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=====

Dokka is a documentation engine for Kotlin, performing the same function as javadoc for Java.
Just like Kotlin itself, Dokka fully supports mixed-language Java/Kotlin projects. It understands
standard Javadoc comments in Java files and [KDoc comments](https://kotlinlang.org/docs/reference/kotlin-doc.html) in Kotlin files,
and can generate documentation in multiple formats including standard Javadoc, HTML and Markdown.

## Using Dokka

### Using the Gradle plugin

```groovy
buildscript {
    repositories {
        jcenter()
    }

    dependencies {
        classpath "org.jetbrains.dokka:dokka-gradle-plugin:${dokka_version}"
    }
}

apply plugin: 'org.jetbrains.dokka'
```

The plugin adds a task named "dokka" to the project.
 
Minimal dokka configuration:

```groovy
dokka {
    outputFormat = 'html' 
    outputDirectory = "$buildDir/javadoc"
}
```

[Output formats](#output_formats)
 
The available configuration options are shown below:

```groovy
dokka {
    moduleName = 'data'
    outputFormat = 'html'
    outputDirectory = "$buildDir/javadoc"
    processConfigurations = ['compile', 'extra']
    includes = ['packages.md', 'extra.md']
    samples = ['samples/basic.kt', 'samples/advanced.kt']
    
    jdkVersion = 6 // Used for linking to JDK
    
    skipDeprecated = false // Do not output deprecated members, applies globally, can be overridden by packageOptions
    reportNotDocumented = true // Emit warnings about not documented members, applies globally, also can be overridden by packageOptions
    
    skipEmptyPackages = true // Do not create index pages for empty packages
 
    impliedPlatforms = ["JVM"] // See platforms section of documentation 
    
    // Selector for resolving dokkaFatJar or File for local path to dokka-fatjar
    dokkaFatJar = "org.jetbrains.dokka:dokka-fatjar:$dokka_version"
    
    // By default, sourceRoots is taken from processConfigurations
    // Short form sourceRoots
    // If specified, processConfigurations are ignored
    sourceDirs = files('src/main/kotlin')
    
    // By default, sourceRoots is taken from processConfigurations
    // Full form sourceRoot declaration
    // If specified, processConfigurations are NOT ignored, and sourceRoots are appended
    // Repeat for multiple sourceRoots
    sourceRoot {
        // Path to source root
        path = "src" 
        // See platforms section of documentation 
        platforms = ["JVM"] 
    }
    
    // Mapping to source
    // Repeat for multiple mappings
    linkMapping {
        dir = "src/main/kotlin"
        url = "https://github.com/cy6erGn0m/vertx3-lang-kotlin/blob/master/src/main/kotlin"
        suffix = "#L"
    }
    
    // No default documentation link to kotlin-stdlib
    noStdlibLink = false
    
    // Repeat for multiple links
    externalDocumentationLink {
        url = new URL("https://example.com/docs")
        // If package-list file located in non-standard location
        // packageListUrl = new URL("file:///home/user/localdocs/package-list") 
    }
    
    // Repeat for multiple packageOptions
    packageOptions {
        prefix = "kotlin" // will match kotlin and all sub-packages of it
        // All options are optional, default values are below:
        skipDeprecated = false
        reportUndocumented = true // Emit warnings about not documented members 
        includeNonPublic = false
    }
}
```

To get it generated use gradle `dokka` task

```bash
./gradlew dokka
```

More dokka tasks can be added to a project like this:

```groovy
task dokkaJavadoc(type: org.jetbrains.dokka.gradle.DokkaTask) {
    outputFormat = 'javadoc'
    outputDirectory = "$buildDir/javadoc"
}
```

Please see the [Dokka Gradle example project](https://github.com/JetBrains/kotlin-examples/tree/master/gradle/dokka-gradle-example) for an example.

#### Android

If you are using Android there is a separate gradle plugin. Just make sure you apply the plugin after
`com.android.library` and `kotlin-android`.

```groovy
buildscript {
    repositories {
        jcenter()
    }

    dependencies {
        classpath "org.jetbrains.dokka:dokka-android-gradle-plugin:${dokka_version}"
    }
}

apply plugin: 'com.android.library'
apply plugin: 'kotlin-android'
apply plugin: 'org.jetbrains.dokka-android'
```

### Using the Maven plugin

The Maven plugin is available in JCenter. You need to add the JCenter repository to the list of plugin repositories if it's not there:

```xml
<pluginRepositories>
    <pluginRepository>
        <id>jcenter</id>
        <name>JCenter</name>
        <url>https://jcenter.bintray.com/</url>
    </pluginRepository>
</pluginRepositories>
```

Minimal maven configuration is

```xml
<plugin>
    <groupId>org.jetbrains.dokka</groupId>
    <artifactId>dokka-maven-plugin</artifactId>
    <version>${dokka.version}</version>
    <executions>
        <execution>
            <phase>pre-site</phase>
            <goals>
                <goal>dokka</goal>
            </goals>
        </execution>
    </executions>
</plugin>
```

By default files will be generated in `target/dokka`.

The following goals are provided by the plugin:

  * `dokka:dokka` - generate HTML documentation in Dokka format (showing declarations in Kotlin syntax);
  * `dokka:javadoc` - generate HTML documentation in JavaDoc format (showing declarations in Java syntax);
  * `dokka:javadocJar` - generate a .jar file with JavaDoc format documentation.

The available configuration options are shown below:

```xml
<plugin>
    <groupId>org.jetbrains.dokka</groupId>
    <artifactId>dokka-maven-plugin</artifactId>
    <version>${dokka.version}</version>
    <executions>
        <execution>
            <phase>pre-site</phase>
            <goals>
                <goal>dokka</goal>
            </goals>
        </execution>
    </executions>
    <configuration>
    
        <!-- Set to true to skip dokka task, default: false -->
        <skip>false</skip>
    
        <!-- Default: ${project.artifactId} -->
        <moduleName>data</moduleName>
        <!-- See list of possible formats below -->
        <outFormat>html</outFormat>
        <!-- Default: ${project.basedir}/target/dokka -->
        <outputDir>some/out/dir</outputDir>
        
        <!-- List of '.md' files with perPackage and module docs -->
        <includes>
            <file>packages.md</file>
            <file>extra.md</file>
        </includes>
        
        <!-- List of sample roots -->
        <samplesDirs>
            <dir>src/test/samples</dir>
        </samplesDirs>
        
        <!-- Used for linking to JDK, default: 6 -->
        <jdkVersion>6</jdkVersion>
        
        <!-- Do not output deprecated members, applies globally, can be overridden by packageOptions -->
        <skipDeprecated>false</skipDeprecated> 
        <!-- Emit warnings about not documented members, applies globally, also can be overridden by packageOptions -->
        <reportNotDocumented>true</reportNotDocumented>             
        <!-- Do not create index pages for empty packages -->
        <skipEmptyPackages>true</skipEmptyPackages> 
        
        <!-- See platforms section of documentation -->
        <impliedPlatforms>
            <platform>JVM</platform>
        </impliedPlatforms>
        
        <!-- Short form list of sourceRoots, by default, set to ${project.compileSourceRoots} -->
        <sourceDirectories>
            <dir>src/main/kotlin</dir>
        </sourceDirectories>
        
        <!-- Full form list of sourceRoots -->
        <sourceRoots>
            <root>
                <path>src/main/kotlin</path>
                <!-- See platforms section of documentation -->
                <platforms>JVM</platforms>
            </root>
        </sourceRoots>
        
        <sourceLinks>
            <link>
                <dir>${project.basedir}/src/main/kotlin</dir>
                <url>http://github.com/me/myrepo</url>
                <!-- Line suffix, e.g #L -> /me/myrepo/some.html#L99 -->
                <urlSuffix>#L</urlSuffix>
            </link>
        </sourceLinks>
        
        <!-- No default documentation link to kotlin-stdlib -->
        <noStdlibLink>false</noStdlibLink>
        
        <externalDocumentationLinks>
            <link>
                <url>https://example.com/docs</url>
                <!-- If package-list file located in non-standard location -->
                <!-- <packageListUrl>file:///home/user/localdocs/package-list</packageListUrl> -->
            </link>
        </externalDocumentationLinks>

        <perPackageOptions>
            <packageOptions>
                <!-- Will match kotlin and all sub-packages of it -->
                <prefix>kotlin</prefix>
                
                <!-- All options are optional, default values are below: -->
                <skipDeprecated>false</skipDeprecated>
                <!-- Emit warnings about not documented members  -->
                <reportUndocumented>true</reportUndocumented>
                <includeNonPublic>false</includeNonPublic>
            </packageOptions>
        </perPackageOptions>
    </configuration>
</plugin>
```

Please see the [Dokka Maven example project](https://github.com/JetBrains/kotlin-examples/tree/master/maven/dokka-maven-example) for an example.

[Output formats](#output_formats)

### Using the Ant task

The Ant task definition is also contained in the dokka-fatjar.jar referenced above. Here's an example of using it:

```xml
<project name="Dokka" default="document">
    <typedef resource="dokka-antlib.xml" classpath="dokka-fatjar.jar"/>

    <target name="document">
        <dokka src="src" outputdir="doc" modulename="myproject"/>
    </target>
</project>
```

The Ant task supports the following attributes:

  * `outputDir` - the output directory where the documentation is generated
  * `outputFormat` - the output format (see the list of supported formats above)
  * `classpath` - list of directories or .jar files to include in the classpath (used for resolving references)
  * `samples` - list of directories containing sample code (documentation for those directories is not generated but declarations from them can be referenced using the `@sample` tag)
  * `moduleName` - the name of the module being documented (used as the root directory of the generated documentation)
  * `include` - names of files containing the documentation for the module and individual packages
  * `skipDeprecated` - if set, deprecated elements are not included in the generated documentation
  * `jdkVersion` - version for linking to JDK
  * `impliedPlatforms` - See [platforms](#platforms) section
  * `<sourceRoot path="src" platforms="JVM" />` - analogue of src, but allows to specify [platforms](#platforms) 
  * `<packageOptions prefix="kotlin" includeNonPublic="false" reportUndocumented="true" skipDeprecated="false"/>` - 
    Per package options for package `kotlin` and sub-packages of it
  * `noStdlibLink` - No default documentation link to kotlin-stdlib
  * `<externalDocumentationLink url="https://example.com/docs" packageListUrl="file:///home/user/localdocs/package-list"/>` -
    linking to external documentation, packageListUrl should be used if package-list located not in standard location
    

### Using the Command Line

To run Dokka from the command line, download the [Dokka jar](https://github.com/Kotlin/dokka/releases/download/0.9.10/dokka-fatjar.jar).
To generate documentation, run the following command:

    java -jar dokka-fatjar.jar <source directories> <arguments>

Dokka supports the following command line arguments:

  * `-output` - the output directory where the documentation is generated
  * `-format` - the output format:
    * `html` - HTML (default)
    * `markdown` - Markdown
    * `gfm` - GitHub-Flavored Markdown
    * `jekyll` - Markdown adapted for Jekyll sites
    * `javadoc` - Javadoc (showing how the project can be accessed from Java)
  * `-classpath` - list of directories or .jar files to include in the classpath (used for resolving references)
  * `-samples` - list of directories containing sample code (documentation for those directories is not generated but declarations from them can be referenced using the `@sample` tag)
  * `-module` - the name of the module being documented (used as the root directory of the generated documentation)
  * `-include` - names of files containing the documentation for the module and individual packages
  * `-nodeprecated` - if set, deprecated elements are not included in the generated documentation
  * `-impliedPlatforms` - List of implied platforms (comma-separated)
  * `-packageOptions` - List of package options in format `prefix,-deprecated,-privateApi,+warnUndocumented;...` 
  * `-links` - External documentation links in format `url^packageListUrl^^url2...`
  * `-noStdlibLink` - Disable documentation link to stdlib

### Output formats<a name="output_formats"></a>
  * `html` - minimalistic html format used by default
  * `javadoc` - Dokka mimic to javadoc
  * `html-as-java` - as `html` but using java syntax
  * `markdown` - Markdown structured as `html`
    * `gfm` - GitHub flavored markdown  
    * `jekyll` - Jekyll compatible markdown 
  * `kotlin-website*` - internal format used for documentation on [kotlinlang.org](https://kotlinlang.org)

### Platforms<a name="platforms"></a>
Dokka can annotate elements with special `platform` block with platform requirements 

Example of usage can be found on [kotlinlang.org](https://kotlinlang.org/api/latest/jvm/stdlib/)

Each source root has list of platforms for which members are suitable. 
Also, the list of 'implied' platforms is passed to Dokka, 
if member suitable for all platforms from implied platform set, 
then only platforms which not contained in the set will be shown.

## Dokka Internals

### Documentation Model

Dokka uses Kotlin-as-a-service technology to build `code model`, then processes it into `documentation model`.
`Documentation model` is graph of items describing code elements such as classes, packages, functions, etc.

Each node has semantic attached, e.g. Value:name -> Type:String means that some value `name` is of type `String`.

Each reference between nodes also has semantic attached, and there are three of them:

1. Member - reference means that target is member of the source, form tree.
2. Detail - reference means that target describes source in more details, form tree.
3. Link - any link to any other node, free form.

Member & Detail has reverse Owner reference, while Link's back reference is also Link.

Nodes that are Details of other nodes cannot have Members.

### Rendering Docs

When we have documentation model, we can render docs in various formats, languages and layouts. We have some core services:

* FormatService -- represents output format
* LocationService -- represents folder and file layout
* SignatureGenerator -- represents target language by generating class/function/package signatures from model

Basically, given the `documentation` as a model, we do this:

```kotlin
    val signatureGenerator = KotlinSignatureGenerator()
    val locationService = FoldersLocationService(arguments.outputDir)
    val markdown = JekyllFormatService(locationService, signatureGenerator)
    val generator = FileGenerator(signatureGenerator, locationService, markdown)
    generator.generate(documentation)
```

## Building Dokka

Dokka is built with Gradle. To build it, use `./gradlew build`.
Alternatively, open the project directory in IntelliJ IDEA and use the IDE to build and run Dokka.