import { useState, useEffect, useMemo, useRef } from "react";
import DOMPurify from "dompurify";
import { useQuery } from "@tanstack/react-query";
import { orderDetailOptions, type OrderItem } from "../lib/queries/orders";
import { useApiMutation } from "../lib/queries/mutations";
import { useAlert } from "../context/AlertContext";
import { useAuth } from "../context/AuthContext";
import { useParams, useNavigate, Link as RouterLink } from "react-router-dom";
import Box from "@mui/material/Box";
import Typography from "@mui/material/Typography";
import OrderConfirmationModal from "../components/OrderConfirmationModal";
import Forbidden from "../components/Forbidden";
import apiFetch from "../utils/api";
import {
  formatCurrency,
  formatDate,
  restoreQuillBlankLines,
} from "../utils/formatters";
import { ORDER_STATUS, statusLabel, statusColor } from "../lib/documentStatus";
import {
  Button,
  Card,
  Field,
  TextField,
  DataTable,
  StatusChip,
  CheckboxField,
  ConfirmDialog,
  EmptyState,
  LoadingState,
  PageEnter,
  RichTextView,
  headerActionsSx,
  type DataColumn,
} from "../ui";

const API_BASE = "/api/admin";

type ItemRow = OrderItem & { _index: number };

const TRANSITION_LABELS: Record<string, string> = {
  v_realizaci: "Zahájit realizaci",
  dokoncena: "Dokončit",
};

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>
);

const FileIcon = (
  <svg
    width="16"
    height="16"
    viewBox="0 0 24 24"
    fill="none"
    stroke="currentColor"
    strokeWidth="2"
  >
    <path d="M14 2H6a2 2 0 0 0-2 2v16a2 2 0 0 0 2 2h12a2 2 0 0 0 2-2V8z" />
    <polyline points="14 2 14 8 20 8" />
  </svg>
);

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

  const orderQuery = useQuery(orderDetailOptions(id));
  const order = orderQuery.data;
  const loading = orderQuery.isPending;

  const [notes, setNotes] = useState("");
  const [saving, setSaving] = useState(false);
  const [statusChanging, setStatusChanging] = useState<string | null>(null);
  const [statusConfirm, setStatusConfirm] = useState<{
    show: boolean;
    status: string | null;
  }>({ show: false, status: null });
  const [attachmentLoading, setAttachmentLoading] = useState(false);
  const [deleteConfirm, setDeleteConfirm] = useState(false);
  const [deleting, setDeleting] = useState(false);
  const [deleteFiles, setDeleteFiles] = useState(false);
  const [showConfirmationModal, setShowConfirmationModal] = useState(false);
  const [confirmationLoading, setConfirmationLoading] = useState(false);
  const initialNotesRef = useRef<string | null>(null);
  const formInitializedRef = useRef(false);
  const blobTimeoutsRef = useRef<ReturnType<typeof setTimeout>[]>([]);

  // Reset form sync when navigating to a different order
  useEffect(() => {
    formInitializedRef.current = false;
  }, [id]);

  // Sync order data to local form state on first load
  useEffect(() => {
    if (orderQuery.data && !formInitializedRef.current) {
      const orderData = orderQuery.data!;
      setNotes(orderData.notes || "");
      initialNotesRef.current = orderData.notes || "";
      formInitializedRef.current = true;
    }
  }, [orderQuery.data]);

  // Navigate away on fetch error
  useEffect(() => {
    if (orderQuery.error) {
      alert.error("Nepodařilo se načíst objednávku");
      navigate("/orders?tab=prijate");
    }
  }, [orderQuery.error]); // eslint-disable-line react-hooks/exhaustive-deps

  useEffect(() => {
    const blobTimeouts = blobTimeoutsRef.current;
    return () => {
      blobTimeouts.forEach(clearTimeout);
    };
  }, []);

  const isDirty = useMemo(() => {
    if (!initialNotesRef.current) return false;
    return notes !== initialNotesRef.current;
  }, [notes]);

  useEffect(() => {
    if (!isDirty) return;
    const handler = (e: BeforeUnloadEvent) => {
      e.preventDefault();
      e.returnValue = "";
    };
    window.addEventListener("beforeunload", handler);
    return () => window.removeEventListener("beforeunload", handler);
  }, [isDirty]);

  // NET only — received orders are not tax documents (no VAT on them).
  const totals = useMemo(() => {
    if (!order?.items) return { total: 0 };
    const total = order.items.reduce((sum, item) => {
      if (Number(item.is_included_in_total)) {
        return (
          sum + (Number(item.quantity) || 0) * (Number(item.unit_price) || 0)
        );
      }
      return sum;
    }, 0);
    return { total };
  }, [order]);

  const statusMutation = useApiMutation<{ status: string }, unknown>({
    url: () => `${API_BASE}/orders/${id}`,
    method: () => "PUT",
    invalidate: ["orders", "offers", "projects", "invoices"],
  });

  const notesMutation = useApiMutation<{ notes: string }, unknown>({
    url: () => `${API_BASE}/orders/${id}`,
    method: () => "PUT",
    invalidate: ["orders", "offers", "projects", "invoices"],
  });

  const orderDeleteMutation = useApiMutation<
    { delete_files: boolean },
    unknown
  >({
    url: () => `${API_BASE}/orders/${id}`,
    method: () => "DELETE",
    invalidate: ["orders", "offers", "projects", "invoices"],
  });

  if (!hasPermission("orders.view")) return <Forbidden />;

  const handleStatusChange = async () => {
    if (!statusConfirm.status) return;
    const newStatus = statusConfirm.status;
    setStatusChanging(newStatus);
    setStatusConfirm({ show: false, status: null });
    try {
      await statusMutation.mutateAsync({ status: newStatus });
      alert.success("Stav byl změněn");
    } catch (e) {
      alert.error(e instanceof Error ? e.message : "Chyba připojení");
    } finally {
      setStatusChanging(null);
    }
  };

  const handleSaveNotes = async () => {
    setSaving(true);
    try {
      await notesMutation.mutateAsync({ notes });
      alert.success("Poznámky byly uloženy");
      initialNotesRef.current = notes;
    } catch (e) {
      alert.error(e instanceof Error ? e.message : "Chyba připojení");
    } finally {
      setSaving(false);
    }
  };

  const handleViewAttachment = async () => {
    const newWindow = window.open("", "_blank");
    setAttachmentLoading(true);
    try {
      const response = await apiFetch(`${API_BASE}/orders/${id}/attachment`);
      if (!response.ok) {
        newWindow?.close();
        alert.error("Nepodařilo se stáhnout přílohu");
        return;
      }
      const blob = await response.blob();
      const url = URL.createObjectURL(blob);
      if (newWindow) newWindow.location.href = url;
      const timeoutId = setTimeout(() => URL.revokeObjectURL(url), 60000);
      blobTimeoutsRef.current.push(timeoutId);
    } catch {
      newWindow?.close();
      alert.error("Chyba připojení");
    } finally {
      setAttachmentLoading(false);
    }
  };

  const handleGenerateConfirmation = async (
    lang: string,
    customItems?: Array<{
      description: string;
      quantity: number;
      unit: string;
      unit_price: number;
      is_included_in_total: boolean;
    }>,
  ) => {
    setConfirmationLoading(true);
    try {
      const response = await apiFetch(
        `${API_BASE}/orders-pdf/${id}/confirmation`,
        {
          method: "POST",
          headers: { "Content-Type": "application/json" },
          body: JSON.stringify({ lang, items: customItems }),
        },
      );
      if (!response.ok) {
        const result = await response.json().catch(() => ({}));
        alert.error(result.error || "Nepodařilo se vygenerovat PDF");
        return;
      }
      const blob = await response.blob();
      const url = URL.createObjectURL(blob);
      const a = document.createElement("a");
      a.href = url;
      a.download = `Potvrzeni-${order?.order_number || String(id)}.pdf`;
      document.body.appendChild(a);
      a.click();
      document.body.removeChild(a);
      const timeoutId = setTimeout(() => URL.revokeObjectURL(url), 60000);
      blobTimeoutsRef.current.push(timeoutId);
    } catch {
      alert.error("Chyba připojení");
    } finally {
      setConfirmationLoading(false);
    }
  };

  const handleDelete = async () => {
    setDeleting(true);
    try {
      await orderDeleteMutation.mutateAsync({ delete_files: deleteFiles });
      alert.success("Objednávka byla smazána");
      navigate("/orders?tab=prijate");
    } catch (e) {
      alert.error(e instanceof Error ? e.message : "Chyba připojení");
    } finally {
      setDeleting(false);
      setDeleteConfirm(false);
    }
  };

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

  if (!order) return null;

  const itemRows: ItemRow[] = (order.items ?? []).map((item, index) => ({
    ...item,
    _index: index,
  }));

  const itemColumns: DataColumn<ItemRow>[] = [
    {
      key: "index",
      header: "#",
      width: "2.5rem",
      render: (item) => (
        <Box component="span" sx={{ color: "text.secondary", fontWeight: 500 }}>
          {item._index + 1}
        </Box>
      ),
    },
    {
      key: "description",
      header: "Popis",
      render: (item) => (
        <Box>
          <Typography variant="body2" sx={{ fontWeight: 500 }}>
            {item.description || "—"}
          </Typography>
          {item.item_description && (
            <Typography
              variant="caption"
              color="text.secondary"
              sx={{ display: "block", mt: 0.25 }}
            >
              {item.item_description}
            </Typography>
          )}
        </Box>
      ),
    },
    {
      key: "quantity",
      header: "Množství",
      width: "5.5rem",
      render: (item) => String(item.quantity),
    },
    {
      key: "unit",
      header: "Jednotka",
      width: "5.5rem",
      render: (item) => item.unit || "—",
    },
    {
      key: "unit_price",
      header: "Jedn. cena",
      width: "8rem",
      align: "right",
      mono: true,
      render: (item) => formatCurrency(item.unit_price, order.currency),
    },
    {
      key: "is_included_in_total",
      header: "V ceně",
      width: "4rem",
      render: (item) => (Number(item.is_included_in_total) ? "Ano" : "Ne"),
    },
    {
      key: "total",
      header: "Celkem",
      width: "9rem",
      align: "right",
      mono: true,
      bold: true,
      render: (item) =>
        formatCurrency(
          (Number(item.quantity) || 0) * (Number(item.unit_price) || 0),
          order.currency,
        ),
    },
  ];

  return (
    <PageEnter>
      {/* Header */}
      <Box>
        <Box
          sx={{
            display: "flex",
            alignItems: "flex-start",
            justifyContent: "space-between",
            flexWrap: "wrap",
            gap: 2,
            mb: 3,
          }}
        >
          {/* flexWrap: the title must drop below the Zpět button on phones
              instead of overflowing the viewport (same as Offer/Invoice
              detail headers). */}
          <Box
            sx={{
              display: "flex",
              alignItems: "center",
              gap: 2,
              flexWrap: "wrap",
            }}
          >
            <Button
              component={RouterLink}
              to="/orders?tab=prijate"
              variant="outlined"
              color="inherit"
              startIcon={BackIcon}
            >
              Zpět
            </Button>
            <Box
              sx={{
                display: "flex",
                alignItems: "center",
                gap: 1.5,
                flexWrap: "wrap",
              }}
            >
              <Typography variant="h4">
                Objednávka
                <Box
                  component="span"
                  sx={{ color: "text.secondary", ml: 1, fontWeight: 400 }}
                >
                  {order.order_number}
                </Box>
              </Typography>
              <StatusChip
                label={statusLabel(ORDER_STATUS, order.status)}
                color={statusColor(ORDER_STATUS, order.status)}
              />
            </Box>
          </Box>
          <Box sx={headerActionsSx}>
            {order.invoice ? (
              <Button
                component={RouterLink}
                to={`/invoices/${order.invoice.id}`}
                variant="outlined"
                color="inherit"
                startIcon={FileIcon}
              >
                Faktura {order.invoice.invoice_number}
              </Button>
            ) : (
              hasPermission("invoices.create") &&
              order.status === "dokoncena" && (
                <Button
                  component={RouterLink}
                  to={`/invoices/new?fromOrder=${order.id}`}
                  variant="outlined"
                  color="inherit"
                  startIcon={FileIcon}
                >
                  Vytvořit fakturu
                </Button>
              )
            )}
            {hasPermission("orders.view") && (
              <Button
                variant="outlined"
                color="inherit"
                startIcon={FileIcon}
                onClick={() => setShowConfirmationModal(true)}
                disabled={confirmationLoading}
              >
                Potvrzení objednávky
              </Button>
            )}
            {hasPermission("orders.edit") &&
              (order.valid_transitions?.filter((s) => s !== "stornovana")
                .length ?? 0) > 0 &&
              order
                .valid_transitions!.filter((s) => s !== "stornovana")
                .map((status) => (
                  <Button
                    key={status}
                    onClick={() => setStatusConfirm({ show: true, status })}
                    disabled={statusChanging === status}
                  >
                    {statusChanging === status
                      ? "Zpracovávám…"
                      : TRANSITION_LABELS[status] || status}
                  </Button>
                ))}
            {hasPermission("orders.delete") && (
              <Button
                variant="outlined"
                color="error"
                onClick={() => setDeleteConfirm(true)}
              >
                Smazat
              </Button>
            )}
          </Box>
        </Box>
      </Box>

      {/* Info card */}
      <Card sx={{ mb: 3 }}>
        <Typography variant="subtitle2" sx={{ mb: 2, fontWeight: 600 }}>
          Informace
        </Typography>
        <Box
          sx={{
            display: "grid",
            gridTemplateColumns: { xs: "1fr", sm: "1fr 1fr 1fr" },
            gap: 2,
          }}
        >
          <Box>
            <Typography variant="caption" color="text.secondary">
              Nabídka
            </Typography>
            <Typography
              variant="body2"
              sx={{
                fontFamily: "'DM Mono', Menlo, monospace",
                fontWeight: 500,
              }}
            >
              <Box
                component={RouterLink}
                to={`/offers/${order.quotation_id}`}
                sx={{
                  color: "primary.main",
                  textDecoration: "none",
                  "&:hover": { textDecoration: "underline" },
                }}
              >
                {order.quotation_number}
              </Box>
              {order.project_code && (
                <Box component="span" sx={{ color: "text.secondary", ml: 1 }}>
                  ({order.project_code})
                </Box>
              )}
            </Typography>
          </Box>
          <Box>
            <Typography variant="caption" color="text.secondary">
              Projekt
            </Typography>
            <Typography
              variant="body2"
              sx={{
                fontFamily: "'DM Mono', Menlo, monospace",
                fontWeight: 500,
              }}
            >
              {order.project ? (
                <Box
                  component={RouterLink}
                  to={`/projects/${order.project.id}`}
                  sx={{
                    color: "primary.main",
                    textDecoration: "none",
                    "&:hover": { textDecoration: "underline" },
                  }}
                >
                  {order.project.project_number} — {order.project.name}
                </Box>
              ) : (
                "—"
              )}
            </Typography>
          </Box>
          <Box>
            <Typography variant="caption" color="text.secondary">
              Zákazník
            </Typography>
            <Typography
              variant="body2"
              sx={{
                fontFamily: "'DM Mono', Menlo, monospace",
                fontWeight: 500,
              }}
            >
              {order.customer_name || "—"}
            </Typography>
          </Box>
          <Box>
            <Typography variant="caption" color="text.secondary">
              Číslo obj. zákazníka
            </Typography>
            <Typography
              variant="body2"
              sx={{ fontFamily: "'DM Mono', Menlo, monospace" }}
            >
              {order.customer_order_number || "—"}
            </Typography>
          </Box>
          <Box>
            <Typography variant="caption" color="text.secondary">
              Měna
            </Typography>
            <Typography
              variant="body2"
              sx={{ fontFamily: "'DM Mono', Menlo, monospace" }}
            >
              {order.currency}
            </Typography>
          </Box>
          <Box>
            <Typography variant="caption" color="text.secondary">
              Datum vytvoření
            </Typography>
            <Typography
              variant="body2"
              sx={{ fontFamily: "'DM Mono', Menlo, monospace" }}
            >
              {formatDate(order.created_at)}
            </Typography>
          </Box>
          <Box>
            <Typography variant="caption" color="text.secondary">
              Příloha
            </Typography>
            <Box sx={{ mt: 0.5 }}>
              {order.attachment_name ? (
                <Button
                  variant="outlined"
                  color="inherit"
                  startIcon={FileIcon}
                  onClick={handleViewAttachment}
                  disabled={attachmentLoading}
                >
                  {order.attachment_name}
                </Button>
              ) : (
                <Typography variant="body2">—</Typography>
              )}
            </Box>
          </Box>
        </Box>
      </Card>

      {/* Items (read-only) */}
      <Card sx={{ mb: 3 }}>
        <Typography variant="subtitle2" sx={{ mb: 2, fontWeight: 600 }}>
          Položky
        </Typography>
        <DataTable<ItemRow>
          columns={itemColumns}
          rows={itemRows}
          rowKey={(item) => item.id ?? item._index}
          empty={<EmptyState title="Žádné položky." />}
        />

        {/* Totals (NET only — orders are not tax documents) */}
        <Box
          sx={{
            mt: 2,
            ml: "auto",
            maxWidth: 360,
            display: "flex",
            flexDirection: "column",
            gap: 0.5,
          }}
        >
          <Box
            sx={{
              display: "flex",
              justifyContent: "space-between",
              pt: 0.5,
              mt: 0.5,
              borderTop: 1,
              borderColor: "divider",
            }}
          >
            <Typography variant="body2" sx={{ fontWeight: 700 }}>
              Celkem bez DPH:
            </Typography>
            <Typography
              variant="body2"
              sx={{
                fontFamily: "'DM Mono', Menlo, monospace",
                fontWeight: 700,
              }}
            >
              {formatCurrency(totals.total, order.currency)}
            </Typography>
          </Box>
        </Box>
      </Card>

      {/* Sections (read-only) */}
      {order.sections?.length > 0 && (
        <Card sx={{ mb: 3 }}>
          <Typography variant="subtitle2" sx={{ mb: 2, fontWeight: 600 }}>
            Rozsah projektu
          </Typography>
          {order.scope_title && (
            <Typography variant="body2" sx={{ fontWeight: 500, mb: 1 }}>
              {order.scope_title}
            </Typography>
          )}
          {order.scope_description && (
            <Typography variant="body2" color="text.secondary" sx={{ mb: 2 }}>
              {order.scope_description}
            </Typography>
          )}
          <Box sx={{ display: "flex", flexDirection: "column", gap: 1.5 }}>
            {order.sections.map((section, index) => (
              <Box
                key={section.id || index}
                sx={{
                  border: 1,
                  borderColor: "divider",
                  borderRadius: 2,
                  overflow: "hidden",
                }}
              >
                <Box
                  sx={{
                    display: "flex",
                    alignItems: "center",
                    gap: 1,
                    px: 2,
                    py: 1,
                    bgcolor: "action.hover",
                  }}
                >
                  <Typography
                    variant="body2"
                    color="text.secondary"
                    sx={{ fontWeight: 600 }}
                  >
                    {index + 1}.
                  </Typography>
                  <Typography variant="body2" sx={{ fontWeight: 600 }}>
                    {(order.language === "CZ"
                      ? section.title_cz || section.title
                      : section.title || section.title_cz) ||
                      `Sekce ${index + 1}`}
                  </Typography>
                </Box>
                {section.content && (
                  <RichTextView
                    sx={{ p: 2 }}
                    dangerouslySetInnerHTML={{
                      __html: DOMPurify.sanitize(
                        restoreQuillBlankLines(section.content),
                      ),
                    }}
                  />
                )}
              </Box>
            ))}
          </Box>
        </Card>
      )}

      {/* Notes (editable) */}
      <Card sx={{ mb: 3 }}>
        <Typography variant="subtitle2" sx={{ mb: 2, fontWeight: 600 }}>
          Poznámky
        </Typography>
        <Field label="Poznámky">
          <TextField
            value={notes}
            onChange={(e) => setNotes(e.target.value)}
            multiline
            minRows={4}
            placeholder="Interní poznámky k objednávce..."
            fullWidth
            disabled={!hasPermission("orders.edit")}
          />
        </Field>
        {hasPermission("orders.edit") && (
          <Box sx={{ mt: 1 }}>
            <Button
              variant="outlined"
              color="inherit"
              onClick={handleSaveNotes}
              disabled={saving}
            >
              {saving ? "Ukládání..." : "Uložit poznámky"}
            </Button>
          </Box>
        )}
      </Card>

      {/* Status change confirmation */}
      <ConfirmDialog
        isOpen={statusConfirm.show}
        onClose={() => setStatusConfirm({ show: false, status: null })}
        onConfirm={handleStatusChange}
        title="Změnit stav objednávky"
        message={`Opravdu chcete změnit stav objednávky "${order.order_number}" na "${statusLabel(ORDER_STATUS, statusConfirm.status)}"?${statusConfirm.status === "dokoncena" ? " Projekt bude automaticky dokončen." : ""}`}
        confirmText={
          TRANSITION_LABELS[statusConfirm.status || ""] || "Potvrdit"
        }
        cancelText="Zrušit"
      />

      {/* Delete confirmation */}
      <ConfirmDialog
        isOpen={deleteConfirm}
        onClose={() => {
          setDeleteConfirm(false);
          setDeleteFiles(false);
        }}
        onConfirm={handleDelete}
        title="Smazat objednávku"
        message={`Opravdu chcete smazat objednávku „${order.order_number}"? Bude smazán i přidružený projekt. Tato akce je nevratná.`}
        confirmText="Smazat"
        confirmVariant="danger"
        loading={deleting}
      >
        {order.project?.has_nas_folder && (
          <CheckboxField
            label="Smazat i soubory projektu na disku"
            checked={deleteFiles}
            onChange={setDeleteFiles}
          />
        )}
      </ConfirmDialog>

      {/* Order confirmation PDF modal */}
      {order && (
        <OrderConfirmationModal
          isOpen={showConfirmationModal}
          onClose={() => setShowConfirmationModal(false)}
          onGenerate={handleGenerateConfirmation}
          initialItems={order.items.map((it) => ({
            description: it.description || "",
            quantity: Number(it.quantity) || 0,
            unit: it.unit || "",
            unit_price: Number(it.unit_price) || 0,
            is_included_in_total: Number(it.is_included_in_total) !== 0,
          }))}
          orderNumber={order.order_number}
        />
      )}
    </PageEnter>
  );
}