import { useEffect, useState } from "react";
import { useTranslation } from "react-i18next";
import { useMutation, useQuery, useQueryClient } from "@tanstack/react-query";
import {
  ApiError,
  fetchBackupStatus,
  runBackup,
  setBackupConfig,
  testBackupTarget,
  type BackupStatus,
  type TargetCheck,
} from "./api.js";
import { formatRelativeDateTime } from "./lib/format.js";

// Admin screen for the on-site encrypted DB backup. The admin picks the TARGET DIRECTORY here
// (stored in site_config; a mounted USB/SATA/SMB/NFS path) — the encryption key stays a server
// secret. Shows status + last-run outcome, a "Test target" probe, and a manual "Back up now".
// Gated by backup:read (config/test by backup:update, run by backup:create). RESTORE is absent
// by design — out-of-band on a fresh appliance. See wiki/concepts/backup-recovery.md.

function formatBytes(n: number): string {
  if (n < 1024) return `${n} B`;
  const mb = n / 1048576;
  if (mb < 1024) return `${mb.toFixed(1)} MB`;
  return `${(mb / 1024).toFixed(2)} GB`;
}

/** Map a target-check result to a localized message. */
function checkMessage(c: TargetCheck, t: (k: string) => string): string {
  if (c.ok) return t("backup.testOk");
  switch (c.reason) {
    case "empty":
      return t("backup.testEmpty");
    case "not_a_dir":
      return t("backup.testNotDir");
    case "not_writable":
      return t("backup.testNotWritable");
    default:
      return t("backup.testMissing");
  }
}

function StatusBadge({ status }: { status: BackupStatus }) {
  const { t } = useTranslation();
  if (!status.configured) {
    return <span className="text-[0.75rem] font-semibold text-term-muted">{t("backup.notConfigured")}</span>;
  }
  if (status.running) {
    return <span className="text-[0.75rem] font-semibold text-term-amber">{t("backup.running")}</span>;
  }
  return <span className="text-[0.75rem] font-semibold text-term-green">{t("backup.configured")}</span>;
}

export function BackupSettings() {
  const { t } = useTranslation();
  const qc = useQueryClient();
  const [toast, setToast] = useState<{ kind: "ok" | "err"; msg: string } | null>(null);
  const [target, setTarget] = useState("");
  const [keepLast, setKeepLast] = useState("");
  const [keepDaily, setKeepDaily] = useState("");
  const [check, setCheck] = useState<{ kind: "ok" | "err"; msg: string } | null>(null);

  const q = useQuery({
    queryKey: ["backup-status"],
    queryFn: fetchBackupStatus,
    refetchInterval: (query) => (query.state.data?.running ? 2000 : false),
  });
  const status = q.data;

  // Seed the editable fields from the saved values once they load (and on server-side change).
  useEffect(() => {
    if (status) {
      setTarget(status.targetDir ?? "");
      setKeepLast(String(status.keepLast));
      setKeepDaily(String(status.keepDailyDays));
    }
  }, [status?.targetDir, status?.keepLast, status?.keepDailyDays]);

  const save = useMutation({
    mutationFn: () =>
      setBackupConfig({
        targetDir: target.trim() || null,
        keepLast: keepLast.trim() === "" ? null : Number(keepLast),
        keepDailyDays: keepDaily.trim() === "" ? null : Number(keepDaily),
      }),
    onSuccess: (next) => {
      setToast({ kind: "ok", msg: t("backup.saved") });
      setCheck(null);
      qc.setQueryData(["backup-status"], next);
    },
    onError: () => setToast({ kind: "err", msg: t("backup.runFailed") }),
  });

  const test = useMutation({
    mutationFn: () => testBackupTarget(target.trim()),
    onSuccess: (res) => setCheck({ kind: res.ok ? "ok" : "err", msg: checkMessage(res, t) }),
  });

  const run = useMutation({
    mutationFn: runBackup,
    onSuccess: () => {
      setToast({ kind: "ok", msg: t("backup.runSuccess") });
      void qc.invalidateQueries({ queryKey: ["backup-status"] });
    },
    onError: (err: unknown) => {
      const code = err instanceof ApiError ? err.message : "";
      setToast({
        kind: "err",
        msg: code === "backup_not_configured" ? t("backup.notConfiguredError") : t("backup.runFailed"),
      });
      void qc.invalidateQueries({ queryKey: ["backup-status"] });
    },
  });

  const dirty =
    (status?.targetDir ?? "") !== target.trim() ||
    String(status?.keepLast ?? "") !== keepLast.trim() ||
    String(status?.keepDailyDays ?? "") !== keepDaily.trim();

  return (
    <div className="">
      <div className="mb-3 flex items-center justify-between">
        <h1 className="text-sm font-bold uppercase tracking-widest text-term-amber">{t("backup.title")}</h1>
        <button
          type="button"
          className="btn btn-primary btn-sm"
          disabled={!status?.configured || status?.running || run.isPending || dirty}
          onClick={() => {
            setToast(null);
            run.mutate();
          }}
        >
          {status?.running || run.isPending ? t("backup.running") : t("backup.runNow")}
        </button>
      </div>

      <p className="mb-3 max-w-2xl text-[0.75rem] text-term-muted">{t("backup.intro")}</p>

      {toast && (
        <div
          className={`mb-3 rounded-term border px-3 py-2 text-[0.75rem] ${
            toast.kind === "ok"
              ? "border-term-green/40 bg-term-green/5 text-term-green"
              : "border-term-red/40 bg-term-red/5 text-term-red"
          }`}
        >
          {toast.msg}
        </div>
      )}

      {/* Config — admin-chosen destination + retention policy. */}
      <div className="card mb-3 p-4">
        {/* Target directory + its Test probe. */}
        <div className="field">
          <span className="label">{t("backup.targetLabel")}</span>
          <div className="flex flex-wrap items-center gap-2">
            <input
              className="input w-96 max-w-full"
              value={target}
              placeholder={t("backup.targetPlaceholder")}
              onChange={(e) => {
                setTarget(e.target.value);
                setCheck(null);
              }}
            />
            <button
              type="button"
              className="btn btn-ghost btn-sm"
              disabled={test.isPending || !target.trim()}
              onClick={() => test.mutate()}
            >
              {t("backup.test")}
            </button>
          </div>
          <span className="mt-1 text-[0.6875rem] text-term-muted">{t("backup.targetHint")}</span>
          {check && (
            <span className={`mt-1 text-[0.75rem] ${check.kind === "ok" ? "text-term-green" : "text-term-red"}`}>
              {check.msg}
            </span>
          )}
        </div>

        {/* Retention — admin-tuned policy (how many backups to keep at the target). */}
        <div className="mt-4 flex flex-wrap items-start gap-6">
          <div className="field">
            <span className="label">{t("backup.keepLastLabel")}</span>
            <input
              type="number"
              min={0}
              className="input w-28"
              value={keepLast}
              onChange={(e) => setKeepLast(e.target.value)}
            />
            <span className="mt-1 text-[0.6875rem] text-term-muted">{t("backup.keepLastHint")}</span>
          </div>
          <div className="field">
            <span className="label">{t("backup.keepDailyLabel")}</span>
            <input
              type="number"
              min={0}
              className="input w-28"
              value={keepDaily}
              onChange={(e) => setKeepDaily(e.target.value)}
            />
            <span className="mt-1 text-[0.6875rem] text-term-muted">{t("backup.keepDailyHint")}</span>
          </div>
        </div>

        <div className="mt-4 flex items-center gap-3">
          <button
            type="button"
            className="btn btn-primary btn-sm"
            disabled={save.isPending || !dirty}
            onClick={() => {
              setToast(null);
              save.mutate();
            }}
          >
            {t("backup.save")}
          </button>
        </div>
      </div>

      <div className="card p-4">
        {q.isLoading || !status ? (
          <div className="text-[0.75rem] text-term-muted">{t("common.loading")}</div>
        ) : (
          <dl className="grid grid-cols-[10rem_1fr] gap-x-4 gap-y-2 text-[0.8125rem]">
            <dt className="text-term-muted">{t("backup.statusTitle")}</dt>
            <dd>
              <StatusBadge status={status} />
            </dd>

            {!status.keyPresent && (
              <>
                <dt className="text-term-muted" />
                <dd className="text-[0.75rem] text-term-amber">{t("backup.keyMissing")}</dd>
              </>
            )}

            <dt className="text-term-muted">{t("backup.lastSuccess")}</dt>
            <dd className="text-term-text">
              {status.lastSuccessAt ? formatRelativeDateTime(status.lastSuccessAt, t) : t("backup.never")}
            </dd>

            {status.lastResult && (
              <>
                <dt className="text-term-muted">{t("backup.size")}</dt>
                <dd className="text-term-text tabular-nums">
                  {formatBytes(status.lastResult.bytes)}
                  {status.lastResult.prunedFiles > 0 && (
                    <span className="ml-2 text-term-muted">
                      ({t("backup.pruned")}: {status.lastResult.prunedFiles})
                    </span>
                  )}
                </dd>
              </>
            )}

            {status.lastError && (
              <>
                <dt className="text-term-muted">{t("backup.lastError")}</dt>
                <dd className="text-term-red">
                  {status.lastError}
                  {status.lastErrorAt && (
                    <span className="ml-2 text-term-muted">
                      ({formatRelativeDateTime(status.lastErrorAt, t)})
                    </span>
                  )}
                </dd>
              </>
            )}
          </dl>
        )}
      </div>

      <p className="mt-3 max-w-2xl text-[0.6875rem] text-term-muted">{t("backup.restoreNote")}</p>
    </div>
  );
}