Function sliceInsertDelta

packages/yjs-transform/src/delta.ts:47–86

(delta: InsertDelta, start: number, length: number)

}

export function sliceInsertDelta(delta: InsertDelta, start: number, length: number): InsertDelta {
  if (length < 1) {
    return []
  }

  let currentOffset = 0
  const sliced: InsertDelta = []
  const end = start + length

  for (let i = 0; i < delta.length; i++) {
    if (currentOffset >= end) {
      break
    }

    const element = delta[i]
    const elementLength = getInsertLength(element)

    if (currentOffset + elementLength <= start) {
      currentOffset += elementLength
      continue
    }

    if (typeof element.insert !== 'string') {
      currentOffset += elementLength
      sliced.push(element)
      continue
    }

    const startOffset = Math.max(0, start - currentOffset)
    const endOffset = Math.min(elementLength, elementLength - (currentOffset + elementLength - end))

    sliced.push({
      ...element,
      insert: element.insert.slice(startOffset, endOffset),
    })
    currentOffset += elementLength
  }

  return sliced
}