@sap-cloud-sdk/resilience/dist/middleware.js

SAP Cloud SDK for JavaScript resilience

"use strict";
Object.defineProperty(exports, "__esModule", { value: true });
exports.executeWithMiddleware = executeWithMiddleware;
/**
 * Helper function to join a list of middlewares given an initial input.
 * @param middlewares - Middlewares to be layered around the function.
 * @param context - Context for the middleware execution.
 * @param fn - Function around which the middlewares are added.
 * @returns Function with middlewares layered around it.
 * @internal
 */
function executeWithMiddleware(middlewares, { fn, context, fnArgument }) {
    if (!middlewares?.length) {
        return fn(fnArgument);
    }
    const initial = { context, fn };
    const functionWithMiddlewares = addMiddlewaresToInitialFunction(middlewares, initial);
    return functionWithMiddlewares(fnArgument);
}
/**
 * This functions adds the middlewares to the initial functions.
 * You start with a function (axios request function) and add a timeout, circuit-breaker etc..
 * The result is new a function containing a timeout, circuit-breaker etc..
 * Note that the actual function is not executed.
 * @param middlewares - Middlewares added to the function. Added from right to function.
 * @param initial - Initial function and context.
 * @returns The function with the middlewares added.
 */
function addMiddlewaresToInitialFunction(middlewares, initial) {
    const { context } = initial;
    // Reduce right is in line with the composition operator [g,f] relates g o f means g after f.
    const functionWithMiddlewares = middlewares.reduceRight((prev, curr) => ({ fn: curr(prev), context }), initial);
    return functionWithMiddlewares.fn;
}
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