package org.jetbrains.dokka.base.translators.psi

import com.intellij.psi.*
import com.intellij.psi.impl.source.javadoc.PsiDocParamRef
import com.intellij.psi.impl.source.tree.JavaDocElementType
import com.intellij.psi.impl.source.tree.LeafPsiElement
import com.intellij.psi.javadoc.*
import com.intellij.psi.tree.java.IJavaDocElementType
import com.intellij.psi.util.PsiTreeUtil
import org.jetbrains.dokka.links.DRI
import org.jetbrains.dokka.model.doc.*
import org.jetbrains.dokka.model.doc.Deprecated
import org.jetbrains.dokka.utilities.DokkaLogger
import org.jetbrains.kotlin.utils.addToStdlib.firstIsInstanceOrNull
import org.jsoup.Jsoup
import org.jsoup.nodes.Element
import org.jsoup.nodes.Node
import org.jsoup.nodes.TextNode

interface JavaDocumentationParser {
    fun parseDocumentation(element: PsiNamedElement): DocumentationNode
}

class JavadocParser(
    private val logger: DokkaLogger // TODO: Add logging
) : JavaDocumentationParser {

    override fun parseDocumentation(element: PsiNamedElement): DocumentationNode {
        val docComment = (element as? PsiDocCommentOwner)?.docComment ?: return DocumentationNode(emptyList())
        val nodes = mutableListOf<TagWrapper>()
        docComment.getDescription()?.let { nodes.add(it) }
        nodes.addAll(docComment.tags.mapNotNull { tag ->
            when (tag.name) {
                "param" -> Param(P(convertJavadocElements(tag.dataElements.toList())), tag.text)
                "throws" -> Throws(P(convertJavadocElements(tag.dataElements.toList())), tag.text)
                "return" -> Return(P(convertJavadocElements(tag.dataElements.toList())))
                "author" -> Author(P(convertJavadocElements(tag.dataElements.toList())))
                "see" -> See(P(getSeeTagElementContent(tag)), tag.referenceElement()?.text.orEmpty())
                "deprecated" -> Deprecated(P(convertJavadocElements(tag.dataElements.toList())))
                else -> null
            }
        })
        return DocumentationNode(nodes)
    }

    private fun getSeeTagElementContent(tag: PsiDocTag): List<DocTag> =
        listOfNotNull(tag.referenceElement()?.toDocumentationLink())

    private fun PsiDocComment.getDescription(): Description? =
        convertJavadocElements(descriptionElements.dropWhile {
            it.text.trim().isEmpty()
        }).takeIf { it.isNotEmpty() }?.let { list ->
            Description(P(list))
        }

    private fun convertJavadocElements(elements: Iterable<PsiElement>): List<DocTag> =
        elements.mapNotNull {
            when (it) {
                is PsiReference -> convertJavadocElements(it.children.toList())
                is PsiInlineDocTag -> listOfNotNull(convertInlineDocTag(it))
                is PsiDocParamRef -> listOfNotNull(it.toDocumentationLink())
                is PsiDocTagValue,
                is LeafPsiElement -> Jsoup.parse(it.text).body().childNodes().mapNotNull { convertHtmlNode(it) }
                else -> null
            }
        }.flatten()

    private fun convertHtmlNode(node: Node, insidePre: Boolean = false): DocTag? = when (node) {
        is TextNode -> Text(body = if (insidePre) node.wholeText else node.text())
        is Element -> createBlock(node)
        else -> null
    }

    private fun createBlock(element: Element): DocTag {
        val children = element.childNodes().mapNotNull { convertHtmlNode(it) }
        return when (element.tagName()) {
            "p" -> P(listOf(Br, Br) + children)
            "b" -> B(children)
            "strong" -> Strong(children)
            "i" -> I(children)
            "em" -> Em(children)
            "code" -> Code(children)
            "pre" -> Pre(children)
            "ul" -> Ul(children)
            "ol" -> Ol(children)
            "li" -> Li(children)
            "a" -> createLink(element, children)
            else -> Text(body = element.ownText())
        }
    }

    private fun createLink(element: Element, children: List<DocTag>): DocTag {
        return when {
            element.hasAttr("docref") -> {
                A(children, params = mapOf("docref" to element.attr("docref")))
            }
            element.hasAttr("href") -> {
                A(children, params = mapOf("href" to element.attr("href")))
            }
            else -> Text(children = children)
        }
    }

    private fun PsiDocToken.isSharpToken() = tokenType.toString() == "DOC_TAG_VALUE_SHARP_TOKEN"

    private fun PsiElement.toDocumentationLink(labelElement: PsiElement? = null) =
        reference?.resolve()?.let {
            val dri = DRI.from(it)
            val label = labelElement ?: children.firstOrNull {
                it is PsiDocToken && it.text.isNotBlank() && !it.isSharpToken()
            } ?: this
            DocumentationLink(dri, convertJavadocElements(listOfNotNull(label)))
        }

    private fun convertInlineDocTag(tag: PsiInlineDocTag) = when (tag.name) {
        "link", "linkplain" -> {
            tag.referenceElement()?.toDocumentationLink(tag.dataElements.firstIsInstanceOrNull<PsiDocToken>())
        }
        "code", "literal" -> {
            Code(listOf(Text(tag.text)))
        }
        else -> Text(tag.text)
    }

    private fun PsiDocTag.referenceElement(): PsiElement? =
        linkElement()?.let {
            if (it.node.elementType == JavaDocElementType.DOC_REFERENCE_HOLDER) {
                PsiTreeUtil.findChildOfType(it, PsiJavaCodeReferenceElement::class.java)
            } else {
                it
            }
        }

    private fun PsiDocTag.linkElement(): PsiElement? =
        valueElement ?: dataElements.firstOrNull { it !is PsiWhiteSpace }
}