import { useState } from "react";
import { useParams, Link as RouterLink } from "react-router-dom";
import { useQuery } from "@tanstack/react-query";
import Box from "@mui/material/Box";
import Typography from "@mui/material/Typography";
import { useAlert } from "../context/AlertContext";
import { useAuth } from "../context/AuthContext";
import Forbidden from "../components/Forbidden";

import { formatDate } from "../utils/formatters";
import {
  warehouseInventoryDetailOptions,
  type WarehouseInventorySession,
  type WarehouseInventoryItem,
} from "../lib/queries/warehouse";
import { useApiMutation } from "../lib/queries/mutations";
import {
  Button,
  Card,
  DataTable,
  StatusChip,
  EmptyState,
  LoadingState,
  PageHeader,
  PageEnter,
  ConfirmDialog,
  headerActionsSx,
  type DataColumn,
} from "../ui";

const STATUS_COLOR: Record<
  string,
  "default" | "success" | "error" | "warning" | "info"
> = {
  DRAFT: "warning",
  CONFIRMED: "success",
};

const STATUS_LABEL: Record<string, string> = {
  DRAFT: "Návrh",
  CONFIRMED: "Potvrzeno",
};

const BackIcon = (
  <svg
    width="20"
    height="20"
    viewBox="0 0 24 24"
    fill="none"
    stroke="currentColor"
    strokeWidth="2"
  >
    <path d="M19 12H5M12 19l-7-7 7-7" />
  </svg>
);

export default function WarehouseInventoryDetail() {
  const { id } = useParams();
  const alert = useAlert();
  const { hasPermission } = useAuth();

  const [showConfirmModal, setShowConfirmModal] = useState(false);

  const {
    data: session,
    isPending,
    error,
  } = useQuery(warehouseInventoryDetailOptions(id));

  const confirmMutation = useApiMutation<number, void>({
    url: (sessionId) =>
      `/api/admin/warehouse/inventory-sessions/${sessionId}/confirm`,
    method: () => "POST",
    invalidate: ["warehouse"],
    onSuccess: () => {
      setShowConfirmModal(false);
      alert.success("Inventura byla potvrzena");
    },
  });

  // All hooks above this line — permission gate is the last thing before render.
  if (!hasPermission("warehouse.inventory")) return <Forbidden />;

  const handleConfirm = async () => {
    if (!session) return;
    try {
      await confirmMutation.mutateAsync(session.id);
    } catch (e) {
      alert.error(e instanceof Error ? e.message : "Chyba připojení");
    }
  };

  const confirming = confirmMutation.isPending;

  if (isPending) {
    return <LoadingState />;
  }

  if (error || !session) {
    return (
      <Box>
        <PageHeader
          title="Inventura"
          actions={
            <Button
              component={RouterLink}
              to="/warehouse/inventory"
              variant="outlined"
              color="inherit"
              startIcon={BackIcon}
            >
              Zpět
            </Button>
          }
        />
        <Card>
          <EmptyState title="Inventura nebyla nalezena." />
        </Card>
      </Box>
    );
  }

  const s = session as WarehouseInventorySession;
  const items = s.items ?? [];

  const itemColumns: DataColumn<WarehouseInventoryItem>[] = [
    {
      key: "item",
      header: "Položka",
      width: "25%",
      bold: true,
      render: (row) => row.item?.name || `ID: ${row.item_id}`,
    },
    {
      key: "location",
      header: "Lokace",
      width: "15%",
      mono: true,
      render: (row) => row.location?.code || "—",
    },
    {
      key: "system_qty",
      header: "Systémové množství",
      width: "18%",
      mono: true,
      render: (row) => String(Number(row.system_qty)),
    },
    {
      key: "actual_qty",
      header: "Skutečné množství",
      width: "18%",
      mono: true,
      render: (row) => String(Number(row.actual_qty)),
    },
    {
      key: "difference",
      header: "Rozdíl",
      width: "12%",
      render: (row) => {
        const diff = Number(row.difference);
        const color =
          diff > 0
            ? "success.main"
            : diff < 0
              ? "error.main"
              : "text.secondary";
        return (
          <Typography
            variant="body2"
            sx={{
              fontFamily: "'DM Mono', Menlo, monospace",
              fontWeight: 500,
              color,
            }}
          >
            {diff > 0 ? `+${diff}` : diff}
          </Typography>
        );
      },
    },
    {
      key: "notes",
      header: "Poznámka",
      width: "12%",
      render: (row) => row.notes || "—",
    },
  ];

  return (
    <PageEnter>
      {/* Header */}
      <PageHeader
        title={s.session_number || "Inventura"}
        actions={
          <Box sx={headerActionsSx}>
            <Button
              component={RouterLink}
              to="/warehouse/inventory"
              variant="outlined"
              color="inherit"
              startIcon={BackIcon}
            >
              Zpět
            </Button>
            <StatusChip
              label={STATUS_LABEL[s.status] ?? s.status}
              color={STATUS_COLOR[s.status] ?? "default"}
            />
            {s.status === "DRAFT" && (
              <Button
                onClick={() => setShowConfirmModal(true)}
                disabled={confirming}
              >
                {confirming ? "Potvrzování..." : "Potvrdit inventuru"}
              </Button>
            )}
          </Box>
        }
      />

      {/* Header info */}
      <Card sx={{ mb: 3 }}>
        <Typography variant="subtitle2" sx={{ mb: 2, fontWeight: 600 }}>
          Základní údaje
        </Typography>
        <Box
          sx={{
            display: "grid",
            gridTemplateColumns: { xs: "1fr", sm: "1fr 1fr" },
            gap: 2,
          }}
        >
          <Box>
            <Typography variant="caption" color="text.secondary">
              Číslo inventury
            </Typography>
            <Typography
              variant="body2"
              sx={{
                fontFamily: "'DM Mono', Menlo, monospace",
                fontWeight: 500,
              }}
            >
              {s.session_number || "—"}
            </Typography>
          </Box>
          <Box>
            <Typography variant="caption" color="text.secondary">
              Vytvořeno
            </Typography>
            <Typography
              variant="body2"
              sx={{ fontFamily: "'DM Mono', Menlo, monospace" }}
            >
              {formatDate(s.created_at)}
            </Typography>
          </Box>
          {s.notes && (
            <Box sx={{ gridColumn: { sm: "1 / -1" } }}>
              <Typography variant="caption" color="text.secondary">
                Poznámky
              </Typography>
              <Typography variant="body2" sx={{ whiteSpace: "pre-wrap" }}>
                {s.notes}
              </Typography>
            </Box>
          )}
        </Box>
      </Card>

      {/* Lines table */}
      <Card sx={{ mb: 3 }}>
        <Typography variant="subtitle2" sx={{ mb: 2, fontWeight: 600 }}>
          Položky
        </Typography>
        <DataTable<WarehouseInventoryItem>
          columns={itemColumns}
          rows={items}
          rowKey={(row) => row.id}
          empty={<EmptyState title="Žádné řádky" />}
        />
      </Card>

      {/* Confirm modal */}
      <ConfirmDialog
        isOpen={showConfirmModal}
        onClose={() => setShowConfirmModal(false)}
        onConfirm={handleConfirm}
        title="Potvrdit inventuru"
        message={`Opravdu chcete potvrdit inventuru „${s.session_number || s.id}"? Potvrzením se aktualizují skladové zásoby.`}
        confirmText="Potvrdit inventuru"
        loading={confirming}
      />
    </PageEnter>
  );
}