package sbt

	import java.lang.reflect.{Array => _, _}
	import java.lang.annotation.Annotation
	import xsbti.api
	import xsbti.SafeLazy
	import SafeLazy.strict

object ClassToAPI
{
	def apply(c: Seq[Class[_]]): api.Source =
	{
		val pkgs = packages(c).map(p => new api.Package(p))
		val defs = c.filter(isTopLevel).flatMap(toDefinitions)
		new api.Source(pkgs.toArray, defs.toArray)
	}

	def packages(c: Seq[Class[_]]): Set[String] = 
		c.flatMap(packageName).toSet

	def isTopLevel(c: Class[_]): Boolean =
		c.getEnclosingClass eq null

	def toDefinitions(c: Class[_]): Seq[api.ClassLike] =
	{
			import api.DefinitionType.{ClassDef, Module, Trait}
		val enclPkg = packageName(c)
		val mods = modifiers(c.getModifiers)
		val acc = access(c.getModifiers, enclPkg)
		val annots = annotations(c.getAnnotations)
		val name = c.getName
		val tpe = if(Modifier.isInterface(c.getModifiers)) Trait else ClassDef
		lazy val (static, instance) = structure(c, enclPkg)
		val cls = new api.ClassLike(tpe, strict(Empty), lzy(instance), typeParameters(c.getTypeParameters), name, acc, mods, annots)
		def makeStatic(s: api.Structure) = 
			new api.ClassLike(Module, strict(Empty), strict(s), Array(), name, acc, mods, annots)
		cls :: static.map(makeStatic).toList
	}

	def structure(c: Class[_], enclPkg: Option[String]): (Option[api.Structure], api.Structure) =
	{
		val methods = mergeMap(c, c.getMethods, c.getDeclaredMethods, methodToDef(enclPkg))
		val fields = mergeMap(c, c.getFields, c.getDeclaredFields, fieldToDef(enclPkg))
		val constructors = mergeMap(c, c.getConstructors, c.getDeclaredConstructors, constructorToDef(enclPkg))
		val classes = merge[Class[_]](c, c.getClasses, c.getDeclaredClasses, toDefinitions, (_: Seq[Class[_]]).partition(isStatic), _.getEnclosingClass != c)
		val all = (methods ++ fields ++ constructors ++ classes)
		val parentTypes = parents(c)
		val instanceStructure = new api.Structure(lzy(parentTypes.toArray), lzy(all.declared.toArray), lzy(all.inherited.toArray))
		def static = new api.Structure(emptyTpeArray, lzy(all.staticDeclared.toArray), lzy(all.staticInherited.toArray))
		val staticStructure = if(all.staticDeclared.isEmpty && all.staticInherited.isEmpty) None else Some(static)
		(staticStructure, instanceStructure)
	}
	def lzy[T <: AnyRef](t: => T): xsbti.api.Lazy[T] = xsbti.SafeLazy(t)
	private val emptyTpeArray = lzy(Array[xsbti.api.Type]())
	private val emptyDefArray = lzy(Array[xsbti.api.Definition]())

	def parents(c: Class[_]): Seq[api.Type] =
		types(c.getGenericSuperclass +: c.getGenericInterfaces)
	def types(ts: Seq[Type]): Array[api.Type] = ts filter (_ ne null) map reference toArray;
	def upperBounds(ts: Array[Type]): api.Type =
		new api.Structure(lzy(types(ts)), emptyDefArray, emptyDefArray)

	def fieldToDef(enclPkg: Option[String])(f: Field): api.FieldLike =
	{
		val name = f.getName
		val accs = access(f.getModifiers, enclPkg)
		val mods = modifiers(f.getModifiers)
		val annots = annotations(f.getDeclaredAnnotations)
		val tpe = reference(f.getGenericType)
		if(mods.isFinal) new api.Val(tpe, name, accs, mods, annots) else new api.Var(tpe, name, accs, mods, annots)
	}

	def methodToDef(enclPkg: Option[String])(m: Method): api.Def =
		defLike(m.getName, m.getModifiers, m.getDeclaredAnnotations, m.getTypeParameters, m.getParameterAnnotations, m.getGenericParameterTypes, Some(m.getGenericReturnType), m.getGenericExceptionTypes, m.isVarArgs, enclPkg)

	def constructorToDef(enclPkg: Option[String])(c: Constructor[_]): api.Def =
		defLike("<init>", c.getModifiers, c.getDeclaredAnnotations, c.getTypeParameters, c.getParameterAnnotations, c.getGenericParameterTypes, None, c.getGenericExceptionTypes, c.isVarArgs, enclPkg)

	def defLike[T <: GenericDeclaration](name: String, mods: Int, annots: Array[Annotation], tps: Array[TypeVariable[T]], paramAnnots: Array[Array[Annotation]], paramTypes: Array[Type], retType: Option[Type], exceptions: Array[Type], varArgs: Boolean, enclPkg: Option[String]): api.Def =
	{
		val varArgPosition = if(varArgs) paramTypes.length - 1 else -1
		val isVarArg = List.tabulate(paramTypes.length)(_ == varArgPosition)
		val pa = (paramAnnots, paramTypes, isVarArg).zipped map { case (a,p,v) => parameter(a,p,v) }
		val params = new api.ParameterList(pa, false)
		val ret = retType match { case Some(rt) => reference(rt); case None => Empty }
		new api.Def(Array(params), ret, typeParameters(tps), name, access(mods, enclPkg), modifiers(mods), annotations(annots) ++ exceptionAnnotations(exceptions))
	}

	def exceptionAnnotations(exceptions: Array[Type]): Array[api.Annotation] =
		exceptions map { t => new api.Annotation(Throws, Array(new api.AnnotationArgument("value", t.toString))) }

	def parameter(annots: Array[Annotation], parameter: Type, varArgs: Boolean): api.MethodParameter =
		new api.MethodParameter("", annotated(reference(parameter),annots), false, if(varArgs) api.ParameterModifier.Repeated else api.ParameterModifier.Plain)

	def annotated(t: api.SimpleType, annots: Array[Annotation]): api.Type =
		if(annots.isEmpty) t else new api.Annotated(t, annotations(annots))

	case class Defs(declared: Seq[api.Definition], inherited: Seq[api.Definition], staticDeclared: Seq[api.Definition], staticInherited: Seq[api.Definition])
	{
		def ++(o: Defs) = Defs(declared ++ o.declared, inherited ++ o.inherited, staticDeclared ++ o.staticDeclared, staticInherited ++ o.staticInherited)
	}
	def mergeMap[T <: Member](of: Class[_], self: Seq[T], public: Seq[T], f: T => api.Definition): Defs =
		merge[T](of, self, public, x => f(x) :: Nil, splitStatic _, _.getDeclaringClass != of)

	def merge[T](of: Class[_], self: Seq[T], public: Seq[T], f: T => Seq[api.Definition], splitStatic: Seq[T] => (Seq[T],Seq[T]), isInherited: T => Boolean): Defs =
	{
		val (selfStatic, selfInstance) = splitStatic(self)
		val (inheritedStatic, inheritedInstance) = splitStatic(public filter isInherited)
		Defs(selfInstance flatMap f, inheritedInstance flatMap f, selfStatic flatMap f, inheritedStatic flatMap f)
	}

	def splitStatic[T <: Member](defs: Seq[T]): (Seq[T], Seq[T]) =
		defs partition isStatic

	def isStatic(c: Class[_]): Boolean = Modifier.isStatic(c.getModifiers)
	def isStatic(a: Member): Boolean = Modifier.isStatic(a.getModifiers)

	def typeParameters[T <: GenericDeclaration](tps: Array[TypeVariable[T]]): Array[api.TypeParameter] =
		tps map typeParameter
	def typeParameter[T <: GenericDeclaration](tp: TypeVariable[T]): api.TypeParameter =
		new api.TypeParameter(typeVariable(tp), Array(), Array(), api.Variance.Invariant, NothingRef, upperBounds(tp.getBounds))

	// needs to be stable across compilations
	//  preferably, it would be a proper unique id based on de Bruijn index
	def typeVariable[T <: GenericDeclaration](tv: TypeVariable[T]): Int =
		reduceHash((name(tv.getGenericDeclaration) + " " + tv.getName).getBytes)

	def reduceHash(in: Array[Byte]): Int =
		(0 /: in)( (acc, b) => (acc * 43) ^ b)

	def name(gd: GenericDeclaration): String =
		gd match
		{
			case c: Class[_] => c.getName
			case m: Method => m.getName
			case c: Constructor[_] => c.getName
		}

	def modifiers(i: Int): api.Modifiers =
	{
		import Modifier.{isAbstract, isFinal}
		new api.Modifiers( isAbstract(i), false, isFinal(i), false, false, false)
	}
	def access(i: Int, pkg: Option[String]): api.Access =
	{
		import Modifier.{isPublic, isPrivate, isProtected}
		if(isPublic(i)) Public else if(isPrivate(i)) Private else if(isProtected(i)) Protected else packagePrivate(pkg)
	}

	def annotations(a: Array[Annotation]): Array[api.Annotation] = a map annotation
	def annotation(a: Annotation): api.Annotation =
		new api.Annotation( reference(a.annotationType), Array(javaAnnotation(a.toString)))

	// full information not available from reflection
	def javaAnnotation(s: String): api.AnnotationArgument =
		new api.AnnotationArgument("toString", s)

	def array(tpe: api.Type): api.SimpleType = new api.Parameterized(ArrayRef, Array(tpe))
	def reference(c: Class[_]): api.SimpleType =
		if(c.isArray) array(reference(c.getComponentType)) else if(c.isPrimitive) primitive(c.getName) else reference(c.getName)

	// does not handle primitives
	def reference(s: String): api.SimpleType =
	{
		val (pkg, cls) = packageAndName(s)
		pkg match
		{
			// translate all primitives?
			case None => new api.Projection(EmptyPrefix, cls)
			case Some(p) =>
				new api.Projection(new api.Singleton(pathFromString(p)), cls)
		}
	}
	def referenceP(t: ParameterizedType): api.Parameterized =
	{
		val args = t.getActualTypeArguments.map(reference)
		val base = reference(t.getRawType)
		new api.Parameterized(base, args.toArray[api.Type])
	}
	def reference(t: Type): api.SimpleType =
		t match
		{
			case w: WildcardType => reference("_")
			case tv: TypeVariable[_] => new api.ParameterRef(typeVariable(tv))
			case pt: ParameterizedType => referenceP(pt)
			case gat: GenericArrayType => array(reference(gat.getGenericComponentType))
			case c: Class[_] => reference(c)
		}

	def pathFromString(s: String): api.Path =
		new api.Path(s.split("\\.").map(new api.Id(_)) :+ ThisRef )
	def packageName(c: Class[_]) = packageAndName(c)._1
	def packageAndName(c: Class[_]): (Option[String], String) =
		packageAndName(c.getName)
	def packageAndName(name: String): (Option[String], String) =
	{
		val lastDot = name.lastIndexOf('.')
		if(lastDot >= 0)
			(Some(name.substring(0, lastDot)), name.substring(lastDot+1))
		else
			 (None, name)
	}

	val Empty = new api.EmptyType
	val EmptyPath = new api.Path(Array())
	val EmptyPrefix = new api.Singleton(EmptyPath)
	val ThisRef = new api.This

	val Public = new api.Public
	val Private = new api.Private(Unqualified)
	val Protected = new api.Protected(Unqualified)
	val Unqualified = new api.Unqualified
	def packagePrivate(pkg: Option[String]): api.Access = new api.Private(new api.IdQualifier(pkg getOrElse ""))

	val ArrayRef = reference("scala.Array")
	val Throws = reference("scala.throws")
	val NothingRef = reference("scala.Nothing")

	private[this] def PrimitiveNames = Seq("boolean", "byte", "char", "short", "int", "long", "float", "double")
	private[this] def PrimitiveMap = PrimitiveNames.map( j => (j, j.capitalize)) :+ ("void" -> "Unit")
	private[this] val PrimitiveRefs = PrimitiveMap.map { case (n, sn) => (n, reference("scala." + sn)) }.toMap
	def primitive(name: String): api.SimpleType = PrimitiveRefs(name)
}