/*
* Pointers in Go
* In a value-model lang you need pointers to have a recursive structure like a tree.
*
* @author gtowell
* Created: Aug 23, 2021
*/


package main

import "fmt"

// node is a tree. It has pointers to two other nodes.
type treenode struct {
	payload int
	right   *treenode
	left    *treenode
}

// recursive method on treenode to do in-order printing
// Methods can be on pointers as well as the thing itself!
func (tn *treenode) ptn() {
	if (tn==nil) {
		return
	} else {
		tn.left.ptn()
		fmt.Printf("%d\n", tn.payload)
		tn.right.ptn()
	}
}

// Recursive Method on treenode to add a new value into tree
func (tp *treenode) appendToTree(val int) {
	if tp.payload <= val {
		if tp.right == nil {
			tp.right = new (treenode)
			tp.right.payload = val
		} else {
			tp.right.appendToTree(val)
		}
	} else {
		if tp.left == nil {
			tp.left = new(treenode)
			tp.left.payload = val
		} else {
			tp.left.appendToTree(val)
		}
	}
}

// a struct to hold the root of a tree.
// Kind of annoying, but doing it this way means that the thing
// holding the root never changes even if the root changes.
// Of course, once set root will only change if I wrote delete or balance
type tree struct {
	root *treenode
}

// Method to print the tree
// Question -- why have this as a method on pointer?
func (mt *tree) ptree() {
	if mt.root == nil {
		fmt.Println("Empty tree")
	} else {
		mt.root.ptn()
	}
}

// Method to add to tree.
// Question -- why have this as a method on pointer?
func (mt *tree) addToTree(newval int) {
	if mt.root == nil {
		mt.root = new(treenode)
		mt.root.payload = newval
	} else {
		mt.root.appendToTree(newval)
	}
}

func main() {
	mytree := new(tree)
	mytree.addToTree( 8)
	mytree.addToTree(16)
	mytree.addToTree(4)
	mytree.addToTree(12)
	mytree.addToTree(2)
	mytree.ptree()
}