The quickest way to get started is to copy an existing extension's folder structure and renaming it as needed. Of course, that also means that there's plenty of existing extensions that you can reference as you go!
| `pkgNameSuffix` | A unique suffix added to `eu.kanade.tachiyomi.extension`. The language and the site name should be enough. Remember your catalogue code implementation must be placed in this package. |
| `extClass` | Points to the catalogue class. You can use a relative path starting with a dot (the package name is the base path). This is required for Tachiyomi to instantiate the catalogue. |
| `extVersionCode` | The version code of the catalogue. This must be increased with any change to the implementation and cannot be `0`. |
| `libVersion` | The version of the [extensions library](https://github.com/inorichi/tachiyomi-extensions-lib)* used. |
The catalogue's version name is based off of `libVersion` and `extVersionCode`. With the example used above, the version of the catalogue would be `1.2.1`.
You may find yourself needing additional functionality and wanting to add more dependencies to your `build.gradle` file. Since extensions are run within the main Tachiyomi app, you can make use of [its dependencies](https://github.com/inorichi/tachiyomi/blob/master/app/build.gradle).
For example, an extension that needs Gson could add the following:
```
dependencies {
compileOnly 'com.google.code.gson:gson:2.8.2'
}
```
Notice that we're using `compileOnly` instead of `implementation`, since the app already contains it. You could use `implementation` instead, if it's a new dependency, or you prefer not to rely on whatever the main app has (at the expensive of app size).
### Core stubs and libraries
#### Extensions library
Extensions rely on stubs defined in [tachiyomi-extensions-lib](https://github.com/inorichi/tachiyomi-extensions-lib), which simply provides some interfaces for compiling extensions. These interfaces match what's found in the main Tachiyomi app. The exact version used is configured with `libVersion`. The latest version should be preferred.
#### Preference stub
[`preference-stub`](https://github.com/inorichi/tachiyomi-extensions/tree/master/lib/preference-stub) provides the [`ConfigurableSource` interface](https://github.com/inorichi/tachiyomi-extensions/blob/master/lib/preference-stub/src/main/java/eu/kanade/tachiyomi/source/ConfigurableSource.java) for extensions, as well as stubs for Android preferences.
```
dependencies {
compileOnly project(':preference-stub')
}
```
#### Duktape stub
[`duktape-stub`](https://github.com/inorichi/tachiyomi-extensions/tree/master/lib/duktape-stub) provides stubs for using Duktape functionality without pulling in the full library. Functionality is bundled into the main Tachiyomi app.
```
dependencies {
compileOnly project(':duktape-stub')
}
```
#### Rate limiting library
[`lib-ratelimit`](https://github.com/inorichi/tachiyomi-extensions/tree/master/lib/ratelimit) is a library for adding rate limiting functionality.
```
dependencies {
implementation project(':lib-ratelimit')
}
```
### Useful knowledge
An extension should at least extend the [`ParsedHttpSource`](https://github.com/inorichi/tachiyomi-extensions-lib/blob/master/library/src/main/java/eu/kanade/tachiyomi/source/online/ParsedHttpSource.kt) class.
