Add `common` subproject containing shared files

Move classes in `model` to their own `common` package.
Now, the client and server can import `common` as a library.
This is the first step to eventually migrate all the source code at the root of the
project to an `old-server` package.

GitLab: #55
Change-Id: I4b7a52e80171d9c3399416ab524bcdd6915ac540
diff --git a/common/src/Conversation.ts b/common/src/Conversation.ts
new file mode 100644
index 0000000..01b70cd
--- /dev/null
+++ b/common/src/Conversation.ts
@@ -0,0 +1,171 @@
+/*
+ * Copyright (C) 2022 Savoir-faire Linux Inc.
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU Affero General Public License as
+ * published by the Free Software Foundation; either version 3 of the
+ * License, or (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU Affero General Public License for more details.
+ *
+ * You should have received a copy of the GNU Affero General Public
+ * License along with this program.  If not, see
+ * <https://www.gnu.org/licenses/>.
+ */
+import { Socket } from 'socket.io';
+
+import { Contact } from './Contact.js';
+import { PromiseExecutor, Session } from './util.js';
+
+export interface ConversationMember {
+  contact: Contact;
+  role?: 'admin' | 'member' | 'invited' | 'banned' | 'left';
+}
+
+type ConversationInfos = Record<string, unknown>;
+
+export type Message = Record<string, string>;
+type ConversationRequest = PromiseExecutor<Message[]>;
+
+type ConversationListeners = Record<
+  string,
+  {
+    socket: Socket;
+    session: Session;
+  }
+>;
+
+export class Conversation {
+  private readonly id: string | undefined;
+  private readonly accountId: string;
+  private readonly members: ConversationMember[];
+  private messages: Message[];
+  private _infos: ConversationInfos;
+  private _requests: Record<string, ConversationRequest>;
+  private _listeners: ConversationListeners;
+
+  constructor(id: string | undefined, accountId: string, members?: ConversationMember[]) {
+    this.id = id;
+    this.accountId = accountId;
+    this.members = members || [];
+
+    this.messages = [];
+    this._infos = {};
+    this._requests = {};
+    this._listeners = {};
+  }
+
+  static from(accountId: string, object: any) {
+    const conversation = new Conversation(
+      object.id,
+      accountId,
+      object.members.map((member: any) => {
+        member.contact = Contact.from(member.contact);
+        return member;
+      })
+    );
+    conversation.messages = object.messages;
+    return conversation;
+  }
+  static fromSingleContact(accountId: string, contact: Contact) {
+    return new Conversation(undefined, accountId, [{ contact }]);
+  }
+
+  getId() {
+    return this.id;
+  }
+
+  getAccountId() {
+    return this.accountId;
+  }
+
+  getDisplayName() {
+    if (this.members.length !== 0) {
+      return this.members[0].contact.getDisplayName();
+    }
+    return this.getDisplayUri();
+  }
+
+  getDisplayNameNoFallback() {
+    if (this.members.length !== 0) {
+      return this.members[0].contact.getDisplayNameNoFallback();
+    }
+  }
+
+  async getObject(params?: {
+    memberFilter: (value: ConversationMember, index: number, array: ConversationMember[]) => boolean;
+  }) {
+    const members = params?.memberFilter ? this.members.filter(params.memberFilter) : this.members;
+    return {
+      id: this.id,
+      messages: this.messages,
+      members: await Promise.all(
+        members.map(async (member) => {
+          //Object.assign({}, member);
+          return {
+            role: member.role,
+            contact: await member.contact.getObject(),
+          };
+        })
+      ),
+    };
+  }
+
+  getSummary() {
+    return this.getObject();
+  }
+
+  getDisplayUri() {
+    return this.getId() || this.getFirstMember().contact.getUri();
+  }
+
+  getFirstMember() {
+    return this.members[0];
+  }
+
+  getMembers() {
+    return this.members;
+  }
+
+  addMessage(message: Message) {
+    if (this.messages.length === 0) this.messages.push(message);
+    else if (message.id === this.messages[this.messages.length - 1].linearizedParent) {
+      this.messages.push(message);
+    } else if (message.linearizedParent === this.messages[0].id) {
+      this.messages.unshift(message);
+    } else {
+      console.log("Can't insert message " + message.id);
+    }
+  }
+
+  addLoadedMessages(messages: Message[]) {
+    messages.forEach((message) => this.addMessage(message));
+  }
+
+  getMessages() {
+    return this.messages;
+  }
+
+  set infos(infos: ConversationInfos) {
+    this._infos = infos;
+  }
+
+  get requests(): Record<string, ConversationRequest> {
+    return this._requests;
+  }
+
+  set requests(value: Record<string, ConversationRequest>) {
+    this._requests = value;
+  }
+
+  get listeners(): ConversationListeners {
+    return this._listeners;
+  }
+
+  set listeners(listeners: ConversationListeners) {
+    this._listeners = listeners;
+  }
+}