import type { OutlineItem } from '@shared/types'

export function buildOutlineTree(items: OutlineItem[]): OutlineItem[] {
  const byParent = new Map<string | null, OutlineItem[]>()
  for (const item of items) {
    const key = item.parentId
    if (!byParent.has(key)) byParent.set(key, [])
    byParent.get(key)!.push({ ...item, children: [] })
  }
  const attach = (parentId: string | null): OutlineItem[] => {
    const nodes = byParent.get(parentId) ?? []
    nodes.sort((a, b) => a.sortOrder - b.sortOrder)
    for (const node of nodes) {
      node.children = attach(node.id)
    }
    return nodes
  }
  return attach(null)
}

export function flattenOutlineTree(items: OutlineItem[]): OutlineItem[] {
  const result: OutlineItem[] = []
  const walk = (nodes: OutlineItem[]): void => {
    for (const node of nodes) {
      result.push(node)
      if (node.children?.length) walk(node.children)
    }
  }
  walk(items)
  return result
}

export function calcDeviation(expected: number | null, actual: number): number | null {
  if (!expected || expected <= 0) return null
  return Math.round(((actual - expected) / expected) * 100)
}