// Makes the Basis Universal transcoder that three.js 0.160.1 ships for its
// KTX2Loader run under a Content Security Policy without 'unsafe-eval', and
// writes it, with the unmodified .wasm, to vendor/local/basis@1/.
//
//   node wasm-src/basis/patch.mjs            (from frontend/)
//
// The JavaScript glue is Emscripten output whose embind layer generates source
// text and compiles it with new Function in four places: createNamedFunction,
// craftInvokerFunction, __emval_get_method_caller and craftEmvalAllocator. The
// site's CSP forbids that, so the 3D Model Viewer could not decode KTX2
// textures. Each is replaced by a closure doing the same steps in the same
// order, as Emscripten does when built with -sDYNAMIC_EXECUTION=0, the same
// treatment as wasm-src/occt/patch.mjs. Nothing else changes.

import { createHash } from 'node:crypto';
import { mkdirSync, writeFileSync } from 'node:fs';
import { dirname, join } from 'node:path';
import { fileURLToPath } from 'node:url';

const here = dirname(fileURLToPath(import.meta.url));
const out = join(here, '..', '..', 'vendor', 'local', 'basis@1');
const BASE = 'https://cdn.jsdelivr.net/npm/three@0.160.1/examples/jsm/libs/basis/';
const FILES = {
  'basis_transcoder.js': '+HVwcKS+KxiFvM8L/5uF8ao5eOF3XKCNjgmgsDaBHRHNUhSQ+bDYb8M4TwHu+uUh',
  // The hash vendor.lock.json held for it.
  'basis_transcoder.wasm': 'IepP9ATxmX8VViM/sMCldlp27yXZkp+o43K4Td38/HXAefQFz1IrmPBo12JEYG2t',
};

const fetched = {};
for (const [name, sha384] of Object.entries(FILES)) {
  const bytes = Buffer.from(await (await fetch(BASE + name)).arrayBuffer());
  const got = createHash('sha384').update(bytes).digest('base64');
  if (got !== sha384) throw new Error(`${name} is not the expected file (sha384 ${got})`);
  fetched[name] = bytes;
}
let js = fetched['basis_transcoder.js'].toString('utf8');

/** Replaces the whole function that starts with `head`, after checking it is the code-generating version. */
function replaceFunction(head, mustContain, replacement) {
  const start = js.indexOf(head);
  if (start < 0) throw new Error(`${head} not found`);
  let depth = 0;
  let end = js.indexOf('{', start);
  for (; end < js.length; end++) {
    if (js[end] === '{') depth++;
    else if (js[end] === '}' && --depth === 0) break;
  }
  if (!js.slice(start, end + 1).includes(mustContain)) throw new Error(`${head} is not the code-generating version`);
  js = js.slice(0, start) + replacement + js.slice(end + 1);
}

const NOTE = '/* Patched by johnmcm.com: no generated code (see wasm-src/basis/patch.mjs). */';

// A function with a given name that forwards to body, so it can also be used with new.
replaceFunction('function createNamedFunction(', 'new Function', `function createNamedFunction(name,body){
  ${NOTE}
  var f=function(){return body.apply(this,arguments)};
  try{Object.defineProperty(f,"name",{value:makeLegalFunctionName(name)})}catch(e){}
  return f
}`);

replaceFunction('function craftInvokerFunction(', 'new_(Function,args1)', `function craftInvokerFunction(humanName,argTypes,classType,cppInvokerFunc,cppTargetFunc){
  ${NOTE}
  var argCount=argTypes.length;
  if(argCount<2){throwBindingError("argTypes array size mismatch! Must at least get return value and 'this' types!")}
  var isClassMethodFunc=argTypes[1]!==null&&classType!==null;
  var needsDestructorStack=false;
  for(var i=1;i<argTypes.length;++i){if(argTypes[i]!==null&&argTypes[i].destructorFunction===undefined){needsDestructorStack=true;break}}
  var returns=argTypes[0].name!=="void";
  var expected=argCount-2;
  var first=isClassMethodFunc?2:1;
  var invokerFn=function(){
    if(arguments.length!==expected){throwBindingError("function "+humanName+" called with "+arguments.length+" arguments, expected "+expected+" args!")}
    var destructors=needsDestructorStack?[]:null;
    var wired=[cppTargetFunc];
    if(isClassMethodFunc){wired.push(argTypes[1].toWireType(destructors,this))}
    for(var i=0;i<expected;++i){wired.push(argTypes[i+2].toWireType(destructors,arguments[i]))}
    var rv=cppInvokerFunc.apply(null,wired);
    if(needsDestructorStack){runDestructors(destructors)}
    else{
      for(var i=isClassMethodFunc?1:2;i<argTypes.length;++i){
        var dtor=argTypes[i].destructorFunction;
        if(dtor!==null){dtor(i===1?wired[1]:wired[first+i-2])}
      }
    }
    if(returns){return argTypes[0].fromWireType(rv)}
  };
  return createNamedFunction(humanName,invokerFn)
}`);

replaceFunction('function __emval_get_method_caller(', 'new_(Function,params)', `function __emval_get_method_caller(argCount,argTypes){
  ${NOTE}
  var types=__emval_lookupTypes(argCount,argTypes);var retType=types[0];
  var offsets=[];var offset=0;
  for(var i=0;i<argCount-1;++i){offsets.push(offset);offset+=types[i+1]["argPackAdvance"]}
  var invokerFunction=function(handle,name,destructors,args){
    var vals=[];
    for(var i=0;i<argCount-1;++i){vals.push(types[i+1].readValueFromPointer(args+offsets[i]))}
    var rv=handle[name].apply(handle,vals);
    for(var i=0;i<argCount-1;++i){if(types[i+1]["deleteObject"]){types[i+1].deleteObject(vals[i])}}
    if(!retType.isVoid){return retType.toWireType(destructors,rv)}
  };
  return __emval_addMethodCaller(invokerFunction)
}`);

replaceFunction('function craftEmvalAllocator(', 'new Function', `function craftEmvalAllocator(argCount){
  ${NOTE}
  return function(constructor,argTypes,args){
    var vals=[];
    for(var i=0;i<argCount;++i){
      var argType=requireRegisteredType(Module["HEAP32"][(argTypes>>>2)+i],"parameter "+i);
      vals.push(argType.readValueFromPointer(args));
      args+=argType["argPackAdvance"];
    }
    var obj=new (Function.prototype.bind.apply(constructor,[null].concat(vals)));
    return __emval_register(obj)
  }
}`);

const left = js.match(/new_\(Function|new Function|\beval\(/g);
if (left) throw new Error(`string evaluation left in the glue: ${left.join(', ')}`);

const header = '/* Basis Universal transcoder (Apache-2.0) from three.js 0.160.1, patched by johnmcm.com to run without eval: see wasm-src/basis/patch.mjs */\n';
mkdirSync(out, { recursive: true });
writeFileSync(join(out, 'basis_transcoder.js'), header + js);
writeFileSync(join(out, 'basis_transcoder.wasm'), fetched['basis_transcoder.wasm']);
console.log(`wrote ${out}`);