// dd_RandomDamage(antiGrav).js
// anitgravityify if threshold met for frame

let threshold = 98;
// global variable holding forward motion vectors from previous frames
var old_mvs = [ ];
// a variable for gravity
var rt = 0;
var gravity = 0
var orig_gravity = 5;
var TRIGGERED = 0;
var frameCount = 10;
var count = 0;

function glitch_frame(frame)
{
	var do_or_not = Math.random() * 100;
	// only do the glitch if our random number crosses the threshold
	if(do_or_not > threshold | TRIGGERED == 1){
		if(TRIGGERED == 0){
			gravity = orig_gravity;
			TRIGGERED = 1;
			rt = 0;
		}
		// bail out if we have no motion vectors
		let mvs = frame["mv"];
		if ( !mvs )
			return;
		// bail out if we have no forward motion vectors
		let fwd_mvs = mvs["forward"];
		if ( !fwd_mvs )
			return;

		// buffer first set of vectors. . .
		if(rt == 0){
			let json_str = JSON.stringify(fwd_mvs);
			let deep_copy = JSON.parse(json_str);
			// push to the end of array
			old_mvs[0] = (deep_copy);
			rt = 1;
		}

		// clear horizontal element of all motion vectors
		for ( let i = 0; i < fwd_mvs.length; i++ )
		{
			// loop through all rows
			let row = fwd_mvs[i];
			let old_row = old_mvs[0][i];
			for ( let j = 0; j < row.length; j++ )
			{
				// loop through all macroblocks
				let mv = row[j];
				let omv = old_row[j];
				// THIS IS WHERE THE MAGIC HAPPENS

				mv[0] = mv[0];
				//if(mv[1] < 0){
					var nmv = mv[1];
					mv[1] = omv[1];
					omv[1] = nmv + omv[1] + gravity;
					//gravity++;
				//}else{
				//	mv[1] = mv[1];
				//}

			}
		}
		count++;
		if(count >= frameCount){
			TRIGGERED = 0;
			count = 0;
		}
	}
}