var prefetchStateMachine = function()

in JSLib/src/cache.js [1041:1107]
37 lines of code
14 McCabe index (conditional complexity)

        var prefetchStateMachine = function (operation, opTargetState, cacheState, data) {
            /// <summary>State machine describing the behavior of a prefetch operation.</summary>
            /// <param name="operation" type="DataCacheOperation">Operation being run.</param>
            /// <param name="opTargetState" type="Object">Operation state to transition to.</param>
            /// <param name="cacheState" type="Object">Current cache state.</param>
            /// <param name="data" type="Object" optional="true">Additional data passed to the state.</param>
            /// <remarks>
            /// Prefetch operations have the lowest priority and will be interrupted by operations of
            /// other kinds. A preempted prefetch operation will resume its execution only when the state
            /// of the cache returns to idle.
            ///
            /// If a clear operation starts executing then all the prefetch operations are canceled,
            /// even if they haven't started executing yet.
            /// </remarks>

            // Handle cancelation
            if (!cancelStateMachine(operation, opTargetState, cacheState, data)) {

                var transition = operation.transition;

                // Handle preemption
                if (cacheState !== CACHE_STATE_PREFETCH) {
                    if (cacheState === CACHE_STATE_DESTROY) {
                        if (opTargetState !== OPERATION_STATE_CANCEL) {
                            operation.cancel();
                        }
                    } else if (cacheState === CACHE_STATE_IDLE) {
                        // Signal the cache that a prefetch operation is running.
                        changeState(CACHE_STATE_PREFETCH);
                    }
                    return true;
                }

                switch (opTargetState) {
                    case OPERATION_STATE_START:
                        // Initial state of the operation.
                        if (prefetchOperations[0] === operation) {
                            transition(READ_STATE_LOCAL, operation.i);
                        }
                        break;

                    case READ_STATE_DONE:
                        // State that determines if the operation can be resolved or has to
                        // continue processing.
                        // Data is expected to be the read page.
                        var pending = operation.pending;

                        if (pending > 0) {
                            pending -= Math.min(pending, data.c);
                        }

                        // Are we done, or has all the data been stored?
                        if (allDataLocal || pending === 0 || data.c < pageSize || overflowed) {
                            operation.complete();
                        } else {
                            // Continue processing the operation.
                            operation.pending = pending;
                            transition(READ_STATE_LOCAL, data.i + pageSize);
                        }
                        break;

                    default:
                        return readSaveStateMachine(operation, opTargetState, cacheState, data, true);
                }
            }
            return true;
        };