package org.jetbrains.dokka

import com.google.inject.Inject
import com.intellij.openapi.util.text.StringUtil
import com.intellij.psi.PsiJavaFile
import org.jetbrains.dokka.DocumentationNode.Kind
import org.jetbrains.dokka.Kotlin.DescriptorDocumentationParser
import org.jetbrains.kotlin.builtins.KotlinBuiltIns
import org.jetbrains.kotlin.descriptors.*
import org.jetbrains.kotlin.descriptors.annotations.Annotated
import org.jetbrains.kotlin.descriptors.annotations.AnnotationDescriptor
import org.jetbrains.kotlin.descriptors.impl.EnumEntrySyntheticClassDescriptor
import org.jetbrains.kotlin.idea.caches.resolve.KotlinCacheService
import org.jetbrains.kotlin.idea.caches.resolve.getModuleInfo
import org.jetbrains.kotlin.idea.kdoc.KDocFinder
import org.jetbrains.kotlin.kdoc.psi.impl.KDocSection
import org.jetbrains.kotlin.lexer.KtTokens
import org.jetbrains.kotlin.load.java.structure.impl.JavaClassImpl
import org.jetbrains.kotlin.name.FqName
import org.jetbrains.kotlin.psi.KtModifierListOwner
import org.jetbrains.kotlin.psi.KtParameter
import org.jetbrains.kotlin.resolve.DescriptorUtils
import org.jetbrains.kotlin.resolve.constants.CompileTimeConstant
import org.jetbrains.kotlin.resolve.constants.ConstantValue
import org.jetbrains.kotlin.resolve.constants.TypedCompileTimeConstant
import org.jetbrains.kotlin.resolve.descriptorUtil.fqNameSafe
import org.jetbrains.kotlin.resolve.descriptorUtil.isDocumentedAnnotation
import org.jetbrains.kotlin.resolve.jvm.JavaDescriptorResolver
import org.jetbrains.kotlin.resolve.jvm.platform.JvmPlatform
import org.jetbrains.kotlin.resolve.source.PsiSourceElement
import org.jetbrains.kotlin.resolve.source.getPsi
import org.jetbrains.kotlin.types.ErrorUtils
import org.jetbrains.kotlin.types.KtType
import org.jetbrains.kotlin.types.TypeProjection

public data class DocumentationOptions(val outputDir: String,
                                       val outputFormat: String,
                                       val includeNonPublic: Boolean = false,
                                       val reportUndocumented: Boolean = true,
                                       val skipEmptyPackages: Boolean = true,
                                       val skipDeprecated: Boolean = false,
                                       val sourceLinks: List<SourceLinkDefinition>)

private fun isSamePackage(descriptor1: DeclarationDescriptor, descriptor2: DeclarationDescriptor): Boolean {
    val package1 = DescriptorUtils.getParentOfType(descriptor1, PackageFragmentDescriptor::class.java)
    val package2 = DescriptorUtils.getParentOfType(descriptor2, PackageFragmentDescriptor::class.java)
    return package1 != null && package2 != null && package1.fqName == package2.fqName
}

interface PackageDocumentationBuilder {
    fun buildPackageDocumentation(documentationBuilder: DocumentationBuilder,
                                  packageName: FqName,
                                  packageNode: DocumentationNode,
                                  declarations: List<DeclarationDescriptor>)
}

class DocumentationBuilder
        @Inject constructor(val resolutionFacade: DokkaResolutionFacade,
                            val descriptorDocumentationParser: DescriptorDocumentationParser,
                            val options: DocumentationOptions,
                            val refGraph: NodeReferenceGraph,
                            val logger: DokkaLogger)
{
    val visibleToDocumentation = setOf(Visibilities.PROTECTED, Visibilities.PUBLIC)
    val boringBuiltinClasses = setOf(
            "kotlin.Unit", "kotlin.Byte", "kotlin.Short", "kotlin.Int", "kotlin.Long", "kotlin.Char", "kotlin.Boolean",
            "kotlin.Float", "kotlin.Double", "kotlin.String", "kotlin.Array", "kotlin.Any")
    val knownModifiers = setOf(
            KtTokens.PUBLIC_KEYWORD, KtTokens.PROTECTED_KEYWORD, KtTokens.INTERNAL_KEYWORD, KtTokens.PRIVATE_KEYWORD,
            KtTokens.OPEN_KEYWORD, KtTokens.FINAL_KEYWORD, KtTokens.ABSTRACT_KEYWORD, KtTokens.SEALED_KEYWORD,
            KtTokens.OVERRIDE_KEYWORD)

    fun link(node: DocumentationNode, descriptor: DeclarationDescriptor, kind: DocumentationReference.Kind) {
        refGraph.link(node, descriptor.signature(), kind)
    }

    fun link(fromDescriptor: DeclarationDescriptor?, toDescriptor: DeclarationDescriptor?, kind: DocumentationReference.Kind) {
        if (fromDescriptor != null && toDescriptor != null) {
            refGraph.link(fromDescriptor.signature(), toDescriptor.signature(), kind)
        }
    }

    fun register(descriptor: DeclarationDescriptor, node: DocumentationNode) {
        refGraph.register(descriptor.signature(), node)
    }

    fun <T> nodeForDescriptor(descriptor: T, kind: Kind): DocumentationNode where T : DeclarationDescriptor, T : Named {
        val (doc, callback) = descriptorDocumentationParser.parseDocumentationAndDetails(descriptor, kind == Kind.Parameter)
        val node = DocumentationNode(descriptor.name.asString(), doc, kind).withModifiers(descriptor)
        callback(node)
        return node
    }

    private fun DocumentationNode.withModifiers(descriptor: DeclarationDescriptor) : DocumentationNode{
        if (descriptor is MemberDescriptor) {
            appendVisibility(descriptor)
            if (descriptor !is ConstructorDescriptor) {
                appendModality(descriptor)
            }
        }
        return this
    }

    fun DocumentationNode.appendModality(descriptor: MemberDescriptor) {
        var modality = descriptor.modality
        if (modality == Modality.OPEN) {
            val containingClass = descriptor.containingDeclaration as? ClassDescriptor
            if (containingClass?.modality == Modality.FINAL) {
                modality = Modality.FINAL
            }
        }
        val modifier = modality.name.toLowerCase()
        appendTextNode(modifier, DocumentationNode.Kind.Modifier)
    }

    fun DocumentationNode.appendVisibility(descriptor: DeclarationDescriptorWithVisibility) {
        val modifier = descriptor.visibility.normalize().displayName
        appendTextNode(modifier, DocumentationNode.Kind.Modifier)
    }

    fun DocumentationNode.appendSupertypes(descriptor: ClassDescriptor) {
        val superTypes = descriptor.typeConstructor.supertypes
        for (superType in superTypes) {
            if (!ignoreSupertype(superType)) {
                appendType(superType, DocumentationNode.Kind.Supertype)
                val superclass = superType?.constructor?.declarationDescriptor
                link(superclass, descriptor, DocumentationReference.Kind.Inheritor)
                link(descriptor, superclass, DocumentationReference.Kind.Superclass)
            }
        }
    }

    private fun ignoreSupertype(superType: KtType): Boolean {
        val superClass = superType.constructor.declarationDescriptor as? ClassDescriptor
        if (superClass != null) {
            val fqName = DescriptorUtils.getFqNameSafe(superClass).asString()
            return fqName == "kotlin.Annotation" || fqName == "kotlin.Enum" || fqName == "kotlin.Any"
        }
        return false
    }

    fun DocumentationNode.appendProjection(projection: TypeProjection, kind: DocumentationNode.Kind = DocumentationNode.Kind.Type) {
        if (projection.isStarProjection) {
            appendTextNode("*", Kind.Type)
        }
        else {
            appendType(projection.type, kind, projection.projectionKind.label)
        }
    }

    fun DocumentationNode.appendType(jetType: KtType?, kind: DocumentationNode.Kind = DocumentationNode.Kind.Type, prefix: String = "") {
        if (jetType == null)
            return
        val classifierDescriptor = jetType.constructor.declarationDescriptor
        val name = when (classifierDescriptor) {
            is ClassDescriptor -> {
                if (classifierDescriptor.isCompanionObject) {
                    classifierDescriptor.containingDeclaration.name.asString() +
                            "." + classifierDescriptor.name.asString()
                }
                else {
                    classifierDescriptor.name.asString()
                }
            }
            is Named -> classifierDescriptor.name.asString()
            else -> "<anonymous>"
        }
        val node = DocumentationNode(name, Content.Empty, kind)
        if (prefix != "") {
            node.appendTextNode(prefix, Kind.Modifier)
        }
        if (jetType.isMarkedNullable) {
            node.appendTextNode("?", Kind.NullabilityModifier)
        }
        if (classifierDescriptor != null) {
            link(node, classifierDescriptor,
                    if (classifierDescriptor.isBoringBuiltinClass()) DocumentationReference.Kind.HiddenLink else DocumentationReference.Kind.Link)
        }

        append(node, DocumentationReference.Kind.Detail)
        node.appendAnnotations(jetType)
        for (typeArgument in jetType.arguments) {
            node.appendProjection(typeArgument)
        }
    }

    fun ClassifierDescriptor.isBoringBuiltinClass(): Boolean =
        DescriptorUtils.getFqName(this).asString() in boringBuiltinClasses

    fun DocumentationNode.appendAnnotations(annotated: Annotated) {
        annotated.annotations.filter { it.isDocumented() }.forEach {
            val annotationNode = it.build()
            if (annotationNode != null) {
                append(annotationNode,
                        if (annotationNode.isDeprecation()) DocumentationReference.Kind.Deprecation else DocumentationReference.Kind.Annotation)
            }
        }
    }

    fun DocumentationNode.appendModifiers(descriptor: DeclarationDescriptor) {
        val psi = (descriptor as DeclarationDescriptorWithSource).source.getPsi() as? KtModifierListOwner ?: return
        KtTokens.MODIFIER_KEYWORDS_ARRAY.filter { it !in knownModifiers }.forEach {
            if (psi.hasModifier(it)) {
                appendTextNode(it.value, Kind.Modifier)
            }
        }
    }

    fun DocumentationNode.isDeprecation() = name == "Deprecated" || name == "deprecated"

    fun DocumentationNode.appendSourceLink(sourceElement: SourceElement) {
        appendSourceLink(sourceElement.getPsi(), options.sourceLinks)
    }

    fun DocumentationNode.appendChild(descriptor: DeclarationDescriptor, kind: DocumentationReference.Kind): DocumentationNode? {
        // do not include generated code
        if (descriptor is CallableMemberDescriptor && descriptor.kind != CallableMemberDescriptor.Kind.DECLARATION)
            return null

        if (descriptor.isDocumented()) {
            val node = descriptor.build()
            append(node, kind)
            return node
        }
        return null
    }

    fun DeclarationDescriptor.isDocumented(): Boolean {
        return (options.includeNonPublic
                || this !is MemberDescriptor
                || this.visibility in visibleToDocumentation) &&
                !isDocumentationSuppressed() &&
                (!options.skipDeprecated || !isDeprecated())
    }

    fun DocumentationNode.appendMembers(descriptors: Iterable<DeclarationDescriptor>): List<DocumentationNode> {
        val nodes = descriptors.map { descriptor ->
            if (descriptor is CallableMemberDescriptor && descriptor.kind == CallableMemberDescriptor.Kind.FAKE_OVERRIDE) {
                val baseDescriptor = descriptor.overriddenDescriptors.firstOrNull()
                if (baseDescriptor != null) {
                    link(this, baseDescriptor, DocumentationReference.Kind.InheritedMember)
                }
                null
            }
            else {
                appendChild(descriptor, DocumentationReference.Kind.Member)
            }
        }
        return nodes.filterNotNull()
    }

    fun DocumentationNode.appendInPageChildren(descriptors: Iterable<DeclarationDescriptor>, kind: DocumentationReference.Kind) {
        descriptors.forEach { descriptor ->
            val node = appendChild(descriptor, kind)
            node?.addReferenceTo(this, DocumentationReference.Kind.TopLevelPage)
        }
    }

    fun DocumentationModule.appendFragments(fragments: Collection<PackageFragmentDescriptor>,
                                            packageContent: Map<String, Content>,
                                            packageDocumentationBuilder: PackageDocumentationBuilder) {
        val allFqNames = fragments.map { it.fqName }.distinct()

        for (packageName in allFqNames) {
            val declarations = fragments.filter { it.fqName == packageName }.flatMap { it.getMemberScope().getAllDescriptors() }

            if (options.skipEmptyPackages && declarations.none { it.isDocumented() }) continue
            logger.info("  package $packageName: ${declarations.count()} declarations")
            val packageNode = findOrCreatePackageNode(packageName.asString(), packageContent)
            packageDocumentationBuilder.buildPackageDocumentation(this@DocumentationBuilder, packageName, packageNode, declarations)
        }
    }

    fun DeclarationDescriptor.build(): DocumentationNode = when (this) {
        is ClassDescriptor -> build()
        is ConstructorDescriptor -> build()
        is ScriptDescriptor -> build()
        is PropertyDescriptor -> build()
        is FunctionDescriptor -> build()
        is TypeParameterDescriptor -> build()
        is ValueParameterDescriptor -> build()
        is ReceiverParameterDescriptor -> build()
        else -> throw IllegalStateException("Descriptor $this is not known")
    }

    fun ScriptDescriptor.build(): DocumentationNode = classDescriptor.build()

    fun ClassDescriptor.build(): DocumentationNode {
        val kind = when (kind) {
            ClassKind.OBJECT -> Kind.Object
            ClassKind.INTERFACE -> Kind.Interface
            ClassKind.ENUM_CLASS -> Kind.Enum
            ClassKind.ANNOTATION_CLASS -> Kind.AnnotationClass
            ClassKind.ENUM_ENTRY -> Kind.EnumItem
            else -> Kind.Class
        }
        val node = nodeForDescriptor(this, kind)
        node.appendSupertypes(this)
        if (getKind() != ClassKind.OBJECT && getKind() != ClassKind.ENUM_ENTRY) {
            node.appendInPageChildren(typeConstructor.parameters, DocumentationReference.Kind.Detail)
            val constructorsToDocument = if (getKind() == ClassKind.ENUM_CLASS)
                constructors.filter { it.valueParameters.size > 0 }
            else
                constructors
            node.appendMembers(constructorsToDocument)
        }
        val members = defaultType.memberScope.getAllDescriptors().filter { it != companionObjectDescriptor }
        node.appendMembers(members)
        node.appendMembers(staticScope.getDescriptors()).forEach {
            it.appendTextNode("static", Kind.Modifier)
        }
        val companionObjectDescriptor = companionObjectDescriptor
        if (companionObjectDescriptor != null) {
            node.appendMembers(companionObjectDescriptor.defaultType.memberScope.getAllDescriptors())
        }
        node.appendAnnotations(this)
        node.appendModifiers(this)
        node.appendSourceLink(source)
        register(this, node)
        return node
    }

    fun ConstructorDescriptor.build(): DocumentationNode {
        val node = nodeForDescriptor(this, Kind.Constructor)
        node.appendInPageChildren(valueParameters, DocumentationReference.Kind.Detail)
        register(this, node)
        return node
    }

    private fun CallableMemberDescriptor.inCompanionObject(): Boolean {
        val containingDeclaration = containingDeclaration
        if ((containingDeclaration as? ClassDescriptor)?.isCompanionObject ?: false) {
            return true
        }
        val receiver = extensionReceiverParameter
        return (receiver?.type?.constructor?.declarationDescriptor as? ClassDescriptor)?.isCompanionObject ?: false
    }

    fun FunctionDescriptor.build(): DocumentationNode {
        if (ErrorUtils.containsErrorType(this)) {
            logger.warn("Found an unresolved type in ${signatureWithSourceLocation()}")
        }

        val node = nodeForDescriptor(this, if (inCompanionObject()) Kind.CompanionObjectFunction else Kind.Function)

        node.appendInPageChildren(typeParameters, DocumentationReference.Kind.Detail)
        extensionReceiverParameter?.let { node.appendChild(it, DocumentationReference.Kind.Detail) }
        node.appendInPageChildren(valueParameters, DocumentationReference.Kind.Detail)
        node.appendType(returnType)
        node.appendAnnotations(this)
        node.appendModifiers(this)
        node.appendSourceLink(source)

        overriddenDescriptors.forEach {
            addOverrideLink(it, this)
        }

        register(this, node)
        return node
    }

    fun addOverrideLink(baseClassFunction: CallableMemberDescriptor, overridingFunction: CallableMemberDescriptor) {
        val source = baseClassFunction.original.source.getPsi()
        if (source != null) {
            link(overridingFunction, baseClassFunction, DocumentationReference.Kind.Override)
        } else {
            baseClassFunction.overriddenDescriptors.forEach {
                addOverrideLink(it, overridingFunction)
            }
        }
    }

    fun PropertyDescriptor.build(): DocumentationNode {
        val node = nodeForDescriptor(this, if (inCompanionObject()) Kind.CompanionObjectProperty else Kind.Property)
        node.appendInPageChildren(typeParameters, DocumentationReference.Kind.Detail)
        extensionReceiverParameter?.let { node.appendChild(it, DocumentationReference.Kind.Detail) }
        node.appendType(returnType)
        node.appendAnnotations(this)
        node.appendModifiers(this)
        node.appendSourceLink(source)
        if (isVar) {
            node.appendTextNode("var", DocumentationNode.Kind.Modifier)
        }
        getter?.let {
            if (!it.isDefault) {
                node.addAccessorDocumentation(descriptorDocumentationParser.parseDocumentation(it), "Getter")
            }
        }
        setter?.let {
            if (!it.isDefault) {
                node.addAccessorDocumentation(descriptorDocumentationParser.parseDocumentation(it), "Setter")
            }
        }

        overriddenDescriptors.forEach {
            addOverrideLink(it, this)
        }

        register(this, node)
        return node
    }

    fun DocumentationNode.addAccessorDocumentation(documentation: Content, prefix: String) {
        if (documentation == Content.Empty) return
        updateContent {
            if (!documentation.children.isEmpty()) {
                val section = addSection(prefix, null)
                documentation.children.forEach { section.append(it) }
            }
            documentation.sections.forEach {
                val section = addSection("$prefix ${it.tag}", it.subjectName)
                it.children.forEach { section.append(it) }
            }
        }
    }

    fun ValueParameterDescriptor.build(): DocumentationNode {
        val node = nodeForDescriptor(this, Kind.Parameter)
        node.appendType(varargElementType ?: type)
        if (declaresDefaultValue()) {
            val psi = source.getPsi() as? KtParameter
            if (psi != null) {
                val defaultValueText = psi.defaultValue?.text
                if (defaultValueText != null) {
                    node.appendTextNode(defaultValueText, Kind.Value)
                }
            }
        }
        node.appendAnnotations(this)
        node.appendModifiers(this)
        if (varargElementType != null && node.details(Kind.Modifier).none { it.name == "vararg" }) {
            node.appendTextNode("vararg", Kind.Modifier)
        }
        register(this, node)
        return node
    }

    fun TypeParameterDescriptor.build(): DocumentationNode {
        val doc = descriptorDocumentationParser.parseDocumentation(this)
        val name = name.asString()
        val prefix = variance.label

        val node = DocumentationNode(name, doc, DocumentationNode.Kind.TypeParameter)
        if (prefix != "") {
            node.appendTextNode(prefix, Kind.Modifier)
        }
        if (isReified) {
            node.appendTextNode("reified", Kind.Modifier)
        }

        for (constraint in upperBounds) {
            if (KotlinBuiltIns.isDefaultBound(constraint)) {
                continue
            }
            node.appendType(constraint, Kind.UpperBound)
        }

        for (constraint in lowerBounds) {
            if (KotlinBuiltIns.isNothing(constraint))
                continue
            node.appendType(constraint, Kind.LowerBound)
        }
        return node
    }

    fun ReceiverParameterDescriptor.build(): DocumentationNode {
        var receiverClass: DeclarationDescriptor = type.constructor.declarationDescriptor!!
        if ((receiverClass as? ClassDescriptor)?.isCompanionObject ?: false) {
            receiverClass = receiverClass.containingDeclaration!!
        }
        link(receiverClass,
                containingDeclaration,
                DocumentationReference.Kind.Extension)

        val node = DocumentationNode(name.asString(), Content.Empty, Kind.Receiver)
        node.appendType(type)
        return node
    }

    fun AnnotationDescriptor.build(): DocumentationNode? {
        val annotationClass = type.constructor.declarationDescriptor
        if (annotationClass == null || ErrorUtils.isError(annotationClass)) {
            return null
        }
        val node = DocumentationNode(annotationClass.name.asString(), Content.Empty, DocumentationNode.Kind.Annotation)
        val arguments = allValueArguments.toList().sortedBy { it.first.index }
        arguments.forEach {
            val valueNode = it.second.toDocumentationNode()
            if (valueNode != null) {
                val paramNode = DocumentationNode(it.first.name.asString(), Content.Empty, DocumentationNode.Kind.Parameter)
                paramNode.append(valueNode, DocumentationReference.Kind.Detail)
                node.append(paramNode, DocumentationReference.Kind.Detail)
            }
        }
        return node
    }

    fun CompileTimeConstant<Any?>.build(): DocumentationNode? = when (this) {
        is TypedCompileTimeConstant -> constantValue.toDocumentationNode()
        else -> null
    }

    fun ConstantValue<*>.toDocumentationNode(): DocumentationNode? = value?.let { value ->
        when (value) {
            is String ->
                "\"" + StringUtil.escapeStringCharacters(value) + "\""
            is EnumEntrySyntheticClassDescriptor ->
                value.containingDeclaration.name.asString() + "." + value.name.asString()
            else -> value.toString()
        }.let { valueString ->
            DocumentationNode(valueString, Content.Empty, DocumentationNode.Kind.Value)
        }
    }
}

class KotlinPackageDocumentationBuilder : PackageDocumentationBuilder {
    override fun buildPackageDocumentation(documentationBuilder: DocumentationBuilder,
                                           packageName: FqName,
                                           packageNode: DocumentationNode,
                                           declarations: List<DeclarationDescriptor>) {
        val externalClassNodes = hashMapOf<FqName, DocumentationNode>()
        declarations.forEach { descriptor ->
            with(documentationBuilder) {
                if (descriptor.isDocumented()) {
                    val parent = packageNode.getParentForPackageMember(descriptor, externalClassNodes)
                    parent.appendChild(descriptor, DocumentationReference.Kind.Member)
                }
            }
        }
    }
}

class KotlinJavaDocumentationBuilder
        @Inject constructor(val documentationBuilder: DocumentationBuilder,
                            val logger: DokkaLogger) : JavaDocumentationBuilder
{
    override fun appendFile(file: PsiJavaFile, module: DocumentationModule, packageContent: Map<String, Content>) {
        val packageNode = module.findOrCreatePackageNode(file.packageName, packageContent)

        file.classes.forEach {
            val javaDescriptorResolver = KotlinCacheService.getInstance(file.project).getProjectService(JvmPlatform,
                    it.getModuleInfo(), javaClass<JavaDescriptorResolver>())

            val descriptor = javaDescriptorResolver.resolveClass(JavaClassImpl(it))
            if (descriptor == null) {
                logger.warn("Cannot find descriptor for Java class ${it.qualifiedName}")
            }
            else {
                with(documentationBuilder) {
                    packageNode.appendChild(descriptor, DocumentationReference.Kind.Member)
                }
            }
        }
    }
}

private fun AnnotationDescriptor.isDocumented(): Boolean {
    if (source.getPsi() != null && mustBeDocumented()) return true
    val annotationClassName = type.constructor.declarationDescriptor?.fqNameSafe?.asString()
    return annotationClassName == "kotlin.Extension"
}

fun AnnotationDescriptor.mustBeDocumented(): Boolean {
    val annotationClass = type.constructor.declarationDescriptor as? Annotated ?: return false
    return annotationClass.isDocumentedAnnotation()
}

fun DeclarationDescriptor.isDocumentationSuppressed(): Boolean {
    val doc = KDocFinder.findKDoc(this)
    return doc is KDocSection && doc.findTagByName("suppress") != null
}

fun DeclarationDescriptor.isDeprecated(): Boolean = annotations.any {
    DescriptorUtils.getFqName(it.type.constructor.declarationDescriptor!!).asString() == "kotlin.Deprecated"
} || (this is ConstructorDescriptor && containingDeclaration.isDeprecated())

fun DocumentationNode.getParentForPackageMember(descriptor: DeclarationDescriptor,
                                                externalClassNodes: MutableMap<FqName, DocumentationNode>): DocumentationNode {
    if (descriptor is CallableMemberDescriptor) {
        val extensionClassDescriptor = descriptor.getExtensionClassDescriptor()
        if (extensionClassDescriptor != null && !isSamePackage(descriptor, extensionClassDescriptor) &&
                !ErrorUtils.isError(extensionClassDescriptor)) {
            val fqName = DescriptorUtils.getFqNameSafe(extensionClassDescriptor)
            return externalClassNodes.getOrPut(fqName, {
                val newNode = DocumentationNode(fqName.asString(), Content.Empty, Kind.ExternalClass)
                append(newNode, DocumentationReference.Kind.Member)
                newNode
            })
        }
    }
    return this
}

fun CallableMemberDescriptor.getExtensionClassDescriptor(): ClassifierDescriptor? {
    val extensionReceiver = extensionReceiverParameter
    if (extensionReceiver != null) {
        val type = extensionReceiver.type
        return type.constructor.declarationDescriptor as? ClassDescriptor
    }
    return null
}

fun DeclarationDescriptor.signature(): String = when(this) {
    is ClassDescriptor, is PackageFragmentDescriptor -> DescriptorUtils.getFqName(this).asString()
    is PropertyDescriptor -> containingDeclaration.signature() + "#" + name + receiverSignature()
    is FunctionDescriptor -> containingDeclaration.signature() + "#" + name + parameterSignature()
    is ValueParameterDescriptor -> containingDeclaration.signature() + ":" + name
    is TypeParameterDescriptor -> containingDeclaration.signature() + "<" + name

    else -> throw UnsupportedOperationException("Don't know how to calculate signature for $this")
}

fun PropertyDescriptor.receiverSignature(): String {
    val receiver = extensionReceiverParameter
    if (receiver != null) {
        return "#" + receiver.type.signature()
    }
    return ""
}

fun CallableMemberDescriptor.parameterSignature(): String {
    val params = valueParameters.map { it.type }.toArrayList()
    val extensionReceiver = extensionReceiverParameter
    if (extensionReceiver != null) {
        params.add(0, extensionReceiver.type)
    }
    return "(" + params.map { it.signature() }.joinToString() + ")"
}

fun KtType.signature(): String {
    val declarationDescriptor = constructor.declarationDescriptor ?: return "<null>"
    val typeName = DescriptorUtils.getFqName(declarationDescriptor).asString()
    if (typeName == "Array" && arguments.size == 1) {
        return "Array<" + arguments.first().type.signature() + ">"
    }
    return typeName
}

fun DeclarationDescriptor.signatureWithSourceLocation(): String {
    val signature = signature()
    val sourceLocation = sourceLocation()
    return if (sourceLocation != null) "$signature ($sourceLocation)" else signature
}

fun DeclarationDescriptor.sourceLocation(): String? {
    if (this is DeclarationDescriptorWithSource) {
        val psi = (this.source as? PsiSourceElement)?.getPsi()
        if (psi != null) {
            val fileName = psi.containingFile.name
            val lineNumber = psi.lineNumber()
            return if (lineNumber != null) "$fileName:$lineNumber" else fileName
        }
    }
    return null
}