import { useState } from 'react';
import { useForm } from 'react-hook-form';
import { zodResolver } from '@hookform/resolvers/zod';
import {
  Box,
  Typography,
  Card,
  CardContent,
  Table,
  TableBody,
  TableCell,
  TableContainer,
  TableHead,
  TableRow,
  TablePagination,
  TextField,
  InputAdornment,
  Button,
  Skeleton,
  IconButton,
  Tooltip,
  Dialog,
  DialogTitle,
  DialogContent,
  DialogActions,
  Alert,
} from '@mui/material';
import SearchIcon from '@mui/icons-material/Search';
import AddIcon from '@mui/icons-material/Add';
import EditIcon from '@mui/icons-material/Edit';
import ErrorOutlineIcon from '@mui/icons-material/ErrorOutlined';
import {
  useCustomerList,
  useCreateCustomer,
  useUpdateCustomer,
} from '../../../domain/customers/use-cases';
import type { Customer } from '../../../domain/customers/types';
import {
  customerFormSchema,
  toCustomerRequest,
  type CustomerFormValues,
} from '../../../domain/customers/schemas';
import { DEFAULT_PAGE, DEFAULT_PAGE_SIZE, DEBOUNCE_SEARCH } from '../../../constants';
import { useDocumentTitle } from '../../../hooks/useDocumentTitle';
import { useDebouncedValue } from '../../../hooks/useDebouncedValue';

const COL_COUNT = 4; // Name, Address, Contact Email, Actions

const EMPTY_FORM: CustomerFormValues = { name: '', address: '', contactEmail: '' };

export default function CustomerManagementPage() {
  useDocumentTitle('Customer Management');

  // --- List state ---
  const [search, setSearch] = useState('');
  const [page, setPage] = useState(DEFAULT_PAGE);
  const [pageSize, setPageSize] = useState(DEFAULT_PAGE_SIZE);

  // Debounced search resets to page 1 (shared hook — the previous inline
  // timer leaked on unmount).
  const debouncedSearch = useDebouncedValue(search, DEBOUNCE_SEARCH, () => setPage(1));
  const handleSearchChange = (value: string) => setSearch(value);

  const { data, isLoading, isError, refetch } = useCustomerList({
    search: debouncedSearch || undefined,
    page,
    pageSize,
  });

  const rows = data?.items ?? [];
  const totalCount = data?.totalCount ?? 0;

  // --- Dialog state ---
  const [dialogOpen, setDialogOpen] = useState(false);
  const [editingCustomer, setEditingCustomer] = useState<Customer | null>(null);

  const isEditing = editingCustomer !== null;

  const {
    register,
    handleSubmit,
    reset,
    formState: { errors },
  } = useForm<CustomerFormValues>({
    resolver: zodResolver(customerFormSchema),
    defaultValues: EMPTY_FORM,
  });

  const openCreateDialog = () => {
    setEditingCustomer(null);
    reset(EMPTY_FORM);
    setDialogOpen(true);
  };

  const openEditDialog = (customer: Customer) => {
    setEditingCustomer(customer);
    reset({
      name: customer.name,
      address: customer.addresses?.[0] ?? '',
      contactEmail: customer.contactEmail ?? '',
    });
    setDialogOpen(true);
  };

  const closeDialog = () => {
    setDialogOpen(false);
    setEditingCustomer(null);
    reset(EMPTY_FORM);
  };

  // --- Mutations (domain hooks: invalidation + toasts live in the hooks) ---
  const createMutation = useCreateCustomer();
  const updateMutation = useUpdateCustomer();

  const onSubmit = (values: CustomerFormValues) => {
    // Fix: WEB-M5 — the API contract is addresses: string[] (CustomerDtos.cs);
    // the old singular `address` field was silently dropped by model binding.
    // The form edits the primary address; any additional addresses are preserved
    // (toCustomerRequest maps to addresses: [primary, ...rest]).
    const payload = toCustomerRequest(values, editingCustomer?.addresses ?? []);

    if (isEditing) {
      updateMutation.mutate(
        { id: editingCustomer.id, data: payload },
        { onSuccess: closeDialog }
      );
    } else {
      createMutation.mutate(payload, { onSuccess: closeDialog });
    }
  };

  const isSaving = createMutation.isPending || updateMutation.isPending;

  return (
    <Box>
      <Box sx={{ display: 'flex', alignItems: 'center', justifyContent: 'space-between', mb: 3 }}>
        <Typography variant="h5">Customer Management</Typography>
        <Button
          variant="contained"
          startIcon={<AddIcon />}
          onClick={openCreateDialog}
        >
          New Customer
        </Button>
      </Box>

      <Card>
        <CardContent sx={{ pb: 0 }}>
          {/* Search bar */}
          <Box sx={{ display: 'flex', gap: 2, mb: 2, flexWrap: 'wrap' }}>
            <TextField
              size="small"
              placeholder="Search customers..."
              value={search}
              onChange={(e) => handleSearchChange(e.target.value)}
              sx={{ width: 300 }}
              slotProps={{
                input: {
                  startAdornment: (
                    <InputAdornment position="start">
                      <SearchIcon fontSize="small" />
                    </InputAdornment>
                  ),
                },
              }}
            />
          </Box>

          {/* Error state */}
          {isError && (
            <Alert
              severity="error"
              icon={<ErrorOutlineIcon />}
              action={
                <Button color="inherit" size="small" onClick={() => refetch()}>
                  Retry
                </Button>
              }
              sx={{ mb: 2 }}
            >
              Failed to load customers. Please try again.
            </Alert>
          )}

          {/* Table */}
          <TableContainer>
            <Table size="small">
              <TableHead>
                <TableRow>
                  <TableCell>Name</TableCell>
                  <TableCell>Address</TableCell>
                  <TableCell>Contact Email</TableCell>
                  <TableCell sx={{ width: 60 }} />
                </TableRow>
              </TableHead>
              <TableBody>
                {isLoading
                  ? Array.from({ length: 5 }).map((_, i) => (
                      <TableRow key={i}>
                        {Array.from({ length: COL_COUNT }).map((_, j) => (
                          <TableCell key={j}>
                            <Skeleton variant="text" />
                          </TableCell>
                        ))}
                      </TableRow>
                    ))
                  : rows.map((customer) => (
                      <TableRow key={customer.id} hover>
                        <TableCell sx={{ fontWeight: 600 }}>{customer.name}</TableCell>
                        <TableCell>{customer.addresses?.[0] ?? '-'}</TableCell>
                        <TableCell>
                          {customer.contactEmail ? (
                            customer.contactEmail
                          ) : (
                            <Typography
                              component="span"
                              sx={{ color: '#94A3B8', fontStyle: 'italic', fontSize: 'inherit' }}
                            >
                              No email
                            </Typography>
                          )}
                        </TableCell>
                        <TableCell>
                          <Tooltip title="Edit customer" arrow>
                            <IconButton
                              size="small"
                              onClick={() => openEditDialog(customer)}
                            >
                              <EditIcon fontSize="small" />
                            </IconButton>
                          </Tooltip>
                        </TableCell>
                      </TableRow>
                    ))}
                {!isLoading && rows.length === 0 && !isError && (
                  <TableRow>
                    <TableCell colSpan={COL_COUNT} align="center" sx={{ py: 4 }}>
                      <Typography color="text.secondary">
                        {debouncedSearch
                          ? 'No customers match your search.'
                          : 'No customers yet. Click "New Customer" to add one.'}
                      </Typography>
                    </TableCell>
                  </TableRow>
                )}
              </TableBody>
            </Table>
          </TableContainer>

          <TablePagination
            component="div"
            count={totalCount}
            page={page - 1}
            onPageChange={(_, newPage) => setPage(newPage + 1)}
            rowsPerPage={pageSize}
            onRowsPerPageChange={(e) => setPageSize(parseInt(e.target.value, 10))}
            rowsPerPageOptions={[12, 24, 48]}
          />
        </CardContent>
      </Card>

      {/* Create / Edit Dialog */}
      <Dialog open={dialogOpen} onClose={closeDialog} maxWidth="sm" fullWidth>
        <form onSubmit={handleSubmit(onSubmit)} noValidate>
          <DialogTitle>{isEditing ? 'Edit Customer' : 'New Customer'}</DialogTitle>
          <DialogContent>
            <Box sx={{ display: 'flex', flexDirection: 'column', gap: 2, mt: 1 }}>
              <TextField
                label="Name"
                {...register('name')}
                error={!!errors.name}
                helperText={errors.name?.message}
                size="small"
                required
                fullWidth
                autoFocus
              />
              <TextField
                label="Address"
                {...register('address')}
                error={!!errors.address}
                helperText={errors.address?.message}
                size="small"
                required
                fullWidth
              />
              <TextField
                label="Contact Email"
                type="email"
                {...register('contactEmail')}
                error={!!errors.contactEmail}
                helperText={errors.contactEmail?.message || 'Optional. Used for proposal PDF delivery.'}
                size="small"
                fullWidth
              />
            </Box>
          </DialogContent>
          <DialogActions>
            <Button onClick={closeDialog} disabled={isSaving}>
              Cancel
            </Button>
            <Button
              type="submit"
              variant="contained"
              disabled={isSaving}
            >
              {isSaving ? (isEditing ? 'Saving...' : 'Creating...') : isEditing ? 'Save Changes' : 'Create Customer'}
            </Button>
          </DialogActions>
        </form>
      </Dialog>
    </Box>
  );
}