class  BinaryHeap{
  constructor(){
    this.heap = [30, 20, 10, 7, 9, 5]
  }
  
   insert(value){

    this.heap.push(value)
     this.bubbleUp();
  }

  //using iterative approach
     bubbleUp(){
       let index =  this.heap.length-1;

    while( index > 0){
       let element = this.heap[index],
           parentIndex = Math.floor((index-1)/2),
           parent = this.heap[parentIndex];

       if(parent >= element) break
          this.heap[index] = parent;
         this.heap[parentIndex] = element;
          index = parentIndex

    }
  }
  
  extractMax(){
    const max = this.heap[0];
    this.heap[0]= this.heap.pop()
    this.sinkDown(0)
    return max
  }
  
 sinkDown(index){
     
     let   left = 2*index+1,
           right = 2*index+2,
           largest = index;
     const length = this.heap.length
    
 
     
      if(left <= length &&  this.heap[left]>this.heap[largest] ){
         largest = left
       }
      if(right <= length && this.heap[right]>this.heap[largest]) {
        largest = right
      }
     // swap
     if(largest !== index){
        [this.heap[largest],this.heap[index]] = [this.heap[index],this.heap[largest]]
       this.sinkDown(largest)
     }
    } 
 
}



mocha.setup('bdd');


var assert = chai.assert;

describe('Heaps(Binary heap)',()=>{
  
  it("should add insert a new node to the heap",()=>{
    
     const heap = new BinaryHeap();
     heap.insert(90)
     heap.insert(49)
   
     assert.deepEqual([90, 49, 30, 20, 9, 5, 10, 7],heap.heap)
  
  })

  it("should  remove a max node from the heap",()=>{
     const heap = new BinaryHeap();
     assert.equal(30,heap.extractMax())
    console.log(heap)
     assert.deepEqual([20, 9, 10, 7, 5],heap.heap)
  })
  
})



mocha.run()