Thanks for helping us reverse engineer *The Legend of Zelda: Majora's Mask* for the N64!
All contributions are welcome. This is a group effort, and even small contributions can make a difference. Some tasks also don't require much knowledge to get started.
This document is meant to be a set of tips and guidelines for contributing to the project.
For general information about the project, see [our readme](https://github.com/zeldaret/mm/blob/master/README.md).
Most discussions happen on our [Discord Server](https://discord.zelda64.dev) where you are welcome to ask if you need help getting started, or if you have any questions regarding this project and other decompilation projects.
- [Trello board](https://trello.com/b/ruxw9n6m/majoras-mask-decompilation) - We use this to track decompilation progress, not GitHub Issues.
- [Installation guide](https://github.com/zeldaret/mm/blob/master/README.md#installation) - Instructions for getting this repository set up and built on your machine.
- [Code Review Guidelines](REVIEWING.md) - These are the guidelines that reviewers will be using when reviewing your code. Good to be familiar with these before submitting your code.
- [Zelda 64 Reverse Engineering Website](https://zelda64.dev/) - Our homepage, with links to other resources.
- [Introduction to OOT decomp](https://github.com/zeldaret/oot/blob/master/docs/tutorial/contents.md) - A very detailed tutorial on how to get started with decomp. For OOT, but largely applicable to MM as well.
- The `#resources` channel on the Discord contains many more links
Getting Started
---------------
### What should I know to take part?
Basic knowledge of C, particularly arrays and pointers, is extremely useful. Knowledge of MIPS is not required initially, you can pick it up as you work through some decompilation.
You should be familiar with using git and GitHub. There are a number of tutorials available online, [such as this one](https://github.com/firstcontributions/first-contributions) which can help you get started.
The most useful knowledge to have is a general understanding of how the game works. An afternoon of constructive mucking about in the [OOT Practice Rom](http://practicerom.com/) (aka GZ) or the [MM Practice Rom](https://kz.zeldacodes.org/) (aka KZ) will be very beneficial if you have not looked at either of the N64 Zelda's internals before.
The [OOT Decompilation Project](https://github.com/zeldaret/oot) is farther along than this project, so it can also be a great resource.
This project only uses *publicly available code*.
Anyone who wishes to contribute to the OOT or MM projects **must not have accessed leaked source code at any point in time** for Nintendo 64 SDK, iQue player SDK, libultra, Ocarina of Time, Majora's Mask, Animal Crossing/Animal Forest, or any other game that shares the same game engine or significant portions of code to a Zelda 64 game or any other console similar to the Nintendo 64.
### Environment Setup
Get started by following the [installation guide in the readme](https://github.com/zeldaret/mm/blob/master/README.md#installation).
You should be able to build a matching ROM before you start making any changes.
### First Contribution
Usually, the best place to get started is to decompile an actor overlay.
An *actor* is any thing in the game that moves or performs actions or interactions. This includes things like Link, enemies, NPCs, doors, pots, etc.
You should [join the Discord](https://discord.zelda64.dev/) to say hello and get suggestions on where to start on the `#mm-decomp` channel.
We track who is working on what on the [Trello board](https://trello.com/b/ruxw9n6m/majoras-mask-decompilation).
After joining the Discord, ask to be added to the Trello board so you can claim your code file and avoid duplicate work. You may need to add a card if a card for your file does not currently exist.
The work flow is: Reserve a file, decompile it, submit a PR, and then repeat while addressing review comments. The expectation is that one reservation goes to one file which ends up in a one file PR.
Please note that unless it is communicated beforehand you will be expected to fully complete the file if you reserve it on Trello. Exceptions are always easy to approve if it's communicated to the team. Real life circumstances can prevent someone from finishing. In these cases they should link their repo/branch in the trello and unreserve immediately. Communicate any issues with your reservations as early as possible.
- Word order in names are from least-to-most specific (`DM_RAVINE_STATE_ACTIVE`, not `DM_RAVINE_ACTIVE_STATE`)
- Functions, structs, unions, enums, and typedefs are `TitleCase` (`DmRavine`)
- "Methods" for objects separate the object from the verb with an underscore (`DmRavine_Init`)
- Variable names are `camelCase` (`actionFunc`)
- Global variables start with `g` (`gSaveContext`)
- Static global variables start with `s` (`sSphereInit`)
- Macros and enum constants are `SCREAMING_SNAKE_CASE` (`DM_RAVINE_STATE_ACTIVE`)
- Public structs, enums, and constants should be defined in the header file in the following cases:
- The primary `Actor` struct (`DmRavine`)
- The actor's `InitVars`, as an `extern` symbol (`Dm_Ravine_InitVars`)
- Types used in other public declarations, like `actionFunc` typedefs (`DmRavineActionFunc`)
- Macros and enums for accessing & setting actor `params`
- The struct/enum/define is needed by other files
- Trailing commas in array and struct definitions (see `EnJcMatoDamageTable`)
- Constants converted to whichever looks best in context: hexadecimal, decimal, or float
- Rotation angles should always be in hexadecimal
- Define macros for bitwise access to `actor->params`
### `NON_MATCHING` & `NON_EQUIVALENT`
If you make significant progress on decompiling a function, but can't get it to match perfectly, you can use a `NON_MATCHING` block to commit your code but have it excluded from the build, like so:
Before using `NON_MATCHING`, first try to use the [decomp-permuter](tools/decomp-permuter) tool to find a closer match.
`NON_EQUIVALENT` can be used with the same syntax as `NON_MATCHING`, but it is used to mark sections of code which do not match *and* do not have the same behavior as the original code.
### Matching vs. Documenting
Usually, the first step of decompiling a section of code is to get it *matching*: to produce a C version of the code that can be compiled into an identical ROM.
However, the goal of this project is to produce a codebase that can be understood and modified.
So, beyond producing matching C code, the next steps are *documenting* the code.
Documenting is more than just adding comments. Documenting also includes:
- Renaming functions, variables, and struct members
- Using (or adding) constants, enums, and macros when possible
- Explaining sections of code that are not straightforward
Overlays are not required to be documented at this time, but `code/` and `boot/` should be documented. When documentation on a file has been started it should be as complete as possible.
If there is an error, double-check that you can successfully `make clean && make` locally. If the build is OK, the next thing to check is that all added/modified files were `git add`-ed to your commit. The final check before posting on Discord for help is that there are no new warnings added to the code causing Jenkins to fail. You can check this by running: `tools/warnings_count/check_new_warnings.sh`.
Each PR needs a review from one reviewer and the project lead.
The PR author marks the comments as resolved: the commenter may not have permissions to do so.
Once all comments are addressed, it is courteous to ping the reviewer on either Discord or GitHub via re-requesting a review.
After all the comments are addressed and at least one contributor has approved the review, the project lead can then review and merge the code.
The project lead is also responsible for ensuring that all of these procedures are followed.
Throughout the PR process, you (the author) should update the card on [Trello board](https://trello.com/b/ruxw9n6m/majoras-mask-decompilation) with the appropriate column and labels.
