import { ITriggerFunctions } from 'n8n-core';
import {
	IBinaryData,
	IDataObject,
	INodeExecutionData,
	INodeType,
	INodeTypeDescription,
	ITriggerResponse,
} from 'n8n-workflow';

import { connect as imapConnect, ImapSimple, ImapSimpleOptions, getParts, Message }  from 'imap-simple';

export class EmailReadImap implements INodeType {
	description: INodeTypeDescription = {
		displayName: 'EmailReadImap',
		name: 'emailReadImap',
		icon: 'fa:inbox',
		group: ['trigger'],
		version: 1,
		description: 'Triggers the workflow when a new email gets received',
		defaults: {
			name: 'IMAP Email',
			color: '#44AA22',
		},
		inputs: [],
		outputs: ['main'],
		credentials: [
			{
				name: 'imap',
				required: true,
			}
		],
		properties: [
			{
				displayName: 'Mailbox Name',
				name: 'mailbox',
				type: 'string',
				default: 'INBOX',
			},
			{
				displayName: 'Action',
				name: 'postProcessAction',
				type: 'options',
				options: [
					{
						name: 'Mark as read',
						value: 'read'
					},
					{
						name: 'Nothing',
						value: 'nothing'
					},
				],
				default: 'read',
				description: 'What to do after the email has been received. If "nothing" gets<br />selected it will be processed multiple times.',
			},
			{
				displayName: 'Download Attachments',
				name: 'downloadAttachments',
				type: 'boolean',
				default: false,
				description: 'If attachments of emails should be downloaded.<br />Only set if needed as it increases processing.',
			},
			{
				displayName: 'Property Prefix Name',
				name: 'dataPropertyAttachmentsPrefixName',
				type: 'string',
				default: 'attachment_',
				displayOptions: {
					show: {
						downloadAttachments: [
							true
						],
					},
				},
				description: 'Prefix for name of the binary property to which to<br />write the attachments. An index starting with 0 will be added.<br />So if name is "attachment_" the first attachment is saved to "attachment_0"',
			},
			{
				displayName: 'Options',
				name: 'options',
				type: 'collection',
				placeholder: 'Add Option',
				default: {},
				options: [
					{
						displayName: 'Ignore SSL Issues',
						name: 'allowUnauthorizedCerts',
						type: 'boolean',
						default: false,
						description: 'Do connect even if SSL certificate validation is not possible.',
					},
				],
			},
		],
	};



	async trigger(this: ITriggerFunctions): Promise<ITriggerResponse> {
		const credentials = this.getCredentials('imap');

		if (credentials === undefined) {
			throw new Error('No credentials got returned!');
		}

		const mailbox = this.getNodeParameter('mailbox') as string;
		const postProcessAction = this.getNodeParameter('postProcessAction') as string;
		const downloadAttachments = this.getNodeParameter('downloadAttachments') as boolean;
		const options = this.getNodeParameter('options', {}) as IDataObject;


		// Returns the email text
		const getText = async (parts: any[], message: Message, subtype: string) => { // tslint:disable-line:no-any
			if (!message.attributes.struct) {
				return '';
			}

			const textParts = parts.filter((part) => {
				return part.type.toUpperCase() === 'TEXT' && part.subtype.toUpperCase() === subtype.toUpperCase();
			});

			if (textParts.length === 0) {
				return '';
			}

			return await connection.getPartData(message, textParts[0]);
		};


		// Returns the email attachments
		const getAttachment = async (connection: ImapSimple, parts: any[], message: Message): Promise<IBinaryData[]> => { // tslint:disable-line:no-any
			if (!message.attributes.struct) {
				return [];
			}

			// Check if the message has attachments and if so get them
			const attachmentParts = parts.filter((part) => {
				return part.disposition && part.disposition.type.toUpperCase() === 'ATTACHMENT';
			});

			const attachmentPromises = [];
			let attachmentPromise;
			for (const attachmentPart of attachmentParts) {
				attachmentPromise = connection.getPartData(message, attachmentPart)
					.then((partData) => {
						// Return it in the format n8n expects
						return this.helpers.prepareBinaryData(partData, attachmentPart.disposition.params.filename);
					});

				attachmentPromises.push(attachmentPromise);
			}

			return Promise.all(attachmentPromises);
		};


		// Returns all the new unseen messages
		const getNewEmails = async (connection: ImapSimple): Promise<INodeExecutionData[]> => {

			const searchCriteria = [
				'UNSEEN'
			];

			const fetchOptions = {
				bodies: ['HEADER', 'TEXT'],
				markSeen: postProcessAction === 'read',
				struct: true,
			};

			const results = await connection.search(searchCriteria, fetchOptions);

			const newEmails: INodeExecutionData[] = [];
			let newEmail: INodeExecutionData, messageHeader, messageBody;
			let attachments: IBinaryData[];
			let propertyName: string;

			let dataPropertyAttachmentsPrefixName = '';
			if (downloadAttachments === true) {
				dataPropertyAttachmentsPrefixName = this.getNodeParameter('dataPropertyAttachmentsPrefixName') as string;
			}

			// All properties get by default moved to metadata except the ones
			// which are defined here which get set on the top level.
			const topLevelProperties = [
				'cc',
				'date',
				'from',
				'subject',
				'to',
			];
			for (const message of results) {

				const parts = getParts(message.attributes.struct!);

				newEmail = {
					json: {
						textHtml: await getText(parts, message, 'html'),
						textPlain: await getText(parts, message, 'plain'),
						metadata: {} as IDataObject,
					}
				};

				messageHeader = message.parts.filter((part) => {
					return part.which === 'HEADER';
				});

				messageBody = messageHeader[0].body;
				for (propertyName of Object.keys(messageBody)) {
					if (messageBody[propertyName].length) {
						if (topLevelProperties.includes(propertyName)) {
							newEmail.json[propertyName] = messageBody[propertyName][0];
						} else {
							(newEmail.json.metadata as IDataObject)[propertyName] = messageBody[propertyName][0];
						}
					}
				}

				if (downloadAttachments === true) {
					// Get attachments and add them if any get found
					attachments = await getAttachment(connection, parts, message);
					if (attachments.length) {
						newEmail.binary = {};
						for (let i = 0; i < attachments.length; i++) {
							newEmail.binary[`${dataPropertyAttachmentsPrefixName}${i}`] = attachments[i];
						}
					}
				}

				newEmails.push(newEmail);
			}

			return newEmails;
		};



		let connection: ImapSimple;

		const config: ImapSimpleOptions = {
			imap: {
				user: credentials.user as string,
				password: credentials.password as string,
				host: credentials.host as string,
				port: credentials.port as number,
				tls: credentials.secure as boolean,
				authTimeout: 3000
			},
			onmail: async () => {
				const returnData = await getNewEmails(connection);

				if (returnData.length) {
					this.emit([returnData]);
				}
			},
		};

		if (options.allowUnauthorizedCerts === true) {
			config.imap.tlsOptions = {
				rejectUnauthorized: false
			};
		}

		// Connect to the IMAP server and open the mailbox
		// that we get informed whenever a new email arrives
		connection = await imapConnect(config);
		await connection.openBox(mailbox);


		// When workflow and so node gets set to inactive close the connectoin
		async function closeFunction() {
			await connection.end();
		}

		return {
			closeFunction,
		};

	}
}