@typespec/http-server-js/dist/src/helpers/router.js

TypeSpec HTTP server code generator for JavaScript

// Copyright (c) Microsoft Corporation
// Licensed under the MIT license.
/**
 * Create a function from a chain of policies.
 *
 * This returns a single function that will apply the policy chain and eventually call the provided `next()` function.
 *
 * @param name - The name to give to the policy chain function.
 * @param policies - The policies to apply to the request.
 * @param out - The function to call after the policies have been applied.
 */
export function createPolicyChain(name, policies, out) {
    let outParams;
    if (policies.length === 0) {
        return out;
    }
    function applyPolicy(ctx, index) {
        if (index >= policies.length) {
            return out(ctx, ...outParams);
        }
        policies[index](ctx, function nextPolicy(nextRequest) {
            applyPolicy({
                ...ctx,
                request: nextRequest ?? ctx.request,
            }, index + 1);
        });
    }
    return {
        [name](ctx, ...params) {
            outParams = params;
            applyPolicy(ctx, 0);
        },
    }[name];
}
/**
 * Create a policy chain for a given route.
 *
 * This function calls `createPolicyChain` internally and orders the policies based on the route configuration.
 *
 * Interface-level `before` policies run first, then method-level policies, then Interface-level `after` policies.
 *
 * @param name - The name to give to the policy chain function.
 * @param routePolicies - The policies to apply to the routes (part of the route configuration).
 * @param interfaceName - The name of the interface that the route belongs to.
 * @param methodName - The name of the method that the route corresponds to.
 * @param out - The function to call after the policies have been applied.
 */
export function createPolicyChainForRoute(name, routePolicies, interfaceName, methodName, out) {
    return createPolicyChain(name, [
        ...(routePolicies[interfaceName]?.before ?? []),
        ...(routePolicies[interfaceName]?.methodPolicies?.[methodName] ?? []),
        ...(routePolicies[interfaceName]?.after ?? []),
    ], out);
}
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