merge.ts

import is from '@sindresorhus/is';
import {Options} from './utils/types';
import knownHookEvents, {Hooks, HookEvent, HookType} from './known-hook-events';

export default function merge<Target extends Record<string, any>, Source extends Record<string, any>>(target: Target, ...sources: Source[]): Target & Source {
	for (const source of sources) {
		for (const [key, sourceValue] of Object.entries(source)) {
			if (is.undefined(sourceValue)) {
				continue;
			}

			const targetValue = target[key];
			if (targetValue instanceof URLSearchParams && sourceValue instanceof URLSearchParams) {
				const params = new URLSearchParams();

				const append = (value: string, key: string): void => params.append(key, value);
				targetValue.forEach(append);
				sourceValue.forEach(append);

				// @ts-ignore https://github.com/microsoft/TypeScript/issues/31661
				target[key] = params;
			} else if (is.urlInstance(targetValue) && (is.urlInstance(sourceValue) || is.string(sourceValue))) {
				// @ts-ignore
				target[key] = new URL(sourceValue as string, targetValue);
			} else if (is.plainObject(sourceValue)) {
				if (is.plainObject(targetValue)) {
					// @ts-ignore
					target[key] = merge({}, targetValue, sourceValue);
				} else {
					// @ts-ignore
					target[key] = merge({}, sourceValue);
				}
			} else if (is.array(sourceValue)) {
				// @ts-ignore
				target[key] = sourceValue.slice();
			} else {
				// @ts-ignore
				target[key] = sourceValue;
			}
		}

		if (Reflect.has(source, 'context')) {
			Object.defineProperty(target, 'context', {
				writable: true,
				configurable: true,
				enumerable: false,
				// @ts-ignore
				value: source.context
			});
		}
	}

	return target as Target & Source;
}

export function mergeOptions<T extends Options>(...sources: T[]): T & {hooks: Partial<Hooks>} {
	sources = sources.map(source => {
		if (!source) {
			return {};
		}

		if (is.object(source.retry)) {
			return source;
		}

		return {
			...source,
			retry: {
				retries: source.retry
			}
		};
	}) as T[];

	const mergedOptions = merge({} as T & {hooks: Partial<Hooks>}, ...sources);

	const hooks = knownHookEvents.reduce((accumulator, current) => ({...accumulator, [current]: []}), {}) as Record<HookEvent, HookType[]>;

	for (const source of sources) {
		// We need to check `source` to allow calling `.extend()` with no arguments.
		if (source && source.hooks) {
			for (const hook of knownHookEvents) {
				hooks[hook] = hooks[hook].concat(source.hooks[hook] || []);
			}
		}
	}

	mergedOptions.hooks = hooks as Hooks;

	return mergedOptions;
}