/*!
 * @license
 * Copyright Squiz Australia Pty Ltd. All Rights Reserved.
 */

import {
  SLACK_ALERT_LEVEL_ERROR,
  SLACK_ALERT_LEVEL_INFO,
  SLACK_ALERT_LEVEL_SUCCESS,
  SLACK_ALERT_LEVEL_WARNING,
  SlackAlertLevel,
  SlackAlertRequestBody,
} from './types/SlackClient.types';

export class SlackClient {
  private static instance: SlackClient;
  protected static application: string;
  protected static environment: string;
  protected static region: string;
  protected static webhookUrl: string;

  /**
   * Initializes the Slack Client with the required environment vars.
   * @param {string} environment Deployment environment of application.
   * @param {string} region Region application is deployed to 'us' | 'uk' | 'au' as per AWS environment.
   * @param {string} webhookUrl Webhook URL for sending Slack messages.
   * @param {string} application Name of the application.
   */
  public static initialize(environment = '', region = '', webhookUrl = '', application = ''): void {
    if (environment === '' || region === '' || webhookUrl === '' || application === '') {
      throw new Error('Failed to initialize SlackClient, environment vars not set');
    } else {
      SlackClient.environment = `${environment[0].toUpperCase()}${environment.slice(1)}`;
      SlackClient.region = region.toUpperCase();
      SlackClient.webhookUrl = webhookUrl;
      SlackClient.application = application;
    }
  }

  /**
   * The static method that controls the access to the singleton instance for Slack Client.
   * @returns {SlackClient} The singleton instance.
   */
  public static getClient(): SlackClient {
    if (!SlackClient.instance) {
      SlackClient.instance = new SlackClient();
    }

    return SlackClient.instance;
  }

  /**
   * Generate the body of the request for sending to Slack.
   * @param {SlackAlertLevel} level Level associated with alert.
   * @returns {string | null} The icon matching the alert level.
   */
  public static getIcon = (level: SlackAlertLevel = SLACK_ALERT_LEVEL_INFO): string | null => {
    let icon = null;

    switch (level) {
      case SLACK_ALERT_LEVEL_ERROR:
        icon = ':alert:';
        break;
      case SLACK_ALERT_LEVEL_WARNING:
        icon = '⚠️';
        break;
      case SLACK_ALERT_LEVEL_INFO:
        icon = 'ℹ️';
        break;
      case SLACK_ALERT_LEVEL_SUCCESS:
        icon = '✅';
        break;
      default:
        icon = null;
        break;
    }

    return icon;
  };

  /**
   * Generate the body of the request for sending to Slack.
   * @param {string} message Message to be sent to Slack channel.
   * @param {SlackAlertLevel} level Level associated with alert.
   * @returns {SlackAlertRequestBody} Slack alert request body.
   */
  public static getRequestBody = (
    message: string,
    level: SlackAlertLevel = SLACK_ALERT_LEVEL_INFO,
  ): SlackAlertRequestBody => {
    const icon = this.getIcon(level);

    const header = `${icon} *[${SlackClient.environment}] ${SlackClient.application} ${SlackClient.region}*`;
    const text = `${header}\n${message}`;

    const requestBody: SlackAlertRequestBody = {
      text,
    };
    return requestBody;
  };

  /**
   * Post a new message/alert to the Webhook URL.
   * @param {string} message Message to be sent.
   * @param {SlackAlertLevel} level Level associated with message.
   */
  public sendAlert = async (message: string, level: SlackAlertLevel = SLACK_ALERT_LEVEL_INFO): Promise<void> => {
    const requestBody = SlackClient.getRequestBody(message, level);

    try {
      const request = new Request(`${SlackClient.webhookUrl}`, {
        method: 'POST',
        body: JSON.stringify(requestBody),
        headers: {
          'Content-Type': 'application/json',
        },
      });

      const response = await fetch(request);

      if (response.status !== 200) {
        // eslint-disable-next-line no-console
        console.log(`SlackClient failed with ${response.status} status`);
        return;
      }
    } catch (e) {
      /* eslint-disable-next-line no-console */
      console.log(`Slack Client api call: ${e}`);
      throw e;
    }
  };
}