/** @module services */
/** @hidden */
let _ = require('lodash');

import { ApplicationException, ErrorCategory } from 'pip-services3-commons-node';

/**
 * Helper class that handles HTTP-based responses.
 */
export class HttpResponseSender {
    /**
     * Sends error serialized as ErrorDescription object
     * and appropriate HTTP status code.
     * If status code is not defined, it uses 500 status code.
     * 
     * @param req       a HTTP request object.
     * @param res       a HTTP response object.
     * @param error     an error object to be sent.
     */
    public static sendError(req: any, res: any, error: any): void {
        error = error || {};
        error = ApplicationException.unwrapError(error);

        let result = _.pick(error, 'type', 'category', 'code', 'status', 'name', 'details', 'component', 'message', 'stack', 'cause');
        result = _.defaults(result, { category: ErrorCategory.Unknown, code: 'Undefined', status: 500, message: 'Unknown error' });

        res.status(result.status);
        res.json(result);
    }

    /**
     * Creates a callback function that sends result as JSON object.
     * That callack function call be called directly or passed
     * as a parameter to business logic components.
     * 
     * If object is not null it returns 200 status code.
     * For null results it returns 204 status code.
     * If error occur it sends ErrorDescription with approproate status code.
     * 
     * @param req       a HTTP request object.
     * @param res       a HTTP response object.
     * @param callback function that receives execution result or error.
     */
    public static sendResult(req: any, res: any): (err: any, result: any) => void {
        return function (err, result) {
            if (err) {
                HttpResponseSender.sendError(req, res, err);
                return;
            }
            if (result == null) res.send(204);
            else res.json(result);
        }
    }

    /**
     * Creates a callback function that sends an empty result with 204 status code.
     * If error occur it sends ErrorDescription with approproate status code.
     * 
     * @param req       a HTTP request object.
     * @param res       a HTTP response object.
     * @param callback function that receives error or null for success.
     */
    public static sendEmptyResult(req: any, res: any): (err: any) => void {
        return function (err) {
            if (err) {
                HttpResponseSender.sendError(req, res, err);
                return;
            }
            res.send(204);
        }
    }

    /**
     * Creates a callback function that sends newly created object as JSON.
     * That callack function call be called directly or passed
     * as a parameter to business logic components.
     * 
     * If object is not null it returns 201 status code.
     * For null results it returns 204 status code.
     * If error occur it sends ErrorDescription with approproate status code.
     * 
     * @param req       a HTTP request object.
     * @param res       a HTTP response object.
     * @param callback function that receives execution result or error.
     */
    public static sendCreatedResult(req: any, res: any): (err: any, result: any) => void {
        return function (err, result) {
            if (err) {
                HttpResponseSender.sendError(req, res, err);
                return;
            }
            if (result == null) res.status(204)
            else {
                res.status(201)
                res.json(result);
            }
        }
    }

    /**
     * Creates a callback function that sends deleted object as JSON.
     * That callack function call be called directly or passed
     * as a parameter to business logic components.
     * 
     * If object is not null it returns 200 status code.
     * For null results it returns 204 status code.
     * If error occur it sends ErrorDescription with approproate status code.
     * 
     * @param req       a HTTP request object.
     * @param res       a HTTP response object.
     * @param callback function that receives execution result or error.
     */
    public static sendDeletedResult(req: any, res: any): (err: any, result: any) => void {
        return function (err, result) {
            if (err) {
                HttpResponseSender.sendError(req, res, err);
                return;
            }
            if (result == null) res.status(204)
            else {
                res.status(200)
                res.json(result);
            }
        }
    }
}