Which design pattern to use for my use case?

Question

I have a use case where the input is set of parameters (say A, B, C, D) and data (say XYZ). Based on the parameters(A,B,C,D) i have to process the data(XYZ) and respond back. The processing logic can be unique or common based on parameters(say do something#1 only when A, do something#2 when A and C, do something#2 when B, C and D and so on). I might also need to maintain the order of processing.

The current implementation is based on if-else loops. I am looking at chain of responsibility, pipeline design patterns. But is there any other suitable design pattern for the above task ?

Example using if-else blocks:

I/P : A={A1,A2,A3},B={B1,B2,B3},C={C1,C2,C3},D={D1,D2,D3} and XYZ="foo"

if (A == A1)
{
    //dosomething-A1

    if (B == B1)
    {
        //dosomething-B1

        if (C == C2)
        {
            //dosomething-C2
        }
    }
    else if (B == B2)
    {
        //dosomething-B2
    }

    if (C == C2)
    {
        //dosomething-C2

        if (D == D1)
        {
            //dosomething-D1
        }
        else if (D == D3)
        {
            //dosomething-D3
        }
    }
}
else if (A == A2)
{
    //dosomething-A2
    ...
}
else if (A == A3)
{
    //dosomething-A3
    ...
}

Answer 1

Chain seem to fit this very well, if it is reused. Another option is to use handlers stored in a map, where the key is the appropriate parameter value. This works well for limited set of possible values passed as the parameters. You'll get something like:

handlers.get( a ).handle(XYZ)

So, completely if-less on your part. But again, this does not fit all purposes.

Answer 2

Look for something like command pattern. Based on the parameters data need to be processed. Internal implementation should not be exposed outside. So, from exposed interface perspective it has to take parameter and data and command pattern need to identify which method to execute based on parameters.