Implemented Cron activity (#23)

Elsa.sln

@@ -67,6 +67,12 @@ Project("{FAE04EC0-301F-11D3-BF4B-00C04F79EFBC}") = "Elsa.Activities.Email", "sr
 EndProject
 Project("{FAE04EC0-301F-11D3-BF4B-00C04F79EFBC}") = "Elsa.Web.Activities.Email", "src\web\modules\Elsa.Web.Activities.Email\Elsa.Web.Activities.Email.csproj", "{6B5E8D2F-3C4A-407A-B78C-DF4C3B32FF92}"
 EndProject
+Project("{FAE04EC0-301F-11D3-BF4B-00C04F79EFBC}") = "Elsa.Activities.Cron", "src\activities\Elsa.Activities.Cron\Elsa.Activities.Cron.csproj", "{E4B71DC4-3E73-49C3-9B4E-CA13909F222D}"
+EndProject
+Project("{FAE04EC0-301F-11D3-BF4B-00C04F79EFBC}") = "Elsa.Web.Activities.Cron", "src\web\modules\Elsa.Web.Activities.Cron\Elsa.Web.Activities.Cron.csproj", "{FE6ECF63-D3FC-44EA-8405-C2A73F7C00C8}"
+EndProject
+Project("{FAE04EC0-301F-11D3-BF4B-00C04F79EFBC}") = "Elsa.Runtime.Hosting", "src\core\Elsa.Runtime.Hosting\Elsa.Runtime.Hosting.csproj", "{4728D287-E4F4-4219-8066-924B53E6E17C}"
+EndProject
 Global
 	GlobalSection(SolutionConfigurationPlatforms) = preSolution
 		Debug|Any CPU = Debug|Any CPU
@@ -161,6 +167,18 @@ Global
 		{6B5E8D2F-3C4A-407A-B78C-DF4C3B32FF92}.Debug|Any CPU.Build.0 = Debug|Any CPU
 		{6B5E8D2F-3C4A-407A-B78C-DF4C3B32FF92}.Release|Any CPU.ActiveCfg = Release|Any CPU
 		{6B5E8D2F-3C4A-407A-B78C-DF4C3B32FF92}.Release|Any CPU.Build.0 = Release|Any CPU
+		{E4B71DC4-3E73-49C3-9B4E-CA13909F222D}.Debug|Any CPU.ActiveCfg = Debug|Any CPU
+		{E4B71DC4-3E73-49C3-9B4E-CA13909F222D}.Debug|Any CPU.Build.0 = Debug|Any CPU
+		{E4B71DC4-3E73-49C3-9B4E-CA13909F222D}.Release|Any CPU.ActiveCfg = Release|Any CPU
+		{E4B71DC4-3E73-49C3-9B4E-CA13909F222D}.Release|Any CPU.Build.0 = Release|Any CPU
+		{FE6ECF63-D3FC-44EA-8405-C2A73F7C00C8}.Debug|Any CPU.ActiveCfg = Debug|Any CPU
+		{FE6ECF63-D3FC-44EA-8405-C2A73F7C00C8}.Debug|Any CPU.Build.0 = Debug|Any CPU
+		{FE6ECF63-D3FC-44EA-8405-C2A73F7C00C8}.Release|Any CPU.ActiveCfg = Release|Any CPU
+		{FE6ECF63-D3FC-44EA-8405-C2A73F7C00C8}.Release|Any CPU.Build.0 = Release|Any CPU
+		{4728D287-E4F4-4219-8066-924B53E6E17C}.Debug|Any CPU.ActiveCfg = Debug|Any CPU
+		{4728D287-E4F4-4219-8066-924B53E6E17C}.Debug|Any CPU.Build.0 = Debug|Any CPU
+		{4728D287-E4F4-4219-8066-924B53E6E17C}.Release|Any CPU.ActiveCfg = Release|Any CPU
+		{4728D287-E4F4-4219-8066-924B53E6E17C}.Release|Any CPU.Build.0 = Release|Any CPU
 	EndGlobalSection
 	GlobalSection(SolutionProperties) = preSolution
 		HideSolutionNode = FALSE
@@ -192,6 +210,9 @@ Global
 		{089E23E7-0B8D-4BB6-949D-EB669C116D9E} = {35F44BE9-13D0-417C-A01A-F0787BEE6DC3}
 		{D20FCB88-9DCA-49EA-9CC2-5B94DD935D30} = {B43B546E-23F3-46E8-ACB7-D04F05CDA180}
 		{6B5E8D2F-3C4A-407A-B78C-DF4C3B32FF92} = {B33F1927-FF0A-4826-80C6-F480E9C43892}
+		{E4B71DC4-3E73-49C3-9B4E-CA13909F222D} = {B43B546E-23F3-46E8-ACB7-D04F05CDA180}
+		{FE6ECF63-D3FC-44EA-8405-C2A73F7C00C8} = {B33F1927-FF0A-4826-80C6-F480E9C43892}
+		{4728D287-E4F4-4219-8066-924B53E6E17C} = {35F44BE9-13D0-417C-A01A-F0787BEE6DC3}
 	EndGlobalSection
 	GlobalSection(ExtensibilityGlobals) = postSolution
 		SolutionGuid = {8B0975FD-7050-48B0-88C5-48C33378E158}

src/activities/Elsa.Activities.Cron/Activities/CronTrigger.cs

@@ -0,0 +1,12 @@
+using System;
+using Elsa.Expressions;
+using Elsa.Models;
+
+namespace Elsa.Activities.Cron.Activities
+{
+    public class CronTrigger : Activity
+    {
+        public WorkflowExpression<string> CronExpression { get; set; }
+        public DateTime? StartTimestamp { get; set; }
+    }
+}

src/activities/Elsa.Activities.Cron/ActivityDescriptors.cs

@@ -0,0 +1,27 @@
+using System.Collections.Generic;
+using Elsa.Activities.Cron.Activities;
+using Elsa.Models;
+using Microsoft.Extensions.Localization;
+
+namespace Elsa.Activities.Cron
+{
+    public class ActivityDescriptors : ActivityDescriptorProviderBase
+    {
+        public ActivityDescriptors(IStringLocalizer<ActivityDescriptors> localizer)
+        {
+            T = localizer;
+        }
+
+        private IStringLocalizer<ActivityDescriptors> T { get; }
+        private LocalizedString Category => T["Triggers"];
+
+        protected override IEnumerable<ActivityDescriptor> Describe()
+        {
+            yield return ActivityDescriptor.ForTrigger<CronTrigger>(
+                Category,
+                T["Cron Trigger"],
+                T["Triggers at specified intervals using CRON expressions."],
+                T["Done"]);
+        }
+    }
+}

src/activities/Elsa.Activities.Cron/Drivers/CronTriggerDriver.cs

@@ -0,0 +1,55 @@
+using System.Threading;
+using System.Threading.Tasks;
+using Elsa.Activities.Cron.Activities;
+using Elsa.Handlers;
+using Elsa.Models;
+using Elsa.Results;
+using NCrontab;
+using NodaTime;
+using NodaTime.Extensions;
+
+namespace Elsa.Activities.Cron.Drivers
+{
+    public class CronTriggerDriver : ActivityDriver<CronTrigger>
+    {
+        private readonly IWorkflowExpressionEvaluator expressionEvaluator;
+        private readonly IClock clock;
+
+        public CronTriggerDriver(IWorkflowExpressionEvaluator expressionEvaluator, IClock clock)
+        {
+            this.expressionEvaluator = expressionEvaluator;
+            this.clock = clock;
+        }
+
+        protected override async Task<bool> OnCanExecuteAsync(CronTrigger activity, WorkflowExecutionContext workflowContext, CancellationToken cancellationToken)
+        {
+            return activity.StartTimestamp == null || await IsExpiredAsync(activity, workflowContext, cancellationToken);
+        }
+
+        protected override ActivityExecutionResult OnExecute(CronTrigger activity, WorkflowExecutionContext workflowContext)
+        {
+            if (activity.StartTimestamp == null)
+                activity.StartTimestamp = clock.GetCurrentInstant().ToDateTimeUtc();
+
+            return Halt();
+        }
+
+        protected override async Task<ActivityExecutionResult> OnResumeAsync(CronTrigger activity, WorkflowExecutionContext workflowContext, CancellationToken cancellationToken)
+        {
+            var isExpired = await IsExpiredAsync(activity, workflowContext, cancellationToken);
+
+            return isExpired ? (ActivityExecutionResult) Endpoint("Done") : Halt();
+        }
+
+        private async Task<bool> IsExpiredAsync(CronTrigger activity, WorkflowExecutionContext workflowContext, CancellationToken cancellationToken)
+        {
+            var cronExpression = await expressionEvaluator.EvaluateAsync(activity.CronExpression, workflowContext, cancellationToken);
+            var schedule = CrontabSchedule.Parse(cronExpression);
+            var now = clock.GetCurrentInstant().ToDateTimeUtc();
+            var startTimestamp = activity.StartTimestamp ?? now;
+            var nextOccurrence = schedule.GetNextOccurrence(startTimestamp);
+
+            return now >= nextOccurrence;
+        }
+    }
+}

src/activities/Elsa.Activities.Cron/Elsa.Activities.Cron.csproj

@@ -0,0 +1,25 @@
+<Project Sdk="Microsoft.NET.Sdk">
+
+    <PropertyGroup>
+        <TargetFramework>netstandard2.0</TargetFramework>
+        <PackageVersion>1.0.0</PackageVersion>
+        <Authors>Sipke Schoorstra</Authors>
+        <Description>Elsa is a set of workflowing libraries and tools to enable super-fast workflowing capabilities in any .NET Core application.</Description>
+        <Copyright>2019</Copyright>
+        <PackageProjectUrl>https://github.com/sfmskywalker/Elsa</PackageProjectUrl>
+        <RepositoryUrl>https://github.com/sfmskywalker/Elsa</RepositoryUrl>
+        <RepositoryType>GitHub</RepositoryType>
+        <PackageTags>elsa, workflows, orchard</PackageTags>
+    </PropertyGroup>
+
+    <ItemGroup>
+        <ProjectReference Include="..\..\core\Elsa.Core\Elsa.Core.csproj" />
+        <ProjectReference Include="..\..\core\Elsa.Runtime.Abstractions\Elsa.Runtime.Abstractions.csproj" />
+    </ItemGroup>
+
+    <ItemGroup>
+        <PackageReference Include="Microsoft.Extensions.Hosting.Abstractions" Version="2.2.0" />
+        <PackageReference Include="NCrontab" Version="3.3.1" />
+    </ItemGroup>
+
+</Project>

src/activities/Elsa.Activities.Cron/Extensions/ServiceCollectionExtensions.cs

@@ -0,0 +1,27 @@
+using Elsa.Activities.Cron.Drivers;
+using Elsa.Activities.Cron.HostedServices;
+using Elsa.Activities.Cron.Options;
+using Elsa.Extensions;
+using Microsoft.Extensions.Configuration;
+using Microsoft.Extensions.DependencyInjection;
+
+namespace Elsa.Activities.Cron.Extensions
+{
+    public static class ServiceCollectionExtensions
+    {
+        public static IServiceCollection AddCronDescriptors(this IServiceCollection services)
+        {
+            return services.AddActivityDescriptors<ActivityDescriptors>();
+        }
+
+        public static IServiceCollection AddCronDrivers(this IServiceCollection services, IConfiguration configuration)
+        {
+            return services
+                .AddCronDescriptors()
+                .AddOptions()
+                .Configure<CronOptions>(configuration)
+                .AddHostedService<CronHostedService>()
+                .AddActivityDriver<CronTriggerDriver>();
+        }
+    }
+}

src/activities/Elsa.Activities.Cron/HostedServices/CronHostedService.cs

@@ -0,0 +1,45 @@
+using System;
+using System.Threading;
+using System.Threading.Tasks;
+using Elsa.Activities.Cron.Activities;
+using Elsa.Activities.Cron.Options;
+using Elsa.Models;
+using Elsa.Runtime;
+using Microsoft.Extensions.DependencyInjection;
+using Microsoft.Extensions.Hosting;
+using Microsoft.Extensions.Logging;
+using Microsoft.Extensions.Options;
+
+namespace Elsa.Activities.Cron.HostedServices
+{
+    public class CronHostedService : BackgroundService
+    {
+        private readonly IWorkflowHost workflowHost;
+        private readonly IOptions<CronOptions> options;
+        private readonly ILogger<CronHostedService> logger;
+
+        public CronHostedService(IWorkflowHost workflowHost, IOptions<CronOptions> options, ILogger<CronHostedService> logger)
+        {
+            this.workflowHost = workflowHost;
+            this.options = options;
+            this.logger = logger;
+        }
+
+        protected override async Task ExecuteAsync(CancellationToken stoppingToken)
+        {
+            while (!stoppingToken.IsCancellationRequested)
+            {
+                try
+                {
+                    await workflowHost.TriggerWorkflowAsync(nameof(CronTrigger), Variables.Empty, stoppingToken);
+                }
+                catch (Exception ex)
+                {
+                    logger.LogError(ex, $"Exception occurred while invoking workflows.");
+                }
+
+                await Task.Delay(options.Value.SweepInterval.ToDuration().ToTimeSpan(), stoppingToken);
+            }
+        }
+    }
+}

src/activities/Elsa.Activities.Cron/Options/CronOptions.cs

@@ -0,0 +1,14 @@
+using NodaTime;
+
+namespace Elsa.Activities.Cron.Options
+{
+    public class CronOptions
+    {
+        public CronOptions()
+        {
+            SweepInterval = Period.FromMinutes(1);
+        }
+        
+        public Period SweepInterval { get; set; }
+    }
+}

src/activities/Elsa.Activities.Email/Drivers/SendEmailDriver.cs

@@ -34,7 +34,7 @@ namespace Elsa.Activities.Email.Drivers
             };
 
             mailMessage.To.Add(to);
-            smtpClient.SendAsync(mailMessage, null);
+            await smtpClient.SendMailAsync(mailMessage);
 
             return Endpoint("Done");
         }

src/core/Elsa.Core/Serialization/Tokenizers/WorkflowTokenizer.cs

@@ -21,7 +21,7 @@ namespace Elsa.Serialization.Tokenizers
         private readonly ITokenizerInvoker tokenizerInvoker;
         private readonly IActivityLibrary activityLibrary;
         private readonly IClock clock;
-        private readonly JsonSerializerSettings _serializerSettings;
+        private readonly JsonSerializerSettings serializerSettings;
         private readonly JsonSerializer jsonSerializer;
 
         public WorkflowTokenizer(ITokenizerInvoker tokenizerInvoker, IActivityLibrary activityLibrary, IClock clock)
@@ -30,14 +30,14 @@ namespace Elsa.Serialization.Tokenizers
             this.activityLibrary = activityLibrary;
             this.clock = clock;
 
-            _serializerSettings = new JsonSerializerSettings
+            serializerSettings = new JsonSerializerSettings
                 {
                     ContractResolver = new CamelCasePropertyNamesContractResolver()
                 }
                 .ConfigureForNodaTime(DateTimeZoneProviders.Tzdb);
 
-            _serializerSettings.Converters.Add(new StringEnumConverter());
-            jsonSerializer = JsonSerializer.Create(_serializerSettings);
+            serializerSettings.Converters.Add(new StringEnumConverter());
+            jsonSerializer = JsonSerializer.Create(serializerSettings);
         }
 
         public async Task<JToken> TokenizeWorkflowAsync(Workflow value, CancellationToken cancellationToken)
@@ -120,7 +120,7 @@ namespace Elsa.Serialization.Tokenizers
             var name = token["name"].Value<string>();
             var descriptor = await GetActivityDescriptorAsync(name, cancellationToken);
             var activityType = descriptor?.ActivityType ?? typeof(UnknownActivity);
-            var activity = (IActivity) token.ToObject(activityType);
+            var activity = (IActivity) jsonSerializer.Deserialize(token.CreateReader(), activityType);
 
             activity.Descriptor = descriptor;
             return activity;
@@ -267,7 +267,7 @@ namespace Elsa.Serialization.Tokenizers
         {
             var models = (JArray) token["executionLog"] ?? new JArray();
 
-            return JsonConvert.DeserializeObject<IList<LogEntry>>(models.ToString(), _serializerSettings);
+            return JsonConvert.DeserializeObject<IList<LogEntry>>(models.ToString(), serializerSettings);
         }
 
         private IEnumerable<Connection> DeserializeConnections(JToken token, IDictionary<string, IActivity> activityDictionary)

src/core/Elsa.Runtime.Hosting/Elsa.Runtime.Hosting.csproj

@@ -0,0 +1,11 @@
+<Project Sdk="Microsoft.NET.Sdk">
+
+    <PropertyGroup>
+        <TargetFramework>netstandard2.0</TargetFramework>
+    </PropertyGroup>
+
+    <ItemGroup>
+      <PackageReference Include="NodaTime" Version="2.4.4" />
+    </ItemGroup>
+
+</Project>

src/core/Elsa.Runtime.Hosting/Extensions/ProgramExtensions.cs

@@ -0,0 +1,16 @@
+using System.ComponentModel;
+using Elsa.Runtime.Hosting.TypeConverters;
+using NodaTime;
+
+namespace Elsa.Runtime.Hosting.Extensions
+{
+    public static class ProgramExtensions
+    {
+        public static void ConfigureTypeConverters()
+        {
+            TypeDescriptor.AddAttributes(
+                typeof(Period),
+                new TypeConverterAttribute(typeof(PeriodTypeConverter)));
+        }
+    }
+}

src/core/Elsa.Runtime.Hosting/TypeConverters/PeriodTypeConverter.cs

@@ -0,0 +1,25 @@
+using System;
+using System.ComponentModel;
+using System.Globalization;
+using NodaTime.Text;
+
+namespace Elsa.Runtime.Hosting.TypeConverters
+{
+    public class PeriodTypeConverter : TypeConverter
+    {
+        public override bool CanConvertFrom(ITypeDescriptorContext context, Type sourceType)
+        {
+            return sourceType == typeof(string) || base.CanConvertFrom(context, sourceType);
+        }
+
+        public override object ConvertFrom(ITypeDescriptorContext context, CultureInfo culture, object value)
+        {
+            if (value is string s)
+            {
+                return PeriodPattern.Roundtrip.Parse(s).Value;
+            }
+
+            return base.ConvertFrom(context, culture, value);
+        }
+    }
+}

src/core/Elsa.Runtime/Extensions/ServiceCollectionExtensions.cs

@@ -10,7 +10,7 @@ namespace Elsa.Runtime.Extensions
             return services
                 .AddWorkflowsCore()
                 .AddWorkflowsInvoker()
-                .AddScoped<IWorkflowHost, WorkflowHost>();
+                .AddSingleton<IWorkflowHost, WorkflowHost>();
         }
     }
 }

src/core/Elsa.Runtime/WorkflowHost.cs

@@ -31,6 +31,7 @@ namespace Elsa.Runtime
         public async Task<WorkflowExecutionContext> StartWorkflowAsync(Workflow workflow, IActivity startActivity, Variables arguments, CancellationToken cancellationToken)
         {
             var workflowInstance = await workflowSerializer.DeriveAsync(workflow, cancellationToken);
+            startActivity = workflowInstance.Activities.Single(x => x.Id == startActivity.Id);
             return await invoker.InvokeAsync(workflowInstance, startActivity, arguments, cancellationToken);
         }
 

src/samples/SampleDashboard.Web/SampleDashboard.Web.csproj

@@ -24,6 +24,7 @@
 
     <ItemGroup>
         <ProjectReference Include="..\..\web\modules\Elsa.Web.Activities.Console\Elsa.Web.Activities.Console.csproj" />
+        <ProjectReference Include="..\..\web\modules\Elsa.Web.Activities.Cron\Elsa.Web.Activities.Cron.csproj" />
         <ProjectReference Include="..\..\web\modules\Elsa.Web.Activities.Email\Elsa.Web.Activities.Email.csproj" />
         <ProjectReference Include="..\..\web\modules\Elsa.Web.Activities.Http\Elsa.Web.Activities.Http.csproj" />
         <ProjectReference Include="..\..\web\modules\Elsa.Web.Activities.Primitives\Elsa.Web.Activities.Primitives.csproj" />

src/samples/SampleHost.Web/Program.cs

@@ -1,4 +1,5 @@
 using System.Threading.Tasks;
+using Elsa.Runtime.Hosting.Extensions;
 using Microsoft.AspNetCore;
 using Microsoft.AspNetCore.Hosting;
 
@@ -13,7 +14,10 @@ namespace SampleHost.Web
             await host.RunAsync();
         }
 
-        public static IWebHostBuilder CreateWebHostBuilder(string[] args) =>
-            WebHost.CreateDefaultBuilder<Startup>(args);
+        public static IWebHostBuilder CreateWebHostBuilder(string[] args)
+        {
+            ProgramExtensions.ConfigureTypeConverters();
+            return WebHost.CreateDefaultBuilder<Startup>(args);
+        }
     }
 }

src/samples/SampleHost.Web/SampleHost.Web.csproj

@@ -20,11 +20,13 @@
 
     <ItemGroup>
       <ProjectReference Include="..\..\activities\Elsa.Activities.Console\Elsa.Activities.Console.csproj" />
+      <ProjectReference Include="..\..\activities\Elsa.Activities.Cron\Elsa.Activities.Cron.csproj" />
       <ProjectReference Include="..\..\activities\Elsa.Activities.Email\Elsa.Activities.Email.csproj" />
       <ProjectReference Include="..\..\activities\Elsa.Activities.Http\Elsa.Activities.Http.csproj" />
       <ProjectReference Include="..\..\activities\Elsa.Activities.Primitives\Elsa.Activities.Primitives.csproj" />
       <ProjectReference Include="..\..\core\Elsa.Core\Elsa.Core.csproj" />
       <ProjectReference Include="..\..\core\Elsa.Persistence.FileSystem\Elsa.Persistence.FileSystem.csproj" />
+      <ProjectReference Include="..\..\core\Elsa.Runtime.Hosting\Elsa.Runtime.Hosting.csproj" />
       <ProjectReference Include="..\..\core\Elsa.Runtime\Elsa.Runtime.csproj" />
     </ItemGroup>
 

src/samples/SampleHost.Web/Startup.cs

@@ -1,4 +1,5 @@
 using Elsa.Activities.Console.Extensions;
+using Elsa.Activities.Cron.Extensions;
 using Elsa.Activities.Email.Extensions;
 using Elsa.Activities.Http.Extensions;
 using Elsa.Activities.Primitives.Extensions;
@@ -31,7 +32,8 @@ namespace SampleHost.Web
                 .AddPrimitiveWorkflowDrivers()
                 .AddConsoleWorkflowDrivers()
                 .AddHttpWorkflowDrivers()
-                .AddEmailDrivers(Configuration.GetSection("Smtp"));
+                .AddEmailDrivers(Configuration.GetSection("Smtp"))
+                .AddCronDrivers(Configuration.GetSection("Cron"));
             
             services
                 .AddMvc()

src/samples/SampleHost.Web/appsettings.json

@@ -15,5 +15,8 @@
         "Credentials": {
             "Type": "None"
         }
+    },
+    "Cron": {
+        "SweepInterval": "PT10S"
     }
 }

src/web/modules/Elsa.Web.Activities.Cron/Display/CronTriggerDisplay.cs

@@ -0,0 +1,20 @@
+using Elsa.Activities.Cron.Activities;
+using Elsa.Web.Activities.Cron.ViewModels;
+using Elsa.Web.Components.ViewModels;
+using Elsa.Web.Drivers;
+
+namespace Elsa.Web.Activities.Cron.Display
+{
+    public class CronTriggerDisplay : ActivityDisplayDriver<CronTrigger, CronTriggerViewModel>
+    {
+        protected override void EditActivity(CronTrigger activity, CronTriggerViewModel model)
+        {
+            model.CronExpression = new ExpressionViewModel(activity.CronExpression);
+        }
+
+        protected override void UpdateActivity(CronTriggerViewModel model, CronTrigger activity)
+        {
+            activity.CronExpression = model.CronExpression.ToWorkflowExpression<string>();
+        }
+    }
+}

src/web/modules/Elsa.Web.Activities.Cron/Elsa.Web.Activities.Cron.csproj

@@ -0,0 +1,25 @@
+<Project Sdk="Microsoft.NET.Sdk.Razor">
+
+    <PropertyGroup>
+        <TargetFramework>netstandard2.0</TargetFramework>
+        <PackageVersion>1.0.0</PackageVersion>
+        <Authors>Sipke Schoorstra</Authors>
+        <Description>Elsa is a set of workflowing libraries and tools to enable super-fast workflowing capabilities in any .NET Core application.</Description>
+        <Copyright>2019</Copyright>
+        <PackageProjectUrl>https://github.com/sfmskywalker/Elsa</PackageProjectUrl>
+        <RepositoryUrl>https://github.com/sfmskywalker/Elsa</RepositoryUrl>
+        <RepositoryType>GitHub</RepositoryType>
+        <PackageTags>elsa, workflows, orchard</PackageTags>
+    </PropertyGroup>
+
+    <ItemGroup>
+        <ProjectReference Include="..\..\..\activities\Elsa.Activities.Cron\Elsa.Activities.Cron.csproj" />
+        <ProjectReference Include="..\Elsa.Web.Abstractions\Elsa.Web.Abstractions.csproj" />
+        <ProjectReference Include="..\Elsa.Web.Components\Elsa.Web.Components.csproj" />
+    </ItemGroup>
+
+    <ItemGroup>
+        <PackageReference Include="OrchardCore.Module.Targets" Version="1.0.0-beta3-70705" />
+    </ItemGroup>
+
+</Project>

src/web/modules/Elsa.Web.Activities.Cron/Manifest.cs

@@ -0,0 +1,7 @@
+using OrchardCore.Modules.Manifest;
+
+[assembly: Module(
+    Name = "Cron Activities",
+    Category = "Elsa Workflows",
+    Description = "Provides a Cron Trigger activity."
+)]

src/web/modules/Elsa.Web.Activities.Cron/Startup.cs

@@ -0,0 +1,18 @@
+using Elsa.Activities.Cron.Extensions;
+using Elsa.Web.Activities.Cron.Display;
+using Elsa.Web.Extensions;
+using Microsoft.Extensions.DependencyInjection;
+using OrchardCore.Modules;
+
+namespace Elsa.Web.Activities.Cron
+{
+    public class Startup : StartupBase
+    {
+        public override void ConfigureServices(IServiceCollection services)
+        {
+            services
+                .AddCronDescriptors()
+                .AddActivityDisplay<CronTriggerDisplay>();
+        }
+    }
+}

src/web/modules/Elsa.Web.Activities.Cron/ViewModels/CronTriggerViewModel.cs

@@ -0,0 +1,9 @@
+using Elsa.Web.Components.ViewModels;
+
+namespace Elsa.Web.Activities.Cron.ViewModels
+{
+    public class CronTriggerViewModel
+    {
+        public ExpressionViewModel CronExpression { get; set; }
+    }
+}

src/web/modules/Elsa.Web.Activities.Cron/Views/CronTrigger.Card.cshtml

@@ -0,0 +1,6 @@
+@model ActivityShapeModel<CronTrigger>
+@{
+    var activityDescriptor = Model.Activity.Descriptor;
+}
+<h4 class="card-title"><i class="fas fa-globe"></i>@activityDescriptor.DisplayText</h4>
+<p>@activityDescriptor.Description</p>

src/web/modules/Elsa.Web.Activities.Cron/Views/CronTrigger.Design.cshtml

@@ -0,0 +1,6 @@
+@model ActivityShapeModel<CronTrigger>
+
+<header>
+    <h4><i class="fas fa-globe"></i>@Model.DisplayText</h4>
+    <i>&quot;@($"{Model.Activity.CronExpression}")&quot;</i>
+</header>

src/web/modules/Elsa.Web.Activities.Cron/Views/CronTrigger.Edit.cshtml

@@ -0,0 +1,7 @@
+@model CronTriggerViewModel
+<div class="form-group">
+    <label asp-for="CronExpression">@T["Cron Expression"]</label>
+    <vc:expression-editor model="@Model.CronExpression" prefix="@Html.NameFor(m => m.CronExpression)"></vc:expression-editor>
+    <span asp-validation-for="CronExpression" class="text-danger"></span>
+    <small class="form-text text-muted">@T["Enter a crontab expression. See https://crontab.guru/."]</small>
+</div>

src/web/modules/Elsa.Web.Activities.Cron/Views/_ViewImports.cshtml

@@ -0,0 +1,7 @@
+@using Elsa.Web.ViewModels
+@using Elsa.Web.Activities.Cron.ViewModels
+@using Elsa.Activities.Cron.Activities
+@using OrchardCore.Mvc.Core.Utilities
+@inherits OrchardCore.DisplayManagement.Razor.RazorPage<TModel>
+@addTagHelper *, Microsoft.AspNetCore.Mvc.TagHelpers
+@addTagHelper *, Elsa.Web.Components