/// <summary>
/// Data which can be sent with various ship events.
/// </summary>
public class ShipEventData
{
        /// <summary>
        /// Name of the ship.
        /// </summary>
        public string Ship { get; set; }
 
        /// <summary>
        /// Type of event.
        /// </summary>
        public string Type { get; set; }
 
        /// <summary>
        /// Device received in the event.
        /// </summary>
        public string Device { get; set; }
 
        /// <summary>
        /// Description received in the event.
        /// </summary>
        public string Description { get; set; }
 
        /// <summary>
        /// Product received in the event.
        /// </summary>
        public string Product { get; set; }
 
        /// <summary>
        /// Amount received in the event.
        /// </summary>
        public int? Amount { get; set; }
}

/// <summary>
/// Class used to receive ship event values.
/// </summary>
public class ShipEventValue
{
        /// <summary>
        /// Time when event was created.
        /// </summary>
        public string EventTime;
 
        /// <summary>
        /// Data of the event.
        /// </summary>
        public ShipEventData Data;
}

/// <summary>
/// Defines a subscription with its filters.
/// </summary>
public class Subscription
{
        /// <summary>
        /// Name of the subscription.
        /// </summary>
        public string Name;
 
        /// <summary>
        /// Filter which will look at the start of the subscription's subject.
        /// </summary>
        public string PrefixFilter;
 
        /// <summary>
        /// Filter which will look at the end of the subscription's subject.
        /// </summary>
        public string SuffixFilter;
}

/// <summary>
/// Used to insert ship events to Table Storage.
/// </summary>
public class ShipEventEntity : TableEntity
{
        /// <summary>
        /// Constructor.
        /// </summary>
        public ShipEventEntity(string ship, string dateTime)
        {
                PartitionKey = ship;
                RowKey = dateTime;
        }
 
        /// <summary>
        /// Type of event.
        /// </summary>
        public string Type { get; set; }
 
        /// <summary>
        /// Device received in the event.
        /// </summary>
        public string Device { get; set; }
 
        /// <summary>
        /// Description received in the event.
        /// </summary>
        public string Description { get; set; }
 
        /// <summary>
        /// Product received in the event.
        /// </summary>
        public string Product { get; set; }
 
        /// <summary>
        /// Amount received in the event.
        /// </summary>
        public int? Amount { get; set; }
}

public class SubscribersController : ApiController
    {
        /// <summary>
        /// Storage account used to store to Table Storage.
        /// </summary>
        private readonly CloudStorageAccount _storageAccount = CloudStorageAccount.Parse(CloudConfigurationManager.GetSetting("AzureStorageConnectionString"));
}

/// <summary>
/// Insert Ship Event into table storage.
/// </summary>
private async Task InsertToTable(IReadOnlyList<ShipEventValue> value, string tableName)
{
        // Check if any events were received
        if (value == null || value.Count == 0)
        {
                return;
        }
 
        // Create the table client
        var tableClient = _storageAccount.CreateCloudTableClient();
 
        // Retrieve a reference to the table
        var table = tableClient.GetTableReference(tableName);
 
        // Create the table if it doesn't exist
        table.CreateIfNotExists();
 
        // Create a new ship event entity
        var shipEventEntity = new ShipEventEntity(value[0].Data.Ship, value[0].EventTime)
        {
                Type = value[0].Data.Type,
                Product = value[0].Data.Product,
                Amount = value[0].Data.Amount,
                Device = value[0].Data.Device,
                Description = value[0].Data.Description
        };
 
        // Create the TableOperation object that inserts the customer entity
        var insertOperation = TableOperation.Insert(shipEventEntity);
 
        // Execute the insert operation
        await table.ExecuteAsync(insertOperation);
}

/// <summary>
/// Receives all events.
/// </summary>
[ActionName("All")]
public async Task<StatusCodeResult> PostAll([FromBody] List<ShipEventValue> value)
{
        await InsertToTable(value, "All");
        return new StatusCodeResult(HttpStatusCode.Created, this);
}
 
/// <summary>
/// Receives all types of events for the ship Hydra.
/// </summary>
[ActionName("Hydra")]
public async Task<StatusCodeResult> PostHydra([FromBody] List<ShipEventValue> value)
{
        await InsertToTable(value, "Hydra");
        return new StatusCodeResult(HttpStatusCode.Created, this);
}
 
/// <summary>
/// Receives repairs for all ships.
/// </summary>
[ActionName("Repairs")]
public async Task<StatusCodeResult> PostRepairs([FromBody] List<ShipEventValue> value)
{
        await InsertToTable(value, "Repairs");
        return new StatusCodeResult(HttpStatusCode.Created, this);
}
 
/// <summary>
/// Receives orders for the ship Aeris.
/// </summary>
[ActionName("AerisOrders")]
public async Task<StatusCodeResult> PostAerisOrders([FromBody] List<ShipEventValue> value)
{
        await InsertToTable(value, "AerisOrders");
        return new StatusCodeResult(HttpStatusCode.Created, this);
}

public static class WebApiConfig
{
        public static void Register(HttpConfiguration config)
        {
                // Web API routes 
                config.MapHttpAttributeRoutes();
                config.Routes.MapHttpRoute(name: "routes", routeTemplate: "api/{controller}/{action}");
        }
}

public class WebApiApplication : HttpApplication
{
        /// <summary>
        /// Subscriptions to be created.
        /// </summary>
        private readonly List<Subscription> _subscriptions = new List<Subscription>
        {
                new Subscription { Name = "All" },
                new Subscription { Name = "Hydra", PrefixFilter = "Hydra" },
                new Subscription { Name = "Repairs", SuffixFilter = "Repair" },
                new Subscription { Name = "AerisOrders", PrefixFilter = "Aeris", SuffixFilter = "Order" }
        };
}

/// <summary>
/// Create HTTP client used to communicate with Azure.
/// </summary>
/// <returns></returns>
private static HttpClient CreateHttpClient()
{
        // Create a HTTP client
        var httpClient = new HttpClient();
 
        // Add key in the request headers
        httpClient.DefaultRequestHeaders.Add("Authorization", $"Bearer {CloudConfigurationManager.GetSetting("AuthorizationToken")}");
 
        // Return the HTTP client
        return httpClient;
}

/// <summary>
/// Check if subscription exists.
/// </summary>
private static async Task<bool> SubscriptionExists(string subscription)
{
        // Check if subscription exists
        var result = await CreateHttpClient()
                .GetAsync(
                        $"https://management.azure.com/subscriptions/{CloudConfigurationManager.GetSetting("SubscriptionID")}/resourceGroups/{CloudConfigurationManager.GetSetting("ResourceGroup")}/providers/Microsoft.EventGrid/topics/{CloudConfigurationManager.GetSetting("EventGridTopic")}/providers/Microsoft.EventGrid/eventSubscriptions/{subscription}?api-version=2017-06-15-preview");
        return result.IsSuccessStatusCode;
}

/// <summary>
/// Create subscription with filters.
/// </summary>
private static async Task CreateSubscription(string subscription, string prefixFilter, string suffixFilter)
{
        // Set up create subscription message
        var createSubscription = new
        {
                properties = new
                {
                        destination = new { endpointType = "webhook", properties = new { endpointUrl = $"{CloudConfigurationManager.GetSetting("ApiAppUrl")}/api/Subscribers/{subscription}" } },
                        filter = new { includedEventTypes = new[] { "shipevent" }, subjectBeginsWith = prefixFilter, subjectEndsWith = suffixFilter, subjectIsCaseSensitive = "false" }
                }
        };
 
        // Create content to be sent
        var json = JsonConvert.SerializeObject(createSubscription);
        var content = new StringContent(json, Encoding.UTF8, "application/json");
 
        // Create subscription
        await CreateHttpClient()
                .PutAsync(
                        $"https://management.azure.com/subscriptions/{CloudConfigurationManager.GetSetting("SubscriptionID")}/resourceGroups/{CloudConfigurationManager.GetSetting("ResourceGroup")}/providers/Microsoft.EventGrid/topics/{CloudConfigurationManager.GetSetting("EventGridTopic")}/providers/Microsoft.EventGrid/eventSubscriptions/{subscription}?api-version=2017-06-15-preview",
                        content);
}

/// <summary>
/// Entry point of application.
/// </summary>
protected async void Application_Start()
{
        GlobalConfiguration.Configure(WebApiConfig.Register);
        await CreateSubscriptions();
}
 
/// <summary>
/// Create subscriptions that don't exist.
/// </summary>
private async Task CreateSubscriptions()
{
        // Check if subscriptions can be created, this will only be done if the endpoint of this API App has been updated in the settings
        if (CloudConfigurationManager.GetSetting("ApiAppUrl").ToLowerInvariant().Contains("tobereplaced"))
        {
                return;
        }
 
        // Loop through subsriptions
        foreach (var subscription in _subscriptions)
        {
                // Check if subscription already exists
                if (await SubscriptionExists(subscription.Name))
                {
                        continue;
                }
 
                // Create subscription
                await CreateSubscription(subscription.Name, subscription.PrefixFilter, subscription.SuffixFilter);
 
                // Wait for a while, to prevent throttling
                Thread.Sleep(5000);
        }
}