// Exercise data in the form of an array of objects
let activities = [{activity:'walking',intensity:'low',calories:176},{activity:'walking',intensity:'medium',calories:232},
	              {activity:'walking',intensity:'high',calories:352},{activity:'cycling',intensity:'low',calories:422},
				  {activity:'cycling',intensity:'medium',calories:563},{activity:'cycling',intensity:'high',calories:704},
				  {activity:'running',intensity:'low',calories:704},{activity:'running',intensity:'medium',calories:880},
				  {activity:'running',intensity:'high',calories:1126},{activity:'swimming',intensity:'low',calories:422},
				  {activity:'swimming',intensity:'medium',calories:563},{activity:'swimming',intensity:'high',calories:704}];
				  
// A helper function to compute the calories per hour for 
// an activity at a certain intensity
function caloriesPerHour(data,activity,intensity) {
	let length = data.length;
	for(let n = 0;n < length;n++) {
		if(data[n].activity==activity && data[n].intensity==intensity)
			return data[n].calories;
	}

	return 0;
}

function computeHandler() {
	// Gather the page elements we need to interact with
	let activitySelector = document.getElementById('activity');
	let intensitySelector = document.getElementById('intensity');
	let durationText = document.getElementById('duration');
	let resultPar = document.getElementById('result');
	
	// Gather inputs
	let activity = activitySelector.value;
	let intensity = intensitySelector.value;
	let duration = durationText.value;

	// Do the computation
	let calories = caloriesPerHour(activities,activity,intensity)*duration/60;
	// Round result to the nearest calorie
	calories = Math.round(calories);
	
	// Present the result
	resultPar.textContent = 'This activity will burn a total of ' + calories + ' calories.';
}

function setup() {
    let computeButton = document.getElementById('compute');
    computeButton.addEventListener('click',computeHandler,false);
}

window.addEventListener('load',setup,false);