src/Model/Content.kt

package org.jetbrains.dokka

public interface ContentNode {
    val textLength: Int
}

public object ContentEmpty : ContentNode {
    override val textLength: Int get() = 0
}

public open class ContentBlock() : ContentNode {
    val children = arrayListOf<ContentNode>()

    fun append(node: ContentNode)  {
        children.add(node)
    }

    fun isEmpty() = children.isEmpty()

    override fun equals(other: Any?): Boolean =
        other is ContentBlock && javaClass == other.javaClass && children == other.children

    override fun hashCode(): Int =
        children.hashCode()

    override val textLength: Int
        get() = children.sumBy { it.textLength }
}

enum class IdentifierKind {
    TypeName,
    ParameterName,
    AnnotationName,
    SummarizedTypeName,
    Other
}

public data class ContentText(val text: String) : ContentNode {
    override val textLength: Int
        get() = text.length
}

public data class ContentKeyword(val text: String) : ContentNode {
    override val textLength: Int
        get() = text.length
}

public data class ContentIdentifier(val text: String, val kind: IdentifierKind = IdentifierKind.Other) : ContentNode {
    override val textLength: Int
        get() = text.length
}

public data class ContentSymbol(val text: String) : ContentNode {
    override val textLength: Int
        get() = text.length
}

public data class ContentEntity(val text: String) : ContentNode {
    override val textLength: Int
        get() = text.length
}

public object ContentNonBreakingSpace: ContentNode {
    override val textLength: Int
        get() = 1
}

public object ContentSoftLineBreak: ContentNode {
    override val textLength: Int
        get() = 0
}

public object ContentIndentedSoftLineBreak: ContentNode {
    override val textLength: Int
        get() = 0
}

public class ContentParagraph() : ContentBlock()
public class ContentEmphasis() : ContentBlock()
public class ContentStrong() : ContentBlock()
public class ContentStrikethrough() : ContentBlock()
public class ContentCode() : ContentBlock()
public class ContentBlockCode(val language: String = "") : ContentBlock()

public abstract class ContentNodeLink() : ContentBlock() {
    abstract val node: DocumentationNode?
}

public class ContentNodeDirectLink(override val node: DocumentationNode): ContentNodeLink() {
    override fun equals(other: Any?): Boolean =
            super.equals(other) && other is ContentNodeDirectLink && node.name == other.node.name

    override fun hashCode(): Int =
            children.hashCode() * 31 + node.name.hashCode()
}

public class ContentNodeLazyLink(val linkText: String, val lazyNode: () -> DocumentationNode?): ContentNodeLink() {
    override val node: DocumentationNode? get() = lazyNode()

    override fun equals(other: Any?): Boolean =
            super.equals(other) && other is ContentNodeLazyLink && linkText == other.linkText

    override fun hashCode(): Int =
            children.hashCode() * 31 + linkText.hashCode()
}

public class ContentExternalLink(val href : String) : ContentBlock() {
    override fun equals(other: Any?): Boolean =
        super.equals(other) && other is ContentExternalLink && href == other.href

    override fun hashCode(): Int =
        children.hashCode() * 31 + href.hashCode()
}

public class ContentUnorderedList() : ContentBlock()
public class ContentOrderedList() : ContentBlock()
public class ContentListItem() : ContentBlock()

public class ContentHeading(val level: Int) : ContentBlock()

public class ContentSection(public val tag: String, public val subjectName: String?) : ContentBlock() {
    override fun equals(other: Any?): Boolean =
        super.equals(other) && other is ContentSection && tag == other.tag && subjectName == other.subjectName

    override fun hashCode(): Int =
        children.hashCode() * 31 * 31 + tag.hashCode() * 31 + (subjectName?.hashCode() ?: 0)
}

public object ContentTags {
    val Description = "Description"
    val SeeAlso = "See Also"
}

fun content(body: ContentBlock.() -> Unit): ContentBlock {
    val block = ContentBlock()
    block.body()
    return block
}

fun ContentBlock.text(value: String) = append(ContentText(value))
fun ContentBlock.keyword(value: String) = append(ContentKeyword(value))
fun ContentBlock.symbol(value: String) = append(ContentSymbol(value))
fun ContentBlock.identifier(value: String, kind: IdentifierKind = IdentifierKind.Other) = append(ContentIdentifier(value, kind))
fun ContentBlock.nbsp() = append(ContentNonBreakingSpace)
fun ContentBlock.softLineBreak() = append(ContentSoftLineBreak)
fun ContentBlock.indentedSoftLineBreak() = append(ContentIndentedSoftLineBreak)

fun ContentBlock.strong(body: ContentBlock.() -> Unit) {
    val strong = ContentStrong()
    strong.body()
    append(strong)
}

fun ContentBlock.code(body: ContentBlock.() -> Unit) {
    val code = ContentCode()
    code.body()
    append(code)
}

fun ContentBlock.link(to: DocumentationNode, body: ContentBlock.() -> Unit) {
    val block = ContentNodeDirectLink(to)
    block.body()
    append(block)
}

public open class Content(): ContentBlock() {
    public open val sections: List<ContentSection> get() = emptyList()
    public open val summary: ContentNode get() = ContentEmpty
    public open val description: ContentNode get() = ContentEmpty

    fun findSectionByTag(tag: String): ContentSection? =
            sections.firstOrNull { tag.equals(it.tag, ignoreCase = true) }

    companion object {
        val Empty = Content()

        fun of(vararg child: ContentNode): Content {
            val result = MutableContent()
            child.forEach { result.append(it) }
            return result
        }
    }
}

public open class MutableContent() : Content() {
    private val sectionList = arrayListOf<ContentSection>()
    public override val sections: List<ContentSection>
        get() = sectionList

    fun addSection(tag: String?, subjectName: String?): ContentSection {
        val section = ContentSection(tag ?: "", subjectName)
        sectionList.add(section)
        return section
    }

    public override val summary: ContentNode get() = children.firstOrNull() ?: ContentEmpty

    public override val description: ContentNode by lazy {
        val descriptionNodes = children.drop(1)
        if (descriptionNodes.isEmpty()) {
            ContentEmpty
        } else {
            val result = ContentSection(ContentTags.Description, null)
            result.children.addAll(descriptionNodes)
            result
        }
    }

    override fun equals(other: Any?): Boolean {
        if (other !is Content)
            return false
        return sections == other.sections && children == other.children
    }

    override fun hashCode(): Int {
        return sections.map { it.hashCode() }.sum()
    }

    override fun toString(): String {
        if (sections.isEmpty())
            return "<empty>"
        return (listOf(summary, description) + sections).joinToString()
    }
}

fun javadocSectionDisplayName(sectionName: String?): String? =
        when(sectionName) {
            "param" -> "Parameters"
            "throws", "exception" -> "Exceptions"
            else -> sectionName?.capitalize()
        }