//
// preCompToLayerDur.jsx (revised 12th June 2008)
//
// This script will pre-compose selected layers with "Move all attributes..."
// The selected layers will be moved in time to begin at the start of the new pre-comp
// The pre-comp will begin at the original in-time of the earliest layer

// Based on an idea by Brian Maffitt
// Original code design by Keiko Yamada
// Major tweaks and enhancements by Dan Ebberts
// Minor tweak (moving in-times) by Chris Zwar

{

  // create undo group

  app.beginUndoGroup("Pre-Compose to Layer Duration");

  // select the active item in the project window
  // and make sure it's a comp

  var myComp = app.project.activeItem;
  if(myComp instanceof CompItem) {

    // make sure one or more layers are selected

    var myLayers = myComp.selectedLayers;
    if(myLayers.length > 0){

      // set new comp's default in and out points to those of first layer

      var newInPoint = myLayers[0].inPoint;
      var newOutPoint = myLayers[0].outPoint;

      // create new comp name of "comp " plus name of first layer

      var newCompName = "Precomp-Layer";
      var layerName = myLayers[0].index;
      if(layerName.length > 26) {
        layerName = layerName.substring(0, 26);
      }
      newCompName += layerName;

      // "precompose" expects an array of layer indices

      var layerIndices = new Array();
      for (var i = 0; i < myLayers.length; i++) {
        layerIndices[layerIndices.length] = myLayers[i].index;

        // make sure new comp in-point is in-point of earliest layer
        // and new comp out-point is out-point of latest layer

        if (myLayers[i].inPoint < newInPoint) newInPoint = myLayers[i].inPoint;
        if (myLayers[i].outPoint > newOutPoint) newOutPoint = myLayers[i].outPoint;
      }

      // move the selected layers to the start of the comp
      // now that we have recorded their original in-points

      for (var i = 0; i < myLayers.length; i++) {
      myLayers[i].startTime = myLayers[i].startTime - newInPoint;
     }

      // create the new pre-comp

      var newComp = myComp.layers.precompose(layerIndices, newCompName, true );

      // make the duration of the new pre-comp match the selected layers

      var preCompLayer = myComp.selectedLayers[0];
      preCompLayer.inPoint = 0;
      preCompLayer.outPoint = newOutPoint-newInPoint;
      preCompLayer.startTime = newInPoint;

    }else{
       alert("select at least one layer to precompose.");
    }
  }else{
    alert("please select a composition.");
  }
  app.endUndoGroup();
}