//     =============================================
//
//     SCROLL A PAGE FROM ONE ELEMENT TO ANOTHER
//     ---------------------------------------------
//
//     By Chris Hill-Scott, except where noted.
//
//     Code is public domain, reuse as desired.
//
//     Requires jQuery
//
//     ---------------------------------------------
//
//     TODO: Add an event queue
//
//     =============================================


var scrollPhotos = (function() { // Module pattern

	var	self = {
	
		to: function(offset, time) { // Animate a scroll

			self.inProgress = true;

			QUIS.$page.animate(
				{
					scrollTop: offset
				},
				time,
				function() {

					self.inProgress = false;

				}
			);

			QUIS.$window.trigger("scroll");

			return false;

		},
		nearestNumber: function(a, n) { // nearestNumber(a: Array, n: Number): Integer

			if ((l = a.length) < 2) {
				return l - 1;
			}

			for (var l, p = Math.abs(a[--l] - n); l--;) {
				if (p < (p = Math.abs(a[l] - n))) {
					break;
				}
			}

			return l + 1;

		},
		go: function() {

			var scrollTop = parseInt(QUIS.$document.scrollTop()),
				current = scrollPhotos.nearest(0).offset(),
				next = scrollPhotos.nearest(self.direction).offset();

			if ((scrollTop < 250) && (-1 == self.direction)) {
				return self.to(0, self.time / 2);
			}

			if ((scrollTop < 150) && (1 == self.direction)) {
				return self.to((current.top - 20), self.time / 2);
			}

			return self.to((next.top - 20), self.time);

		},
		inProgress: false,
		direction: null,
		time: 200
		
	};

	// Public methods
	return {
		go: function goWrapper(direction) {

			self.direction = direction;

			if (self.inProgress) {

				setTimeout(
					goWrapper,
					100
				);

				return false;

			}

			self.go();

		},
		nearest: function(traverse) { // Get nearest image to current scroll position (as jQuery object)

			var $photos = $("img"), // This should use a cache
				offsets = [];

			$photos.each(
				function(i) {
					offsets[i] = parseInt($(this).offset().top);
				}
			);

			return $photos.eq(
				self.nearestNumber(
					offsets,
					parseInt(QUIS.$document.scrollTop())
				)
				+ traverse
			);

		}
	};

}());