_matrix,
        "net_matrix": net_matrix,
    })