import React, { useCallback, useEffect, useRef, useState } from 'react';
import FocusTrap from 'focus-trap-react';
import {
  Box,
  Button,
  Dialog,
  Header,
  Icon,
  Icons,
  Overlay,
  OverlayBackdrop,
  OverlayCenter,
  Text,
  config,
} from 'folds';
import {
  EventStatus,
  HttpApiEvent,
  HttpApiEventHandlerMap,
  MatrixEvent,
  Room,
  RoomEvent,
  RoomEventHandlerMap,
} from 'matrix-js-sdk';
import { useMatrixClient } from '../hooks/useMatrixClient';
import { useModalStyle } from '../hooks/useModalStyle';
import { failedForConsent, safeConsentUri } from '../utils/consent';

// After "Later", don't re-open for every background retry; the next send the
// user makes after this window explains again.
const SNOOZE_MS = 10_000;

/**
 * A homeserver with a consent requirement (e.g. Synapse's user_consent) blocks
 * sending until its terms are accepted, answering 403 M_CONSENT_NOT_GIVEN with a `consent_uri`. Without
 * this the message just shows "Failed to send". The SDK emits
 * HttpApiEvent.NoConsent for every such response; we explain why, link to the
 * acceptance page, and offer to resend what was blocked once accepted.
 */
export function ConsentRequiredPrompt() {
  const mx = useMatrixClient();
  const [consentUri, setConsentUri] = useState<string>();
  const [open, setOpen] = useState(false);
  const [opened, setOpened] = useState(false);
  const [blockedCount, setBlockedCount] = useState(0);
  const snoozedUntil = useRef(0);
  const blocked = useRef(new Map<MatrixEvent, Room>());
  const modalStyle = useModalStyle(440);
  const server = mx.getDomain() ?? 'Your homeserver';

  useEffect(() => {
    const onNoConsent: HttpApiEventHandlerMap[HttpApiEvent.NoConsent] = (_message, uri) => {
      const safe = safeConsentUri(uri);
      if (safe) setConsentUri(safe);
      if (Date.now() >= snoozedUntil.current) setOpen(true);
    };
    const onLocalEcho: RoomEventHandlerMap[RoomEvent.LocalEchoUpdated] = (event, room) => {
      if (failedForConsent(event)) blocked.current.set(event, room);
      else if (!blocked.current.delete(event)) return;
      setBlockedCount(blocked.current.size);
    };
    mx.on(HttpApiEvent.NoConsent, onNoConsent);
    mx.on(RoomEvent.LocalEchoUpdated, onLocalEcho);
    return () => {
      mx.removeListener(HttpApiEvent.NoConsent, onNoConsent);
      mx.removeListener(RoomEvent.LocalEchoUpdated, onLocalEcho);
    };
  }, [mx]);

  const review = useCallback(() => {
    if (!consentUri) return;
    window.open(consentUri, '_blank', 'noopener,noreferrer');
    setOpened(true);
  }, [consentUri]);

  const retry = useCallback(() => {
    setOpen(false);
    setOpened(false);
    const pending = Array.from(blocked.current.entries());
    blocked.current.clear();
    setBlockedCount(0);
    pending.forEach(([event, room]) => {
      if (event.status === EventStatus.NOT_SENT) mx.resendEvent(event, room);
    });
  }, [mx]);

  const later = useCallback(() => {
    snoozedUntil.current = Date.now() + SNOOZE_MS;
    setOpen(false);
  }, []);

  if (!open) return null;
  return (
    <Overlay open backdrop={<OverlayBackdrop />}>
      <OverlayCenter>
        <FocusTrap
          focusTrapOptions={{
            initialFocus: '#consent-review',
            fallbackFocus: '#consent-later',
            onDeactivate: later,
            clickOutsideDeactivates: true,
            escapeDeactivates: true,
          }}
        >
          <Dialog
            variant="Surface"
            role="alertdialog"
            aria-modal="true"
            aria-labelledby="consent-title"
            aria-describedby="consent-body"
            style={modalStyle}
          >
            <Header
              style={{
                padding: `0 ${config.space.S400}`,
                borderBottomWidth: config.borderWidth.B300,
              }}
              variant="Surface"
              size="500"
            >
              <Text as="h2" size="H4" id="consent-title">
                Accept the terms to keep chatting
              </Text>
            </Header>
            <Box style={{ padding: config.space.S400 }} direction="Column" gap="400">
              <Box id="consent-body" direction="Column" gap="200">
                <Text priority="400">
                  Your message wasn&apos;t sent. <b>{server}</b> requires you to review and accept
                  its terms of service before you can send messages.
                </Text>
                <Text priority="400">
                  {consentUri
                    ? 'Nothing you sent is lost: accept the terms, then come back here and retry.'
                    : 'Your homeserver didn’t include a link to its terms. Contact its administrator, or accept them in another Matrix app, then retry.'}
                </Text>
              </Box>
              <Box direction="Column" gap="200">
                {consentUri && (
                  <Button
                    id="consent-review"
                    variant={opened ? 'Secondary' : 'Primary'}
                    fill={opened ? 'Soft' : 'Solid'}
                    onClick={review}
                    after={<Icon size="100" src={Icons.External} />}
                  >
                    <Text size="B400">Review and accept</Text>
                  </Button>
                )}
                <Button
                  variant={opened ? 'Primary' : 'Secondary'}
                  fill={opened ? 'Solid' : 'Soft'}
                  onClick={retry}
                >
                  <Text size="B400">
                    {blockedCount > 0 ? "I've accepted — retry sending" : "I've accepted"}
                  </Text>
                </Button>
                <Button id="consent-later" variant="Secondary" fill="None" onClick={later}>
                  <Text size="B400">Later</Text>
                </Button>
              </Box>
            </Box>
          </Dialog>
        </FocusTrap>
      </OverlayCenter>
    </Overlay>
  );
}