import { useState } from "react";
import { useClient } from "urql";
import { graphql, type ResultOf, type VariablesOf } from "@/graphql";
import { useToast } from "@/hooks/use-toast";
import { fetchAllPages } from "@/lib/fetch-all-pages";
import { csvTimestamp, downloadCsv, toCsv, type CsvColumn } from "@/lib/to-csv";

/** CSV export for the Users dashboard (issue #605). */
const UsersCsvQuery = graphql(`
  query UsersCsv($first: Int, $after: String, $order: [UserOrderInput], $query: UserQueryInput) {
    users(first: $first, after: $after, order: $order, query: $query) {
      pageInfo {
        hasNextPage
        endCursor
      }
      edges {
        node {
          name
          email
          status
          userRoles {
            edges {
              node {
                role {
                  name
                }
              }
            }
          }
        }
      }
    }
  }
`);

type CsvVariables = VariablesOf<typeof UsersCsvQuery>;
type CsvResult = ResultOf<typeof UsersCsvQuery>;
type UserCsvRow = NonNullable<NonNullable<CsvResult["users"]>["edges"]>[number]["node"];

const roleNames = (row: UserCsvRow): string =>
  row.userRoles.edges
    .map((edge) => edge.node.role?.name)
    .filter((name): name is string => Boolean(name))
    .join(", ");

const columns: CsvColumn<UserCsvRow>[] = [
  { header: "Name", value: (r) => r.name },
  { header: "Email", value: (r) => r.email },
  { header: "Status", value: (r) => r.status },
  { header: "Roles", value: (r) => roleNames(r) },
];

export function useExportUsersCsv() {
  const client = useClient();
  const toast = useToast();
  const [isExporting, setIsExporting] = useState(false);

  async function exportCsv(order: CsvVariables["order"], query: CsvVariables["query"]) {
    if (isExporting) return;
    setIsExporting(true);
    try {
      const rows = await fetchAllPages(client, UsersCsvQuery, { order, query }, (d) => d.users);
      if (rows.length === 0) {
        toast.error("No users to export");
        return;
      }
      downloadCsv(toCsv(rows, columns), `users-${csvTimestamp()}.csv`);
      toast.success(`${rows.length.toLocaleString()} rows exported`);
    } catch (err) {
      console.error("CSV export failed:", err);
      toast.error("Failed to export CSV");
    } finally {
      setIsExporting(false);
    }
  }

  return { exportCsv, isExporting };
}