package main

import "golang.org/x/tour/tree"
import "fmt"

//This sample covers Exercise: Equivalent Binary Trees
/*
Reference: 
type Tree struct {
    Left  *Tree
    Value int
    Right *Tree
}
*/

// Walk walks the tree t sending all values
// from the tree to the channel ch.
func Walk(t *tree.Tree, ch chan int) {
	var walker func(t *tree.Tree)
	
	//make a separate synchronous sub-function here so we know when it's finished 
	//so that we can close the channel
	walker = func(t *tree.Tree) {
		if(t == nil) {
			return
		}
		
		walker(t.Left)
		ch <- t.Value
		walker(t.Right)
	}
	
	walker(t)
	close(ch)
}

// Same determines whether the trees
// t1 and t2 contain the same values.
func Same(t1, t2 *tree.Tree) bool {
	ch1 := make(chan int)
	ch2 := make(chan int)
	
	go Walk(t1, ch1)
	go Walk(t2, ch2)
	
	for {
		val1, ok1 := <- ch1
		val2, ok2 := <- ch2
		
		//if the values dont match and the channels contain different amounts of data
		if val1 != val2 || ok1 != ok2 {
			return false
		}
		
		//stop when the channel is closed
		if !ok1 {
			break
		}
	}
	
	return true
}


func main() {
	fmt.Println(Same(tree.New(1), tree.New(1)))
	fmt.Println(Same(tree.New(1), tree.New(2)))
	fmt.Println(Same(tree.New(2), tree.New(2)))
}