@needle-tools/engine/src/engine/engine_patcher.ts

Needle Engine is a web-based runtime for 3D apps. It runs on your machine for development with great integrations into editors like Unity or Blender - and can be deployed onto any device! It is flexible, extensible and networking and XR are built-in.

// https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object/hasOwn

import { getParam } from "./engine_utils.js";

// const _wrappedMethods = new WeakSet();


// export function wrap<T>(prototype: object, methodName: string, before: (t: T) => void, after: (t: T) => void) {

//     const $key = Symbol(methodName + "-patched");

//     const alreadyDefined = Object.getOwnPropertyDescriptor(prototype, methodName);
//     if (alreadyDefined) {
//         const originalRender = alreadyDefined.get;
//         if (originalRender) {
//             // Object.defineProperty(prototype, "render", {
//             //     set: function (this: any, value: Function) {
//             //         originalRender.call(this);
//             //     },
//             //     get: function (this: ) {
//             //         return originalRender.call(this);
//             //     }
//             // });
//         }
//     }
//     else {
//         Object.defineProperty(prototype, methodName, {
//             set: function (this: any, value: Function) {
//                 this[$key] = value;
//             },
//             get: function (this: any) {
//                 return this[$key];
//             }
//         });
//     }
// }


// export declare type FieldPatch = (instance: object, oldValue: any, newValue: any) => any;

export type Prefix = (...args) => any;
export type Postfix = (...args) => any;

const debugPatch = getParam("debugpatch");

/**
 * Use patcher for patching properties insteadof calling Object.defineProperty individually 
 * since this will cause conflicts if multiple patches need to be applied to the same property
 */
export function addPatch<T extends object>(prototype: T, fieldName: string, beforeCallback?: Prefix | null, afterCallback?: Postfix | null) {
    const debug = debugPatch === fieldName;

    // If no callbacks are provided, we don't need to do anything
    if (!beforeCallback && !afterCallback) {
        return;
    }

    // TODO: we probably want to turn this into a symbol to prevent anyone from overriding it
    // But when we need to store the symbol per prototype to allow e.g. material disposing to iterate those and dispose all
    // TODO: making symbols here breaks e.g. progressive textures because they iterate on the property keys
    const backingField = fieldName + "___needle";// Symbol(fieldName);// + " (patched)";

    internalAddPatch(prototype, fieldName, beforeCallback, afterCallback);

    const desc = Object.getOwnPropertyDescriptor(prototype, fieldName);
    const existing = prototype[fieldName];
    if (debug) console.log("Patch", prototype.constructor.name, fieldName, desc, existing);

    if (desc) {
        if (debug) console.log("Apply patch with existing descriptor", prototype.constructor.name, fieldName, desc);
        if (typeof desc.value === "function") {
            prototype[fieldName] = ensureFunctionWrapped(desc.value, prototype, fieldName);
        }
    }
    else {
        if (debug) console.log("Create patch with new property", prototype.constructor.name, fieldName, desc);
        Object.defineProperty(prototype, fieldName, {
            set: function (this: object, value: any) {
                if (typeof value === "function") {
                    // TODO: not sure if this is correct (if the value that is set is a function)
                    this[backingField] = ensureFunctionWrapped(value, prototype, fieldName);
                }
                else {
                    const prev = this[backingField];
                    executePrefixes(prototype, fieldName, this, prev, value);
                    this[backingField] = value;
                    executePostFixes(prototype, fieldName, this, prev, value);
                }
            },
            get: function (this: any) {
                const value = this[backingField];
                if (typeof value === "function") {
                    if (value[backingField]) {
                        return value[backingField];
                    }
                }
                return value;
            }
        });
    }
}

/** Removes prefix or postfix */
export function removePatch(prototype: object, fieldName: string, prefixOrPostfix: Prefix | Postfix) {
    const patches = getPatches(prototype, fieldName);
    if (patches) {
        for (let i = patches.length - 1; i >= 0; i--) {
            const patch = patches[i];
            // Remove either the prefix or postfix
            if (patch.prefix === prefixOrPostfix) {
                patch.prefix = null;
            }
            if (patch.postfix === prefixOrPostfix) {
                patch.postfix = null;
            }
            // If the patch is empty, remove it from the list
            if (!patch.prefix && !patch.postfix) {
                patches.splice(i, 1);
            }
        }
    }
}



const $wrappedFunctionSymbol = Symbol("Needle:Patches:WrappedFunction");

function ensureFunctionWrapped(originalFunction: Function, prototype, fieldname) {
    if (originalFunction[$wrappedFunctionSymbol]) {
        return originalFunction;
    }
    const wrappedFunction = function (this: object, ...args: any[]) {
        executePrefixes(prototype, fieldname, this, ...args);
        const result = originalFunction.apply(this, args);
        executePostFixes(prototype, fieldname, this, result, ...args);
        return result;
    }
    wrappedFunction[$wrappedFunctionSymbol] = true;
    return wrappedFunction;
}


export const NeedlePatchesKey = "Needle:Patches";

declare type PatchInfo = {
    prefix?: Prefix | null;
    postfix?: Postfix | null;
}
function patches(): WeakMap<object, Map<string, PatchInfo[]>> {
    if (!globalThis[NeedlePatchesKey]) {
        globalThis[NeedlePatchesKey] = new WeakMap<object, Map<string, PatchInfo[]>>();
    }
    return globalThis[NeedlePatchesKey];
}

function getPatches(prototype, fieldName: string) {
    const patchesMap = patches().get(prototype);
    if (!patchesMap) {
        return null;
    }
    return patchesMap.get(fieldName);;
}

function internalAddPatch(prototype, fieldName: string, prefix?: Prefix | null, postfix?: Postfix | null) {
    let patchesMap = patches().get(prototype);
    if (!patchesMap) {
        patchesMap = new Map();
        patches().set(prototype, patchesMap);
    }
    let patchList = patchesMap.get(fieldName);
    if (!patchList) {
        patchList = [];
        patchesMap.set(fieldName, patchList);
    }
    patchList.push({
        prefix: prefix,
        postfix: postfix
    });
}

function executePrefixes(prototype, fieldName: string, instance: object, ...args) {
    if (!instance) return;
    const patches = getPatches(prototype, fieldName);
    if (patches) {
        for (const patchInfo of patches) {
            patchInfo.prefix?.call(instance, ...args);
        }
    }
}

function executePostFixes(prototype, fieldName: string, instance: object, result: any, ...args) {
    if (!instance) return;
    const patches = getPatches(prototype, fieldName);
    if (patches) {
        for (const patchInfo of patches) {
            patchInfo.postfix?.call(instance, result, ...args);
        }
    }
}