'use client';

import { useState } from 'react';
import { useQuery, useMutation, useQueryClient } from '@tanstack/react-query';
import { Download, Plus, Edit, Trash2, Train as TrainIcon } from 'lucide-react';
import DataTable from '@/components/ui/DataTable';
import Badge from '@/components/ui/Badge';
import ActionButton from '@/components/ui/ActionButton';
import Modal from '@/components/ui/Modal';
import { schedulesApi, fleetApi } from '@/lib/api';
import { routesApi } from '@/lib/api/routes';
import { formatDateTime, formatCurrency } from '@/lib/utils';

export default function SchedulesPage() {
  const [filters, setFilters] = useState({ search: '', status: '' });
  const [showModal, setShowModal] = useState(false);
  const [showCoachModal, setShowCoachModal] = useState(false);
  const [editingSchedule, setEditingSchedule] = useState<any>(null);
  const [selectedSchedule, setSelectedSchedule] = useState<any>(null);
  const [selectedCoaches, setSelectedCoaches] = useState<Array<{ coachId: string; positionNumber: number }>>([]);
  const queryClient = useQueryClient();

  const { data, isLoading } = useQuery({
    queryKey: ['schedules', filters],
    queryFn: () => schedulesApi.getAll(filters),
  });

  const { data: trainsData } = useQuery({
    queryKey: ['trains'],
    queryFn: () => fleetApi.getTrains(),
  });

  const { data: routesData } = useQuery({
    queryKey: ['routes'],
    queryFn: () => routesApi.getAll(),
  });

  const { data: coachesData } = useQuery({
    queryKey: ['coaches'],
    queryFn: () => fleetApi.getCoaches(),
  });

  const createMutation = useMutation({
    mutationFn: schedulesApi.create,
    onSuccess: () => {
      queryClient.invalidateQueries({ queryKey: ['schedules'] });
      setShowModal(false);
      setEditingSchedule(null);
    },
  });

  const updateMutation = useMutation({
    mutationFn: ({ id, data }: { id: string; data: any }) => schedulesApi.update(id, data),
    onSuccess: () => {
      queryClient.invalidateQueries({ queryKey: ['schedules'] });
      setShowModal(false);
      setEditingSchedule(null);
    },
  });

  const deleteMutation = useMutation({
    mutationFn: schedulesApi.delete,
    onSuccess: () => {
      queryClient.invalidateQueries({ queryKey: ['schedules'] });
    },
  });

  const assignCoachesMutation = useMutation({
    mutationFn: ({ scheduleId, coaches }: { scheduleId: string; coaches: Array<{ coachId: string; positionNumber: number }> }) =>
      schedulesApi.assignCoaches(scheduleId, coaches),
    onSuccess: () => {
      queryClient.invalidateQueries({ queryKey: ['schedules'] });
      setShowCoachModal(false);
      setSelectedSchedule(null);
      setSelectedCoaches([]);
      alert('Coaches assigned successfully');
    },
  });

  const removeCoachMutation = useMutation({
    mutationFn: ({ scheduleId, coachId }: { scheduleId: string; coachId: string }) =>
      schedulesApi.removeCoachAssignment(scheduleId, coachId),
    onSuccess: () => {
      queryClient.invalidateQueries({ queryKey: ['schedules'] });
    },
  });

  const handleSubmit = async (e: React.FormEvent<HTMLFormElement>) => {
    e.preventDefault();
    const formData = new FormData(e.currentTarget);
    
    const departureAt = formData.get('departureAt') as string;
    const arrivalAt = formData.get('arrivalAt') as string;
    
    // Convert datetime-local to ISO 8601
    const departureISO = new Date(departureAt).toISOString();
    const arrivalISO = new Date(arrivalAt).toISOString();
    
    const scheduleData = {
      trainId: formData.get('trainId') as string,
      routeId: formData.get('routeId') as string,
      departureAt: departureISO,
      arrivalAt: arrivalISO,
      plannedTimes: [], // Will be auto-generated by backend based on route stops
    };

    if (editingSchedule) {
      await updateMutation.mutateAsync({ id: editingSchedule.id, data: scheduleData });
    } else {
      await createMutation.mutateAsync(scheduleData);
    }
  };

  const trains = trainsData?.items || trainsData?.data || [];
  const routes = routesData?.items || routesData?.data || [];
  const coaches = coachesData?.items || coachesData?.data || [];

  const handleDelete = async (schedule: any) => {
    if (confirm('Are you sure you want to delete this schedule?')) {
      await deleteMutation.mutateAsync(schedule.id);
    }
  };

  const handleAssignCoaches = (schedule: any) => {
    setSelectedSchedule(schedule);
    setSelectedCoaches([]);
    setShowCoachModal(true);
  };

  const handleRemoveCoach = async (schedule: any, coachId: string) => {
    if (confirm('Remove this coach from the schedule?')) {
      await removeCoachMutation.mutateAsync({ scheduleId: schedule.id, coachId });
    }
  };

  const handleToggleCoach = (coachId: string) => {
    setSelectedCoaches(prev => {
      const exists = prev.find(c => c.coachId === coachId);
      if (exists) {
        return prev.filter(c => c.coachId !== coachId);
      } else {
        const maxPosition = prev.length > 0 ? Math.max(...prev.map(c => c.positionNumber)) : 0;
        return [...prev, { coachId, positionNumber: maxPosition + 1 }];
      }
    });
  };

  const handleSubmitCoaches = async () => {
    if (selectedCoaches.length === 0) {
      alert('Please select at least one coach');
      return;
    }
    await assignCoachesMutation.mutateAsync({
      scheduleId: selectedSchedule.id,
      coaches: selectedCoaches,
    });
  };

  const columns = [
    { key: 'train', label: 'Train', render: (schedule: any) => schedule.train?.name || 'N/A' },
    { key: 'route', label: 'Route', render: (schedule: any) => schedule.route?.name || `${schedule.originStation?.name || 'N/A'} → ${schedule.destinationStation?.name || 'N/A'}` },
    { key: 'departureAt', label: 'Departure', render: (schedule: any) => formatDateTime(schedule.departureAt) },
    { 
      key: 'coaches', 
      label: 'Coaches', 
      render: (schedule: any) => {
        const coachCount = schedule._count?.coachAssignments || 0;
        if (coachCount === 0) {
          return <span className="text-sm text-muted-foreground">No coaches assigned</span>;
        }
        return (
          <div className="flex flex-wrap gap-1">
            {schedule.coachAssignments?.slice(0, 3).map((assignment: any) => (
              <div key={assignment.id} className="group relative inline-flex">
                <Badge variant="status" status="CONFIRMED">
                  {assignment.coach?.coachNumber || 'N/A'}
                </Badge>
                <button
                  onClick={(e) => {
                    e.stopPropagation();
                    handleRemoveCoach(schedule, assignment.coach.id);
                  }}
                  className="absolute -top-1 -right-1 hidden group-hover:flex items-center justify-center w-4 h-4 bg-destructive text-destructive-foreground rounded-full text-xs"
                  title="Remove coach"
                >
                  ×
                </button>
              </div>
            ))}
            {coachCount > 3 && (
              <Badge variant="status" status="PENDING">
                +{coachCount - 3}
              </Badge>
            )}
          </div>
        );
      }
    },
    { key: 'status', label: 'Status', render: (schedule: any) => <Badge variant="status" status={schedule.status}>{schedule.status}</Badge> },
  ];

  const actions = [
    {
      label: 'Assign Coaches',
      onClick: handleAssignCoaches,
      variant: 'primary' as const,
      icon: TrainIcon,
    },
    {
      label: 'Edit',
      onClick: (schedule: any) => {
        setEditingSchedule(schedule);
        setShowModal(true);
      },
      variant: 'secondary' as const,
      icon: Edit,
    },
    {
      label: 'Delete',
      onClick: handleDelete,
      variant: 'danger' as const,
      icon: Trash2,
    },
  ];

  return (
    <div className="space-y-6">
      <div className="flex items-center justify-between">
        <div>
          <h1 className="text-2xl font-bold text-foreground">Schedules</h1>
          <p className="text-muted-foreground">Manage train schedules and trips</p>
        </div>
        <div className="flex gap-2">
          <ActionButton icon={Download} variant="secondary">Export</ActionButton>
          <ActionButton
            icon={Plus}
            onClick={() => {
              setEditingSchedule(null);
              setShowModal(true);
            }}
          >
            Add Schedule
          </ActionButton>
        </div>
      </div>

      <div className="card">
        <div className="grid grid-cols-1 md:grid-cols-3 gap-4">
          <div>
            <label className="label">Search</label>
            <input type="text" placeholder="Search..." className="input" value={filters.search} onChange={(e) => setFilters({ ...filters, search: e.target.value })} />
          </div>
          <div>
            <label className="label">Status</label>
            <select className="input" value={filters.status} onChange={(e) => setFilters({ ...filters, status: e.target.value })}>
              <option value="">All Status</option>
              <option value="SCHEDULED">Scheduled</option>
              <option value="ACTIVE">Active</option>
              <option value="COMPLETED">Completed</option>
              <option value="CANCELLED">Cancelled</option>
            </select>
          </div>
        </div>
      </div>

      <DataTable
        data={(data as any)?.items || (Array.isArray(data) ? data : [])}
        columns={columns}
        actions={actions}
        loading={isLoading}
        emptyMessage="No schedules found"
      />

      {/* Add/Edit Modal */}
      <Modal
        isOpen={showModal}
        onClose={() => {
          setShowModal(false);
          setEditingSchedule(null);
        }}
        title={`${editingSchedule ? 'Edit' : 'Add'} Schedule`}
        size="lg"
      >
        <form onSubmit={handleSubmit} className="space-y-4">
          <div className="grid grid-cols-1 gap-4">
            <div>
              <label className="label">Train *</label>
              <select
                name="trainId"
                className="input"
                defaultValue={editingSchedule?.trainId}
                required
              >
                <option value="">Select Train</option>
                {trains.map((train: any) => (
                  <option key={train.id} value={train.id}>
                    {train.trainNumber || train.name}
                  </option>
                ))}
              </select>
            </div>
            <div>
              <label className="label">Route *</label>
              <select
                name="routeId"
                className="input"
                defaultValue={editingSchedule?.routeId}
                required
              >
                <option value="">Select Route</option>
                {routes.map((route: any) => (
                  <option key={route.id} value={route.id}>
                    {route.code} - {route.name}
                  </option>
                ))}
              </select>
            </div>
            <div>
              <label className="label">Departure Time *</label>
              <input
                type="datetime-local"
                name="departureAt"
                className="input"
                defaultValue={editingSchedule?.departureAt?.slice(0, 16)}
                required
              />
            </div>
            <div>
              <label className="label">Arrival Time *</label>
              <input
                type="datetime-local"
                name="arrivalAt"
                className="input"
                defaultValue={editingSchedule?.arrivalAt?.slice(0, 16)}
                required
              />
            </div>
            <div>
              <label className="label">Status</label>
              <select
                name="status"
                className="input"
                defaultValue={editingSchedule?.status || 'SCHEDULED'}
              >
                <option value="SCHEDULED">Scheduled</option>
                <option value="ACTIVE">Active</option>
                <option value="COMPLETED">Completed</option>
                <option value="CANCELLED">Cancelled</option>
              </select>
            </div>
          </div>
          
          <div className="flex justify-end gap-2 pt-4">
            <ActionButton
              type="button"
              variant="secondary"
              onClick={() => {
                setShowModal(false);
                setEditingSchedule(null);
              }}
            >
              Cancel
            </ActionButton>
            <ActionButton
              type="submit"
              loading={createMutation.isPending || updateMutation.isPending}
            >
              {editingSchedule ? 'Update' : 'Create'} Schedule
            </ActionButton>
          </div>
        </form>
      </Modal>

      {/* Coach Assignment Modal */}
      <Modal
        isOpen={showCoachModal}
        onClose={() => {
          setShowCoachModal(false);
          setSelectedSchedule(null);
          setSelectedCoaches([]);
        }}
        title="Assign Coaches to Schedule"
        size="lg"
      >
        <div className="space-y-4">
          <p className="text-sm text-muted-foreground">
            Select coaches to assign to this schedule. Coaches will be ordered by selection.
          </p>

          <div className="grid grid-cols-1 gap-3 max-h-96 overflow-y-auto">
            {coaches.map((coach: any) => {
              const isSelected = selectedCoaches.some(c => c.coachId === coach.id);
              const position = selectedCoaches.find(c => c.coachId === coach.id)?.positionNumber;

              return (
                <div
                  key={coach.id}
                  onClick={() => handleToggleCoach(coach.id)}
                  className={`p-4 border rounded-lg cursor-pointer transition-colors ${
                    isSelected
                      ? 'border-edr-green-600 bg-edr-green-50 dark:bg-edr-green-900/20'
                      : 'border-gray-200 dark:border-gray-700 hover:border-gray-300 dark:hover:border-gray-600'
                  }`}
                >
                  <div className="flex items-center justify-between">
                    <div>
                      <div className="font-medium">{coach.label}</div>
                      <div className="text-sm text-muted-foreground">
                        {coach.coachNumber} • {coach.seatClass?.name || 'N/A'} • {coach.totalUnits} seats
                      </div>
                    </div>
                    {isSelected && (
                      <div className="flex items-center gap-2">
                        <Badge variant="status" status="CONFIRMED">
                          Position {position}
                        </Badge>
                      </div>
                    )}
                  </div>
                </div>
              );
            })}
          </div>

          {selectedCoaches.length > 0 && (
            <div className="p-3 bg-gray-50 dark:bg-gray-800 rounded-lg">
              <div className="text-sm font-medium mb-2">Selected Coaches ({selectedCoaches.length}):</div>
              <div className="flex flex-wrap gap-2">
                {selectedCoaches
                  .sort((a, b) => a.positionNumber - b.positionNumber)
                  .map(sc => {
                    const coach = coaches.find((c: any) => c.id === sc.coachId);
                    return (
                      <Badge key={sc.coachId} variant="status" status="CONFIRMED">
                        {sc.positionNumber}. {coach?.label || 'Unknown'}
                      </Badge>
                    );
                  })}
              </div>
            </div>
          )}

          <div className="flex justify-end gap-2 pt-4">
            <ActionButton
              type="button"
              variant="secondary"
              onClick={() => {
                setShowCoachModal(false);
                setSelectedSchedule(null);
                setSelectedCoaches([]);
              }}
            >
              Cancel
            </ActionButton>
            <ActionButton
              type="button"
              onClick={handleSubmitCoaches}
              loading={assignCoachesMutation.isPending}
              disabled={selectedCoaches.length === 0}
            >
              Assign {selectedCoaches.length} Coach{selectedCoaches.length !== 1 ? 'es' : ''}
            </ActionButton>
          </div>
        </div>
      </Modal>
    </div>
  );
}