wasi-demo.ts

/**
 * WASI is enabled through asconfig.json in post 0.20.x versions of AssemblyScript.
 * The module, @assemblyscript/wasi-shim is required to enable a WASI environment.
 * 
 * This demo is meant to showcase some abilities of WASI utilized through the AssemblyScript language.
 * It uses the latest version of AssemblyScript and will not work in older (<0.20.x) versions.
**/

// Import module that allows colors in the console as long as supported by WASI.
import { rainbow } from "as-rainbow/assembly";

// Call console.log which is overridden to use WASI syscalls by @assemblyscript/wasi-shim.
console.log(rainbow.blue(rainbow.boldMk("Hello from WasmTime WASI through AssemblyScript!")));

console.log(rainbow.boldMk("Press ctrl+c to exit this demo at any time."));

// Get the current time and print it.
console.log("\nWASI can read the system time and display it with the AssemblyScript Date API");
console.log(rainbow.boldMk("The current time is: ") + rainbow.italicMk(new Date(Date.now()).toString()));

// Read user input from process.stdin (API provided by AssemblyScript Wasi-Shim and WasmTime WASI API).

// Create a buffer to hold up to 100 characters of user input.
const buffer = new ArrayBuffer(100);
console.log("\nWASI can read user input from stdin. Write any word and return");

// Read data from stdin and write to buffer.
process.stdin.read(buffer);

// Print text and decode the buffer with String.UTF8.decode
console.log(rainbow.red("You said: " + String.UTF8.decode(buffer)))

waitForUserEnter("\nPlease press return to continue");

// Demonstrate the retrieval of cryptographically-safe random numbers through WASI.
console.log("WASI can fetch cryptographically-safe random numbers from the runtime\nSeries of random numbers:");

for (let i = 0; i < 5; i++) {
    console.log(Math.random().toString());
}

// End
console.log(rainbow.red("\nThat's all! :D"));

function waitForUserEnter(text: string): void {
    console.log(rainbow.italicMk(text));
    const buf = new ArrayBuffer(1);
    process.stdin.read(buf);
    return;
}