README_generator.md

Adding Generators

The generator types are the moustache formatted values inside the template JSON which dictate how the values will be created in the output JSON. A quick example is {{bool()}} which will randomly output either true or false. The interface to implement for this is IDataGenerator. Your plugin will reference that assembly, compile, and then the executing program will reference your plugin. Here is a walkthrough of a fairly simply generator that is included in the core library:

 public sealed class IntegerGenerator : IDataGenerator
{
    private readonly long _max;
    private readonly long _min;

    // IDataGenerator properties
    public string Description { get; } = "Generates random 64-bit integers between min and max";

    public string Signature { get; } = "{{integer(min: int64 = int64.min / 2, max: int64 = int64.max / 2)}}";

    public IntegerGenerator(string input)
    {
        // This constructor is optional in general, but required for
        // generators that accept arguments

        // See link below for this class
        var parser = new IntegerGeneratorArgs(input);
        var (min, max) = parser.Parse();
        _min = min;
        _max = max;
    }

    public IntegerGenerator()
    {
        // This constructor is not used in general, but rather for the
        // --list-generators mode so its functionality can be arbitrary
        var parser = new IntegerGeneratorArgs("()");
        var (min, max) = parser.Parse();
        _min = min;
        _max = max;
    }

    public Task<object> GenerateValueAsync()
    {
        // ThreadSafeRandom is just a locked wrapper around a static Random
        // instance and NextInt64 is an extension method for creating
        // 64-bit random numbers.
        return Task.FromResult<object>(ThreadSafeRandom.NextInt64(_min, _max));
    }
}

The IntegerGeneratorArgs class is somewhat large and complex looking so it is not included above but you can find it here. It makes use of the csly lexer/parser library to parse the arguments out of the string.

There are two properties and one method to implement in the interface:

• Description: Used for the --list-generators argument of the program to give an indication of what the generator does.
• Signature: Also used for the --list-generators argument to show the arguments used. Optional arguments will have = <default value> after them.
• GenerateValueAsync: Generates the next value for use in the output JSON. Most are non-async and will return Task.FromResult but for future-proofing the ability to run asynchronously was used (random numbers from an Internet hardware source?)