core-mvc/src/instrumented.ts

Simple but powerful MVC framework for NodeJS.

import { log } from './util/log';

const isPromise = (value: unknown): value is Promise<unknown> => {
    const { then } = value as { then?: unknown };

    if (!then) {
        return false;
    }

    return typeof then === 'function';
};

export const instrumented =
    ({
        argumentFormat,
        includeResult,
        singleArgument,
        minDuration = -1,
        maxDuration,
    }: {
        includeResult?: boolean;
        singleArgument?: boolean;
        minDuration?: number;
        maxDuration?: number;
        argumentFormat?: (...args: any[]) => unknown;
    } = {}) =>
    (
        target: Object,
        propertyName: string,
        propertyDescriptor: PropertyDescriptor
    ): PropertyDescriptor => {
        // propertyName === "doSomething"
        // propertyDescriptor === Object.getOwnPropertyDescriptor(MyClass.prototype, "doSomething")
        const method = propertyDescriptor.value;

        const source = target.constructor.name;

        propertyDescriptor.value = function (...args: any[]) {
            const startTime = Date.now();

            const maxTimeout = maxDuration
                ? setTimeout(() => {
                      const duration = (Date.now() - startTime) / 1000;
                      log({
                          event: propertyName,
                          source,
                          stage: 'timeout',
                          args: argValue,
                          duration,
                      });
                  }, maxDuration * 1_000)
                : undefined;

            const result = method.apply(this, args);

            const argValue = singleArgument
                ? args[0]
                : argumentFormat
                ? argumentFormat(...args)
                : args;

            if (isPromise(result)) {
                return result.then(value => {
                    if (maxTimeout) {
                        clearTimeout(maxTimeout);
                    }

                    const duration = (Date.now() - startTime) / 1000;
                    if (duration > minDuration) {
                        log({
                            event: propertyName,
                            source,
                            args: argValue,
                            result: includeResult ? value : undefined,
                            duration,
                        });
                    }
                    return value;
                });
            }

            if (maxTimeout) {
                clearTimeout(maxTimeout);
            }

            const duration = (Date.now() - startTime) / 1000;

            if (duration > minDuration) {
                log({
                    event: propertyName,
                    source,
                    args: argValue,
                    result: includeResult ? result : undefined,
                    duration,
                });
            }

            return result;
        };

        return propertyDescriptor;
    };