import React, { useCallback, useEffect, useState } from 'react';
import { useAtomValue, useSetAtom } from 'jotai';
import { SyncState } from 'matrix-js-sdk';
import { CryptoApi } from 'matrix-js-sdk/lib/crypto-api';
import { Icons } from 'folds';
import { ErrorBoundary } from 'react-error-boundary';
import { useMatrixClient } from '../../hooks/useMatrixClient';
import { useCrossSigningActive } from '../../hooks/useCrossSigning';
import {
  useDeviceVerificationStatus,
  VerificationStatus,
} from '../../hooks/useDeviceVerificationStatus';
import { useKeyBackupInfo, useKeyBackupStatusChange } from '../../hooks/useKeyBackup';
import { useAlive } from '../../hooks/useAlive';
import { useSyncState } from '../../hooks/useSyncState';
import { settingsRequestAtom } from '../../state/settingsRequest';
import { serverStatusAtom } from '../../state/serverStatus';
import { pickBanner } from '../../utils/kumaStatus';
import {
  dismissNudge,
  NUDGE_COPY,
  NUDGE_KEY_PREFIX,
  nudgeFor,
  NudgeRecord,
  parseNudgeRecord,
  shouldShowNudge,
} from '../../utils/securityNudge';
import { StatusStrip } from '../server-status/ServerStatusBanner';

/** This device's backup connection: undefined until known, then true/false. */
const useBackupActive = (crypto: CryptoApi): boolean | undefined => {
  const alive = useAlive();
  const [active, setActive] = useState<boolean>();
  useEffect(() => {
    crypto.getActiveSessionBackupVersion().then((v) => {
      if (alive()) setActive(typeof v === 'string');
    });
  }, [crypto, alive]);
  useKeyBackupStatusChange(useCallback((enabled: boolean) => setActive(enabled), []));
  return active;
};

const readRecord = (key: string): NudgeRecord => {
  let raw: string | null = null;
  try {
    raw = localStorage.getItem(key);
  } catch {
    /* storage unavailable */
  }
  const record = parseNudgeRecord(raw, Date.now());
  if (!raw) {
    try {
      localStorage.setItem(key, JSON.stringify(record));
    } catch {
      /* best effort */
    }
  }
  return record;
};

function SecurityBannerFor({ crypto }: { crypto: CryptoApi }) {
  const mx = useMatrixClient();
  const deviceId = mx.getDeviceId() ?? undefined;
  const crossSigning = useCrossSigningActive();
  const status = useDeviceVerificationStatus(crypto, mx.getSafeUserId(), deviceId);
  const backupInfo = useKeyBackupInfo(crypto);
  const backupActive = useBackupActive(crypto);
  const { status: serverStatus, syncLost } = useAtomValue(serverStatusAtom);
  const requestSettings = useSetAtom(settingsRequestAtom);
  // Not urgent: wait until sync has settled (two SYNCING in a row), so it
  // never stacks under the "Connecting…" strip at startup.
  const [settled, setSettled] = useState(false);
  useSyncState(
    mx,
    useCallback((state: SyncState | null, prev?: SyncState | null) => {
      setSettled(state === SyncState.Syncing && prev === SyncState.Syncing);
    }, []),
  );

  const key = `${NUDGE_KEY_PREFIX}${deviceId ?? 'unknown'}`;
  const [record, setRecord] = useState(() => readRecord(key));

  let deviceVerified: boolean | undefined;
  if (status === VerificationStatus.Verified) deviceVerified = true;
  else if (status === VerificationStatus.Unverified) deviceVerified = false;
  const kind = nudgeFor({
    crossSigning,
    deviceVerified,
    backupOnServer: backupInfo === undefined ? undefined : backupInfo !== null,
    backupActive,
  });

  // One strip at a time: outages, maintenance and a lost connection win.
  const otherStrip = syncLost || !!pickBanner(serverStatus, { syncLost, where: 'client' });
  if (!settled || !deviceId || !kind || otherStrip || !shouldShowNudge(kind, record, Date.now()))
    return null;

  const copy = NUDGE_COPY[kind];
  const dismiss = () => {
    const next = dismissNudge(kind, record, Date.now());
    try {
      localStorage.setItem(key, JSON.stringify(next));
    } catch {
      /* dismissed for this session only */
    }
    setRecord(next);
  };
  return (
    <StatusStrip
      banner={{ key: kind, tone: 'Primary', text: copy.text, dismissable: true }}
      icon={Icons.ShieldUser}
      action={{ label: copy.action, onClick: () => requestSettings('devices') }}
      dismissLabel="Not now"
      onDismiss={dismiss}
    />
  );
}

/**
 * [Gitea #110, #123] The device-security nudge: verify this device, connect
 * it to the key backup, or set up key backup. See utils/securityNudge.ts.
 */
function SecurityBannerInner() {
  const mx = useMatrixClient();
  const crypto = mx.getCrypto();
  if (!crypto) return null;
  return <SecurityBannerFor crypto={crypto} />;
}

// A nudge must never take the app down: any error just hides it.
export function SecurityBanner() {
  return (
    <ErrorBoundary fallback={null}>
      <SecurityBannerInner />
    </ErrorBoundary>
  );
}