import { runMiddleware } from './runMiddleware';
import { Application } from 'express';
import { assignIn } from 'lodash';

export interface ICallOptions {
    method: "post",
    headers?: { 'Content-Type': 'application/json' },

    body: { 
        [index: string]: any 
    }
}

/**
 * Function that will generate an async accessor Function.
 * @param app the provided Express App.
 */
export function getBackendAccesors(app: Application){
    // Create a Run-Middle-Ware
    runMiddleware(app);

    // Define a apiCall Function, which could be used to perform internal
    // Request on the API.
    function apiCall<T>(url: string, options: ICallOptions){
        return new Promise<T>((resolve, reject) => {

            // Define the Default Options
            const defaults: Partial<ICallOptions> = {
                headers: { 'Content-Type': 'application/json' }
            }
            // Mix the Options.
            const opts: ICallOptions = assignIn(defaults, options);

            // Perform the Call            
            (app as any).runMiddleware(url,opts,(responseCode: number,body: T) => {
                // Based on the Response code, decide whether the call was a Fail or not.
                if (responseCode === 200){
                    // If everything is fine,
                    // Just return the body.
                    return resolve(body);
                } else {
                    const error = new Error('Call Ended with responseCode = ' + responseCode.toString());
                    return reject(error)
                }
            })
        })
    }

    return apiCall;
}