JavaScript (または TypeScript) を AssemblyScript に移植する方法

const prettyMilliseconds = require("pretty-ms");

function getPrettyExecutionTime() {
  // Get our start time in milliseconds (Unix Timestamp)
  const start = Date.now();

  // Do a random amount of busy work
  let iterations = 100000 + Math.floor(Math.random() * 10000000);
  for (let i = 0; i < iterations; i++) {
    iterations -= 1;
  }

  // Get our start time in milliseconds (Unix Timestamp)
  const end = Date.now();

  // Log out the Execution time in a human readable format
let responseString = "";
responseString +=
  "Pretty Unix timestamp: " +
  prettyMilliseconds(start, { verbose: true }) +
  "\n";
responseString +=
  "Busy work execution time: " +
  prettyMilliseconds(end - start, {
    verbose: true,
    formatSubMilliseconds: true,
  });

return responseString;
}

console.log(getPrettyExecutionTime());

// This file is a port of:
// https://github.com/sindresorhus/parse-ms/blob/326500f7395fba4f47e73e36e6e770ad47c358d2/index.js
// The file is commented respective to how this is ported.

// As of 2020, AssemblyScript closure support is still in progress, and only supports pure nested functions
// Thus, we will pull out the nested function into its own function.
// This isn't required, but can avoid headaches in the future.
// This function takes in a float, but rounds it to an integer.
// In Typescript, `f64` would have been `number` types, but we must be explicit with the type of number in AS
// Ported from: https://github.com/sindresorhus/parse-ms/blob/326500f7395fba4f47e73e36e6e770ad47c358d2/index.js#L7
function roundTowardsZero(valueToRound: f64): f64 {
  if (valueToRound > 0) {
    return Math.floor(valueToRound);
  } else {
    return Math.ceil(valueToRound);
  }
}

// Define a class that represents the returned object fom the exported function
// We are exporting this as well, that way the type can be used
// Also, the `f64` type in TypeScript would be `number`, but in AS we must be explicit with the number type
// Ported from: https://github.com/sindresorhus/parse-ms/blob/326500f7395fba4f47e73e36e6e770ad47c358d2/index.js#L9
export class ParsedMilliseconds {
  days: f64;
  hours: f64;
  minutes: f64;
  seconds: f64;
  milliseconds: f64;
  microseconds: f64;
  nanoseconds: f64;
}

// Export a function to parse our milliseconds into our return type.
// Also, the `f64` type in TypeScript would be `number`, but in AS we must be explicit with the number type.
// Ported from: https://github.com/sindresorhus/parse-ms/blob/master/index.js#L2
export function parseMilliseconds(milliseconds: f64): ParsedMilliseconds {

  // We don't need to do a type check here, since we are using a typed language!
  // Referring to: https://github.com/sindresorhus/parse-ms/blob/326500f7395fba4f47e73e36e6e770ad47c358d2/index.js#L3

  // We moved roundTowardsZero into its own function
  // Referring to: https://github.com/sindresorhus/parse-ms/blob/326500f7395fba4f47e73e36e6e770ad47c358d2/index.js#L7

  // AssemblyScript will construct an instance of our return type (e.g new ParsedMilliseconds())
  // Since the return object has all the same properties of our return type.
  // This is so that we can pass a float into our `roundTowardsZero` function to handle the special rounding.
  return {
    days: roundTowardsZero(milliseconds / 86400000),
    hours: roundTowardsZero(milliseconds / 3600000) % 24,
    minutes: roundTowardsZero(milliseconds / 60000) % 60,
    seconds: roundTowardsZero(milliseconds / 1000) % 60,
    milliseconds: roundTowardsZero(milliseconds) % 1000,
    microseconds: roundTowardsZero(milliseconds * 1000) % 1000,
    nanoseconds: roundTowardsZero(milliseconds * 1e6) % 1000,
  };
}

// This file is a port of:
// https://github.com/sindresorhus/pretty-ms/blob/eda21362097d47ab309dca8cf07dc79b25fb0efa/index.js
// The file is commented respective to how this is ported.

// Import our ported ported `parse-ms` module
// This ports the `require()` call:
// Ported From: https://github.com/sindresorhus/pretty-ms/blob/eda21362097d47ab309dca8cf07dc79b25fb0efa/index.js#L2
import { parseMilliseconds } from "./parse-ms";

const SECOND_ROUNDING_EPSILON: f32 = 0.0000001;

// Define our options object that will be passed into our exported `prettyMilliseconds` function
// The options are from the documentation: https://github.com/sindresorhus/pretty-ms#options
// However, we removed the `DecimalDigits` options and `keepDecimalsOnWholeSeconds`, as Float.toFixed is in progress:
// https://github.com/AssemblyScript/assemblyscript/issues/1163
// In Typescript, `f64` and `i32` would have been `number` types, but we must be explicit with the type of number in AS
// Ported from: https://github.com/sindresorhus/pretty-ms/blob/eda21362097d47ab309dca8cf07dc79b25fb0efa/index.js#L8
export class PrettyMillisecondsOptions {
  compact: boolean = false;
  unitCount: i32 = 0;
  verbose: boolean = false;
  separateMilliseconds: boolean = false;
  formatSubMilliseconds: boolean = false;
  colonNotation: boolean = false;
}

// This function takes in our word (which would be a string),
// and the count of that word (a float), to pluralize it.
// Also, the `i32` type in TypeScript would be `number`, but in AS, we must be explicit with the number type.
// Ported from: https://github.com/sindresorhus/pretty-ms/blob/eda21362097d47ab309dca8cf07dc79b25fb0efa/index.js#L4
function pluralize(word: string, count: f64): string {

  // Since AssemblyScript is type checked, there is no need for ===
  // We can use the standard ==
  // Referring to: https://github.com/sindresorhus/pretty-ms/blob/eda21362097d47ab309dca8cf07dc79b25fb0efa/index.js#L4
  if (count == 1) {
    return word;
  }

  return word + "s";
}

// As of 2020, AssemblyScript closure support is still in progress and only supports pure nested functions
// Thus, we will pull out the nested function into its own function.
// We pass in the options and results that were previously accessible by the closure, and return the results
// We also typed all of the parameters, to their respective types they would have been in JS or TS.
// One notable parameter is `valueString`. In JavaScript, optional parameters will default to `undefined`.
// In AssemblyScript, we would want to initialize this parameter with a value of its type and check that value later.
// We could have done a `valueString: string | null = null` to also signify it's an optional high-level typed parameter in a more
// JS-like fashion, but we use an empty string as it is a simpler replacement to check for.
// Ported from: https://github.com/sindresorhus/pretty-ms/blob/eda21362097d47ab309dca8cf07dc79b25fb0efa/index.js#L33
function add(
  options: PrettyMillisecondsOptions,
  result: Array<string>,
  value: f64,
  long: string,
  short: string,
  valueString: string = ""
): Array<string> {
  if (
    (result.length === 0 || !options.colonNotation) &&
    value === 0 &&
    !(options.colonNotation && short === "m")
  ) {
    return result;
  }

  // AssemblyScript doesn't have `undefined`, so we need to be
  // a bit more explicit with our typecheck here
  // Referring to: https://github.com/sindresorhus/pretty-ms/blob/eda21362097d47ab309dca8cf07dc79b25fb0efa/index.js#L38
  if (valueString == "") {
    valueString = value.toString();
  }

  // AssemblyScript would normally default types to i32, if the compiler can't figure out what
  // the type is from its initial assignment. So we need to define these types as strings,
  // since they are being used as strings
  // Ported from: https://github.com/sindresorhus/pretty-ms/blob/eda21362097d47ab309dca8cf07dc79b25fb0efa/index.js#L39
  let prefix: string = "";
  let suffix: string = "";
  if (options.colonNotation) {
    prefix = result.length > 0 ? ":" : "";
    suffix = "";
    const wholeDigits = valueString.includes(".")
      ? valueString.split(".")[0].length
      : valueString.length;
    const minLength = result.length > 0 ? 2 : 1;
    valueString =
      "0".repeat(<i32>Math.max(0, minLength - wholeDigits)) + valueString;
  } else {
    prefix = "";

    // Since we removed the `DecimalDigits` options and `keepDecimalsOnWholeSeconds`, as Float.toFixed is in progress:
    // https://github.com/AssemblyScript/assemblyscript/issues/1163
    // Let's remove the trailing `.0` to clean things up by parsing our f64 into an i32
    valueString = I32.parseInt(valueString).toString();

    suffix = options.verbose ? " " + pluralize(long, value) : short;
  }

  result.push(prefix + valueString + suffix);
  return result;
}

// Export a function to parse our milliseconds into our human readable milliseconds string.
// Also, the `i32` type in TypeScript would be `number`, but in AS we must be explicit with the number type.
// Ported from: https://github.com/sindresorhus/pretty-ms/blob/eda21362097d47ab309dca8cf07dc79b25fb0efa/index.js#L8
export function prettyMilliseconds(
  milliseconds: f64,
  options: PrettyMillisecondsOptions
): string {
  if (!Number.isFinite(milliseconds)) {
    throw new Error("Expected a finite number");
  }

  if (options.colonNotation) {
    options.compact = false;
    options.formatSubMilliseconds = false;
    options.separateMilliseconds = false;
    options.verbose = false;
  }

  // Since we aren't supporting DecimalDigits options in this port, we don't need to modify them
  // Referring to: https://github.com/sindresorhus/pretty-ms/blob/eda21362097d47ab309dca8cf07dc79b25fb0efa/index.js#L20

  // It is best to define most high-level types by their object and type
  // Therefore our Array is defined as `new Array<string>()` instead of `[]`
  // Ported from: https://github.com/sindresorhus/pretty-ms/blob/eda21362097d47ab309dca8cf07dc79b25fb0efa/index.js#L25
  let result = new Array<string>();

  const parsed = parseMilliseconds(milliseconds);

  // As mentioned earlier, we pulled the add function into its own function.
  // Thus, we update our result as we add instead of using the closure.
  // We also updated the other `add()` calls below, but only commenting here for brevity.
  // Also, we don't need the Math.trunc() call since we are doing integer division by default, unlike JavaScript
  // Ported from: https://github.com/sindresorhus/pretty-ms/blob/eda21362097d47ab309dca8cf07dc79b25fb0efa/index.js#L57
  result = add(options, result, Math.floor(parsed.days / 365), "year", "y");
  result = add(options, result, parsed.days % 365, "day", "d");
  result = add(options, result, parsed.hours, "hour", "h");
  result = add(options, result, parsed.minutes, "minute", "m");

  if (
    options.separateMilliseconds ||
    options.formatSubMilliseconds ||
    (!options.colonNotation && milliseconds < 1000)
  ) {
    result = add(options, result, parsed.seconds, "second", "s");
    if (options.formatSubMilliseconds) {
      result = add(options, result, parsed.milliseconds, "millisecond", "ms");
      result = add(options, result, parsed.microseconds, "microsecond", "µs");
      result = add(options, result, parsed.nanoseconds, "nanosecond", "ns");
    } else {
      const millisecondsAndBelow =
        parsed.milliseconds +
        parsed.microseconds / 1000 +
        parsed.nanoseconds / 1e6;

      // Since we aren't supporting DecimalDigits options in this port, we don't need `millisecondsDecimalDigits`
      // Referring to: https://github.com/sindresorhus/pretty-ms/blob/eda21362097d47ab309dca8cf07dc79b25fb0efa/index.js#L78

      const roundedMilliseconds =
        millisecondsAndBelow >= 1
          ? Math.round(millisecondsAndBelow)
          : Math.ceil(millisecondsAndBelow);

      // Since we aren't supporting DecimalDigits options in this port, we don't need `millisecondsDecimalDigits`
      // Referring to: https://github.com/sindresorhus/pretty-ms/blob/eda21362097d47ab309dca8cf07dc79b25fb0efa/index.js#L87
      const millisecondsString: string = roundedMilliseconds.toString();

      result = add(
        options,
        result,
        parseFloat(millisecondsString),
        "millisecond",
        "ms",
        millisecondsString
      );
    }
  } else {
    const seconds = (milliseconds / 1000) % 60;

    // Since we aren't supporting DecimalDigits options in this port, we don't need `secondsDecimalDigits`
    // Referring to: https://github.com/sindresorhus/pretty-ms/blob/eda21362097d47ab309dca8cf07dc79b25fb0efa/index.js#L78

    const secondsString = seconds.toString();
    result = add(
      options,
      result,
      parseFloat(secondsString),
      "second",
      "s",
      secondsString
    );
  }

  if (result.length === 0) {
    return "0" + (options.verbose ? " milliseconds" : "ms");
  }

  if (options.compact) {
    return result[0];
  }

  // We can replace the type check with a `> 0` check since we are using a typed language!
  // Referring to: https://github.com/sindresorhus/pretty-ms/blob/eda21362097d47ab309dca8cf07dc79b25fb0efa/index.js#L119
  if (options.unitCount > 0) {
    const separator = options.colonNotation ? "" : " ";
    return result.slice(0, <i32>Math.max(options.unitCount, 1)).join(separator);
  }

  return options.colonNotation ? result.join("") : result.join(" ");
}

import "wasi";
import { Date } from "as-wasi";
import { prettyMilliseconds } from "./pretty-ms";

export function getPrettyExecutionTime(): string {
  // Get our start time in milliseconds (Unix Timestamp)
  // In "as-wasi" this returns the milliseconds as a float
  // However, we will cast this to an integer for prettyMilliseconds
  const start = Date.now();

  // Do a random amount of busy work
  let iterations = 100000 + Math.floor(Math.random() * 10000000);
  for (let i = 0; i < iterations; i++) {
    iterations -= 1;
  }

  // Get our start time in milliseconds (Unix Timestamp)
  const end = Date.now();

  let responseString = "";
  responseString +=
    "Pretty Unix timestamp: " +
    prettyMilliseconds(start, { verbose: true }) +
    "\n";
  responseString +=
    "Busy work execution time: " +
    prettyMilliseconds(end - start, {
      verbose: true,
      formatSubMilliseconds: true,
    });

  return responseString;
}

import { Request, Response, Fastly } from "@fastly/as-compute";

// Import our pretty-execution time
import { getPrettyExecutionTime } from "./pretty-execution-time";

// Remove the unnecessary backend constants for our application
// Referring to: https://github.com/fastly/compute-starter-kit-assemblyscript-default/blob/78e536b046cff9e2a3e81945ef8b02ddc7bf2a75/assembly/index.ts#L3

// The entry point for your application.
//
// Use this function to define your main request handling logic. It could be
// used to route based on the request properties (such as method or path), send
// the request to a backend, make completely new requests, and/or generate
// synthetic responses.
function main(req: Request): Response {
  // Make any desired changes to the client request.
  req.headers().set("Host", "example.com");

  // We can filter requests that have unexpected methods.
  const VALID_METHODS = ["HEAD", "GET", "POST"];
  if (!VALID_METHODS.includes(req.method())) {
    return new Response(String.UTF8.encode("This method is not allowed"), {
      status: 405,
    });
  }

  let method = req.method();
  let urlParts = req.url().split("//").pop().split("/");
  let host = urlParts.shift();
  let path = "/" + urlParts.join("/");

  // If request is a `GET` to the `/` path, send a default response.
  if (method == "GET" && path == "/") {
    return new Response(String.UTF8.encode(getPrettyExecutionTime()), {
      status: 200,
    });
  }

  // Remove the unnecessary routes for our application
  // Referring to: https://github.com/fastly/compute-starter-kit-assemblyscript-default/blob/78e536b046cff9e2a3e81945ef8b02ddc7bf2a75/assembly/index.ts#L42

  // Catch all other requests and return a 404.
  return new Response(
    String.UTF8.encode("The page you requested could not be found"),
    {
      status: 404,
    }
  );
}

// Get the request from the client.
let req = Fastly.getClientRequest();

// Pass the request to the main request handler function.
let resp = main(req);

// Send the response back to the client.
Fastly.respondWith(resp);