✨ Add Amazon Comprehend Node (#1415)

* ✨ Add Amazon Comprehend node

* ⚡ Improvements to #1413

Co-authored-by: Rei Maruyama <rei.maruyama@serverworks.co.jp>

packages/nodes-base/nodes/Aws/Comprehend/GenericFunctions.ts

@@ -0,0 +1,101 @@
+import {
+	URL,
+} from 'url';
+
+import {
+	sign,
+} from 'aws4';
+
+import {
+	OptionsWithUri,
+} from 'request';
+
+import {
+	parseString,
+} from 'xml2js';
+
+import {
+	IExecuteFunctions,
+	IHookFunctions,
+	ILoadOptionsFunctions,
+	IWebhookFunctions,
+} from 'n8n-core';
+
+import {
+	ICredentialDataDecryptedObject,
+} from 'n8n-workflow';
+
+function getEndpointForService(service: string, credentials: ICredentialDataDecryptedObject): string {
+	let endpoint;
+	if (service === 'lambda' && credentials.lambdaEndpoint) {
+		endpoint = credentials.lambdaEndpoint;
+	} else if (service === 'sns' && credentials.snsEndpoint) {
+		endpoint = credentials.snsEndpoint;
+	} else {
+		endpoint = `https://${service}.${credentials.region}.amazonaws.com`;
+	}
+	return (endpoint as string).replace('{region}', credentials.region as string);
+}
+
+export async function awsApiRequest(this: IHookFunctions | IExecuteFunctions | ILoadOptionsFunctions | IWebhookFunctions, service: string, method: string, path: string, body?: string, headers?: object): Promise<any> { // tslint:disable-line:no-any
+	const credentials = this.getCredentials('aws');
+	if (credentials === undefined) {
+		throw new Error('No credentials got returned!');
+	}
+
+	// Concatenate path and instantiate URL object so it parses correctly query strings
+	const endpoint = new URL(getEndpointForService(service, credentials) + path);
+
+	// Sign AWS API request with the user credentials
+	const signOpts = { headers: headers || {}, host: endpoint.host, method, path, body };
+	sign(signOpts, { accessKeyId: `${credentials.accessKeyId}`.trim(), secretAccessKey: `${credentials.secretAccessKey}`.trim() });
+
+
+	const options: OptionsWithUri = {
+		headers: signOpts.headers,
+		method,
+		uri: endpoint.href,
+		body: signOpts.body,
+	};
+
+	try {
+		return await this.helpers.request!(options);
+	} catch (error) {
+		const errorMessage = (error.response && error.response.body.message) || (error.response && error.response.body.Message) || error.message;
+
+		if (error.statusCode === 403) {
+			if (errorMessage === 'The security token included in the request is invalid.') {
+				throw new Error('The AWS credentials are not valid!');
+			} else if (errorMessage.startsWith('The request signature we calculated does not match the signature you provided')) {
+				throw new Error('The AWS credentials are not valid!');
+			}
+		}
+
+		throw new Error(`AWS error response [${error.statusCode}]: ${errorMessage}`);
+	}
+}
+
+export async function awsApiRequestREST(this: IHookFunctions | IExecuteFunctions | ILoadOptionsFunctions, service: string, method: string, path: string, body?: string, headers?: object): Promise<any> { // tslint:disable-line:no-any
+	const response = await awsApiRequest.call(this, service, method, path, body, headers);
+	try {
+		return JSON.parse(response);
+	} catch (e) {
+		return response;
+	}
+}
+
+export async function awsApiRequestSOAP(this: IHookFunctions | IExecuteFunctions | ILoadOptionsFunctions | IWebhookFunctions, service: string, method: string, path: string, body?: string, headers?: object): Promise<any> { // tslint:disable-line:no-any
+	const response = await awsApiRequest.call(this, service, method, path, body, headers);
+	try {
+		return await new Promise((resolve, reject) => {
+			parseString(response, { explicitArray: false }, (err, data) => {
+				if (err) {
+					return reject(err);
+				}
+				resolve(data);
+			});
+		});
+	} catch (e) {
+		return response;
+	}
+}