import type { FlattenNode, Key } from '../interface'

export function findExpandedKeys(prev: Key[] = [], next: Key[] = []) {
  const prevLen = prev.length
  const nextLen = next.length

  if (Math.abs(prevLen - nextLen) !== 1) {
    return { add: false, key: null }
  }

  function find(shorter: Key[], longer: Key[]) {
    const cache: Map<Key, boolean> = new Map()
    shorter.forEach((key) => {
      cache.set(key, true)
    })

    const keys = longer.filter((key) => !cache.has(key))

    return keys.length === 1 ? keys[0] : null
  }

  if (prevLen < nextLen) {
    return {
      add: true,
      key: find(prev, next),
    }
  }

  return {
    add: false,
    key: find(next, prev),
  }
}

export function getExpandRange(shorter: FlattenNode[], longer: FlattenNode[], key: Key) {
  const shorterStartIndex = shorter.findIndex((item) => item.key === key)
  const shorterEndNode = shorter[shorterStartIndex + 1]
  const longerStartIndex = longer.findIndex((item) => item.key === key)

  if (shorterEndNode) {
    const longerEndIndex = longer.findIndex((item) => item.key === shorterEndNode.key)
    return longer.slice(longerStartIndex + 1, longerEndIndex)
  }
  return longer.slice(longerStartIndex + 1)
}
