Add conversations API (#8832)

* Add conversations API

* Add web UI for conversations

* Add test for conversations API

* Add tests for ConversationAccount

* Improve web UI

* Rename ConversationAccount to AccountConversation

* Remove conversations on block and mute

* Change last_status_id to be a denormalization of status_ids

* Add optimistic locking

app/javascript/mastodon/features/direct_timeline/components/conversation.js

@@ -0,0 +1,85 @@
+import React from 'react';
+import PropTypes from 'prop-types';
+import ImmutablePropTypes from 'react-immutable-proptypes';
+import ImmutablePureComponent from 'react-immutable-pure-component';
+import StatusContent from '../../../components/status_content';
+import RelativeTimestamp from '../../../components/relative_timestamp';
+import DisplayName from '../../../components/display_name';
+import Avatar from '../../../components/avatar';
+import AttachmentList from '../../../components/attachment_list';
+import { HotKeys } from 'react-hotkeys';
+
+export default class Conversation extends ImmutablePureComponent {
+
+  static contextTypes = {
+    router: PropTypes.object,
+  };
+
+  static propTypes = {
+    conversationId: PropTypes.string.isRequired,
+    accounts: ImmutablePropTypes.list.isRequired,
+    lastStatus: ImmutablePropTypes.map.isRequired,
+    onMoveUp: PropTypes.func,
+    onMoveDown: PropTypes.func,
+  };
+
+  handleClick = () => {
+    if (!this.context.router) {
+      return;
+    }
+
+    const { lastStatus } = this.props;
+    this.context.router.history.push(`/statuses/${lastStatus.get('id')}`);
+  }
+
+  handleHotkeyMoveUp = () => {
+    this.props.onMoveUp(this.props.conversationId);
+  }
+
+  handleHotkeyMoveDown = () => {
+    this.props.onMoveDown(this.props.conversationId);
+  }
+
+  render () {
+    const { accounts, lastStatus, lastAccount } = this.props;
+
+    if (lastStatus === null) {
+      return null;
+    }
+
+    const handlers = {
+      moveDown: this.handleHotkeyMoveDown,
+      moveUp: this.handleHotkeyMoveUp,
+      open: this.handleClick,
+    };
+
+    let media;
+
+    if (lastStatus.get('media_attachments').size > 0) {
+      media = <AttachmentList compact media={lastStatus.get('media_attachments')} />;
+    }
+
+    return (
+      <HotKeys handlers={handlers}>
+        <div className='conversation focusable' tabIndex='0' onClick={this.handleClick} role='button'>
+          <div className='conversation__header'>
+            <div className='conversation__avatars'>
+              <div>{accounts.map(account => <Avatar key={account.get('id')} size={36} account={account} />)}</div>
+            </div>
+
+            <div className='conversation__time'>
+              <RelativeTimestamp timestamp={lastStatus.get('created_at')} />
+              <br />
+              <DisplayName account={lastAccount} withAcct={false} />
+            </div>
+          </div>
+
+          <StatusContent status={lastStatus} onClick={this.handleClick} />
+
+          {media}
+        </div>
+      </HotKeys>
+    );
+  }
+
+}