public async Task TryCreateAsync()

in src/WebJobs.Extensions.CosmosDB/Trigger/CosmosDBTriggerAttributeBindingProvider.cs [40:128]
77 lines of code
15 McCabe index (conditional complexity)

        public async Task<ITriggerBinding> TryCreateAsync(TriggerBindingProviderContext context)
        {
            // Tries to parse the context parameters and see if it belongs to this [CosmosDBTrigger] binder
            if (context == null)
            {
                throw new ArgumentNullException("context");
            }

            ParameterInfo parameter = context.Parameter;
            CosmosDBTriggerAttribute attribute = parameter.GetCustomAttribute<CosmosDBTriggerAttribute>(inherit: false);
            if (attribute == null)
            {
                return null;
            }

            Container monitoredContainer;
            Container leasesContainer;
            string monitoredDatabaseName = ResolveAttributeValue(attribute.DatabaseName);
            string monitoredCollectionName = ResolveAttributeValue(attribute.ContainerName);
            string leasesDatabaseName = ResolveAttributeValue(attribute.LeaseDatabaseName);
            string leasesCollectionName = ResolveAttributeValue(attribute.LeaseContainerName);
            string processorName = ResolveAttributeValue(attribute.LeaseContainerPrefix) ?? string.Empty;
            string preferredLocations = ResolveAttributeValue(attribute.PreferredLocations);

            try
            {
                string triggerConnection = ResolveAttributeConnection(attribute);
                if (string.IsNullOrEmpty(triggerConnection))
                {
                    throw new InvalidOperationException($"The attribute {nameof(attribute.Connection)} for the monitored container is in an invalid format, please use AccountEndpoint=XXXXXX;AccountKey=XXXXXX; or a node representing token authentication information.");
                }

                string leasesConnection = ResolveAttributeLeasesConnection(attribute);
                if (string.IsNullOrEmpty(leasesConnection))
                {
                    throw new InvalidOperationException($"The attribute {nameof(attribute.LeaseConnection)} for the leases container is in an invalid format, please use AccountEndpoint=XXXXXX;AccountKey=XXXXXX;. or a node representing token authentication information.");
                }

                if (string.IsNullOrEmpty(monitoredDatabaseName)
                    || string.IsNullOrEmpty(monitoredCollectionName)
                    || string.IsNullOrEmpty(leasesDatabaseName)
                    || string.IsNullOrEmpty(leasesCollectionName))
                {
                    throw new InvalidOperationException("Cannot establish database and container values. If you are using environment and configuration values, please ensure these are correctly set.");
                }

                if (triggerConnection.Equals(leasesConnection, StringComparison.InvariantCultureIgnoreCase)
                    && monitoredDatabaseName.Equals(leasesDatabaseName, StringComparison.InvariantCultureIgnoreCase)
                    && monitoredCollectionName.Equals(leasesCollectionName, StringComparison.InvariantCultureIgnoreCase))
                {
                    throw new InvalidOperationException("The monitored container cannot be the same as the container storing the leases.");
                }

                CosmosClient monitoredCosmosDBService = _configProvider.GetService(
                    connection: triggerConnection, 
                    preferredLocations: preferredLocations, 
                    userAgent: CosmosDBTriggerUserAgentSuffix);
                CosmosClient leaseCosmosDBService = _configProvider.GetService(
                    connection: leasesConnection, 
                    preferredLocations: preferredLocations, 
                    userAgent: CosmosDBTriggerUserAgentSuffix);

                if (attribute.CreateLeaseContainerIfNotExists)
                {
                    await CreateLeaseCollectionIfNotExistsAsync(leaseCosmosDBService, leasesDatabaseName, leasesCollectionName, attribute.LeasesContainerThroughput);
                }

                monitoredContainer = monitoredCosmosDBService.GetContainer(monitoredDatabaseName, monitoredCollectionName);
                leasesContainer = leaseCosmosDBService.GetContainer(leasesDatabaseName, leasesCollectionName);

                if (!string.IsNullOrEmpty(attribute.StartFromTime))
                {
                    attribute.StartFromTime = ResolveAttributeValue(attribute.StartFromTime);
                }
            }
            catch (Exception ex)
            {
                throw new InvalidOperationException(string.Format("Cannot create container information for {0} in database {1} with lease {2} in database {3} : {4}", attribute.ContainerName, attribute.DatabaseName, attribute.LeaseContainerName, attribute.LeaseDatabaseName, ex.Message), ex);
            }

            return new CosmosDBTriggerBinding<T>(
                parameter,
                processorName,
                monitoredContainer,
                leasesContainer, 
                attribute,
                _drainModeManager,
                _logger);
        }