export interface HasChildren<Type> {
  children: Type[]
}

// Depth-first tree-traversal
export const traverse = <Type extends HasChildren<Type>>(
  list: Type[],
  func: (a: Type) => void
) => {
  for (const obj of list) {
    func(obj)

    if (obj?.children) {
      if (!Array.isArray(obj.children)) {
        throw new Error(`obj.children is not an Array: ${JSON.stringify(obj)}`)
      }

      traverse(obj.children, func)
    }
  }
}

export const traverseLeafsFirst = <Type extends HasChildren<Type>>(
  list: Type[],
  func: (a: Type) => void
) => {
  for (const obj of list) {
    if (obj?.children) {
      if (!Array.isArray(obj.children)) {
        throw new Error(`obj.children is not an Array: ${JSON.stringify(obj)}`)
      }

      traverseLeafsFirst(obj.children, func)
    }
    func(obj)
  }
}

export const deepMap = <
  InputType extends HasChildren<InputType>,
  OutputType extends HasChildren<OutputType>
>(
  inputs: InputType[],
  func: (a: InputType) => OutputType
): OutputType[] => {
  return inputs.map(input => {
    const output = func(input)
    if (input?.children) {
      if (!Array.isArray(input.children)) {
        throw new Error(
          `obj.children is not an Array: ${JSON.stringify(input)}`
        )
      }
      output.children = deepMap(input.children, func)
    }
    return output
  })
}

export const deepFilter = <Type extends HasChildren<Type>>(
  objects: Type[],
  func: (a: Type) => boolean
): Type[] => {
  const result = []

  for (const obj of objects) {
    if (!func(obj)) {
      // eslint-disable-next-line no-continue
      continue
    }

    let newObj = { ...obj }

    if (obj.children) {
      newObj = {
        ...obj,
        children: deepFilter(obj.children, func),
      }
    }

    result.push(newObj)
  }

  return result
}