import { HttpHeaders } from '@angular/common/http';

export interface HeaderOptions {
    readonly authorization?: boolean;
    readonly accept?: boolean;
    readonly contentType?: boolean;
}

export class HeadersConfiguration {
    static getHeaders(options?: HeaderOptions): HttpHeaders {
        let headers = new HttpHeaders();

        if (options?.accept === undefined || options.accept) {
            const httpHeaderAcceptSelected = HeadersConfiguration.selectHeaderAccept(['application/json']);
            if (httpHeaderAcceptSelected !== undefined) {
                headers = headers.set('Accept', httpHeaderAcceptSelected);
            }
        }

        if (options?.contentType === undefined || options.contentType) {
            const httpContentTypeSelected = HeadersConfiguration.selectHeaderContentType(['application/json']);
            if (httpContentTypeSelected !== undefined) {
                headers = headers.set('Content-Type', httpContentTypeSelected);
            }
        }

        return headers;
    }

    /**
     * Select the correct content-type to use for a request.
     * Uses {@link HeadersConfiguration#isJsonMime} to determine the correct content-type.
     * If no content type is found return the first found type if the contentTypes is not empty
     * @param contentTypes - the array of content types that are available for selection
     * @returns the selected content-type or <code>undefined</code> if no selection could be made.
     */
    static selectHeaderContentType(contentTypes: string[]): string | undefined {
        if (contentTypes.length === 0) {
            return undefined;
        }

        const type = contentTypes.find(x => this.isJsonMime(x));
        if (type === undefined) {
            return contentTypes[0];
        }
        return type;
    }

    /**
     * Select the correct accept content-type to use for a request.
     * Uses {@link HeadersConfiguration#isJsonMime} to determine the correct accept content-type.
     * If no content type is found return the first found type if the contentTypes is not empty
     * @param accepts - the array of content types that are available for selection.
     * @returns the selected content-type or <code>undefined</code> if no selection could be made.
     */
    static selectHeaderAccept(accepts: string[]): string | undefined {
        if (accepts.length === 0) {
            return undefined;
        }

        const type = accepts.find(x => this.isJsonMime(x));
        if (type === undefined) {
            return accepts[0];
        }
        return type;
    }

    /**
     * Check if the given MIME is a JSON MIME.
     * JSON MIME examples:
     *   application/json
     *   application/json; charset=UTF8
     *   APPLICATION/JSON
     *   application/vnd.company+json
     * @param mime - MIME (Multipurpose Internet Mail Extensions)
     * @return True if the given MIME is JSON, false otherwise.
     */
    static isJsonMime(mime: string): boolean {
        // eslint-disable-next-line no-control-regex
        const jsonMime = new RegExp('^(application/json|[^;/ \t]+/[^;/ \t]+[+]json)[ \t]*(;.*)?$', 'i');
        return mime !== null && (jsonMime.test(mime) || mime.toLowerCase() === 'application/json-patch+json');
    }
}