Collect Files - Script

I need of a Script which do the following:

1. Search Footage composition in active item;
2. Within Footage composition, search the number of items that exist within (the number of items may vary);
3. Collect all these items to use in the Script.

• Then;

1. Sum the time duration of all the items that are within the Footage composition.
2. And apply this calculated time, in time duration of the active composition.

Thanks.