import { useState, useEffect } from 'react';
import {
  Dialog,
  DialogTitle,
  DialogContent,
  DialogActions,
  Button,
  FormGroup,
  FormControlLabel,
  Checkbox,
  Typography,
  Alert,
  Box,
} from '@mui/material';
import type { SubscriptionTier } from '../types/subscription.types';
import { getVehicleLabel } from '@/core/utils/vehicleDisplay';

interface Vehicle {
  id: string;
  make?: string;
  model?: string;
  year?: number;
  nickname?: string;
}

interface VehicleSelectionDialogProps {
  open: boolean;
  onClose: () => void;
  onConfirm: (selectedVehicleIds: string[]) => void;
  vehicles: Vehicle[];
  maxSelections: number;
  targetTier: SubscriptionTier;
  /** When true, dialog cannot be dismissed - user must make a selection */
  blocking?: boolean;
}

export const VehicleSelectionDialog = ({
  open,
  onClose,
  onConfirm,
  vehicles,
  maxSelections,
  targetTier,
  blocking = false,
}: VehicleSelectionDialogProps) => {
  const [selectedVehicleIds, setSelectedVehicleIds] = useState<string[]>([]);

  // Pre-select first N vehicles when dialog opens
  useEffect(() => {
    if (open && vehicles.length > 0) {
      const initialSelection = vehicles.slice(0, maxSelections).map((v) => v.id);
      setSelectedVehicleIds(initialSelection);
    }
  }, [open, vehicles, maxSelections]);

  const handleToggle = (vehicleId: string) => {
    setSelectedVehicleIds((prev) => {
      if (prev.includes(vehicleId)) {
        return prev.filter((id) => id !== vehicleId);
      } else {
        // Only add if under the limit
        if (prev.length < maxSelections) {
          return [...prev, vehicleId];
        }
        return prev;
      }
    });
  };

  const handleConfirm = () => {
    onConfirm(selectedVehicleIds);
  };


  const canConfirm = selectedVehicleIds.length > 0 && selectedVehicleIds.length <= maxSelections;

  // Handle dialog close - prevent if blocking
  const handleClose = (_event: object, reason: string) => {
    if (blocking && (reason === 'backdropClick' || reason === 'escapeKeyDown')) {
      return;
    }
    onClose();
  };

  return (
    <Dialog
      open={open}
      onClose={handleClose}
      maxWidth="sm"
      fullWidth
      disableEscapeKeyDown={blocking}
    >
      <DialogTitle>
        {blocking ? 'Vehicle Selection Required' : 'Select Vehicles to Keep'}
      </DialogTitle>
      <DialogContent>
        <Alert severity={blocking ? 'info' : 'warning'} sx={{ mb: 2 }}>
          {blocking ? (
            <>
              Your subscription has been downgraded to the {targetTier} tier, which allows{' '}
              {maxSelections} vehicle{maxSelections > 1 ? 's' : ''}. Please select which vehicles
              you want to keep active to continue using the app. Unselected vehicles will be hidden
              but not deleted, and you can unlock them by upgrading later.
            </>
          ) : (
            <>
              You are downgrading to the {targetTier} tier, which allows {maxSelections} vehicle
              {maxSelections > 1 ? 's' : ''}. Select which vehicles you want to keep active.
              Unselected vehicles will be hidden but not deleted, and you can unlock them by
              upgrading later.
            </>
          )}
        </Alert>

        <Box sx={{ mb: 2 }}>
          <Typography variant="body2" color="text.secondary">
            Selected {selectedVehicleIds.length} of {maxSelections} allowed
          </Typography>
        </Box>

        <FormGroup>
          {vehicles.map((vehicle) => (
            <FormControlLabel
              key={vehicle.id}
              control={
                <Checkbox
                  checked={selectedVehicleIds.includes(vehicle.id)}
                  onChange={() => handleToggle(vehicle.id)}
                  disabled={
                    !selectedVehicleIds.includes(vehicle.id) &&
                    selectedVehicleIds.length >= maxSelections
                  }
                />
              }
              label={getVehicleLabel(vehicle)}
            />
          ))}
        </FormGroup>

        {selectedVehicleIds.length === 0 && (
          <Alert severity="error" sx={{ mt: 2 }}>
            You must select at least one vehicle.
          </Alert>
        )}

        {selectedVehicleIds.length > maxSelections && (
          <Alert severity="error" sx={{ mt: 2 }}>
            You can only select up to {maxSelections} vehicle{maxSelections > 1 ? 's' : ''}.
          </Alert>
        )}
      </DialogContent>
      <DialogActions>
        {!blocking && <Button onClick={onClose}>Cancel</Button>}
        <Button onClick={handleConfirm} variant="contained" disabled={!canConfirm}>
          {blocking ? 'Confirm Selection' : 'Confirm Downgrade'}
        </Button>
      </DialogActions>
    </Dialog>
  );
};