11 files changed, 662 insertions, 0 deletions
diff --git a/web_src/js/utils/color.js b/web_src/js/utils/color.js
new file mode 100644
index 00000000..198f97c4
--- /dev/null
+++ b/web_src/js/utils/color.js
@@ -0,0 +1,33 @@
+import tinycolor from 'tinycolor2';
+
+// Returns relative luminance for a SRGB color - https://en.wikipedia.org/wiki/Relative_luminance
+// Keep this in sync with modules/util/color.go
+function getRelativeLuminance(color) {
+  const {r, g, b} = tinycolor(color).toRgb();
+  return (0.2126729 * r + 0.7151522 * g + 0.072175 * b) / 255;
+}
+
+function useLightText(backgroundColor) {
+  return getRelativeLuminance(backgroundColor) < 0.453;
+}
+
+// Given a background color, returns a black or white foreground color that the highest
+// contrast ratio. In the future, the APCA contrast function, or CSS `contrast-color` will be better.
+// https://github.com/color-js/color.js/blob/eb7b53f7a13bb716ec8b28c7a56f052cd599acd9/src/contrast/APCA.js#L42
+export function contrastColor(backgroundColor) {
+  return useLightText(backgroundColor) ? '#fff' : '#000';
+}
+
+function resolveColors(obj) {
+  const styles = window.getComputedStyle(document.documentElement);
+  const getColor = (name) => styles.getPropertyValue(name).trim();
+  return Object.fromEntries(Object.entries(obj).map(([key, value]) => [key, getColor(value)]));
+}
+
+export const chartJsColors = resolveColors({
+  text: '--color-text',
+  border: '--color-secondary-alpha-60',
+  commits: '--color-primary-alpha-60',
+  additions: '--color-green',
+  deletions: '--color-red',
+});
diff --git a/web_src/js/utils/color.test.js b/web_src/js/utils/color.test.js
new file mode 100644
index 00000000..fee9afc7
--- /dev/null
+++ b/web_src/js/utils/color.test.js
@@ -0,0 +1,22 @@
+import {contrastColor} from './color.js';
+
+test('contrastColor', () => {
+  expect(contrastColor('#d73a4a')).toBe('#fff');
+  expect(contrastColor('#0075ca')).toBe('#fff');
+  expect(contrastColor('#cfd3d7')).toBe('#000');
+  expect(contrastColor('#a2eeef')).toBe('#000');
+  expect(contrastColor('#7057ff')).toBe('#fff');
+  expect(contrastColor('#008672')).toBe('#fff');
+  expect(contrastColor('#e4e669')).toBe('#000');
+  expect(contrastColor('#d876e3')).toBe('#000');
+  expect(contrastColor('#ffffff')).toBe('#000');
+  expect(contrastColor('#2b8684')).toBe('#fff');
+  expect(contrastColor('#2b8786')).toBe('#fff');
+  expect(contrastColor('#2c8786')).toBe('#000');
+  expect(contrastColor('#3bb6b3')).toBe('#000');
+  expect(contrastColor('#7c7268')).toBe('#fff');
+  expect(contrastColor('#7e716c')).toBe('#fff');
+  expect(contrastColor('#81706d')).toBe('#fff');
+  expect(contrastColor('#807070')).toBe('#fff');
+  expect(contrastColor('#84b6eb')).toBe('#000');
+});
diff --git a/web_src/js/utils/dom.js b/web_src/js/utils/dom.js
new file mode 100644
index 00000000..a2a79e91
--- /dev/null
+++ b/web_src/js/utils/dom.js
@@ -0,0 +1,298 @@
+import {debounce} from 'throttle-debounce';
+
+function elementsCall(el, func, ...args) {
+  if (typeof el === 'string' || el instanceof String) {
+    el = document.querySelectorAll(el);
+  }
+  if (el instanceof Node) {
+    func(el, ...args);
+  } else if (el.length !== undefined) {
+    // this works for: NodeList, HTMLCollection, Array, jQuery
+    for (const e of el) {
+      func(e, ...args);
+    }
+  } else {
+    throw new Error('invalid argument to be shown/hidden');
+  }
+}
+
+/**
+ * @param el string (selector), Node, NodeList, HTMLCollection, Array or jQuery
+ * @param force force=true to show or force=false to hide, undefined to toggle
+ */
+function toggleShown(el, force) {
+  if (force === true) {
+    el.classList.remove('tw-hidden');
+  } else if (force === false) {
+    el.classList.add('tw-hidden');
+  } else if (force === undefined) {
+    el.classList.toggle('tw-hidden');
+  } else {
+    throw new Error('invalid force argument');
+  }
+}
+
+export function showElem(el) {
+  elementsCall(el, toggleShown, true);
+}
+
+export function hideElem(el) {
+  elementsCall(el, toggleShown, false);
+}
+
+export function toggleElem(el, force) {
+  elementsCall(el, toggleShown, force);
+}
+
+export function isElemHidden(el) {
+  const res = [];
+  elementsCall(el, (e) => res.push(e.classList.contains('tw-hidden')));
+  if (res.length > 1) throw new Error(`isElemHidden doesn't work for multiple elements`);
+  return res[0];
+}
+
+function applyElemsCallback(elems, fn) {
+  if (fn) {
+    for (const el of elems) {
+      fn(el);
+    }
+  }
+  return elems;
+}
+
+export function queryElemSiblings(el, selector = '*', fn) {
+  return applyElemsCallback(Array.from(el.parentNode.children).filter((child) => child !== el && child.matches(selector)), fn);
+}
+
+// it works like jQuery.children: only the direct children are selected
+export function queryElemChildren(parent, selector = '*', fn) {
+  return applyElemsCallback(parent.querySelectorAll(`:scope > ${selector}`), fn);
+}
+
+export function queryElems(selector, fn) {
+  return applyElemsCallback(document.querySelectorAll(selector), fn);
+}
+
+export function onDomReady(cb) {
+  if (document.readyState === 'loading') {
+    document.addEventListener('DOMContentLoaded', cb);
+  } else {
+    cb();
+  }
+}
+
+// checks whether an element is owned by the current document, and whether it is a document fragment or element node
+// if it is, it means it is a "normal" element managed by us, which can be modified safely.
+export function isDocumentFragmentOrElementNode(el) {
+  try {
+    return el.ownerDocument === document && el.nodeType === Node.ELEMENT_NODE || el.nodeType === Node.DOCUMENT_FRAGMENT_NODE;
+  } catch {
+    // in case the el is not in the same origin, then the access to nodeType would fail
+    return false;
+  }
+}
+
+// autosize a textarea to fit content. Based on
+// https://github.com/github/textarea-autosize
+// ---------------------------------------------------------------------
+// Copyright (c) 2018 GitHub, Inc.
+//
+// Permission is hereby granted, free of charge, to any person obtaining
+// a copy of this software and associated documentation files (the
+// "Software"), to deal in the Software without restriction, including
+// without limitation the rights to use, copy, modify, merge, publish,
+// distribute, sublicense, and/or sell copies of the Software, and to
+// permit persons to whom the Software is furnished to do so, subject to
+// the following conditions:
+//
+// The above copyright notice and this permission notice shall be
+// included in all copies or substantial portions of the Software.
+// ---------------------------------------------------------------------
+export function autosize(textarea, {viewportMarginBottom = 0} = {}) {
+  let isUserResized = false;
+  // lastStyleHeight and initialStyleHeight are CSS values like '100px'
+  let lastMouseX, lastMouseY, lastStyleHeight, initialStyleHeight;
+
+  function onUserResize(event) {
+    if (isUserResized) return;
+    if (lastMouseX !== event.clientX || lastMouseY !== event.clientY) {
+      const newStyleHeight = textarea.style.height;
+      if (lastStyleHeight && lastStyleHeight !== newStyleHeight) {
+        isUserResized = true;
+      }
+      lastStyleHeight = newStyleHeight;
+    }
+
+    lastMouseX = event.clientX;
+    lastMouseY = event.clientY;
+  }
+
+  function overflowOffset() {
+    let offsetTop = 0;
+    let el = textarea;
+
+    while (el !== document.body && el !== null) {
+      offsetTop += el.offsetTop || 0;
+      el = el.offsetParent;
+    }
+
+    const top = offsetTop - document.defaultView.scrollY;
+    const bottom = document.documentElement.clientHeight - (top + textarea.offsetHeight);
+    return {top, bottom};
+  }
+
+  function resizeToFit() {
+    if (isUserResized) return;
+    if (textarea.offsetWidth <= 0 && textarea.offsetHeight <= 0) return;
+
+    try {
+      const {top, bottom} = overflowOffset();
+      const isOutOfViewport = top < 0 || bottom < 0;
+
+      const computedStyle = getComputedStyle(textarea);
+      const topBorderWidth = parseFloat(computedStyle.borderTopWidth);
+      const bottomBorderWidth = parseFloat(computedStyle.borderBottomWidth);
+      const isBorderBox = computedStyle.boxSizing === 'border-box';
+      const borderAddOn = isBorderBox ? topBorderWidth + bottomBorderWidth : 0;
+
+      const adjustedViewportMarginBottom = bottom < viewportMarginBottom ? bottom : viewportMarginBottom;
+      const curHeight = parseFloat(computedStyle.height);
+      const maxHeight = curHeight + bottom - adjustedViewportMarginBottom;
+
+      textarea.style.height = 'auto';
+      let newHeight = textarea.scrollHeight + borderAddOn;
+
+      if (isOutOfViewport) {
+        // it is already out of the viewport:
+        // * if the textarea is expanding: do not resize it
+        if (newHeight > curHeight) {
+          newHeight = curHeight;
+        }
+        // * if the textarea is shrinking, shrink line by line (just use the
+        //   scrollHeight). do not apply max-height limit, otherwise the page
+        //   flickers and the textarea jumps
+      } else {
+        // * if it is in the viewport, apply the max-height limit
+        newHeight = Math.min(maxHeight, newHeight);
+      }
+
+      textarea.style.height = `${newHeight}px`;
+      lastStyleHeight = textarea.style.height;
+    } finally {
+      // ensure that the textarea is fully scrolled to the end, when the cursor
+      // is at the end during an input event
+      if (textarea.selectionStart === textarea.selectionEnd &&
+          textarea.selectionStart === textarea.value.length) {
+        textarea.scrollTop = textarea.scrollHeight;
+      }
+    }
+  }
+
+  function onFormReset() {
+    isUserResized = false;
+    if (initialStyleHeight !== undefined) {
+      textarea.style.height = initialStyleHeight;
+    } else {
+      textarea.style.removeProperty('height');
+    }
+  }
+
+  textarea.addEventListener('mousemove', onUserResize);
+  textarea.addEventListener('input', resizeToFit);
+  textarea.form?.addEventListener('reset', onFormReset);
+  initialStyleHeight = textarea.style.height ?? undefined;
+  if (textarea.value) resizeToFit();
+
+  return {
+    resizeToFit,
+    destroy() {
+      textarea.removeEventListener('mousemove', onUserResize);
+      textarea.removeEventListener('input', resizeToFit);
+      textarea.form?.removeEventListener('reset', onFormReset);
+    },
+  };
+}
+
+export function onInputDebounce(fn) {
+  return debounce(300, fn);
+}
+
+// Set the `src` attribute on an element and returns a promise that resolves once the element
+// has loaded or errored. Suitable for all elements mention in:
+// https://developer.mozilla.org/en-US/docs/Web/API/HTMLElement/load_event
+export function loadElem(el, src) {
+  return new Promise((resolve) => {
+    el.addEventListener('load', () => resolve(true), {once: true});
+    el.addEventListener('error', () => resolve(false), {once: true});
+    el.src = src;
+  });
+}
+
+// some browsers like PaleMoon don't have "SubmitEvent" support, so polyfill it by a tricky method: use the last clicked button as submitter
+// it can't use other transparent polyfill patches because PaleMoon also doesn't support "addEventListener(capture)"
+const needSubmitEventPolyfill = typeof SubmitEvent === 'undefined';
+
+export function submitEventSubmitter(e) {
+  return needSubmitEventPolyfill ? (e.target._submitter || null) : e.submitter;
+}
+
+function submitEventPolyfillListener(e) {
+  const form = e.target.closest('form');
+  if (!form) return;
+  form._submitter = e.target.closest('button:not([type]), button[type="submit"], input[type="submit"]');
+}
+
+export function initSubmitEventPolyfill() {
+  if (!needSubmitEventPolyfill) return;
+  console.warn(`This browser doesn't have "SubmitEvent" support, use a tricky method to polyfill`);
+  document.body.addEventListener('click', submitEventPolyfillListener);
+  document.body.addEventListener('focus', submitEventPolyfillListener);
+}
+
+/**
+ * Check if an element is visible, equivalent to jQuery's `:visible` pseudo.
+ * Note: This function doesn't account for all possible visibility scenarios.
+ * @param {HTMLElement} element The element to check.
+ * @returns {boolean} True if the element is visible.
+ */
+export function isElemVisible(element) {
+  if (!element) return false;
+
+  return Boolean(element.offsetWidth || element.offsetHeight || element.getClientRects().length);
+}
+
+// extract text and images from "paste" event
+export function getPastedContent(e) {
+  const images = [];
+  for (const item of e.clipboardData?.items ?? []) {
+    if (item.type?.startsWith('image/')) {
+      images.push(item.getAsFile());
+    }
+  }
+  const text = e.clipboardData?.getData?.('text') ?? '';
+  return {text, images};
+}
+
+// replace selected text in a textarea while preserving editor history, e.g. CTRL-Z works after this
+export function replaceTextareaSelection(textarea, text) {
+  const before = textarea.value.slice(0, textarea.selectionStart ?? undefined);
+  const after = textarea.value.slice(textarea.selectionEnd ?? undefined);
+  let success = true;
+
+  textarea.contentEditable = 'true';
+  try {
+    success = document.execCommand('insertText', false, text);
+  } catch {
+    success = false;
+  }
+  textarea.contentEditable = 'false';
+
+  if (success && !textarea.value.slice(0, textarea.selectionStart ?? undefined).endsWith(text)) {
+    success = false;
+  }
+
+  if (!success) {
+    textarea.value = `${before}${text}${after}`;
+    textarea.dispatchEvent(new CustomEvent('change', {bubbles: true, cancelable: true}));
+  }
+}
diff --git a/web_src/js/utils/image.js b/web_src/js/utils/image.js
new file mode 100644
index 00000000..ed5d98e3
--- /dev/null
+++ b/web_src/js/utils/image.js
@@ -0,0 +1,47 @@
+export async function pngChunks(blob) {
+  const uint8arr = new Uint8Array(await blob.arrayBuffer());
+  const chunks = [];
+  if (uint8arr.length < 12) return chunks;
+  const view = new DataView(uint8arr.buffer);
+  if (view.getBigUint64(0) !== 9894494448401390090n) return chunks;
+
+  const decoder = new TextDecoder();
+  let index = 8;
+  while (index < uint8arr.length) {
+    const len = view.getUint32(index);
+    chunks.push({
+      name: decoder.decode(uint8arr.slice(index + 4, index + 8)),
+      data: uint8arr.slice(index + 8, index + 8 + len),
+    });
+    index += len + 12;
+  }
+
+  return chunks;
+}
+
+// decode a image and try to obtain width and dppx. If will never throw but instead
+// return default values.
+export async function imageInfo(blob) {
+  let width = 0; // 0 means no width could be determined
+  let dppx = 1; // 1 dot per pixel for non-HiDPI screens
+
+  if (blob.type === 'image/png') { // only png is supported currently
+    try {
+      for (const {name, data} of await pngChunks(blob)) {
+        const view = new DataView(data.buffer);
+        if (name === 'IHDR' && data?.length) {
+          // extract width from mandatory IHDR chunk
+          width = view.getUint32(0);
+        } else if (name === 'pHYs' && data?.length) {
+          // extract dppx from optional pHYs chunk, assuming pixels are square
+          const unit = view.getUint8(8);
+          if (unit === 1) {
+            dppx = Math.round(view.getUint32(0) / 39.3701) / 72; // meter to inch to dppx
+          }
+        }
+      }
+    } catch {}
+  }
+
+  return {width, dppx};
+}
diff --git a/web_src/js/utils/image.test.js b/web_src/js/utils/image.test.js
new file mode 100644
index 00000000..ba475825
--- /dev/null
+++ b/web_src/js/utils/image.test.js
@@ -0,0 +1,29 @@
+import {pngChunks, imageInfo} from './image.js';
+
+const pngNoPhys = 'data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAAEAAAABCAAAAAA6fptVAAAADUlEQVQIHQECAP3/AAAAAgABzePRKwAAAABJRU5ErkJggg==';
+const pngPhys = 'data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAAIAAAACCAIAAAD91JpzAAAACXBIWXMAABYlAAAWJQFJUiTwAAAAEElEQVQI12OQNZcAIgYIBQAL8gGxdzzM0A==';
+const pngEmpty = 'data:image/png;base64,';
+
+async function dataUriToBlob(datauri) {
+  return await (await globalThis.fetch(datauri)).blob();
+}
+
+test('pngChunks', async () => {
+  expect(await pngChunks(await dataUriToBlob(pngNoPhys))).toEqual([
+    {name: 'IHDR', data: new Uint8Array([0, 0, 0, 1, 0, 0, 0, 1, 8, 0, 0, 0, 0])},
+    {name: 'IDAT', data: new Uint8Array([8, 29, 1, 2, 0, 253, 255, 0, 0, 0, 2, 0, 1])},
+    {name: 'IEND', data: new Uint8Array([])},
+  ]);
+  expect(await pngChunks(await dataUriToBlob(pngPhys))).toEqual([
+    {name: 'IHDR', data: new Uint8Array([0, 0, 0, 2, 0, 0, 0, 2, 8, 2, 0, 0, 0])},
+    {name: 'pHYs', data: new Uint8Array([0, 0, 22, 37, 0, 0, 22, 37, 1])},
+    {name: 'IDAT', data: new Uint8Array([8, 215, 99, 144, 53, 151, 0, 34, 6, 8, 5, 0, 11, 242, 1, 177])},
+  ]);
+  expect(await pngChunks(await dataUriToBlob(pngEmpty))).toEqual([]);
+});
+
+test('imageInfo', async () => {
+  expect(await imageInfo(await dataUriToBlob(pngNoPhys))).toEqual({width: 1, dppx: 1});
+  expect(await imageInfo(await dataUriToBlob(pngPhys))).toEqual({width: 2, dppx: 2});
+  expect(await imageInfo(await dataUriToBlob(pngEmpty))).toEqual({width: 0, dppx: 1});
+});
diff --git a/web_src/js/utils/match.js b/web_src/js/utils/match.js
new file mode 100644
index 00000000..17fdfed1
--- /dev/null
+++ b/web_src/js/utils/match.js
@@ -0,0 +1,43 @@
+import emojis from '../../../assets/emoji.json';
+
+const maxMatches = 6;
+
+function sortAndReduce(map) {
+  const sortedMap = new Map(Array.from(map.entries()).sort((a, b) => a[1] - b[1]));
+  return Array.from(sortedMap.keys()).slice(0, maxMatches);
+}
+
+export function matchEmoji(queryText) {
+  const query = queryText.toLowerCase().replaceAll('_', ' ');
+  if (!query) return emojis.slice(0, maxMatches).map((e) => e.aliases[0]);
+
+  // results is a map of weights, lower is better
+  const results = new Map();
+  for (const {aliases} of emojis) {
+    const mainAlias = aliases[0];
+    for (const [aliasIndex, alias] of aliases.entries()) {
+      const index = alias.replaceAll('_', ' ').indexOf(query);
+      if (index === -1) continue;
+      const existing = results.get(mainAlias);
+      const rankedIndex = index + aliasIndex;
+      results.set(mainAlias, existing ? existing - rankedIndex : rankedIndex);
+    }
+  }
+
+  return sortAndReduce(results);
+}
+
+export function matchMention(queryText) {
+  const query = queryText.toLowerCase();
+
+  // results is a map of weights, lower is better
+  const results = new Map();
+  for (const obj of window.config.mentionValues ?? []) {
+    const index = obj.key.toLowerCase().indexOf(query);
+    if (index === -1) continue;
+    const existing = results.get(obj);
+    results.set(obj, existing ? existing - index : index);
+  }
+
+  return sortAndReduce(results);
+}
diff --git a/web_src/js/utils/match.test.js b/web_src/js/utils/match.test.js
new file mode 100644
index 00000000..1e30b451
--- /dev/null
+++ b/web_src/js/utils/match.test.js
@@ -0,0 +1,50 @@
+import {matchEmoji, matchMention} from './match.js';
+
+test('matchEmoji', () => {
+  expect(matchEmoji('')).toEqual([
+    '+1',
+    '-1',
+    '100',
+    '1234',
+    '1st_place_medal',
+    '2nd_place_medal',
+  ]);
+
+  expect(matchEmoji('hea')).toEqual([
+    'headphones',
+    'headstone',
+    'health_worker',
+    'hear_no_evil',
+    'heard_mcdonald_islands',
+    'heart',
+  ]);
+
+  expect(matchEmoji('hear')).toEqual([
+    'hear_no_evil',
+    'heard_mcdonald_islands',
+    'heart',
+    'heart_decoration',
+    'heart_eyes',
+    'heart_eyes_cat',
+  ]);
+
+  expect(matchEmoji('poo')).toEqual([
+    'poodle',
+    'hankey',
+    'spoon',
+    'bowl_with_spoon',
+  ]);
+
+  expect(matchEmoji('1st_')).toEqual([
+    '1st_place_medal',
+  ]);
+
+  expect(matchEmoji('jellyfis')).toEqual([
+    'jellyfish',
+  ]);
+});
+
+test('matchMention', () => {
+  expect(matchMention('')).toEqual(window.config.mentionValues.slice(0, 6));
+  expect(matchMention('user4')).toEqual([window.config.mentionValues[3]]);
+});
diff --git a/web_src/js/utils/time.js b/web_src/js/utils/time.js
new file mode 100644
index 00000000..7c7eabd1
--- /dev/null
+++ b/web_src/js/utils/time.js
@@ -0,0 +1,72 @@
+import dayjs from 'dayjs';
+import utc from 'dayjs/plugin/utc.js';
+import {getCurrentLocale} from '../utils.js';
+
+dayjs.extend(utc);
+
+/**
+ * Returns an array of millisecond-timestamps of start-of-week days (Sundays)
+ *
+ * @param startConfig The start date. Can take any type that `Date` accepts.
+ * @param endConfig The end date. Can take any type that `Date` accepts.
+ */
+export function startDaysBetween(startDate, endDate) {
+  const start = dayjs.utc(startDate);
+  const end = dayjs.utc(endDate);
+
+  let current = start;
+
+  // Ensure the start date is a Sunday
+  while (current.day() !== 0) {
+    current = current.add(1, 'day');
+  }
+
+  const startDays = [];
+  while (current.isBefore(end)) {
+    startDays.push(current.valueOf());
+    current = current.add(1, 'week');
+  }
+
+  return startDays;
+}
+
+export function firstStartDateAfterDate(inputDate) {
+  if (!(inputDate instanceof Date)) {
+    throw new Error('Invalid date');
+  }
+  const dayOfWeek = inputDate.getUTCDay();
+  const daysUntilSunday = 7 - dayOfWeek;
+  const resultDate = new Date(inputDate.getTime());
+  resultDate.setUTCDate(resultDate.getUTCDate() + daysUntilSunday);
+  return resultDate.valueOf();
+}
+
+export function fillEmptyStartDaysWithZeroes(startDays, data) {
+  const result = {};
+
+  for (const startDay of startDays) {
+    result[startDay] = data[startDay] || {'week': startDay, 'additions': 0, 'deletions': 0, 'commits': 0};
+  }
+
+  return Object.values(result);
+}
+
+let dateFormat;
+
+// format a Date object to document's locale, but with 24h format from user's current locale because this
+// option is a personal preference of the user, not something that the document's locale should dictate.
+export function formatDatetime(date) {
+  if (!dateFormat) {
+    // TODO: replace `hour12` with `Intl.Locale.prototype.getHourCycles` once there is broad browser support
+    dateFormat = new Intl.DateTimeFormat(getCurrentLocale(), {
+      day: 'numeric',
+      month: 'short',
+      year: 'numeric',
+      hour: 'numeric',
+      hour12: !Number.isInteger(Number(new Intl.DateTimeFormat([], {hour: 'numeric'}).format())),
+      minute: '2-digit',
+      timeZoneName: 'short',
+    });
+  }
+  return dateFormat.format(date);
+}
diff --git a/web_src/js/utils/time.test.js b/web_src/js/utils/time.test.js
new file mode 100644
index 00000000..dbe5d7d0
--- /dev/null
+++ b/web_src/js/utils/time.test.js
@@ -0,0 +1,40 @@
+import {firstStartDateAfterDate, startDaysBetween, fillEmptyStartDaysWithZeroes} from './time.js';
+
+test('startDaysBetween', () => {
+  expect(startDaysBetween(new Date('2024-02-15'), new Date('2024-04-18'))).toEqual([
+    1708214400000,
+    1708819200000,
+    1709424000000,
+    1710028800000,
+    1710633600000,
+    1711238400000,
+    1711843200000,
+    1712448000000,
+    1713052800000,
+  ]);
+});
+
+test('firstStartDateAfterDate', () => {
+  const expectedDate = new Date('2024-02-18').getTime();
+  expect(firstStartDateAfterDate(new Date('2024-02-15'))).toEqual(expectedDate);
+
+  expect(() => firstStartDateAfterDate('2024-02-15')).toThrowError('Invalid date');
+});
+test('fillEmptyStartDaysWithZeroes with data', () => {
+  expect(fillEmptyStartDaysWithZeroes([1708214400000, 1708819200000, 1708819300000], {
+    1708214400000: {'week': 1708214400000, 'additions': 1, 'deletions': 2, 'commits': 3},
+    1708819200000: {'week': 1708819200000, 'additions': 4, 'deletions': 5, 'commits': 6},
+  })).toEqual([
+    {'week': 1708214400000, 'additions': 1, 'deletions': 2, 'commits': 3},
+    {'week': 1708819200000, 'additions': 4, 'deletions': 5, 'commits': 6},
+    {
+      'additions': 0,
+      'commits': 0,
+      'deletions': 0,
+      'week': 1708819300000,
+    }]);
+});
+
+test('fillEmptyStartDaysWithZeroes with empty array', () => {
+  expect(fillEmptyStartDaysWithZeroes([], {})).toEqual([]);
+});
diff --git a/web_src/js/utils/url.js b/web_src/js/utils/url.js
new file mode 100644
index 00000000..470ece31
--- /dev/null
+++ b/web_src/js/utils/url.js
@@ -0,0 +1,15 @@
+export function pathEscapeSegments(s) {
+  return s.split('/').map(encodeURIComponent).join('/');
+}
+
+function stripSlash(url) {
+  return url.endsWith('/') ? url.slice(0, -1) : url;
+}
+
+export function isUrl(url) {
+  try {
+    return stripSlash((new URL(url).href)).trim() === stripSlash(url).trim();
+  } catch {
+    return false;
+  }
+}
diff --git a/web_src/js/utils/url.test.js b/web_src/js/utils/url.test.js
new file mode 100644
index 00000000..08c6373f
--- /dev/null
+++ b/web_src/js/utils/url.test.js
@@ -0,0 +1,13 @@
+import {pathEscapeSegments, isUrl} from './url.js';
+
+test('pathEscapeSegments', () => {
+  expect(pathEscapeSegments('a/b/c')).toEqual('a/b/c');
+  expect(pathEscapeSegments('a/b/ c')).toEqual('a/b/%20c');
+});
+
+test('isUrl', () => {
+  expect(isUrl('https://example.com')).toEqual(true);
+  expect(isUrl('https://example.com/')).toEqual(true);
+  expect(isUrl('https://example.com/index.html')).toEqual(true);
+  expect(isUrl('/index.html')).toEqual(false);
+});