feat: Add Slack trigger node (#9190)

Co-authored-by: Giulio Andreini <andreini@netseven.it>

packages/nodes-base/nodes/Slack/SlackTriggerHelpers.ts

@@ -0,0 +1,79 @@
+import type { IHttpRequestOptions, IWebhookFunctions } from 'n8n-workflow';
+import { NodeOperationError } from 'n8n-workflow';
+import { slackApiRequest } from './V2/GenericFunctions';
+
+export async function getUserInfo(this: IWebhookFunctions, userId: string): Promise<any> {
+	const user = await slackApiRequest.call(
+		this,
+		'GET',
+		'/users.info',
+		{},
+		{
+			user: userId,
+		},
+	);
+
+	return user.user.name;
+}
+
+export async function getChannelInfo(this: IWebhookFunctions, channelId: string): Promise<any> {
+	const channel = await slackApiRequest.call(
+		this,
+		'GET',
+		'/conversations.info',
+		{},
+		{
+			channel: channelId,
+		},
+	);
+
+	return channel.channel.name;
+}
+
+export async function downloadFile(this: IWebhookFunctions, url: string): Promise<any> {
+	let options: IHttpRequestOptions = {
+		method: 'GET',
+		url,
+	};
+
+	const requestOptions = {
+		encoding: 'arraybuffer',
+		returnFullResponse: true,
+		json: false,
+		useStream: true,
+	};
+
+	options = Object.assign({}, options, requestOptions);
+
+	const response = await this.helpers.requestWithAuthentication.call(this, 'slackApi', options);
+
+	if (response.ok === false) {
+		if (response.error === 'paid_teams_only') {
+			throw new NodeOperationError(
+				this.getNode(),
+				`Your current Slack plan does not include the resource '${
+					this.getNodeParameter('resource', 0) as string
+				}'`,
+				{
+					description:
+						'Hint: Upgrade to a Slack plan that includes the functionality you want to use.',
+					level: 'warning',
+				},
+			);
+		} else if (response.error === 'missing_scope') {
+			throw new NodeOperationError(
+				this.getNode(),
+				'Your Slack credential is missing required Oauth Scopes',
+				{
+					description: `Add the following scope(s) to your Slack App: ${response.needed}`,
+					level: 'warning',
+				},
+			);
+		}
+		throw new NodeOperationError(
+			this.getNode(),
+			'Slack error response: ' + JSON.stringify(response.error),
+		);
+	}
+	return response;
+}