import React, { useEffect, useRef, useState } from 'react';
import { Box, Icon, Icons, Text, color } from 'folds';
import {
  MatrixEvent,
  MatrixEventEvent,
  Room,
  RoomEvent,
  RoomEventHandlerMap,
  RoomStateEvent,
} from 'matrix-js-sdk';
import { Capability, ClientWidgetApi, IRoomEvent, Widget } from 'matrix-widget-api';
import { useMatrixClient } from '../../../hooks/useMatrixClient';
import { GeneralWidgetDriver } from './GeneralWidgetDriver';
import { WidgetPermissionRequest, isWidgetUrlSafe, widgetCompleteUrl } from './widgetUtils';
import { restrictWidgetMessages } from '../../../plugins/widgetTransport';
import { WidgetPermissionPrompt } from './WidgetPermissionPrompt';
import { isFromFilteredTimelineSet } from '../../../utils/room';

type PendingAsk = {
  requests: WidgetPermissionRequest[];
  origin: string;
  resolve: (allowed: Set<Capability>, remember: boolean) => void;
};

type RoomWidgetViewProps = {
  room: Room;
  widget: Widget;
};

// Hosts one room widget in a sandboxed iframe via ClientWidgetApi (so widgets
// that wait on the client handshake load). Display-only access is granted
// silently; reading/sending in this room is asked for (WidgetPermissionPrompt)
// and, once granted, the room's live events are fed to the widget.
// Re-mounts only when the widget id or its (template) URL changes — not on every
// unrelated room-state update — so viewing a widget doesn't reload constantly.
export function RoomWidgetView({ room, widget }: RoomWidgetViewProps) {
  const mx = useMatrixClient();
  const containerRef = useRef<HTMLDivElement>(null);
  const widgetRef = useRef(widget);
  widgetRef.current = widget;
  const [blocked, setBlocked] = useState(false);
  const [pendingAsk, setPendingAsk] = useState<PendingAsk>();

  useEffect(() => {
    const container = containerRef.current;
    if (!container) return undefined;
    const current = widgetRef.current;

    const completeUrl = widgetCompleteUrl(current, mx, room.roomId);

    // Security: never render a same-origin widget with allow-same-origin (a
    // same-origin frame could break out of the sandbox against our own origin).
    if (!isWidgetUrlSafe(completeUrl, window.location.origin)) {
      setBlocked(true);
      return undefined;
    }
    setBlocked(false);

    const iframe = document.createElement('iframe');
    iframe.title = current.name || 'Widget';
    iframe.sandbox.value =
      'allow-forms allow-scripts allow-same-origin allow-popups allow-downloads';
    iframe.allow = 'autoplay; clipboard-write;';
    iframe.src = completeUrl;
    iframe.style.width = '100%';
    iframe.style.height = '100%';
    iframe.style.border = 'none';
    container.append(iframe);

    let origin = completeUrl;
    try {
      origin = new URL(completeUrl).host;
    } catch {
      // isWidgetUrlSafe already rejected unparsable URLs
    }
    let cancelAsk: (() => void) | undefined;
    const driver = new GeneralWidgetDriver(
      mx,
      room.roomId,
      { id: current.id, url: current.templateUrl },
      (requests) =>
        new Promise((resolve) => {
          let settled = false;
          const done = (allowed: Set<Capability>, remember: boolean) => {
            if (settled) return;
            settled = true;
            cancelAsk = undefined;
            setPendingAsk(undefined);
            resolve({ allowed, remember });
          };
          cancelAsk = () => done(new Set(), false);
          setPendingAsk({ requests, origin, resolve: done });
        }),
    );
    const clientApi = new ClientWidgetApi(current, iframe, driver);
    // Only messages from this widget's own frame and origin are handled, so a
    // widget can't impersonate another one (or the call).
    restrictWidgetMessages(clientApi, iframe, current.origin);
    clientApi.setViewedRoomId(room.roomId);

    // Live room events for widgets that were allowed to see them
    // (ClientWidgetApi drops anything the widget has no capability for).
    const feed = (ev: MatrixEvent) => {
      if (ev.getRoomId() !== room.roomId) return;
      if (ev.isBeingDecrypted() || ev.isDecryptionFailure()) return;
      clientApi.feedEvent(ev.getEffectiveEvent() as IRoomEvent).catch(() => undefined);
    };
    const onTimeline: RoomEventHandlerMap[RoomEvent.Timeline] = (ev, r, toStart, removed, data) => {
      if (toStart || removed || !data?.liveEvent) return;
      if (isFromFilteredTimelineSet(data)) return; // [Gitea #259] don't feed widgets each event twice
      if (ev.isBeingDecrypted()) ev.once(MatrixEventEvent.Decrypted, feed);
      else feed(ev);
    };
    const onState = (ev: MatrixEvent) => {
      if (ev.getRoomId() !== room.roomId) return;
      clientApi.feedStateUpdate(ev.getEffectiveEvent() as IRoomEvent).catch(() => undefined);
    };
    mx.on(RoomEvent.Timeline, onTimeline);
    mx.on(RoomStateEvent.Events, onState);

    return () => {
      mx.off(RoomEvent.Timeline, onTimeline);
      mx.off(RoomStateEvent.Events, onState);
      cancelAsk?.();
      clientApi.stop();
      iframe.remove();
    };
  }, [mx, room.roomId, widget.id, widget.templateUrl]);

  if (blocked) {
    return (
      <Box direction="Column" grow="Yes" alignItems="Center" justifyContent="Center" gap="200">
        <Icon size="400" src={Icons.Warning} style={{ color: color.Warning.Main }} />
        <Text size="T300" align="Center">
          This widget can&apos;t be loaded because its URL is on this app&apos;s own origin.
        </Text>
      </Box>
    );
  }

  const addedBy = widget.creatorUserId
    ? (room.getMember(widget.creatorUserId)?.rawDisplayName ?? widget.creatorUserId)
    : undefined;

  return (
    <>
      <Box ref={containerRef} grow="Yes" style={{ height: '100%', minHeight: 0 }} />
      {pendingAsk && (
        <WidgetPermissionPrompt
          widgetName={widget.name || 'Widget'}
          origin={pendingAsk.origin}
          addedBy={addedBy}
          requests={pendingAsk.requests}
          onDone={pendingAsk.resolve}
        />
      )}
    </>
  );
}