Function handleAdd

src/js/app/actions.js:474–532

        item.on('load', () => {
            const handleAdd = shouldAdd => {
                // no should not add this file
                if (!shouldAdd) {
                    dispatch('REMOVE_ITEM', {
                        query: id,
                    });
                    return;
                }

                // now interested in metadata updates
                item.on('metadata-update', change => {
                    dispatch('DID_UPDATE_ITEM_METADATA', { id, change });
                });

                // let plugins decide if the output data should be prepared at this point
                // means we'll do this and wait for idle state
                applyFilterChain('SHOULD_PREPARE_OUTPUT', false, { item, query }).then(
                    shouldPrepareOutput => {
                        // plugins determined the output data should be prepared (or not), can be adjusted with beforePrepareOutput hook
                        const beforePrepareFile = query('GET_BEFORE_PREPARE_FILE');
                        if (beforePrepareFile)
                            shouldPrepareOutput = beforePrepareFile(item, shouldPrepareOutput);

                        const loadComplete = () => {
                            dispatch('COMPLETE_LOAD_ITEM', {
                                query: id,
                                item,
                                data: {
                                    source,
                                    success,
                                },
                            });

                            listUpdated(dispatch, state);
                        };

                        // exit
                        if (shouldPrepareOutput) {
                            // wait for idle state and then run PREPARE_OUTPUT
                            dispatch(
                                'REQUEST_PREPARE_OUTPUT',
                                {
                                    query: id,
                                    item,
                                    success: file => {
                                        dispatch('DID_PREPARE_OUTPUT', { id, file });
                                        loadComplete();
                                    },
                                },
                                true
                            );

                            return;
                        }

                        loadComplete();
                    }
                );