TelegramUpdater.FillMyForm 1.0.4-alpha

TelegramUpdater, FMF ( Fill my form )

This is an extension package for TelegramUpdater to help you fill a form in a blink of an eye.

How ?

FMF uses Channels feature of TelegramUpdater to open a realtime channel between your bot and a target user.

FMF will ask from a user and the user will respond ( probably ). and meanwhile your form is getting filled.

Let's Start

I'm gonna start with a simple form that has 3 felids: FirsName, LastName and Age.

First of all, create your form using a normal class.

// MySimpleForm.cs
internal class MySimpleForm
{
    public string FirstName { get; set; } = null!;

    public string? LastName { get; set; } // can be null, It's Nullable!

    public int Age { get; set; }

    public override string ToString()
    {
        return string.Format("{0} {1}, {2} years old.", FirstName, LastName?? "", Age);
    }
}

! Considerations

• Target properties should be: public, Readable and Writeable ( both get and set )

• Form class Should have a parameterless constructor.

A useable form should implement IForm interface! But AbstractForm is what you need.

Make your form a sub-class of AbstractForm and implement abstract methods.

// MySimpleForm.cs
internal class MySimpleForm : AbstractForm
{
    public string FirstName { get; set; } = null!;

    public string? LastName { get; set; } // can be null, It's Nullable!

    public int Age { get; set; }

    public override string ToString()
    {
        return string.Format("{0} {1}, {2} years old.", FirstName, LastName?? "", Age);
    }

    public override async Task OnBeginAskAsync<TForm>(FormFillterContext<TForm> fillterContext, CancellationToken cancellationToken)
    {
        throw new NotImplementedException();
    }

    public override Task OnSuccessAsync<TForm>(FormFillterContext<TForm> fillterContext, OnSuccessContext onSuccessContext, CancellationToken cancellationToken)
    {
        throw new NotImplementedException();
    }
}

The things that are less requirements, are to ask the user and notify him if input was successful

This things are possible using OnBeginAskAsync and OnSuccessAsync methods.

There are more methods like these to handle different conditions. but these are less required methods.

Let's apply a simple implementation for OnBeginAskAsync.

public override async Task OnBeginAskAsync<TForm>(FormFillterContext<TForm> fillterContext, CancellationToken cancellationToken)
{
    await fillterContext.SendTextMessageAsync(
        $"Please send me a value for {fillterContext.PropertyName}",
        replyMarkup: new ForceReplyMarkup(),
        cancellationToken: cancellationToken);
}

You can customize this the way you like. ( different texts based on property name )

For now i don't want to say anything on partial successes. Therefor:

public override Task OnSuccessAsync<TForm>(FormFillterContext<TForm> fillterContext, OnSuccessContext onSuccessContext, CancellationToken cancellationToken)
{
    return Task.CompletedTask;
}

Create an scoped update handler for /form Command.

// FormHandler.cs
using Telegram.Bot.Types;
using TelegramUpdater;
using TelegramUpdater.FillMyForm;
using TelegramUpdater.UpdateContainer;
using TelegramUpdater.UpdateHandlers.ScopedHandlers.ReadyToUse;

namespace QuickExample;

[ApplyFilter(typeof(FormStartFilter))]
internal class FormHandler : ScopedMessageHandler
{
    protected override async Task HandleAsync(IContainer<Message> updateContainer)
    {
        var filler = new FormFiller<MySimpleForm>(
            updateContainer.Updater,
            defaultCancelTrigger: new MessageCancelTextTrigger());

        var form = await filler.FillAsync(updateContainer.Sender()!);

        if (form is not null)
        {
            await updateContainer.Response($"Thank you, {form}");
        }
        else
        {
            await updateContainer.Response($"Please try again later.");
        }
    }
}

// Create filter.
class FormStartFilter : Filter<Message>
{
    // Filter message text like /form
    public FormStartFilter() : base(FilterCutify.OnCommand("form")) { }
}

Go to Program.cs and setup your Updater.

// Program.cs
using QuickExample;
using Telegram.Bot;
using TelegramUpdater;

await new Updater(new TelegramBotClient("BotToken"))
    .AddScopedMessage<FormHandler>()
    .StartAsync();

Run the app and send /form command to your bot.

Add a cancel trigger

Cancel triggers are responsible for cancel request like /cancel.

Simplest way to add a cancel trigger for /cancel is to use MessageCancelTextTrigger (which is a ready-to-use cancel trigger) and FormPropertyAttribute.

Place attribute on your properties.

// MySimpleForm.cs
// -- sniff --

internal class MySimpleForm : AbstractForm
{
    [FormProperty(CancelTriggerType = typeof(MessageCancelTextTrigger))]
    public string FirstName { get; set; } = null!;

    [FormProperty(CancelTriggerType = typeof(MessageCancelTextTrigger))]
    public string? LastName { get; set; } // can be null, It's Nullable!

    [FormProperty(CancelTriggerType = typeof(MessageCancelTextTrigger))]
    public int Age { get; set; }

// -- sniff --

Run the app again and try sending /cancel while filling a form.

Default cancel trigger

You can also use a default cancel trigger which will be used for all of properties if they has no any cancel triggers already.

var filler = new FormFiller<MySimpleForm>(
    updateContainer.Updater,
    defaultCancelTrigger: new MessageCancelTextTrigger());

Make a property Required

Simply use [Required] from System.ComponentModel.DataAnnotations.

// MySimpleForm.cs
// -- sniff --

internal class MySimpleForm : AbstractForm
{
    [Required]
    [FormProperty(CancelTriggerType = typeof(MessageCancelTextTrigger))]
    public string FirstName { get; set; } = null!;

    [FormProperty(CancelTriggerType = typeof(MessageCancelTextTrigger))]
    public string? LastName { get; set; } // can be null, It's Nullable!

    [Required]
    [FormProperty(CancelTriggerType = typeof(MessageCancelTextTrigger))]
    public int Age { get; set; }

// -- sniff --

Now try using /cancel on required properties and see the form fails.

Other validations

You can set other limitation for user inputs. Eg: MaxLength for string.

// MySimpleForm.cs
// -- sniff --

[Required]
[MinLength(3)]
[MaxLength(32)]
public string FirstName { get; set; } = null!;

[MinLength(3)]
[MaxLength(32)]
public string? LastName { get; set; } // can be null, It's Nullable!

[Required]
[Range(13, 120)]
public int Age { get; set; }

// -- sniff --

At this point you better implement another method to handle invalid inputs response. The method is OnValidationErrorAsync.

I implemented it this way:

public override async Task OnValidationErrorAsync<TForm>(FormFillterContext<TForm> fillterContext, ValidationErrorContext validationErrorContext, CancellationToken cancellationToken)
{
    if (validationErrorContext.RequiredItemNotSupplied)
    {
        await fillterContext.SendTextMessageAsync(
            $"{fillterContext.PropertyName} was required! You can't just leave it.");
    }
    else
    {
        await fillterContext.SendTextMessageAsync(
            $"You input is invalid for {fillterContext.PropertyName}.\n" +
            string.Join("\n", validationErrorContext.ValidationResults.Select(
                x => x.ErrorMessage)));
    }
}

Go ahead! run the bot, try some invalid stuff and watch.

Add retry options

You can add retry option for a property. it means the bot will try again if something gets invalid.

[Required]
[MinLength(3)]
[MaxLength(32)]
[FillPropertyRetry(FillingError.ValidationError, 2)]
public string FirstName { get; set; } = null!;

Now user has two more chances if he/she fails.

What's next?

More control

You can implement more response methods to get more control.

• OnTimeOutAsync
• OnConversationErrorAsync
• OnUnrelatedUpdateAsync
• OnCancelAsync

God like control

In the most advanced use of package you can handle more complex conversations. As instance you may want to show a menu to the user using inline buttons and catch the response.

It's possible using UpdateCrackers.

Take a look at SurveyBot. Crackers are added in handler ( Program.cs )