support matrix.to links (#1849)

* support room via server params and eventId

* change copy link to matrix.to links

* display matrix.to links in messages as pill and stop generating url previews for them

* improve editor mention to include viaServers and eventId

* fix mention custom attributes

* always try to open room in current space

* jump to latest remove target eventId from url

* add create direct search options to open/create dm with url

src/app/plugins/via-servers.ts

@@ -0,0 +1,65 @@
+import { Room } from 'matrix-js-sdk';
+import { IPowerLevels } from '../hooks/usePowerLevels';
+import { getMxIdServer } from '../utils/matrix';
+import { StateEvent } from '../../types/matrix/room';
+import { getStateEvent } from '../utils/room';
+
+export const getViaServers = (room: Room): string[] => {
+  const getHighestPowerUserId = (): string | undefined => {
+    const powerLevels = getStateEvent(room, StateEvent.RoomPowerLevels)?.getContent<IPowerLevels>();
+
+    if (!powerLevels) return undefined;
+    const userIdToPower = powerLevels.users;
+    if (!userIdToPower) return undefined;
+    let powerUserId: string | undefined;
+
+    Object.keys(userIdToPower).forEach((userId) => {
+      if (userIdToPower[userId] <= (powerLevels.users_default ?? 0)) return;
+
+      if (!powerUserId) {
+        powerUserId = userId;
+        return;
+      }
+      if (userIdToPower[userId] > userIdToPower[powerUserId]) {
+        powerUserId = userId;
+      }
+    });
+    return powerUserId;
+  };
+
+  const getServerToPopulation = (): Record<string, number> => {
+    const members = room.getMembers();
+    const serverToPop: Record<string, number> = {};
+
+    members?.forEach((member) => {
+      const { userId } = member;
+      const server = getMxIdServer(userId);
+      if (!server) return;
+      const serverPop = serverToPop[server];
+      if (serverPop === undefined) {
+        serverToPop[server] = 1;
+        return;
+      }
+      serverToPop[server] = serverPop + 1;
+    });
+
+    return serverToPop;
+  };
+
+  const via: string[] = [];
+  const userId = getHighestPowerUserId();
+  if (userId) {
+    const server = getMxIdServer(userId);
+    if (server) via.push(server);
+  }
+  const serverToPop = getServerToPopulation();
+  const sortedServers = Object.keys(serverToPop).sort(
+    (svrA, svrB) => serverToPop[svrB] - serverToPop[svrA]
+  );
+  const mostPop3 = sortedServers.slice(0, 3);
+  if (via.length === 0) return mostPop3;
+  if (mostPop3.includes(via[0])) {
+    mostPop3.splice(mostPop3.indexOf(via[0]), 1);
+  }
+  return via.concat(mostPop3.slice(0, 2));
+};