phil-lib/client-misc.ts

Blazingly fast TypeScript library for Node.js and the browser.

import { assertClass, makePromise } from "./misc.js";

/**
 * This is a wrapper around document.getElementById().
 * This ensures that we find the element and that it has the right type or it throws an exception.
 * Note that the return type of the function matches the requested type.
 * @param id Look for an element with this id.
 * @param ty This is the type we are expecting.  E.g. HtmlButtonElement
 */
export function getById<T extends Element>(id: string, ty: { new (): T }): T {
  // https://stackoverflow.com/a/64780056/971955
  const found = document.getElementById(id);
  if (!found) {
    throw new Error(
      "Could not find element with id " + id + ".  Expected type:  " + ty.name
    );
  }
  if (found instanceof ty) {
    return found;
  } else {
    throw new Error(
      "Element with id " +
        id +
        " has type " +
        found.constructor.name +
        ".  Expected type:  " +
        ty.name
    );
  }
}

/**
 * This is a wrapper around `window.selectorQueryAll()`.
 * This is analogous to `getById()`.
 *
 * This includes a lot of assertions.
 * These have good error messages aimed at a developer.
 * The assumption is that you will run this very early in the main program and store the results in a constant.
 * If there is a problem we want to catch it ASAP.
 *
 * You can set the min and max number of elements.
 * That's another thing that's good to check early.
 * The default range is 1 - Infinity.
 * Set `min` to 0 to completely disable this test.
 *
 * @param selector What you are looking for.  E.g. `"[data-precisionIssues]"`
 * @param ty The expected type of the items.  E.g. `SVGTextElement`
 * @param min The minimum number of items allowed.  Defaults to 1.
 * @param max The maximum number of items allowed.  Defaults to Infinity.
 * @returns An array containing all of the objects that matches the selector.
 * @throws If we don't get the right number of objects or if any of the objects have the wrong type.
 */
export function selectorQueryAll<T extends Element>(
  selector: string,
  ty: { new (): T },
  min = 1,
  max = Infinity,
  start: Pick<Document, "querySelectorAll"> = document
): readonly T[] {
  const result: T[] = [];
  start.querySelectorAll(selector).forEach((element) => {
    result.push(assertClass(element, ty));
  });
  if (result.length < min || result.length > max) {
    throw new Error(
      `Expecting "${selector}" to return [${min} - ${max}] instances of ${ty.name}, found ${result.length}.`
    );
  }
  return result;
}

/**
 * This is a wrapper around `document.selectorQuery()`.
 * 
 * This looks for elements matching the query string.
 * This ensures that exactly one element matches the query string, and that element has the expected type.
 * @param selector What to search for.  E.g. `"#main p:first-child"`
 * @param ty The expected type.  E.g. `HTMLParagraphElement`
 * @param start Where to look for the element.  Defaults to `window.document`.
 * @returns The new element.
 * @throws If we don't find the object, we find multiple matching objects or we find an object of the wrong type.
 */
export function selectorQuery<T extends Element>(
  selector: string,
  ty: { new (): T },
  start: Pick<Document, "querySelectorAll"> = document
): T {
  return selectorQueryAll(selector, ty, 1, 1, start)[0];
}

/**
 * Store the given date and time into the given input element.
 * Everything will be displayed in local time, similar to dateAndTime.toString().
 *
 * Going the other way is easy:  `new Date(input.value)`.
 * @param input This should be set to "datetime-local".
 * @param dateAndTime The date and time to load into the input.
 */
export function loadDateTimeLocal(
  input: HTMLInputElement,
  dateAndTime: Date,
  truncateTo: "minutes" | "seconds" | "milliseconds" = "milliseconds"
) {
  // The element will remember this value.
  // If you store a time like '2021-12-08T14:23:01.001', the display and the editor will show seconds and milliseconds.
  // If you store a time like '2021-12-08T14:23:01.000' or '2021-12-08T14:23:01', the display and the editor will show seconds but not milliseconds.
  // If you store a time like '2021-12-08T14:23:00.000' or '2021-12-08T14:23', the display and the editor will show neither seconds nor milliseconds.
  // Changing the time using the GUI will not change which fields are displayed.
  // Note:  Rounding or truncating will only remove fields, not add them.
  // If you want to display "14:23:00.000", and you want the user to be able to set the seconds via the GUI, I don't think that's possible.
  // Note:  I didn't see this documented anywhere.  I learned this by experimenting with Chrome.
  let truncateBy: number;
  switch (truncateTo) {
    case "minutes": {
      truncateBy =
        dateAndTime.getSeconds() * 1000 + dateAndTime.getMilliseconds();
      break;
    }
    case "seconds": {
      truncateBy = dateAndTime.getMilliseconds();
      break;
    }
    case "milliseconds": {
      truncateBy = 0;
      break;
    }
    default: {
      throw new Error("wtf");
    }
  }
  // This is conversion is surprisingly hard to do.  Advice from MDN and others failed miserably.
  input.valueAsNumber =
    +dateAndTime - dateAndTime.getTimezoneOffset() * 60000 - truncateBy;
}

export function getBlobFromCanvas(canvas: HTMLCanvasElement): Promise<Blob> {
  const { reject, resolve, promise } = makePromise<Blob>();
  canvas.toBlob((blob) => {
    if (!blob) {
      reject(new Error("blob is null!"));
    } else {
      resolve(blob);
    }
  });
  return promise;
}

/**
 *
 * @param audioElement The element to control.
 * @returns A function which will control the balance for the given element.
 * * An input of -1 means all left.
 * * 0 means center / both.
 * * 1 means all right.
 * * Values between -1 and 1 are continuously interpolated.
 */
export function getAudioBalanceControl(audioElement: HTMLAudioElement) {
  //https://stackoverflow.com/a/63193575/971955
  const audioContext = new AudioContext();
  // pass the audio element into the audio context
  const track = audioContext.createMediaElementSource(audioElement);
  // default pan set to 0 - center
  const stereoNode = new StereoPannerNode(audioContext, { pan: 0 });
  track.connect(stereoNode).connect(audioContext.destination);
  return (balance: number) => {
    stereoNode.pan.value = balance;
  };
}

/**
 * Reads the hash (a.k.a the fragment) associated with the current url and
 * parses it like a url query string.  E.g. key1=value1&key2=value2.
 *
 * Keys and values are both decoded by normal url rules.
 *
 * I explicitly allow + to be converted to space.  These might be written by hand
 * and + is convenient for that.
 */
export function getHashInfo(): Map<string, string> {
  const result = new Map<string, string>();
  const hashString = /^#?(.*)$/.exec(location.hash.replace("+", "%20"))![1];
  const pairs = hashString.split("&");
  pairs.forEach((pair) => {
    const kvp = pair.split("=", 2);
    if (kvp.length == 2) {
      const key = decodeURIComponent(kvp[0]);
      const value = decodeURIComponent(kvp[1]);
      result.set(key, value);
    }
  });
  return result;
}

/**
 *
 * @param htmlString A string to convert into an element.
 * @param ty The type of the result.
 * @returns The element that was created.
 * @throws An `Error` if the new element is not of the given type.  Or if we couldn't create an element at all.
 */
export function createElementFromHTML<T extends object>(
  htmlString: string,
  ty: { new (): T }
) {
  // From https://stackoverflow.com/a/494348/971955
  // From that SO question:
  // It's unfortunate that these solutions are so indirect. I wish the standards committee would specify something similar like: var nodes = document.fromString("<b>Hello</b> <br>");
  var div = document.createElement("div");
  div.innerHTML = htmlString.trim();

  // Change div.firstChild to div.childNodes to support multiple top-level nodes.
  return assertClass(div.firstChild, ty, "createElementFromHTML:");
}

/**
 * Save a string to a local file.
 *
 * On chrome this will instantly save the file to the downloads directory.  On Safari I got
 * a security warning the first time, then I was allowed to instantly download things.
 *
 * Chrome will get upset if you do too many downloads.  Consider creating a zip file if
 * you want to save a lot of files.
 * @param filename The preferred file name.  Chrome will add (1) or similar if that filename already exists.
 * @param text The contents of the file.
 */
export function download(filename: string, text: string) {
  // Source:  https://stackoverflow.com/a/18197511/971955
  var pom = document.createElement("a");
  pom.setAttribute(
    "href",
    "data:text/plain;charset=utf-8," + encodeURIComponent(text)
  );
  pom.setAttribute("download", filename);
  if (document.createEvent) {
    var event = document.createEvent("MouseEvents");
    // I wonder why we need this if statement.  initEvent() is deprecated.
    // why not always use the else case?
    event.initEvent("click", true, true);
    pom.dispatchEvent(event);
  } else {
    pom.click();
  }
}

/**
 * This is a wrapper around `requestAnimationFrame()`.
 * It automatically calls `requestAnimationFrame()` over and over until you `cancel()` it.
 */
export class AnimationLoop {
  constructor(private readonly onWake: (time: DOMHighResTimeStamp) => void) {
    this.callback = this.callback.bind(this);
    // This next line isn't quite right.
    // Sometimes this timestamp is greater than the timestamp of the first requestAnimationFrame() callback.
    // It seemed like a good idea at the time.
    // this.callback(performance.now());
    requestAnimationFrame(this.callback);
  }
  #cancelled = false;
  cancel() {
    this.#cancelled = true;
  }
  private callback(time: DOMHighResTimeStamp) {
    if (!this.#cancelled) {
      requestAnimationFrame(this.callback);
      this.onWake(time);
    }
  }
}

/**
 * Convert an image into a data url.
 * @param url A url that points to an image.
 * @returns A data url that represents the same image.
 */
export async function getDataUrl(url: string) {
  const image = document.createElement("img");
  image.src = url;
  await image.decode();
  const height = image.naturalHeight;
  const width = image.naturalWidth;
  if (height == 0 || width == 0) {
    // The documentation suggests that decode() will throw an exception if there is a problem.
    // However, as I recall the promise resolves to undefined as soon as the image succeeds or fails.
    // I'm using this test to know if it failed.
    throw new Error("problem with image");
  }
  const canvas = document.createElement("canvas");
  canvas.width = width;
  canvas.height = height;
  const context = canvas.getContext("2d");
  if (!context) {
    throw new Error("wtf");
  }
  context.drawImage(image, 0, 0, canvas.width, canvas.height);
  return canvas.toDataURL();
}