import { useMutation, useQuery, useQueryClient } from "@tanstack/react-query";
import { useState } from "react";

import { useT } from "../i18n";
import { api, ApiError } from "../lib/api";
import { useMe } from "../lib/auth";

const GIB = 1024 ** 3;

const inputClass =
  "w-full rounded-lg border border-app-border bg-app-surface px-3 py-2 text-app-fg placeholder:text-app-faint focus:border-app-accent focus:outline-none";

/**
 * The admin application. Three states: signed out (login), signed in without the
 * administrator flag (refused), signed in as an administrator (the panel).
 *
 * The login here is the ordinary session login — same cookie, same endpoint as
 * the mail client. What makes this a separate thing is that the bundle is served
 * only on the admin listener, and every action it performs hits /api/admin/*,
 * which the public listener refuses outright.
 */
export function AdminApp() {
  const t = useT();
  const me = useMe();

  return (
    <div className="min-h-screen bg-app-bg text-app-fg">
      <header className="border-b border-app-border px-6 py-3">
        <h1 className="font-semibold">{t("admin.title")}</h1>
      </header>
      <main className="mx-auto max-w-2xl px-6 py-10">
        {me.isPending && <p className="text-sm text-app-muted">{t("common.loading")}</p>}
        {!me.isPending && !me.data && <SignIn />}
        {me.data && !me.data.is_admin && <NotAdmin handle={me.data.handle} />}
        {me.data?.is_admin && <Panel handle={me.data.handle} />}
      </main>
    </div>
  );
}

function SignIn() {
  const t = useT();
  const queryClient = useQueryClient();
  const [handle, setHandle] = useState("");
  const [password, setPassword] = useState("");
  const [totp, setTotp] = useState("");
  const [needTotp, setNeedTotp] = useState(false);

  const login = useMutation({
    mutationFn: () => api.login(handle, password, needTotp ? totp : undefined),
    onSuccess: (user) => queryClient.setQueryData(["me"], user),
    onError: (error) => {
      if (error instanceof ApiError && (error.code === "totp_required" || error.code === "totp_invalid")) {
        setNeedTotp(true);
      }
    },
  });

  const error = login.error instanceof ApiError ? login.error : null;
  const showError = error && !(needTotp && error.code === "totp_required");

  return (
    <section className="mx-auto max-w-sm">
      <h2 className="mb-1 text-2xl font-semibold">{t("admin.signInTitle")}</h2>
      <p className="mb-6 text-sm text-app-muted">{t("admin.signInHint")}</p>
      <form
        className="space-y-3"
        onSubmit={(e) => {
          e.preventDefault();
          login.mutate();
        }}
      >
        <input
          className={inputClass}
          placeholder={t("auth.handlePlaceholder")}
          value={handle}
          onChange={(e) => setHandle(e.target.value)}
          disabled={needTotp}
          autoFocus
        />
        <input
          className={inputClass}
          type="password"
          placeholder={t("auth.password")}
          value={password}
          onChange={(e) => setPassword(e.target.value)}
          disabled={needTotp}
        />
        {needTotp && (
          <div className="space-y-1">
            <input
              className={`${inputClass} tracking-widest`}
              placeholder="123456"
              inputMode="numeric"
              autoComplete="one-time-code"
              value={totp}
              onChange={(e) => setTotp(e.target.value)}
              autoFocus
            />
            <p className="text-xs text-app-muted">{t("auth.totpPrompt")}</p>
          </div>
        )}
        <button
          className="w-full rounded-lg bg-app-accent py-2 font-medium text-app-accent-fg hover:opacity-90 disabled:opacity-50"
          disabled={login.isPending}
          type="submit"
        >
          {login.isPending ? t("auth.signingIn") : t("auth.signIn")}
        </button>
        {showError && <p className="text-sm text-red-500">{error.message}</p>}
      </form>
    </section>
  );
}

function SignOutButton() {
  const t = useT();
  const queryClient = useQueryClient();
  const logout = useMutation({
    mutationFn: api.logout,
    onSuccess: () => queryClient.setQueryData(["me"], null),
  });
  return (
    <button
      className="rounded border border-app-border px-3 py-1 text-sm text-app-muted hover:bg-app-hover"
      onClick={() => logout.mutate()}
    >
      {t("admin.signOut")}
    </button>
  );
}

function NotAdmin({ handle }: { handle: string }) {
  const t = useT();
  return (
    <section className="space-y-3">
      <h2 className="text-2xl font-semibold">{t("admin.notAdminTitle")}</h2>
      <p className="text-sm text-app-muted">{t("admin.notAdmin", { handle })}</p>
      <SignOutButton />
    </section>
  );
}

function Panel({ handle }: { handle: string }) {
  const t = useT();
  const queryClient = useQueryClient();
  const settings = useQuery({ queryKey: ["adminSettings"], queryFn: api.adminSettings });

  // The quota field is a draft until Save — unlike the toggle, you do not want a
  // write per keystroke. `null` means "not edited yet, show the server's value".
  const [quotaDraft, setQuotaDraft] = useState<string | null>(null);

  const save = useMutation({
    mutationFn: api.saveAdminSettings,
    onSuccess: (data) => {
      queryClient.setQueryData(["adminSettings"], data);
      setQuotaDraft(null);
    },
  });

  const open = settings.data?.registration_open ?? false;
  const serverQuotaGib = settings.data ? settings.data.default_quota_bytes / GIB : 0;
  const quotaValue = quotaDraft ?? String(Number(serverQuotaGib.toFixed(3)));
  const quotaGib = Number(quotaValue);
  const quotaValid = Number.isFinite(quotaGib) && quotaGib > 0;
  const quotaDirty = quotaDraft !== null && quotaGib !== serverQuotaGib;

  return (
    <section className="space-y-3">
      <div className="flex items-center justify-between">
        <p className="text-sm text-app-muted">{t("admin.signedInAs", { handle })}</p>
        <SignOutButton />
      </div>

      {settings.isPending && <p className="text-sm text-app-muted">{t("common.loading")}</p>}
      {settings.error instanceof ApiError && (
        <p className="text-sm text-red-500">{settings.error.message}</p>
      )}

      {settings.data && (
        <>
          <div className="border-b border-app-border py-2">
            <div className="flex items-center justify-between text-sm">
              <span className="text-app-muted">{t("admin.registration")}</span>
              <div className="flex gap-1 rounded-lg border border-app-border p-0.5">
                {([true, false] as const).map((value) => (
                  <button
                    key={String(value)}
                    disabled={save.isPending}
                    onClick={() => save.mutate({ registration_open: value })}
                    className={`rounded px-3 py-1 disabled:opacity-50 ${
                      open === value
                        ? "bg-app-active font-medium text-app-fg"
                        : "text-app-muted hover:bg-app-hover"
                    }`}
                  >
                    {t(value ? "admin.registrationOn" : "admin.registrationOff")}
                  </button>
                ))}
              </div>
            </div>
            <p className="mt-1 text-xs text-app-faint">{t("admin.registrationHelp")}</p>
          </div>

          <div className="border-b border-app-border py-2">
            <div className="flex items-center justify-between text-sm">
              <span className="text-app-muted">{t("admin.defaultQuota")}</span>
              <div className="flex items-center gap-2">
                <input
                  className="w-28 rounded border border-app-border bg-app-surface px-2 py-1 text-right focus:border-app-accent focus:outline-none"
                  type="number"
                  min="0.1"
                  step="0.5"
                  value={quotaValue}
                  onChange={(e) => setQuotaDraft(e.target.value)}
                />
                <span className="text-app-muted">GiB</span>
                <button
                  className="rounded bg-app-accent px-3 py-1 font-medium text-app-accent-fg hover:opacity-90 disabled:opacity-50"
                  disabled={!quotaDirty || !quotaValid || save.isPending}
                  onClick={() => save.mutate({ default_quota_bytes: Math.round(quotaGib * GIB) })}
                >
                  {save.isPending ? t("admin.saving") : t("admin.save")}
                </button>
              </div>
            </div>
            <p className="mt-1 text-xs text-app-faint">{t("admin.quotaHelp")}</p>
            {!quotaValid && <p className="mt-1 text-xs text-red-500">{t("admin.quotaInvalid")}</p>}
            {save.error instanceof ApiError && (
              <p className="mt-1 text-xs text-red-500">{save.error.message}</p>
            )}
          </div>
        </>
      )}
    </section>
  );
}