BaseAPI Class — typescript-sdk Architecture

Source Code

src/runtime.ts lines 92–250

export class BaseAPI {

    private static readonly jsonRegex = new RegExp('^(:?application\/json|[^;/ \t]+\/[^;/ \t]+[+]json)[ \t]*(:?;.*)?$', 'i');
    private middleware: Middleware[];

    constructor(protected configuration = DefaultConfig) {
        this.middleware = configuration.middleware;
    }

    withMiddleware<T extends BaseAPI>(this: T, ...middlewares: Middleware[]) {
        const next = this.clone<T>();
        next.middleware = next.middleware.concat(...middlewares);
        return next;
    }

    withPreMiddleware<T extends BaseAPI>(this: T, ...preMiddlewares: Array<Middleware['pre']>) {
        const middlewares = preMiddlewares.map((pre) => ({ pre }));
        return this.withMiddleware<T>(...middlewares);
    }

    withPostMiddleware<T extends BaseAPI>(this: T, ...postMiddlewares: Array<Middleware['post']>) {
        const middlewares = postMiddlewares.map((post) => ({ post }));
        return this.withMiddleware<T>(...middlewares);
    }

    /**
     * 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.
     */
    protected isJsonMime(mime: string | null | undefined): boolean {
        if (!mime) {
            return false;
        }
        return BaseAPI.jsonRegex.test(mime);
    }

    protected async request(context: RequestOpts, initOverrides?: RequestInit | InitOverrideFunction): Promise<Response> {
        const { url, init } = await this.createFetchParams(context, initOverrides);
        const response = await this.fetchApi(url, init);
        if (response && (response.status >= 200 && response.status < 300)) {
            return response;
        }
        throw new ResponseError(response, 'Response returned an error code');
    }

    private async createFetchParams(context: RequestOpts, initOverrides?: RequestInit | InitOverrideFunction) {
        let url = this.configuration.basePath + context.path;
        if (context.query !== undefined && Object.keys(context.query).length !== 0) {
            // only add the querystring to the URL if there are query parameters.
            // this is done to avoid urls ending with a "?" character which buggy webservers
            // do not handle correctly sometimes.
            url += '?' + this.configuration.queryParamsStringify(context.query);
        }

        const headers = Object.assign({}, this.configuration.headers, context.headers);
        Object.keys(headers).forEach(key => headers[key] === undefined ? delete headers[key] : {});

        const initOverrideFn =
            typeof initOverrides === "function"
                ? initOverrides
                : async () => initOverrides;

        const initParams = {
            method: context.method,
            headers,
            body: context.body,
            credentials: this.configuration.credentials,
        };

        const overriddenInit: RequestInit = {
            ...initParams,
            ...(await initOverrideFn({
                init: initParams,
                context,
            }))
        };

        let body: any;
        if (isFormData(overriddenInit.body)
            || (overriddenInit.body instanceof URLSearchParams)
            || isBlob(overriddenInit.body)) {
          body = overriddenInit.body;
        } else if (this.isJsonMime(headers['Content-Type'])) {
          body = JSON.stringify(overriddenInit.body);
        } else {
          body = overriddenInit.body;
        }

        const init: RequestInit = {
            ...overriddenInit,
            body
        };

        return { url, init };
    }

    private fetchApi = async (url: string, init: RequestInit) => {
        let fetchParams = { url, init };
        for (const middleware of this.middleware) {
            if (middleware.pre) {
                fetchParams = await middleware.pre({
                    fetch: this.fetchApi,
                    ...fetchParams,
                }) || fetchParams;
            }
        }
        let response: Response | undefined = undefined;
        try {
            response = await (this.configuration.fetchApi || fetch)(fetchParams.url, fetchParams.init);
        } catch (e) {
            for (const middleware of this.middleware) {
                if (middleware.onError) {
                    response = await middleware.onError({
                        fetch: this.fetchApi,
                        url: fetchParams.url,
                        init: fetchParams.init,
                        error: e,
                        response: response ? response.clone() : undefined,
                    }) || response;
                }
            }
            if (response === undefined) {
              if (e instanceof Error) {
                throw new FetchError(e, 'The request failed and the interceptors did not return an alternative response');
              } else {
                throw e;
              }
            }
        }
        for (const middleware of this.middleware) {
            if (middleware.post) {
                response = await middleware.post({
                    fetch: this.fetchApi,
                    url: fetchParams.url,
                    init: fetchParams.init,
                    response: response.clone(),
                }) || response;
            }
        }
        return response;
    }

    /**
     * Create a shallow clone of `this` by constructing a new instance
     * and then shallow cloning data members.
     */
    private clone<T extends BaseAPI>(this: T): T {
        const constructor = this.constructor as any;
        const next = new constructor(this.configuration);
        next.middleware = this.middleware.slice();
        return next;
    }
};