let path = require('path')

let fs = require('fs')

// Resolve ".wasm" files to a path with a namespace

build.onResolve({ filter: /\.wasm$/ }, (args) => {

// If this is the import inside the stub module, import the

// binary itself. Put the path in the "wasm-binary" namespace

// to tell our binary load callback to load the binary file.

if (args.namespace === 'wasm-stub') {

return {

path: args.path,

namespace: 'wasm-binary',

}

}

// Otherwise, generate the JavaScript stub module for this

// ".wasm" file. Put it in the "wasm-stub" namespace to tell

// our stub load callback to fill it with JavaScript.

//

// Resolve relative paths to absolute paths here since this

// resolve callback is given "resolveDir", the directory to

// resolve imports against.

if (args.resolveDir === '') {

return // Ignore unresolvable paths

}

return {

path: path.isAbsolute(args.path) ? args.path : path.join(args.resolveDir, args.path),

namespace: 'wasm-stub',

}

})

// Virtual modules in the "wasm-stub" namespace are filled with

// the JavaScript code for compiling the WebAssembly binary. The

// binary itself is imported from a second virtual module.

build.onLoad({ filter: /.*/, namespace: 'wasm-stub' }, async (args) => ({

contents: `import wasm from ${JSON.stringify(args.path)}

export default (imports) =>

WebAssembly.instantiate(wasm, imports).then(

result => result.instance.exports)`,

}))

// Virtual modules in the "wasm-binary" namespace contain the

// actual bytes of the WebAssembly file. This uses esbuild's

// built-in "binary" loader instead of manually embedding the

// binary data inside JavaScript code ourselves.

build.onLoad({ filter: /.*/, namespace: 'wasm-binary' }, async (args) => ({

contents: await fs.promises.readFile(args.path),

loader: 'binary',

}))