function refreshRanges()

in src/Clients/Web/winjs/js/winjs.js [27991:28057]
45 lines of code
27 McCabe index (conditional complexity)

                function refreshRanges(slotFirst, allRanges) {
                    // Fetch a few extra items each time, to catch insertions without requiring an extra fetch
                    var refreshFetchExtra = 3;

                    var refreshID = currentRefreshID;

                    var slotFetchFirst,
                        slotRefreshFirst,
                        fetchCount = 0,
                        fetchID;

                    // Walk through the slot list looking for keys we haven't fetched or attempted to fetch yet.  Rely on the
                    // heuristic that items that were close together before the refresh are likely to remain so after, so batched
                    // fetches will locate most of the previously fetched items.
                    for (var slot = slotFirst; slot !== slotsEnd; slot = slot.next) {
                        if (!slotFetchFirst && slot.key && !deletedKeys[slot.key] && !keyFetchInProgress(slot.key)) {
                            var slotRefresh = refreshKeyMap[slot.key];

                            // Keep attempting to fetch an item until at least one item on either side of it has been observed, so
                            // we can determine its position relative to others.
                            if (!slotRefresh || slotRefresh.firstInSequence || slotRefresh.lastInSequence) {
                                slotFetchFirst = slot;
                                slotRefreshFirst = slotRefresh;
                                fetchID = newFetchID();
                            }
                        }

                        if (!slotFetchFirst) {
                            // Also attempt to fetch placeholders for requests for specific keys, just in case those items no
                            // longer exist.
                            if (slot.key && isPlaceholder(slot) && !deletedKeys[slot.key]) {
                                // Fulfill each "itemFromKey" request
                                if (!refreshKeyMap[slot.key]) {
                                    // Fetch at least one item before and after, just to verify item's position in list
                                    fetchID = newFetchID();
                                    fetchItemsForRefresh(slot.key, false, fetchID, itemsFromKey(fetchID, slot.key, 1, 1, slot.hints));
                                }
                            }
                        } else {
                            var keyAlreadyFetched = keyFetchInProgress(slot.key);

                            if (!deletedKeys[slot.key] && !refreshKeyMap[slot.key] && !keyAlreadyFetched) {
                                if (slot.key) {
                                    keyFetchIDs[slot.key] = fetchID;
                                }
                                fetchCount++;
                            }

                            if (slot.lastInSequence || slot.next === slotListEnd || keyAlreadyFetched) {
                                refreshRange(slotFetchFirst, fetchID, (!slotRefreshFirst || slotRefreshFirst.firstInSequence ? refreshFetchExtra : 0), fetchCount - 1 + refreshFetchExtra);

                                if (!allRanges) {
                                    break;
                                }

                                slotFetchFirst = null;
                                fetchCount = 0;
                            }
                        }
                    }

                    if (refreshFetchesInProgress === 0 && !refreshItemsFetched && currentRefreshID === refreshID) {
                        // If nothing was successfully fetched, try fetching the first item, to detect an empty list
                        refreshFirstItem(newFetchID());
                    }

                }