shim.js

// SPDX-License-Identifier: MIT
// Copyright © 2021 fvtt-lib-wrapper Rui Pinheiro


'use strict';

// A shim for the libWrapper library
export let libWrapper = undefined;

export const VERSIONS       = [1,12,2];
export const TGT_SPLIT_RE   = new RegExp("([^.[]+|\\[('([^'\\\\]|\\\\.)+?'|\"([^\"\\\\]|\\\\.)+?\")\\])", 'g');
export const TGT_CLEANUP_RE = new RegExp("(^\\['|'\\]$|^\\[\"|\"\\]$)", 'g');

// Main shim code
Hooks.once('init', () => {
	// Check if the real module is already loaded - if so, use it
	if(globalThis.libWrapper && !(globalThis.libWrapper.is_fallback ?? true)) {
		libWrapper = globalThis.libWrapper;
		return;
	}

	// Fallback implementation
	libWrapper = class {
		static get is_fallback() { return true };

		static get WRAPPER()  { return 'WRAPPER'  };
		static get MIXED()    { return 'MIXED'    };
		static get OVERRIDE() { return 'OVERRIDE' };

		static register(package_id, target, fn, type="MIXED", {chain=undefined, bind=[]}={}) {
			const is_setter = target.endsWith('#set');
			target = !is_setter ? target : target.slice(0, -4);
			const split = target.match(TGT_SPLIT_RE).map((x)=>x.replace(/\\(.)/g, '$1').replace(TGT_CLEANUP_RE,''));
			const root_nm = split.splice(0,1)[0];

			let obj, fn_name;
			if(split.length == 0) {
				obj = globalThis;
				fn_name = root_nm;
			}
			else {
				const _eval = eval;
				fn_name = split.pop();
				obj = split.reduce((x,y)=>x[y], globalThis[root_nm] ?? _eval(root_nm));
			}

			let iObj = obj;
			let descriptor = null;
			while(iObj) {
				descriptor = Object.getOwnPropertyDescriptor(iObj, fn_name);
				if(descriptor) break;
				iObj = Object.getPrototypeOf(iObj);
			}
			if(!descriptor || descriptor?.configurable === false) throw new Error(`libWrapper Shim: '${target}' does not exist, could not be found, or has a non-configurable descriptor.`);

			let original = null;
			const wrapper = (chain ?? (type.toUpperCase?.() != 'OVERRIDE' && type != 3)) ?
				function(...args) { return fn.call(this, original.bind(this), ...bind, ...args); } :
				function(...args) { return fn.call(this, ...bind, ...args); }
			;

			if(!is_setter) {
				if(descriptor.value) {
					original = descriptor.value;
					descriptor.value = wrapper;
				}
				else {
					original = descriptor.get;
					descriptor.get = wrapper;
				}
			}
			else {
				if(!descriptor.set) throw new Error(`libWrapper Shim: '${target}' does not have a setter`);
				original = descriptor.set;
				descriptor.set = wrapper;
			}

			descriptor.configurable = true;
			Object.defineProperty(obj, fn_name, descriptor);
		}
	}
});