package list

import (
	"fmt"
	"strings"
)

type EmptyList struct{}

type List struct {
	Value any
	next  *List
}

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

func New(val any) *List {
	return new(List).Init(val)
}

func (this *List) Init(val any) *List {
	return Init(this, val)
}

func Init(this *List, val any) *List {
	this.Value = val
	this.next = nil
	return this
}

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

func (this *EmptyList) Conj(val any) *List {
	return Conj(nil, val)
}

func Conj(this *List, val any) *List {
	if this == nil {
		return New(val)
	}
	new_head := New(val)
	new_head.next = this
	return new_head
}

func Rest(this *List) *List {
	if this == nil {
		return nil
	}
	return this.next
}

func (this *List) Rest() *List {
	return Rest(this)
}

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

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

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

func IsEmpty(this *List) bool {
	return this == nil
}

func (this *List) IsEmpty() bool {
	return this == nil
}

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

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

func (this *List) String() string {
	return String(this)
}