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

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

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>
      {/* Two columns once there is room: instance settings and users on the
          left, outgoing system mail on the right. Signed out, it stays narrow. */}
      <main className={`mx-auto px-6 py-10 ${me.data?.is_admin ? "max-w-6xl" : "max-w-2xl"}`}>
        {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 && (
          <div className="grid gap-y-10 lg:grid-cols-2">
            <div className="min-w-0 lg:pr-12">
              <Panel handle={me.data.handle} />
              <Users selfId={me.data.id} />
            </div>
            {/* The divider runs the full height of the taller column. */}
            <div className="min-w-0 lg:border-l lg:border-app-border lg:pl-12">
              <SystemMail />
            </div>
          </div>
        )}
      </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);
  // The invitation email settings open in a dialog of their own.
  const [configuring, setConfiguring] = useState(false);

  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.invitations")}</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({ invitations_enabled: value })}
                    className={`rounded px-3 py-1 disabled:opacity-50 ${
                      settings.data.invitations_enabled === value
                        ? "bg-app-active font-medium text-app-fg"
                        : "text-app-muted hover:bg-app-hover"
                    }`}
                  >
                    {t(value ? "admin.invitationsOn" : "admin.invitationsOff")}
                  </button>
                ))}
              </div>
            </div>
            <p className="mt-1 text-xs text-app-faint">{t("admin.invitationsHelp")}</p>
            {settings.data.invitations_enabled && (
              <button
                type="button"
                className="mt-2 rounded border border-app-border px-3 py-1 text-sm hover:bg-app-hover"
                onClick={() => setConfiguring(true)}
              >
                {t("admin.inviteConfigure")}
              </button>
            )}
          </div>
          {configuring && <InvitationEmailDialog onClose={() => setConfiguring(false)} />}

          <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>
  );
}

type MailDraft = Omit<AdminMail, "has_password" | "configured">;

/** The SMTP account the server sends password-reset links from. */
function SystemMail() {
  const t = useT();
  const queryClient = useQueryClient();
  const mail = useQuery({ queryKey: ["adminMail"], queryFn: api.adminMail });
  // Edits are a draft until Save; null means "show what the server has".
  const [draft, setDraft] = useState<MailDraft | null>(null);
  const [password, setPassword] = useState("");
  const [testTo, setTestTo] = useState("");

  const save = useMutation({
    mutationFn: (body: Parameters<typeof api.saveAdminMail>[0]) => api.saveAdminMail(body),
    onSuccess: (data) => {
      queryClient.setQueryData(["adminMail"], data);
      setDraft(null);
      setPassword("");
    },
  });
  const test = useMutation({ mutationFn: () => api.testAdminMail(testTo.trim()) });

  if (!mail.data) {
    return mail.error instanceof ApiError ? (
      <p className="text-sm text-red-500">{mail.error.message}</p>
    ) : null;
  }
  const server = mail.data;
  const value: MailDraft = draft ?? {
    smtp_host: server.smtp_host,
    smtp_port: server.smtp_port,
    smtp_security: server.smtp_security,
    smtp_username: server.smtp_username,
    smtp_from: server.smtp_from,
    public_url: server.public_url,
  };
  const set = (patch: Partial<MailDraft>) => setDraft({ ...value, ...patch });
  const dirty = draft !== null || password !== "";
  const field =
    "w-full rounded border border-app-border bg-app-surface px-2 py-1.5 text-sm focus:border-app-accent focus:outline-none";
  const label = "block space-y-1 text-sm";

  return (
    <section className="space-y-3">
      <h2 className="text-lg font-semibold">{t("admin.mail")}</h2>
      <p className="text-xs text-app-faint">{t("admin.mailHelp")}</p>
      <p className={`text-sm ${server.configured ? "text-emerald-600" : "text-amber-600"}`}>
        {server.configured ? t("admin.mailOn") : t("admin.mailOff")}
      </p>
      <form
        className="space-y-3"
        onSubmit={(e) => {
          e.preventDefault();
          save.mutate({ ...value, ...(password ? { smtp_password: password } : {}) });
        }}
      >
        <div className="grid grid-cols-[1fr_6rem_8rem] gap-2">
          <label className={label}>
            <span className="text-app-muted">{t("admin.smtpHost")}</span>
            <input
              className={field}
              value={value.smtp_host}
              placeholder="smtp.example.com"
              onChange={(e) => set({ smtp_host: e.target.value })}
            />
          </label>
          <label className={label}>
            <span className="text-app-muted">{t("admin.smtpPort")}</span>
            <input
              className={field}
              type="number"
              min="1"
              max="65535"
              value={value.smtp_port}
              onChange={(e) => set({ smtp_port: Number(e.target.value) })}
            />
          </label>
          <label className={label}>
            <span className="text-app-muted">{t("admin.smtpSecurity")}</span>
            <select
              className={field}
              value={value.smtp_security}
              onChange={(e) => {
                const security = e.target.value as MailDraft["smtp_security"];
                // Follow the usual port for the mode, unless a custom one was typed.
                const usual = { starttls: 587, ssl: 465, none: 25 };
                const port = Object.values(usual).includes(value.smtp_port) ? usual[security] : value.smtp_port;
                set({ smtp_security: security, smtp_port: port });
              }}
            >
              <option value="starttls">{t("admin.smtpStarttls")}</option>
              <option value="ssl">{t("admin.smtpSsl")}</option>
              <option value="none">{t("admin.smtpNone")}</option>
            </select>
          </label>
        </div>
        <div className="grid grid-cols-2 gap-2">
          <label className={label}>
            <span className="text-app-muted">{t("admin.smtpUsername")}</span>
            <input
              className={field}
              autoComplete="off"
              value={value.smtp_username}
              placeholder="postmaster@example.com"
              onChange={(e) => set({ smtp_username: e.target.value })}
            />
          </label>
          <label className={label}>
            <span className="text-app-muted">{t("admin.smtpPassword")}</span>
            <input
              className={field}
              type="password"
              autoComplete="new-password"
              value={password}
              placeholder={server.has_password ? t("admin.smtpPasswordKept") : ""}
              onChange={(e) => setPassword(e.target.value)}
            />
          </label>
        </div>
        <label className={label}>
          <span className="text-app-muted">{t("admin.smtpFrom")}</span>
          <input
            className={field}
            type="email"
            value={value.smtp_from}
            placeholder="postmaster@example.com"
            onChange={(e) => set({ smtp_from: e.target.value })}
          />
        </label>
        <label className={label}>
          <span className="text-app-muted">{t("admin.publicUrl")}</span>
          <input
            className={field}
            value={value.public_url}
            placeholder="https://mail.example.com"
            onChange={(e) => set({ public_url: e.target.value })}
          />
          <span className="block text-xs text-app-faint">{t("admin.publicUrlHint")}</span>
        </label>
        <div className="flex items-center justify-between gap-2">
          {server.has_password ? (
            <button
              type="button"
              className="text-xs text-app-muted underline hover:text-app-fg disabled:opacity-50"
              disabled={save.isPending}
              onClick={() => save.mutate({ smtp_password: "" })}
            >
              {t("admin.smtpPasswordRemove")}
            </button>
          ) : (
            <span />
          )}
          <button
            type="submit"
            className="rounded bg-app-accent px-3 py-1 text-sm font-medium text-app-accent-fg hover:opacity-90 disabled:opacity-50"
            disabled={!dirty || save.isPending}
          >
            {save.isPending ? t("admin.saving") : t("admin.save")}
          </button>
        </div>
        {save.error instanceof ApiError && <p className="text-xs text-red-500">{save.error.message}</p>}
      </form>

      <form
        className="flex items-center gap-2 border-t border-app-border pt-3 text-sm"
        onSubmit={(e) => {
          e.preventDefault();
          test.mutate();
        }}
      >
        <span className="shrink-0 text-app-muted">{t("admin.testTo")}</span>
        <input
          className={field}
          type="email"
          value={testTo}
          placeholder="you@example.com"
          onChange={(e) => {
            setTestTo(e.target.value);
            test.reset();
          }}
        />
        <button
          type="submit"
          className="shrink-0 rounded border border-app-border px-3 py-1 hover:bg-app-hover disabled:opacity-50"
          disabled={!server.configured || !testTo.trim() || test.isPending || dirty}
        >
          {test.isPending ? t("auth.sending") : t("admin.sendTest")}
        </button>
      </form>
      {test.isSuccess && <p className="text-xs text-emerald-600">{t("admin.testSent")}</p>}
      {test.error instanceof ApiError && <p className="text-xs text-red-500">{test.error.message}</p>}
    </section>
  );
}

/** "Configure" under Allow invitations: the invitation email settings in a dialog. */
function InvitationEmailDialog({ onClose }: { onClose: () => void }) {
  const t = useT();
  useEffect(() => {
    const onKey = (e: KeyboardEvent) => e.key === "Escape" && onClose();
    window.addEventListener("keydown", onKey);
    return () => window.removeEventListener("keydown", onKey);
  }, [onClose]);
  return createPortal(
    <div
      className="fixed inset-0 z-50 flex items-start justify-center overflow-y-auto bg-black/40 p-4 backdrop-blur-sm sm:items-center"
      onClick={onClose}
    >
      <div
        role="dialog"
        aria-label={t("admin.inviteMail")}
        className="relative my-4 max-h-[calc(100vh-2rem)] w-full max-w-2xl overflow-y-auto rounded-2xl bg-app-bg p-6 shadow-2xl"
        onClick={(e) => e.stopPropagation()}
      >
        <button
          type="button"
          aria-label={t("admin.close")}
          className="absolute right-4 top-4 rounded px-2 py-0.5 text-xl leading-none text-app-muted hover:bg-app-hover hover:text-app-fg"
          onClick={onClose}
        >
          ×
        </button>
        <InvitationEmail />
      </div>
    </div>,
    document.body,
  );
}

/** The invitation email: sender, subject and an uploaded HTML template with
 *  placeholders; previewed with sample names, and sent as a test. */
function InvitationEmail() {
  const t = useT();
  const queryClient = useQueryClient();
  const tpl = useQuery({ queryKey: ["adminInviteTemplate"], queryFn: api.adminInviteTemplate });
  // Sender and subject are drafts until Save; null shows the server's value.
  const [from, setFrom] = useState<string | null>(null);
  const [subject, setSubject] = useState<string | null>(null);
  const [testTo, setTestTo] = useState("");

  const save = useMutation({
    mutationFn: api.saveAdminInviteTemplate,
    onSuccess: (data) => {
      queryClient.setQueryData(["adminInviteTemplate"], data);
      setFrom(null);
      setSubject(null);
    },
  });
  const test = useMutation({ mutationFn: () => api.testInvite(testTo.trim()) });
  const data = tpl.data;
  const preview = useQuery({
    queryKey: ["adminInvitePreview", data?.subject, data?.html],
    queryFn: () => api.previewInvite(data?.subject ?? "", data?.html ?? ""),
    enabled: !!data,
  });

  if (!data) {
    return tpl.error instanceof ApiError ? <p className="text-sm text-red-500">{tpl.error.message}</p> : null;
  }
  const custom = data.html !== "";
  const dirty = (from !== null && from !== data.from_address) || (subject !== null && subject !== data.subject);
  const field =
    "w-full rounded border border-app-border bg-app-surface px-2 py-1.5 text-sm focus:border-app-accent focus:outline-none";
  const label = "block space-y-1 text-sm";

  const upload = async (file: File | undefined) => {
    if (!file) return;
    save.mutate({ html: await file.text() });
  };
  const download = () => {
    const blob = new Blob([data.html || data.default_html], { type: "text/html" });
    const a = document.createElement("a");
    a.href = URL.createObjectURL(blob);
    a.download = custom ? "invitation.html" : "invitation-default.html";
    a.click();
    URL.revokeObjectURL(a.href);
  };

  return (
    <section className="space-y-3">
      <h2 className="text-lg font-semibold">{t("admin.inviteMail")}</h2>
      <p className="text-xs text-app-faint">{t("admin.inviteMailHelp")}</p>
      <form
        className="space-y-3"
        onSubmit={(e) => {
          e.preventDefault();
          save.mutate({
            ...(from !== null ? { from_address: from } : {}),
            ...(subject !== null ? { subject } : {}),
          });
        }}
      >
        <label className={label}>
          <span className="text-app-muted">{t("admin.inviteFrom")}</span>
          <input
            className={field}
            type="email"
            value={from ?? data.from_address}
            placeholder={data.default_from}
            onChange={(e) => setFrom(e.target.value)}
          />
          <span className="block text-xs text-app-faint">{t("admin.inviteFromHint")}</span>
        </label>
        <label className={label}>
          <span className="text-app-muted">{t("admin.inviteSubject")}</span>
          <input
            className={field}
            value={subject ?? data.subject}
            placeholder={data.default_subject}
            onChange={(e) => setSubject(e.target.value)}
          />
        </label>
        <div className="flex justify-end">
          <button
            type="submit"
            className="rounded bg-app-accent px-3 py-1 text-sm font-medium text-app-accent-fg hover:opacity-90 disabled:opacity-50"
            disabled={!dirty || save.isPending}
          >
            {save.isPending ? t("admin.saving") : t("admin.save")}
          </button>
        </div>
      </form>

      <div className="space-y-2 border-t border-app-border pt-3 text-sm">
        <p className="text-app-muted">
          {custom ? t("admin.inviteTemplateCustom") : t("admin.inviteTemplateDefault")}
        </p>
        <div className="flex flex-wrap gap-2">
          <label className="cursor-pointer rounded border border-app-border px-3 py-1 hover:bg-app-hover">
            {t("admin.inviteUpload")}
            <input
              type="file"
              accept=".html,.htm,text/html"
              className="hidden"
              onChange={(e) => {
                void upload(e.target.files?.[0]);
                e.target.value = "";
              }}
            />
          </label>
          <button type="button" className="rounded border border-app-border px-3 py-1 hover:bg-app-hover" onClick={download}>
            {t("admin.inviteDownload")}
          </button>
          {custom && (
            <button
              type="button"
              className="rounded border border-app-border px-3 py-1 hover:bg-app-hover disabled:opacity-50"
              disabled={save.isPending}
              onClick={() => confirm(t("admin.inviteResetConfirm")) && save.mutate({ html: "" })}
            >
              {t("admin.inviteReset")}
            </button>
          )}
        </div>
        <p className="text-xs text-app-faint">
          {t("admin.invitePlaceholders")}{" "}
          {data.placeholders.map((p, i) => (
            <span key={p}>
              {i > 0 && ", "}
              <code className="select-all rounded bg-app-hover px-1">{`{{${p}}}`}</code>
            </span>
          ))}
        </p>
        <p className="text-xs text-app-faint">{t("admin.invitePlaceholdersHelp")}</p>
        {save.error instanceof ApiError && <p className="text-xs text-red-500">{save.error.message}</p>}
      </div>

      {preview.data && (
        <div className="space-y-1">
          <p className="text-xs text-app-muted">
            {t("admin.invitePreview")} <span className="font-medium text-app-fg">{preview.data.subject}</span>
          </p>
          {/* Sandboxed, script-less: the admin's own HTML, shown as mail. */}
          <iframe
            title={t("admin.invitePreview")}
            sandbox=""
            srcDoc={preview.data.html}
            className="h-80 w-full rounded-lg border border-app-border bg-white"
          />
        </div>
      )}

      <form
        className="flex items-center gap-2 border-t border-app-border pt-3 text-sm"
        onSubmit={(e) => {
          e.preventDefault();
          test.mutate();
        }}
      >
        <span className="shrink-0 text-app-muted">{t("admin.testTo")}</span>
        <input
          className={field}
          type="email"
          value={testTo}
          placeholder="you@example.com"
          onChange={(e) => {
            setTestTo(e.target.value);
            test.reset();
          }}
        />
        <button
          type="submit"
          className="shrink-0 rounded border border-app-border px-3 py-1 hover:bg-app-hover disabled:opacity-50"
          disabled={!testTo.trim() || test.isPending || dirty}
        >
          {test.isPending ? t("auth.sending") : t("admin.sendTest")}
        </button>
      </form>
      {test.isSuccess && <p className="text-xs text-emerald-600">{t("admin.inviteTestSent")}</p>}
      {test.error instanceof ApiError && <p className="text-xs text-red-500">{test.error.message}</p>}
    </section>
  );
}

function formatBytes(bytes: number): string {
  if (bytes >= GIB) return `${Number((bytes / GIB).toFixed(2))} GiB`;
  return `${Number((bytes / 1024 ** 2).toFixed(1))} MiB`;
}

/** Find a user by login, mail address or name, and open them to manage. */
function Users({ selfId }: { selfId: string }) {
  const t = useT();
  const [term, setTerm] = useState("");
  const [query, setQuery] = useState("");
  const [openId, setOpenId] = useState<string | null>(null);

  // Search as you type, but not on every keystroke.
  useEffect(() => {
    const id = window.setTimeout(() => setQuery(term.trim()), 250);
    return () => window.clearTimeout(id);
  }, [term]);

  // Only search results are listed: nothing until something is typed.
  const users = useQuery({
    queryKey: ["adminUsers", query],
    queryFn: () => api.adminUsers(query),
    enabled: query !== "",
    placeholderData: keepPreviousData,
  });
  const results = query ? users.data : undefined;
  const open = results?.find((u) => u.id === openId) ?? null;

  return (
    <section className="mt-10 space-y-3">
      <h2 className="text-lg font-semibold">{t("admin.users")}</h2>
      <input
        className={inputClass}
        type="search"
        placeholder={t("admin.userSearch")}
        value={term}
        onChange={(e) => setTerm(e.target.value)}
      />
      {users.error instanceof ApiError && (
        <p className="text-sm text-red-500">{users.error.message}</p>
      )}
      {results && results.length === 0 && (
        <p className="text-sm text-app-muted">{t("admin.noUsers")}</p>
      )}
      {results && results.length > 0 && (
        <ul className="divide-y divide-app-border rounded-lg border border-app-border">
          {results.map((u) => (
            <li key={u.id}>
              <button
                type="button"
                onClick={() => setOpenId(u.id)}
                className="flex w-full items-center gap-3 px-3 py-2 text-left hover:bg-app-hover"
              >
                <span className="min-w-0 flex-1">
                  <span className="flex items-center gap-1.5">
                    <span className="truncate font-medium">{u.handle}</span>
                    <Badges user={u} self={u.id === selfId} />
                  </span>
                  <span className="block truncate text-xs text-app-muted">
                    {u.accounts.length ? u.accounts.join(", ") : t("admin.noMailAccounts")}
                  </span>
                </span>
                <span className="shrink-0 text-xs tabular-nums text-app-muted">
                  {t("admin.usage", {
                    used: formatBytes(u.used_bytes),
                    quota: formatBytes(u.quota_bytes),
                  })}
                </span>
              </button>
            </li>
          ))}
        </ul>
      )}
      {open && <UserDialog user={open} self={open.id === selfId} onClose={() => setOpenId(null)} />}
    </section>
  );
}

function Badges({ user, self }: { user: AdminUser; self: boolean }) {
  const t = useT();
  const badge = "shrink-0 rounded px-1.5 text-[11px] font-medium";
  return (
    <>
      {self && <span className={`${badge} bg-app-hover text-app-muted`}>{t("admin.you")}</span>}
      {user.is_admin && (
        <span className={`${badge} bg-app-accent/15 text-app-accent`}>{t("admin.adminBadge")}</span>
      )}
      {user.blocked_at && (
        <span className={`${badge} bg-red-500/15 text-red-500`}>{t("admin.blockedBadge")}</span>
      )}
    </>
  );
}

/** One user: change their quota, block or unblock them, or delete them. */
function UserDialog({
  user,
  self,
  onClose,
}: {
  user: AdminUser;
  self: boolean;
  onClose: () => void;
}) {
  const t = useT();
  const queryClient = useQueryClient();
  const [quotaDraft, setQuotaDraft] = useState<string | null>(null);
  const [confirm, setConfirm] = useState<null | "block" | "delete">(null);

  const refresh = () => queryClient.invalidateQueries({ queryKey: ["adminUsers"] });
  const update = useMutation({
    mutationFn: (body: { quota_bytes?: number; blocked?: boolean }) =>
      api.updateAdminUser(user.id, body),
    onSuccess: () => {
      setQuotaDraft(null);
      setConfirm(null);
      void refresh();
    },
  });
  const remove = useMutation({
    mutationFn: () => api.deleteAdminUser(user.id),
    onSuccess: () => {
      onClose();
      void refresh();
    },
  });

  useEffect(() => {
    const onKey = (e: KeyboardEvent) => {
      if (e.key !== "Escape") return;
      if (confirm) setConfirm(null);
      else onClose();
    };
    window.addEventListener("keydown", onKey);
    return () => window.removeEventListener("keydown", onKey);
  }, [confirm, onClose]);

  const serverGib = user.quota_bytes / GIB;
  const quotaValue = quotaDraft ?? String(Number(serverGib.toFixed(3)));
  const quotaGib = Number(quotaValue);
  const quotaValid = Number.isFinite(quotaGib) && quotaGib > 0;
  const quotaDirty = quotaDraft !== null && quotaGib !== serverGib;
  const busy = update.isPending || remove.isPending;
  const error = [update.error, remove.error].find((e) => e instanceof ApiError) as
    | ApiError
    | undefined;

  return (
    <div className="fixed inset-0 z-40 flex items-center justify-center bg-black/40 p-4" onClick={onClose}>
      <div
        role="dialog"
        aria-modal="true"
        aria-label={user.handle}
        className="relative w-full max-w-md rounded-xl border border-app-border bg-app-elevated p-5 shadow-2xl"
        onClick={(e) => e.stopPropagation()}
      >
        <div className="mb-4 flex items-start gap-3">
          <div className="min-w-0 flex-1">
            <h3 className="flex items-center gap-1.5 font-semibold">
              <span className="truncate">{user.handle}</span>
              <Badges user={user} self={self} />
            </h3>
            <p className="mt-0.5 text-xs text-app-muted">
              {user.accounts.length ? user.accounts.join(", ") : t("admin.noMailAccounts")}
            </p>
          </div>
          <button
            type="button"
            onClick={onClose}
            title={t("admin.close")}
            aria-label={t("admin.close")}
            className="rounded p-1 text-app-muted hover:bg-app-hover hover:text-app-fg"
          >
            <svg width="16" height="16" viewBox="0 0 16 16" fill="none" stroke="currentColor" strokeWidth="1.5" strokeLinecap="round" aria-hidden>
              <path d="M4 4l8 8M12 4l-8 8" />
            </svg>
          </button>
        </div>

        <div className="border-y border-app-border py-3">
          <div className="flex items-center justify-between gap-2 text-sm">
            <span className="text-app-muted">{t("admin.userQuota")}</span>
            <div className="flex items-center gap-2">
              <input
                className="w-24 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 || busy}
                onClick={() => update.mutate({ quota_bytes: Math.round(quotaGib * GIB) })}
              >
                {update.isPending && quotaDirty ? t("admin.saving") : t("admin.save")}
              </button>
            </div>
          </div>
          <p className="mt-1 text-xs text-app-faint">
            {t("admin.usage", {
              used: formatBytes(user.used_bytes),
              quota: formatBytes(user.quota_bytes),
            })}
          </p>
          {!quotaValid && <p className="mt-1 text-xs text-red-500">{t("admin.quotaInvalid")}</p>}
        </div>

        {user.blocked_at && (
          <p className="mt-3 text-sm text-red-500">
            {t("admin.blockedSince", { date: new Date(user.blocked_at).toLocaleString() })}
          </p>
        )}
        {self ? (
          <p className="mt-3 text-xs text-app-muted">{t("admin.selfNote")}</p>
        ) : (
          <div className="mt-4 flex flex-wrap justify-end gap-2">
            {user.blocked_at ? (
              <button
                className="rounded-lg border border-app-border px-3 py-1.5 text-sm hover:bg-app-hover disabled:opacity-50"
                disabled={busy}
                onClick={() => update.mutate({ blocked: false })}
              >
                {t("admin.unblock")}
              </button>
            ) : (
              <button
                className="rounded-lg border border-app-border px-3 py-1.5 text-sm hover:bg-app-hover disabled:opacity-50"
                disabled={busy}
                onClick={() => setConfirm("block")}
              >
                {t("admin.block")}
              </button>
            )}
            <button
              className="rounded-lg bg-red-600 px-3 py-1.5 text-sm font-medium text-white hover:opacity-90 disabled:opacity-50"
              disabled={busy}
              onClick={() => setConfirm("delete")}
            >
              {t("admin.deleteUser")}
            </button>
          </div>
        )}
        {error && <p className="mt-2 text-xs text-red-500">{error.message}</p>}

        {confirm && (
          <div
            className="absolute inset-0 flex items-center justify-center rounded-xl bg-black/40 p-4"
            onClick={() => setConfirm(null)}
          >
            <div
              role="alertdialog"
              aria-modal="true"
              className="w-full max-w-sm rounded-lg border border-app-border bg-app-elevated p-4 shadow-2xl"
              onClick={(e) => e.stopPropagation()}
            >
              <p className="mb-4 text-sm">
                {t(confirm === "block" ? "admin.blockConfirm" : "admin.deleteConfirm", {
                  handle: user.handle,
                })}
              </p>
              <div className="flex justify-end gap-2">
                <button
                  className="rounded-md px-3 py-1.5 text-sm text-app-muted hover:bg-app-hover"
                  onClick={() => setConfirm(null)}
                  autoFocus
                >
                  {t("admin.cancel")}
                </button>
                <button
                  className="rounded-md bg-red-600 px-3 py-1.5 text-sm font-medium text-white hover:opacity-90 disabled:opacity-50"
                  disabled={busy}
                  onClick={() =>
                    confirm === "block" ? update.mutate({ blocked: true }) : remove.mutate()
                  }
                >
                  {t(confirm === "block" ? "admin.block" : "admin.deleteUser")}
                </button>
              </div>
            </div>
          </div>
        )}
      </div>
    </div>
  );
}