feat: import markdown-it-plugins from https://github.com/hedgedoc/markdown-it-plugins

Signed-off-by: Tilman Vatteroth <git@tilmanvatteroth.de>

markdown-it-plugins/src/image-size/parse-image-size.ts

@@ -0,0 +1,98 @@
+/*
+ * SPDX-FileCopyrightText: 2023 The HedgeDoc developers (see AUTHORS file)
+ *
+ * SPDX-License-Identifier: MIT
+ */
+
+import { SpecialCharacters } from './specialCharacters.js'
+
+export interface ParseImageSize {
+  position: number
+  width: string
+  height: string
+}
+
+export interface ParseNextNumber {
+  position: number
+  value: string
+}
+
+function isCharacterADigit(code: number) {
+  return code >= SpecialCharacters.NUMBER_ZERO && code <= SpecialCharacters.NUMBER_NINE
+}
+
+function findNextNotNumberCharacter(startPosition: number, maximalPosition: number, content: string): number {
+  for (let position = startPosition; position < maximalPosition; position += 1) {
+    const code = content.charCodeAt(position)
+    if (!isCharacterADigit(code) && code !== SpecialCharacters.PERCENTAGE) {
+      return position
+    }
+  }
+
+  return maximalPosition
+}
+
+function parseNextNumber(content: string, startPosition: number, maximalPosition: number): ParseNextNumber {
+  const endCharacterIndex = findNextNotNumberCharacter(startPosition, maximalPosition, content)
+
+  return {
+    position: endCharacterIndex,
+    value: content.slice(startPosition, endCharacterIndex)
+  }
+}
+
+/*
+ size must follow = without any white spaces as follows
+ (1) =300x200
+ (2) =300x
+ (3) =x200
+*/
+const checkImageSizeStart = (code: number): boolean => {
+  return (
+    code === SpecialCharacters.LOWER_CASE_X ||
+    (code >= SpecialCharacters.NUMBER_ZERO && code <= SpecialCharacters.NUMBER_NINE)
+  )
+}
+
+export function parseImageSize(
+  imageSize: string,
+  startCharacterPosition: number,
+  maximalCharacterPosition: number
+): ParseImageSize | undefined {
+  if (startCharacterPosition >= maximalCharacterPosition) {
+    return
+  }
+
+  let currentCharacterPosition = startCharacterPosition
+
+  if (imageSize.charCodeAt(currentCharacterPosition) !== SpecialCharacters.EQUALS /* = */) {
+    return
+  }
+
+  currentCharacterPosition += 1
+
+  if (!checkImageSizeStart(imageSize.charCodeAt(currentCharacterPosition))) {
+    return
+  }
+
+  // parse width
+  const width = parseNextNumber(imageSize, currentCharacterPosition, maximalCharacterPosition)
+  currentCharacterPosition = width.position
+
+  // next charactor must be 'x'
+  const code = imageSize.charCodeAt(currentCharacterPosition)
+  if (code !== SpecialCharacters.LOWER_CASE_X /* x */) {
+    return
+  }
+  currentCharacterPosition += 1
+
+  // parse height
+  const height = parseNextNumber(imageSize, currentCharacterPosition, maximalCharacterPosition)
+  currentCharacterPosition = height.position
+
+  return {
+    width: width.value,
+    height: height.value,
+    position: currentCharacterPosition
+  }
+}