Expression | Stretch Values

t1 = key(1).time;
t2 = key(2).time;
stretch = true;
toTime = function(){
    low = thisComp.duration;
    nextTime = thisComp.duration;
    prevTime = 0;
    for( i = thisComp.numLayers; i > index; i--)
        if(thisComp.layer(i).inPoint < low && thisComp.layer(i).inPoint > time){
            low = thisComp.layer(i+1).inPoint;
            nextTime = thisComp.layer(i).inPoint;
            prevTime = thisComp.layer(i+1).inPoint;
            break;
        }else{
            prevTime = thisComp.layer(index+1).inPoint
        }
    return [prevTime, nextTime];
}
data = toTime();
if(stretch){
linear(time, data[0], data[1], t1, t2)
}else{
linear(time, data[0], data[0]+(t2-t1), t1, t2)
}