function getSelectedProjectItems(){
    var items = [];
    var p = app.project;
    for ( var i = 1 ; i <= p.numItems ; i ++ ){
        var item = p.item(i);
        if ( item.selected ){
            items.push(item);
        }
    }
    return items;
}
function getSelectedProjectComps(){
    var items = [];
    var p = app.project;
    for ( var i = 1 ; i <= p.numItems ; i ++ ){
        var item = p.item(i);
        if ( (item.selected) && (item.typeName == "Composition") ){
            items.push(item);
        }
    }
    return items;
}
function getAllProjectComps(){
    var items = [];
    var p = app.project;
    for ( var i = 1 ; i <= p.numItems ; i ++ ){
        var item = p.item(i);
        if ( item.typeName == "Composition" ){
            items.push(item);
        }
    }
    return items;
}
function selectLayersByParented( isParented ){
    layersToSelect = getLayersByParented( isParented );
    for ( var i = 0; i < layersToSelect.length; i ++ ){
        layerToSelect = layersToSelect[i];
        layerToSelect.selected = true;
    }
}
function getLayersByParented( isParented ){

    /* TODO 
        not use activeItem. but have the function take a comp as an argument, to avoid activItem becoming obsolete.
    */
    var active_comp = app.project.activeItem;
    var filtered_layers = [];

    for ( var i = 1; i <= active_comp.layers.length ; i ++ )
    {
        var my_layer = active_comp.layers[i];

        if ( (my_layer.parent == null) != isParented )
        {
            filtered_layers.push( my_layer );
        };
    }
    
    return filtered_layers 
}
function centerLayer( my_layer , size ){
    my_layer.position[0] = size[0]/2;
    my_layer.position[1] = size[1]/2;
    alert(my_layer.position);
}
function resizeCompCanvas( comp, new_size ){
    comp.width = new_size[0];
    comp.height = new_size[1];
};
function setFPS( comp, newFPS ){
    comp.frameDuration = 1/newFPS;
};
function setDuration( myComp, newSecondsDuration ){
    myComp.duration = newSecondsDuration;
};
function setDurationInFrames( myComp, newFrameDuration ){
    //myComp.
};
function resizeCompCanvasCentered( my_comp, new_size, keep_scaler ){
  //app.beginUndoGroup("Resize Comp Canvas Centered")
    var n  = my_comp.layers.addNull();
    
    //center null on actual comp size
    n.position.setValue([my_comp.width/2,my_comp.height/2]);
    resizeCompCanvas( my_comp , new_size );
    
    //parent unparented layers to MAIN_SCALER
    var unparenterLayers = getLayersByParented( false );
    for ( var i = 0; i < unparenterLayers.length ; i ++ ){
        var current_layer = unparenterLayers[i];
        
        if ( (current_layer != n) && ( true )) {
            current_layer.parent = n;
        }
    }
    
    // center null to new comp size
    n.position.setValue(new_size/2);
   
   //get rid of scaling null or not.
    if (keep_scaler)

    {
        n.name = 'MAIN_SCALER';
    }else{
        n.remove()
    }
    //app.endUndoGroup();
}
function resizeCompsCanvasCentered( new_size, keep_scaler ){
    app.beginUndoGroup("Resize Comps' Canvas Centered")
    var my_comps = getSelectedProjectItems();
    for ( var i = 0 ; i < my_comps.length ; i ++ ){
        var my_comp = my_comps[i];
        //alert( my_comp.name )
        resizeCompCanvasCentered( my_comp, new_size, true );
    }
    app.endUndoGroup();
}
function setCompsFPS( newFPS ){
    app.beginUndoGroup("Change selected Comps' framerates");
    var my_comps = getSelectedProjectItems();
    for ( var i = 0 ; i < my_comps.length ; i++ ){
        var my_comp = my_comps[i];
        setFPS( my_comp, newFPS );
    }
    app.endUndoGroup();
}
function zeroOutLayer( myLayer ){
    myLayer.position.setValue([0,0]);
    myLayer.rotation.setValue(0);
    myLayer.anchorPoint.setValue([0,0]);
    myLayer.scale.setValue([100,100]);
}
function insertAt( text , insertText, pos ){
    var myText = text;
    var insertText = insertText;
    var myPos = pos;
    var newText;
    if( myPos >= 0 ){
        newText= myText.substr(0,myPos)+"_"+insertText+myText.substr(myPos);
    }else{
        newText= myText.substr(0,myText.length+myPos)+insertText+"_"+myText.substr(myText.length+myPos);
    }
    return newText
}
/* Extra for renaming tool, insert stringA
into specified position of stringB.*/
function insertAtSelectedItemsNames( text, pos){
    my_comps = getSelectedProjectItems();
    for ( var i = 0; i < my_comps.length ; i ++ ){
        var myComp = my_comps[i];
        myComp.name = insertAt( myComp.name , text, pos);
    }
}

function addLetterbox(){
    var LetterboxLayer = app.project.activeItem.layers.addShape()
    var aspectControl = LetterboxLayer.property("Effects").addProperty("ADBE Slider Control")
    aspectControl.name = "Aspect Ratio"
    aspectControl.property("Slider").setValue(16/9)
    var colorControl = LetterboxLayer.property("Effects").addProperty("ADBE Color Control")
    colorControl.name = "Color"
    colorControl.property("Color").setValue([0,0,0,1])
    LetterboxLayer.name = "Letterbox"
    var compFrame = LetterboxLayer.property("Contents").addProperty("ADBE Vector Shape - Rect")
    compFrame.name = "CompFrame"
    compFrame.property("Size").expression = "[ thisComp.width , thisComp.height ]"
    var letterboxRect = LetterboxLayer.property("Contents").addProperty("ADBE Vector Shape - Rect")
    letterboxRect.name = "Letterbox"
    letterboxRect.property("Size").expression ='w = thisComp.width;\
    h = thisComp.height;\
    compAspect = w / h ;\
    aspect = effect("Aspect Ratio")("Slider");\
    if (compAspect <= aspect ) {\
     	[ w, w / aspect ]\
    }else{\
        [ h*aspect , h ]\
    }'
    var letterboxMerge = LetterboxLayer.property("Contents").addProperty("ADBE Vector Filter - Merge")
    letterboxMerge.mode.setValue(3)
    var letterboxFill = LetterboxLayer.property("Contents").addProperty("ADBE Vector Graphic - Fill")
    letterboxFill.color.setValue([0,0,0,1])    
}