import type { Permission } from '@/types/admin'

export type PermissionTreeNode = Permission & { children?: PermissionTreeNode[] }
export type PermissionMatcher = (permission: Permission) => boolean

function groupByParent(permissions: Permission[]) {
  const childrenByParent = new Map<string | null, Permission[]>()

  permissions.forEach((permission) => {
    const siblings = childrenByParent.get(permission.parentId) ?? []
    siblings.push(permission)
    childrenByParent.set(permission.parentId, siblings)
  })

  childrenByParent.forEach((siblings) => {
    siblings.sort((left, right) => left.sort - right.sort)
  })

  return childrenByParent
}

export function buildPermissionTree(
  permissions: Permission[],
  matches: PermissionMatcher = () => true,
): PermissionTreeNode[] {
  const childrenByParent = groupByParent(permissions)

  function buildNode(permission: Permission, ancestors: Set<string>): PermissionTreeNode | null {
    if (ancestors.has(permission.id)) return null

    const nextAncestors = new Set(ancestors).add(permission.id)
    const children = (childrenByParent.get(permission.id) ?? [])
      .map((child) => buildNode(child, nextAncestors))
      .filter((child): child is PermissionTreeNode => child !== null)

    if (!matches(permission) && children.length === 0) return null

    return {
      ...permission,
      ...(children.length ? { children } : {}),
    }
  }

  return (childrenByParent.get(null) ?? [])
    .map((permission) => buildNode(permission, new Set()))
    .filter((node): node is PermissionTreeNode => node !== null)
}

export function getDescendantIds(permissions: Permission[], permissionId: string): string[] {
  const childrenByParent = groupByParent(permissions)
  const visited = new Set([permissionId])
  const descendants: string[] = []
  const queue = [...(childrenByParent.get(permissionId) ?? [])]

  while (queue.length) {
    const current = queue.shift()
    if (!current || visited.has(current.id)) continue

    visited.add(current.id)
    descendants.push(current.id)
    queue.push(...(childrenByParent.get(current.id) ?? []))
  }

  return descendants
}

export function summarizePermissionSelection(permissions: Permission[], selectedIds: string[]) {
  const selected = new Set(selectedIds)
  const selectedPermissions = permissions.filter((permission) => selected.has(permission.id))

  return {
    menuCount: selectedPermissions.filter((permission) => permission.type === '菜单').length,
    actionCount: selectedPermissions.filter((permission) => ['按钮', '接口'].includes(permission.type)).length,
  }
}