src/app/util/http/http.util.ts

/********************************************************************************
 * Copyright (c) 2020 Contributors to the Eclipse Foundation
 *
 * See the NOTICE file(s) distributed with this work for additional
 * information regarding copyright ownership.
 *
 * This program and the accompanying materials are made available under the
 * terms of the Eclipse Public License 2.0 which is available at
 * http://www.eclipse.org/legal/epl-2.0
 *
 * SPDX-License-Identifier: EPL-2.0
 ********************************************************************************/

import {HttpErrorResponse, HttpResponse} from "@angular/common/http";
import {Observable, ObservableInput, of, throwError} from "rxjs";
import {catchError, switchMap} from "rxjs/operators";
import {arrayJoin} from "../store";
import {EHttpStatusCodes} from "./EHttpStatusCodes";

/**
 * Safely joins multiple urls to one.
 */
export function urlJoin(...args: string[]): string {
    let result = args.length === 0 ? "" : args.reduce((previous, current) => previous + "/" + current);
    const indexOfProtocol = result.indexOf("://");
    const protocol = indexOfProtocol === -1 ? "" : result.slice(0, indexOfProtocol);

    result = indexOfProtocol === -1 ? result : result.slice(indexOfProtocol + 2);

    while (result.indexOf("//") > -1) {
        result = result.replace("//", "/");
    }

    return indexOfProtocol === -1 ? result : protocol + ":/" + result;
}

/**
 * Transforms a javascript object to a HttpParams object.
 */
export function objectToHttpParams<T extends object>(
    object: { [key: string]: string | number | Array<string | number> }
): { [key: string]: string | string[] } {
    if (object == null) {
        return {};
    }
    const result: { [key: string]: string | string[] } = {};
    Object.entries(object)
        .filter(([key, value]) => value != null)
        .forEach(([key, value]) => {
            result[key] = Array.isArray(value) ? value.map((_) => "" + _) : "" + value;
        });
    return result;
}

/**
 * Returns true if the given error is an instance of HttpErrorResponse and its status is contained in the
 * given list of status values of the function (if empty, all status values are catched).
 */
export function isHttpErrorWithStatus(error: any, ...status: EHttpStatusCodes[]): boolean {
    return error instanceof HttpErrorResponse
        && (arrayJoin(status).length === 0 || status.some((s) => error.status === s));
}

/**
 * Returns an rxjs operator which catches HttpErrorRespones.
 * @param callback Function which is called when an error occurs.
 * @param status List of all response status codes which are catched (if empty, all http errors are catched).
 */
export function catchHttpError<T, O extends ObservableInput<any>>(
    callback: (error: HttpErrorResponse) => O,
    ...status: EHttpStatusCodes[]
) {
    return catchError<T, O | Observable<never>>((error) => {
        if (isHttpErrorWithStatus(error, ...arrayJoin(status))) {
            return callback(error);
        }
        return throwError(error);
    });
}

/**
 * Returns an rxjs operator which catches every http error and maps it to the given value.
 * @param value Value, to which an http error is mapped to.
 * @param status List of all response status codes which are catched (if empty, all http errors are catched).
 */
export function catchHttpErrorTo<T, O>(
    value: O,
    ...status: EHttpStatusCodes[]
) {
    return catchHttpError<T, ObservableInput<O>>(() => of(value), ...status);
}

/**
 * Returns an rxjs operator function which maps a HttpResponse from the server to a Javascript file object.
 * The filename of the returned file will be extracted from the headers of the HttpResponse.
 */
export function mapHttpResponseToFile() {
    return switchMap<HttpResponse<Blob>, Observable<File>>((response) => {
        const blob = response.body;
        if (!(blob instanceof Blob)) {
            return throwError(new TypeError("Http response does not contain blob data"));
        }
        const contentDisposition = response.headers.get("content-disposition");
        const fileName = contentDisposition
            .split(";")
            .map((_) => {
                _ = _.trim();
                if (!_.toLowerCase().startsWith("filename=")) {
                    return;
                }
                return _.slice(9)
                    .replace(/^\s*"/, "")
                    .replace(/"\s*$/, "");
            })
            .find((_) => _ != null);

        return of(new File([blob], fileName, {type: blob.type}));
    });
}