chore: extract and test construction of icon url

src/icon-api.js

@@ -109,11 +109,23 @@ export class IconApi {
 
     const mimeExtension = MIME_TO_EXTENSION[opts.mimeType]
 
-    if (opts.mimeType === 'image/svg+xml') {
-      return base + `${iconId}/${opts.size}${mimeExtension}`
-    }
-
-    return base + `${iconId}/${opts.size}@${opts.pixelDensity}x${mimeExtension}`
+    const pixelDensity =
+      opts.mimeType === 'image/svg+xml' ||
+      // if the pixel density is 1, we can omit the density suffix in the resulting url
+      // and assume the pixel density is 1 for applicable mime types when using the url
+      opts.pixelDensity === 1
+        ? undefined
+        : opts.pixelDensity
+
+    return (
+      base +
+      constructIconPath({
+        pixelDensity,
+        size: opts.size,
+        extension: mimeExtension,
+        iconId,
+      })
+    )
   }
 }
 
@@ -236,3 +248,33 @@ function determineSortValue(target, a, b) {
   // Mix of smaller and larger than desired, prefer smaller of the two
   return a < b ? -1 : 1
 }
+
+/**
+ * General purpose path builder for an icon
+ *
+ * @param {object} opts
+ * @param {string} opts.iconId
+ * @param {string} opts.size
+ * @param {number} [opts.pixelDensity]
+ * @param {string} opts.extension
+ *
+ * @returns {string}
+ */
+export function constructIconPath({ size, pixelDensity, iconId, extension }) {
+  if (iconId.length === 0 || size.length === 0 || extension.length === 0) {
+    throw new Error('iconId, size, and extension cannot be empty strings')
+  }
+
+  let result = `${iconId}/${size}`
+
+  if (typeof pixelDensity === 'number') {
+    if (pixelDensity < 1) {
+      throw new Error('pixelDensity must be a positive number')
+    }
+    result += `@${pixelDensity}x`
+  }
+
+  result += extension.startsWith('.') ? extension : '.' + extension
+
+  return result
+}

tests/icon-api.js

@@ -6,7 +6,12 @@ import { drizzle } from 'drizzle-orm/better-sqlite3'
 import { migrate } from 'drizzle-orm/better-sqlite3/migrator'
 import { randomBytes } from 'node:crypto'
 
-import { IconApi, kGetIconBlob, getBestVariant } from '../src/icon-api.js'
+import {
+  IconApi,
+  kGetIconBlob,
+  getBestVariant,
+  constructIconPath,
+} from '../src/icon-api.js'
 import { DataType } from '../src/datatype/index.js'
 import { DataStore } from '../src/datastore/index.js'
 import { createCoreManager } from './helpers/core-manager.js'
@@ -167,7 +172,7 @@ test(`getIconUrl()`, async (t) => {
 
     t.is(
       url,
-      mediaBaseUrl + `${iconId}/small@1x.png`,
+      mediaBaseUrl + `${iconId}/small.png`,
       'returns expected bitmap icon url'
     )
   }
@@ -616,6 +621,63 @@ test(
   }
 )
 
+test('constructIconPath() - bad inputs', (t) => {
+  // Array of [input, test message]
+  /** @type {Array<[Parameters<typeof constructIconPath>[0], string]>} */
+  const fixtures = [
+    [
+      { iconId: '', size: 'small', extension: 'svg' },
+      'throws when iconId is empty string',
+    ],
+    [
+      { iconId: 'abc', size: '', extension: 'png' },
+      'throws when size is empty string',
+    ],
+    [
+      { iconId: 'abc', size: 'small', extension: '' },
+      'throws when extension is empty string',
+    ],
+    [
+      { iconId: 'abc', size: 'small', extension: 'png', pixelDensity: 0 },
+      'throws when pixelDensity is zero',
+    ],
+    [
+      { iconId: 'abc', size: 'small', extension: 'png', pixelDensity: -1 },
+      'throws when pixelDensity is a negative number',
+    ],
+  ]
+
+  for (const [input, message] of fixtures) {
+    t.exception(() => constructIconPath(input), message)
+  }
+})
+
+test('constructIconPath() - good inputs', (t) => {
+  // Array of [input, expected, test message]
+  /** @type {Array<[Parameters<typeof constructIconPath>[0], string, string]>} */
+  const fixtures = [
+    [
+      { iconId: 'abc', size: 'small', extension: 'svg' },
+      'abc/small.svg',
+      'omitting pixelDensity leaves out density suffix',
+    ],
+    [
+      { iconId: 'abc', size: 'small', extension: 'png', pixelDensity: 2 },
+      'abc/small@2x.png',
+      'including pixelDensity includes density suffix',
+    ],
+    [
+      { iconId: 'abc', size: 'small', extension: '.png' },
+      'abc/small.png',
+      'handles extension starting with `.`',
+    ],
+  ]
+
+  for (const [input, expected, message] of fixtures) {
+    t.is(constructIconPath(input), expected, message)
+  }
+})
+
 /**
  *
  * @param {{ getMediaBaseUrl?: () => Promise<string> }} [opts]