export default function simpleDiffWithCursor(
  a: string,
  b: string,
  cursor: number
): { index: number; insert: string; remove: number } {
  const aLength = a.length
  const bLength = b.length
  let left = 0 // number of same characters counting from left
  let right = 0 // number of same characters counting from right
  // Iterate left to the right until we find a changed character
  // First iteration considers the current cursor position
  while (
    left < aLength &&
    left < bLength &&
    a[left] === b[left] &&
    left < cursor
  ) {
    left++
  }
  // Iterate right to the left until we find a changed character
  while (
    right + left < aLength &&
    right + left < bLength &&
    a[aLength - right - 1] === b[bLength - right - 1]
  ) {
    right++
  }
  // Try to iterate left further to the right without caring about the current cursor position
  while (
    right + left < aLength &&
    right + left < bLength &&
    a[left] === b[left]
  ) {
    left++
  }
  return {
    index: left,
    insert: b.slice(left, bLength - right),
    remove: aLength - left - right,
  }
}