facade.go

package facade

// 【外观模式】

import "fmt"

// 统一接口
type List interface {
	Add(idx int, e interface{}) bool
	AddLast(e interface{}) bool
	Remove(idx int) (interface{}, bool)
	RemoveLast() (interface{}, bool)
	Get(idx int) (interface{}, bool)
}

type ArrayList struct {
	ele  []interface{}
	size int
}

func NewArrayList(capacity int) *ArrayList {
	if capacity < 16 {
		capacity = 16
	}
	return &ArrayList{
		ele:  make([]interface{}, 0, capacity),
		size: 0,
	}
}

func ArrayListOf(ele ...interface{}) *ArrayList {
	return &ArrayList{
		ele:  ele,
		size: len(ele),
	}
}

func (a *ArrayList) Add(idx int, e interface{}) bool {
	if idx > a.size {
		return false
	}
	a.ele = append(a.ele, nil)
	copy(a.ele[idx+1:], a.ele[idx:]) // 后移一位, 把idx位置空出来
	a.ele[idx] = e
	a.size++
	return true
}

func (a *ArrayList) AddLast(e interface{}) bool {
	a.ele = append(a.ele, e)
	a.size++
	return true
}

func (a *ArrayList) Remove(idx int) (interface{}, bool) {
	if idx >= a.size {
		return nil, false
	}
	e := a.ele[idx]
	a.ele = append(a.ele[:idx], a.ele[idx+1:]...) // 跳过idx元素
	a.size--
	return e, true
}

func (a *ArrayList) RemoveLast() (interface{}, bool) {
	e := a.ele[a.size-1]
	a.ele = append(a.ele[:a.size-1])
	a.size--
	return e, true
}

func (a *ArrayList) Get(idx int) (interface{}, bool) {
	if idx >= a.size {
		return nil, false
	}
	e := a.ele[idx]
	return e, true
}

func (a *ArrayList) String() string {
	return fmt.Sprintf("size=%v, %v", a.size, a.ele)
}