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https://github.com/timnew/marsrover

Well, this is an archive of some legacy codes that I wrote in roughly 10 years ago.
https://github.com/timnew/marsrover

Last synced: about 1 month ago
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Well, this is an archive of some legacy codes that I wrote in roughly 10 years ago.

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README 

          
Language and Tools

==========================

This solution is my answer for Mars Rovers Problem

All application is written in C# 4.0 with Visual Studio 2010 and Expression Blend 4.

So to build the solution requires the VS 2010 or .net 4 SDK.



Project Organization

===========================

There are 5 projects included in the solution.

1. MarsRovers

MarsRovers is the kernel class library, which contains the simulation engine and any

other key features related to the simulation.



2. MarsRover.Test

MarsRover.Test is the unit test project for MarsRovers. And for convenience reason,

Mars Rovers is internal visible to it.



3. MarsRovers.Console

MarsRovers.Console is a command-line based shell for MarsRovers. It enables user to

config the MarsRovers simulation engine, and review the result.



4. MarsRovers.Wpf

MarsRovers.Wpf is a super simple wpf application that enables user to watch the simulations

process in visual. For time reason, the app is not in product quality, which is just for fun.

Since I don't have enough time to design and implement full-functional UI for configuration,

I uses a tricky way to collect configuration from a command line window.

Just click the configure button, and type the configuration in command-line as usual.

Then click Start, then simulation will begin.



5. Windy.Foundation

It is actually a subset of classes of my own application framework. It provides some support

mechanism and features.



A not so brief description of the design

==================================================================

Classes in MarsRovers can be divided into following categories:

1. Models

Classes in this category, such as Rover, Plateau, is the foundation models for the simulation,

which are abstracted from the problem description.



2. ConfigurationProviders

Configuration provider is a adapter class that retrieves the simulation configuration from

different sources, such as Console or TextReader(actually can be a text file, by wrapping it

with StreamReader.) or just a hard-coded configuration. It ensures the capability to extend the

simulation engine.

After collection the configuration, then it initializes the models,and drives them into a state ready

for simulation.



3. Actions

IRoverAction is the abstraction of all possible actions that rover can perform. And there are 3 concrete

actions in project by default: move, turn left and turn right.

Actually I implemented a super lightweight dependency injection mechanism in project, which searches the

assemblies and instantiates all the actions it found in a global cache, which I called action pool.

Action can apply to rover to change the rover's state, such as position or orientation. There might be tons

of redundant actions being used in simulation, but actually there are only few instances cached in the pool.

For extensibility purpose, actually the action can be some more complicated action, such as turn back or even

move the boundary of plateau. As you can see, to add a new action into system in super easy.



4. Rover Controllers

In my solution, the instructions are not assigned to the rover itself, instead I assigned them to a controller,

then the controller take the responsibility to parse the instructions and push corresponding action to rover while

timer ticks.

Actually, rover controller shouldn't be push actions to rover according to the predefined command. It can works

in a more intelligent way, such as lead a rover follows another or drives the rover run around the plateau.

To introduce such an AI controller is also not too hard.



5. Timers

Timer is the driver of the simulation, it push time slice to the controllers in a order way, then collects the

feedback from controllers to determine where more time slices are needed.

It is possible to change the simulation pace by choosing different timers.

Timer is also extensible, actually, in WPF Shell, I introduce a new type of timer, which ticks depends on a

Dispatcher Timer, which ensure these is no cross thread violation in the simulation.



Timer-Controller-Rover data flow

Actually, I introduced simplified RX framework into the simulation

engine.

Timer push the time slice to the controller, and then controller push the corresponding instruction to rover.

Then rover changes it state, and then push the property changed notification to UI.

As you can see, the data flow is not pull-based but push-based, which provides a better control to simulation

timing, and the data flow is more smooth than the pull-based.

And there is an interesting design that I'd like to introduce a little bit:

Data in push model can only flows from the observee to observer, which means the data flow in one-way. But timer

need the feedback from the controllers to find out whether all the controllers had pushed all the instructions to

the rovers.

To solve this conflict, I introduce the time slice class, which is a reference type. The timer keep the reference

to it, and then push it to the controllers. Then the time slices passes through all the controllers, and controllers

reports their status to time slice. And finally timer check the data in time slice, then it knows what it need to know.



And another interesting design: the time slice controller

I wants to reuse the time slice rather than create a new one each time, which means the properties of time slice should

be mutable. At the same time, I don't want controller be able to modify the time slice's property

which means the properties should be read-only.

To solve the conflict, I introduces a controller, which is a delegate passed out from time slice internal methods.

the controller works a token, objects can modify the properties of time slice in specific way with the token.



Build Instruction

==========================

And there are 3rd party dependencies involved in the some projects.

For some reason, I didn't include the binaries into the repository, instead I use nuget

to fetch these dependencies while building the project.

To build the solution, you should install nuget first and make sure path of nuget has been

added into the path environment variable, then everything will be done automatically.



Or you can manually install these packages by nuget or just downloading them from CodePlex

or Google Code.



Here is the list of 3rd party dependencies:

MarsRover.Test requires

xunit version: 1.8.0.1545

Moq   version: 4.0.10827



MarsRovers.Wpf requires

Mvvm Light toolkit version: 3.0.2



Besides 3rd libraries, the solution also involved the Code Analysis and Code Contract.

To enable the full features, a Code Contract VS Plug-in might be necessary.