import { Comment, createTextVNode, Fragment, type VNode, type VNodeChild } from 'vue'

// o(n) flatten
export function flatten (
  vNodes: VNodeChild[],
  filterCommentNode = true,
  result: VNode[] = [],
): VNode[] {
  vNodes.forEach((vNode) => {
    if (vNode === null) {
      return
    }

    if (typeof vNode !== 'object') {
      if (typeof vNode === 'string' || typeof vNode === 'number') {
        result.push(createTextVNode(String(vNode)))
      }

      return
    }

    if (Array.isArray(vNode)) {
      flatten(vNode, filterCommentNode, result)

      return
    }

    if (vNode.type === Fragment) {
      if (vNode.children === null) {
        return
      }

      if (Array.isArray(vNode.children)) {
        flatten(vNode.children, filterCommentNode, result)
      }
      // rawSlot
    } else if (vNode.type !== Comment) {
      result.push(vNode)
    }
  })

  return result
}