package list

import (
	"fmt"
	"strings"
)

type ICollection interface {
	Conj(data any) IList
	IsEmpty() bool
	String() string
	Len() int
}

type ISeq interface {
	First() any
	Rest() IList
}

type IList interface {
	ISeq
	ICollection
}

type EmptyList struct{}

type List struct {
	Value any
	next  IList
}

func Empty() IList {
	return new(EmptyList)
}

var emptyList = Empty()

func New(val any) IList {
	this := new(List)
	this.Value = val
	this.next = emptyList
	return this
}

func Cons(val any, rest IList) IList {
	this := new(List)
	this.Value = val
	this.next = rest
	return this
}

func (this *List) Conj(val any) IList {
	return Cons(val, this)

}

func (this *EmptyList) Conj(val any) IList {
	return New(val)
}

func (this *List) Rest() IList {
	return this.next
}

func (this *EmptyList) Rest() IList {
	return emptyList
}

func (this *List) First() any {
	return this.Value
}

func (this *EmptyList) First() any {
	return nil
}

func (this *List) IsEmpty() bool {
	return false
}

func (this *EmptyList) IsEmpty() bool {
	return true
}

func (this *List) String() string {
	var sb strings.Builder
	sb.WriteRune('(')
	// Iterate and print elements
	var e IList
	for e = this; !e.IsEmpty(); e = e.Rest() {
		sb.WriteString(fmt.Sprint(e.First()))
		sb.WriteRune(' ')
	}
	return sb.String()[:sb.Len()-1] + ")"
}

func (this *EmptyList) String() string {
	return "()"
}

func (this *EmptyList) Len() int {
	return 0
}

func (this *List) Len() int {
	return 1 + this.Rest().Len()
}