Function reorderBidi

src/ink/bidi.ts:53–105

(characters: ClusteredChar[])

 * Returns the same array on bidi-capable terminals (no-op).
 */
export function reorderBidi(characters: ClusteredChar[]): ClusteredChar[] {
  if (!needsBidi() || characters.length === 0) {
    return characters
  }

  // Build a plain string from the clustered chars to run through bidi
  const plainText = characters.map(c => c.value).join('')

  // Check if there are any RTL characters — skip bidi if pure LTR
  if (!hasRTLCharacters(plainText)) {
    return characters
  }

  const bidi = getBidi()
  const { levels } = bidi.getEmbeddingLevels(plainText, 'auto')

  // Map bidi levels back to ClusteredChar indices.
  // Each ClusteredChar may be multiple code units in the joined string.
  const charLevels: number[] = []
  let offset = 0
  for (let i = 0; i < characters.length; i++) {
    charLevels.push(levels[offset]!)
    offset += characters[i]!.value.length
  }

  // Get reorder segments from bidi-js, but we need to work at the
  // ClusteredChar level, not the string level. We'll implement the
  // standard bidi reordering: find the max level, then for each level
  // from max down to 1, reverse all contiguous runs >= that level.
  const reordered = [...characters]
  const maxLevel = Math.max(...charLevels)

  for (let level = maxLevel; level >= 1; level--) {
    let i = 0
    while (i < reordered.length) {
      if (charLevels[i]! >= level) {
        // Find the end of this run
        let j = i + 1
        while (j < reordered.length && charLevels[j]! >= level) {
          j++
        }
        // Reverse the run in both arrays
        reverseRange(reordered, i, j - 1)
        reverseRangeNumbers(charLevels, i, j - 1)
        i = j
      } else {
        i++
      }
    }
  }

  return reordered
}

function reverseRange<T>(arr: T[], start: number, end: number): void {
  while (start < end) {