import { useState } from 'react';
import { useQuery, useMutation } from '@tanstack/react-query';
import {
  Box,
  Typography,
  Card,
  CardContent,
  Table,
  TableBody,
  TableCell,
  TableContainer,
  TableHead,
  TableRow,
  TablePagination,
  TextField,
  Button,
  Skeleton,
  IconButton,
  Tooltip,
  Dialog,
  DialogTitle,
  DialogContent,
  DialogActions,
  Alert,
  Chip,
  MenuItem,
} from '@mui/material';
import AddIcon from '@mui/icons-material/Add';
import EditIcon from '@mui/icons-material/Edit';
import DeleteIcon from '@mui/icons-material/Delete';
import ErrorOutlineIcon from '@mui/icons-material/ErrorOutlined';
import { toast } from 'react-toastify';
import {
  pricingLibraryApi,
  type PricingLibraryItem,
  type PagedPricingLibraryResponse,
  type CreatePricingLibraryItemRequest,
  type UpdatePricingLibraryItemRequest,
} from '../../../lib/api/pricingLibrary';
import { queryClient } from '../../../lib/queryClient';
import { QUERY_KEYS } from '../../../constants/queryKeys';
import { DEFAULT_PAGE, DEFAULT_PAGE_SIZE, SERVICE_CATEGORIES } from '../../../constants';
import { useDocumentTitle } from '../../../hooks/useDocumentTitle';

const COL_COUNT = 6; // Title, Category, Unit, Unit Price, Source, Actions

/** Chip color mapping for service categories. */
const CATEGORY_CHIP_STYLES: Record<string, { bgcolor: string; color: string; border: string }> = {
  HVAC: { bgcolor: '#E0F2FE', color: '#075985', border: '1px solid #7DD3FC' },
  Plumbing: { bgcolor: '#DBEAFE', color: '#1E40AF', border: '1px solid #BFDBFE' },
  Electrical: { bgcolor: '#FEF9C3', color: '#854D0E', border: '1px solid #FDE68A' },
  General: { bgcolor: '#F3F4F6', color: '#374151', border: '1px solid #D1D5DB' },
  Renovation: { bgcolor: '#F3E8FF', color: '#6B21A8', border: '1px solid #C084FC' },
  Other: { bgcolor: '#F1F5F9', color: '#475569', border: '1px solid #CBD5E1' },
};

interface ItemFormState {
  title: string;
  serviceCategory: string;
  unit: string;
  unitPrice: string;
  keywords: string;
  description: string;
}

const EMPTY_FORM: ItemFormState = {
  title: '',
  serviceCategory: '',
  unit: '',
  unitPrice: '',
  keywords: '',
  description: '',
};

/** Format a number as $X.XX or return "—" for null/undefined. */
function formatPrice(value: number | null | undefined): string {
  if (value == null) return '—';
  return `$${value.toFixed(2)}`;
}

export default function PricingLibraryPage() {
  useDocumentTitle('Pricing Library');

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

  const {
    data,
    isLoading,
    isError,
    refetch,
  } = useQuery<PagedPricingLibraryResponse>({
    queryKey: [QUERY_KEYS.pricingLibraryList, page, pageSize],
    queryFn: () => pricingLibraryApi.list({ page, pageSize }),
  });

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

  // --- Create/Edit dialog state ---
  const [dialogOpen, setDialogOpen] = useState(false);
  const [editingItem, setEditingItem] = useState<PricingLibraryItem | null>(null);
  const [form, setForm] = useState<ItemFormState>(EMPTY_FORM);
  const [formErrors, setFormErrors] = useState<Partial<Record<keyof ItemFormState, string>>>({});

  const isEditing = editingItem !== null;

  const openCreateDialog = () => {
    setEditingItem(null);
    setForm(EMPTY_FORM);
    setFormErrors({});
    setDialogOpen(true);
  };

  const openEditDialog = (item: PricingLibraryItem) => {
    setEditingItem(item);
    setForm({
      title: item.title,
      serviceCategory: item.serviceCategory,
      unit: item.unit ?? '',
      unitPrice: item.unitPrice != null ? String(item.unitPrice) : '',
      keywords: item.keywords ?? '',
      description: item.description ?? '',
    });
    setFormErrors({});
    setDialogOpen(true);
  };

  const closeDialog = () => {
    setDialogOpen(false);
    setEditingItem(null);
    setForm(EMPTY_FORM);
    setFormErrors({});
  };

  const validateForm = (): boolean => {
    const errors: Partial<Record<keyof ItemFormState, string>> = {};
    if (!form.title.trim()) errors.title = 'Title is required';
    if (!form.serviceCategory) errors.serviceCategory = 'Service category is required';
    if (form.unitPrice.trim() !== '') {
      const parsed = parseFloat(form.unitPrice);
      if (isNaN(parsed) || parsed < 0) {
        errors.unitPrice = 'Must be a number >= 0';
      }
    }
    setFormErrors(errors);
    return Object.keys(errors).length === 0;
  };

  const handleFieldChange = (field: keyof ItemFormState, value: string) => {
    setForm((prev) => ({ ...prev, [field]: value }));
    if (formErrors[field]) {
      setFormErrors((prev) => {
        const next = { ...prev };
        delete next[field];
        return next;
      });
    }
  };

  // --- Delete confirm dialog state ---
  const [deleteTarget, setDeleteTarget] = useState<PricingLibraryItem | null>(null);

  const openDeleteDialog = (item: PricingLibraryItem) => {
    setDeleteTarget(item);
  };

  const closeDeleteDialog = () => {
    setDeleteTarget(null);
  };

  // --- Mutations ---
  const createMutation = useMutation({
    mutationFn: (data: CreatePricingLibraryItemRequest) => pricingLibraryApi.create(data),
    onSuccess: () => {
      queryClient.invalidateQueries({ queryKey: [QUERY_KEYS.pricingLibraryList] });
      closeDialog();
      toast.success('Pricing item created');
    },
    onError: (error: Error) => {
      toast.error(`Failed to create item: ${error.message}`);
    },
  });

  const updateMutation = useMutation({
    mutationFn: ({ id, data }: { id: string; data: UpdatePricingLibraryItemRequest }) =>
      pricingLibraryApi.update(id, data),
    onSuccess: () => {
      queryClient.invalidateQueries({ queryKey: [QUERY_KEYS.pricingLibraryList] });
      closeDialog();
      toast.success('Pricing item updated');
    },
    onError: (error: Error) => {
      toast.error(`Failed to update item: ${error.message}`);
    },
  });

  const deleteMutation = useMutation({
    mutationFn: (id: string) => pricingLibraryApi.remove(id),
    onSuccess: () => {
      queryClient.invalidateQueries({ queryKey: [QUERY_KEYS.pricingLibraryList] });
      closeDeleteDialog();
      toast.success('Pricing item deleted');
    },
    onError: (error: Error) => {
      toast.error(`Failed to delete item: ${error.message}`);
    },
  });

  const handleSubmit = () => {
    if (!validateForm()) return;

    const payload = {
      title: form.title.trim(),
      serviceCategory: form.serviceCategory,
      ...(form.unit.trim() ? { unit: form.unit.trim() } : {}),
      unitPrice: form.unitPrice.trim() !== '' ? parseFloat(form.unitPrice) : null,
      ...(form.keywords.trim() ? { keywords: form.keywords.trim() } : {}),
      ...(form.description.trim() ? { description: form.description.trim() } : {}),
    };

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

  const handleDeleteConfirm = () => {
    if (deleteTarget) {
      deleteMutation.mutate(deleteTarget.id);
    }
  };

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

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

      <Card>
        <CardContent sx={{ pb: 0 }}>
          {/* Error state */}
          {isError && (
            <Alert
              severity="error"
              icon={<ErrorOutlineIcon />}
              action={
                <Button color="inherit" size="small" onClick={() => refetch()}>
                  Retry
                </Button>
              }
              sx={{ mb: 2 }}
            >
              Failed to load pricing library. Please try again.
            </Alert>
          )}

          {/* Table */}
          <TableContainer>
            <Table size="small">
              <TableHead>
                <TableRow>
                  <TableCell>Title</TableCell>
                  <TableCell>Category</TableCell>
                  <TableCell>Unit</TableCell>
                  <TableCell sx={{ textAlign: 'right' }}>Unit Price</TableCell>
                  <TableCell>Source</TableCell>
                  <TableCell sx={{ width: 100 }} />
                </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((item) => {
                      const defaultChip = { bgcolor: '#F1F5F9', color: '#475569', border: '1px solid #CBD5E1' };
                      const chipStyle = CATEGORY_CHIP_STYLES[item.serviceCategory] ?? defaultChip;
                      return (
                        <TableRow key={item.id} hover>
                          <TableCell sx={{ fontWeight: 600 }}>{item.title}</TableCell>
                          <TableCell>
                            <Chip
                              label={item.serviceCategory}
                              size="small"
                              sx={{
                                bgcolor: chipStyle.bgcolor,
                                color: chipStyle.color,
                                border: chipStyle.border,
                                fontWeight: 600,
                                fontSize: '12px',
                              }}
                            />
                          </TableCell>
                          <TableCell>{item.unit ?? '—'}</TableCell>
                          <TableCell sx={{ textAlign: 'right', fontVariantNumeric: 'tabular-nums' }}>
                            {formatPrice(item.unitPrice)}
                          </TableCell>
                          <TableCell>{item.source}</TableCell>
                          <TableCell>
                            <Box sx={{ display: 'flex', gap: 0.5 }}>
                              <Tooltip title="Edit item" arrow>
                                <IconButton
                                  size="small"
                                  onClick={() => openEditDialog(item)}
                                >
                                  <EditIcon fontSize="small" />
                                </IconButton>
                              </Tooltip>
                              <Tooltip title="Delete item" arrow>
                                <IconButton
                                  size="small"
                                  onClick={() => openDeleteDialog(item)}
                                  color="error"
                                >
                                  <DeleteIcon fontSize="small" />
                                </IconButton>
                              </Tooltip>
                            </Box>
                          </TableCell>
                        </TableRow>
                      );
                    })}
                {!isLoading && rows.length === 0 && !isError && (
                  <TableRow>
                    <TableCell colSpan={COL_COUNT} align="center" sx={{ py: 4 }}>
                      <Typography color="text.secondary">
                        No pricing items yet. Click &quot;New Item&quot; 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>
        <DialogTitle>{isEditing ? 'Edit Pricing Item' : 'New Pricing Item'}</DialogTitle>
        <DialogContent>
          <Box sx={{ display: 'flex', flexDirection: 'column', gap: 2, mt: 1 }}>
            <TextField
              label="Title"
              value={form.title}
              onChange={(e) => handleFieldChange('title', e.target.value)}
              error={!!formErrors.title}
              helperText={formErrors.title}
              size="small"
              required
              fullWidth
              autoFocus
            />
            <TextField
              label="Service Category"
              value={form.serviceCategory}
              onChange={(e) => handleFieldChange('serviceCategory', e.target.value)}
              error={!!formErrors.serviceCategory}
              helperText={formErrors.serviceCategory}
              size="small"
              required
              fullWidth
              select
            >
              {SERVICE_CATEGORIES.map((cat) => (
                <MenuItem key={cat} value={cat}>
                  {cat}
                </MenuItem>
              ))}
            </TextField>
            <TextField
              label="Unit"
              value={form.unit}
              onChange={(e) => handleFieldChange('unit', e.target.value)}
              helperText="e.g., each, hour, sq ft"
              size="small"
              fullWidth
            />
            <TextField
              label="Unit Price"
              type="number"
              value={form.unitPrice}
              onChange={(e) => handleFieldChange('unitPrice', e.target.value)}
              error={!!formErrors.unitPrice}
              helperText={formErrors.unitPrice || 'Optional. Leave blank if price varies.'}
              size="small"
              fullWidth
              slotProps={{
                htmlInput: { min: 0, step: '0.01' },
              }}
            />
            <TextField
              label="Keywords"
              value={form.keywords}
              onChange={(e) => handleFieldChange('keywords', e.target.value)}
              helperText="Comma-separated keywords for AI matching."
              size="small"
              fullWidth
              multiline
              minRows={2}
            />
            <TextField
              label="Description"
              value={form.description}
              onChange={(e) => handleFieldChange('description', e.target.value)}
              size="small"
              fullWidth
              multiline
              minRows={2}
            />
          </Box>
        </DialogContent>
        <DialogActions>
          <Button onClick={closeDialog} disabled={isSaving}>
            Cancel
          </Button>
          <Button
            variant="contained"
            onClick={handleSubmit}
            disabled={isSaving}
          >
            {isSaving ? (isEditing ? 'Saving...' : 'Creating...') : isEditing ? 'Save Changes' : 'Create Item'}
          </Button>
        </DialogActions>
      </Dialog>

      {/* Delete Confirm Dialog */}
      <Dialog open={deleteTarget !== null} onClose={closeDeleteDialog} maxWidth="xs" fullWidth>
        <DialogTitle>Delete Pricing Item</DialogTitle>
        <DialogContent>
          <Typography>
            Are you sure you want to delete <strong>{deleteTarget?.title}</strong>? This action cannot be undone.
          </Typography>
        </DialogContent>
        <DialogActions>
          <Button onClick={closeDeleteDialog} disabled={deleteMutation.isPending}>
            Cancel
          </Button>
          <Button
            variant="contained"
            color="error"
            onClick={handleDeleteConfirm}
            disabled={deleteMutation.isPending}
          >
            {deleteMutation.isPending ? 'Deleting...' : 'Delete'}
          </Button>
        </DialogActions>
      </Dialog>
    </Box>
  );
}