import { useState, useEffect, useMemo } from "react";
import { useQueryClient } from "@tanstack/react-query";
import { useNavigate, useParams } from "react-router-dom";
import { useSelector } from "react-redux";
import { createPageUrl } from "@/lib/index";
import { Button } from "@/common/components/ui/button";
import { Loader2, AlertTriangle } from "lucide-react";
import DashboardLayout from "@/features/layouts/DashboardLayout";
import OrderReductionAlert from "./components/OrderReductionAlert";
import EventFormWizard from "./components/EventFormWizard";
import { useToast } from "@/common/components/ui/use-toast";
import { useGetOrderById, useUpdateOrder, useListStaff } from "@/dataconnect-generated/react";
import { dataConnect } from "@/features/auth/firebase";
import type { RootState } from "@/store/store";


export default function EditOrder() {
  const navigate = useNavigate();
  const queryClient = useQueryClient();
  const { toast } = useToast();
  const { id: eventId } = useParams<{ id: string }>();
  const { user } = useSelector((state: RootState) => state.auth);

  const [showReductionAlert, setShowReductionAlert] = useState(false);
  const [pendingUpdate, setPendingUpdate] = useState<any>(null);
  const [originalRequested, setOriginalRequested] = useState(0);

  const { data: orderData, isLoading: isOrderLoading } = useGetOrderById(
    dataConnect,
    { id: eventId || "" },
    { enabled: !!eventId }
  );

  const event = orderData?.order;

  const { data: staffData } = useListStaff(dataConnect);
  const allStaff = staffData?.staffs || [];

  useEffect(() => {
    if (event) {
      setOriginalRequested(event.requested || 0);
    }
  }, [event]);

  const updateOrderMutation = useUpdateOrder(dataConnect, {
    onSuccess: () => {
      queryClient.invalidateQueries({ queryKey: ["listOrders"] });
      queryClient.invalidateQueries({ queryKey: ["getOrderById", { id: eventId }] });
      toast({
        title: "✅ Order Updated",
        description: "Your changes have been saved successfully.",
      });
      navigate(createPageUrl("Events"));
    },
    onError: (error) => {
      toast({
        title: "❌ Update Failed",
        description: error.message || "Could not update the order. Please try again.",
        variant: "destructive",
      });
    },
  });

  const canModify = useMemo(() => {
    if (!event) return false;
    if (!event.startDate) return true;
    const startTime = new Date(event.startDate);
    return startTime > new Date();
  }, [event]);

  const handleSubmit = (eventData: any) => {
    if (!canModify) {
      toast({
        title: "Cannot Edit Order",
        description: "This order has already started and cannot be modified.",
        variant: "destructive",
      });
      return;
    }

    // CRITICAL: Recalculate requested count from current roles
    const totalRequested = eventData.shifts.reduce((sum: number, shift: any) => {
      const roles = Array.isArray(shift.roles) ? shift.roles : [];
      return sum + roles.reduce((roleSum: number, role: any) => roleSum + (parseInt(role.count) || 0), 0);
    }, 0);

    const assignedStaff = Array.isArray(event?.assignedStaff) ? event!.assignedStaff : [];
    const assignedCount = assignedStaff.length;
    const isVendor = user?.userRole === 'vendor' || (user as any)?.role === 'vendor';

    // If client is reducing headcount and vendor has already assigned staff
    if (!isVendor && totalRequested < originalRequested && assignedCount > totalRequested) {
      setPendingUpdate({ ...eventData, requested: totalRequested });
      setShowReductionAlert(true);

      toast({
        title: "⚠️ Headcount Reduced",
        description: "Assigned staff exceeds new headcount. Please resolve assignments.",
      });
      return;
    }

    if (eventId) {
      // Normal update
      updateOrderMutation.mutate({
        id: eventId,
        eventName: eventData.event_name,
        date: eventData.date,
        startDate: eventData.startDate || eventData.date,
        endDate: eventData.endDate,
        notes: eventData.notes,
        shifts: eventData.shifts,
        requested: totalRequested,
        total: eventData.total,
        poReference: eventData.po_reference,
      } as any);
    }
  };

  const handleAutoUnassign = async () => {
    if (!pendingUpdate || !event || !eventId) return;

    const assignedStaff = Array.isArray(event.assignedStaff) ? (event.assignedStaff as any[]) : [];
    const excessCount = assignedStaff.length - pendingUpdate.requested;

    // Calculate reliability scores for assigned staff
    const staffWithScores = assignedStaff.map(assigned => {
      const staffInfo = allStaff.find(s => s.id === assigned.staff_id || s.id === assigned.staffId);
      return {
        ...assigned,
        reliability: staffInfo?.averageRating ? staffInfo.averageRating * 20 : 50, // Convert 0-5 to 0-100
      };
    });

    // Sort by reliability (lowest first)
    staffWithScores.sort((a: any, b: any) => a.reliability - b.reliability);

    // Remove lowest reliability staff
    const staffToKeep = staffWithScores.slice(excessCount);

    await updateOrderMutation.mutateAsync({
      id: eventId,
      ...pendingUpdate,
      assignedStaff: staffToKeep.map((s: any) => ({
        staffId: s.staffId || s.staff_id,
        staffName: s.staffName || s.staff_name,
        role: s.role
      }))
    } as any);

    setShowReductionAlert(false);
    setPendingUpdate(null);

    toast({
      title: "✅ Staff Auto-Unassigned",
      description: `Removed ${excessCount} lowest reliability staff members`,
    });
  };

  const handleManualUnassign = () => {
    setShowReductionAlert(false);
    toast({
      title: "Manual Adjustment Required",
      description: "Please manually remove excess staff from the order",
    });
  };

  if (isOrderLoading) {
    return (
      <div className="flex items-center justify-center min-h-[400px]">
        <Loader2 className="w-8 h-8 animate-spin text-primary" />
      </div>
    );
  }

  if (!event) {
    return (
      <div className="p-12 text-center">
        <h2 className="text-2xl font-bold text-primary-text mb-4">Event Not Found</h2>
        <Button onClick={() => navigate(createPageUrl("Events"))}>
          Back to Events
        </Button>
      </div>
    );
  }

  return (
    <DashboardLayout
      title={`Edit ${event.eventName || "Order"}`}
      subtitle="Update information for your order"
    >
      <div className="max-w-7xl mx-auto">
        {!canModify && (
          <div className="mb-6 p-4 bg-amber-50 border border-amber-200 rounded-xl flex items-center gap-3 text-amber-800">
            <AlertTriangle className="w-5 h-5 flex-shrink-0" />
            <p className="text-sm font-medium">
              This order has already started. Some details may no longer be editable for security and tracking purposes.
            </p>
          </div>
        )}

        {showReductionAlert && pendingUpdate && (
          <div className="mb-6">
            <OrderReductionAlert
              originalRequested={originalRequested}
              newRequested={pendingUpdate.requested}
              currentAssigned={Array.isArray(event.assignedStaff) ? event.assignedStaff.length : 0}
              onAutoUnassign={handleAutoUnassign}
              onManualUnassign={handleManualUnassign}
              lowReliabilityStaff={(Array.isArray(event.assignedStaff) ? event.assignedStaff : []).map((assigned: any) => {
                const staffInfo = allStaff.find(s => s.id === assigned.staffId || s.id === assigned.staff_id);
                return {
                  name: assigned.staffName || assigned.staff_name,
                  reliability: staffInfo?.averageRating ? staffInfo.averageRating * 20 : 50
                };
              }).sort((a, b) => a.reliability - b.reliability)}
            />
          </div>
        )}

        <EventFormWizard
          event={event as any}
          onSubmit={handleSubmit}
          isSubmitting={updateOrderMutation.isPending}
          currentUser={user as any}
          onCancel={() => navigate(createPageUrl("Events"))}
        />
      </div>
    </DashboardLayout>
  );
}