/* sbt -- Simple Build Tool
 * Copyright 2011 Mark Harrah
 */
package sbt

	import java.io.File
	import java.net.URI
	import BuildLoader._
	import Alternatives._
	import Types.{const,idFun}

final class MultiHandler[S,T](builtIn: S=>Option[T], root: Option[S => Option[T]], nonRoots: List[(URI, S => Option[T])], getURI: S => URI, log: S => Logger)
{
	def applyFun: S => Option[T] = apply _
	def apply(info: S): Option[T] =
		(baseLoader(info), applyNonRoots(info)) match
		{
			case (None, Nil) => None
			case (None, xs @ (_, nr) :: ignored ) =>
				if(!ignored.isEmpty) warn("Using first of multiple matching non-root build resolvers for " + getURI(info), log(info), xs)
				Some(nr)
			case (Some(b), xs) =>
				if(!xs.isEmpty) warn("Ignoring shadowed non-root build resolver(s) for " + getURI(info), log(info), xs)
				Some(b)
		}

	def baseLoader: S => Option[T] = root match { case Some(rl) => rl | builtIn; case None => builtIn }

	def addNonRoot(uri: URI, loader: S => Option[T]) = new MultiHandler(builtIn, root, (uri, loader) :: nonRoots, getURI, log)
	def setRoot(resolver: S => Option[T]) = new MultiHandler(builtIn, Some(resolver), nonRoots, getURI, log)
	def applyNonRoots(info: S): List[(URI, T)] =
		nonRoots flatMap { case (definingURI, loader) => loader(info) map { unit => (definingURI, unit) } }

	private[this] def warn(baseMessage: String, log: Logger, matching: Seq[(URI, T)])
	{
		log.warn(baseMessage)
		log.debug("Non-root build resolvers defined in:")
		log.debug(matching.map(_._1).mkString("\n\t"))
	}
}

object BuildLoader
{
	/** in: Build URI and staging directory
	* out: None if unhandled or Some containing the retrieve function, which returns the directory retrieved to (can be the same as the staging directory) */
	type Resolver = ResolveInfo => Option[() => File]
	type Builder = BuildInfo => Option[() => BuildUnit]
	type Transformer = TransformInfo => BuildUnit
	type Loader = LoadInfo => Option[() => BuildUnit]
	type TransformAll = PartBuild => PartBuild

	final class Components(val resolver: Resolver, val builder: Builder, val transformer: Transformer, val full: Loader, val transformAll: TransformAll) {
		def | (cs: Components): Components =
			new Components(resolver | cs.resolver, builder | cs.builder, seq(transformer, cs.transformer), full | cs.full, transformAll andThen cs.transformAll)
	}
	def transform(t: Transformer): Components = components(transformer = t)
	def resolve(r: Resolver): Components = components(resolver = r)
	def build(b: Builder): Components = components(builder = b)
	def full(f: Loader): Components = components(full = f)
	def transformAll(t: TransformAll) = components(transformAll = t)
	def components(resolver: Resolver = const(None), builder: Builder = const(None), transformer: Transformer = _.unit, full: Loader = const(None), transformAll: TransformAll = idFun) =
		new Components(resolver, builder, transformer, full, transformAll)

	def seq(a: Transformer, b: Transformer): Transformer = info => b(info.setUnit(a(info)))

	sealed trait Info {
		def uri: URI
		def config: LoadBuildConfiguration
		def state: State
	}
	final class ResolveInfo(val uri: URI, val staging: File, val config: LoadBuildConfiguration, val state: State) extends Info
	final class BuildInfo(val uri: URI, val base: File, val config: LoadBuildConfiguration, val state: State) extends Info
	final class TransformInfo(val uri: URI, val base: File, val unit: BuildUnit, val config: LoadBuildConfiguration, val state: State) extends Info {
		def setUnit(newUnit: BuildUnit): TransformInfo = new TransformInfo(uri, base, newUnit, config, state)
	}

	final class LoadInfo(val uri: URI, val staging: File, val config: LoadBuildConfiguration, val state: State, val components: Components) extends Info

	def apply(base: Components, fail: URI => Nothing, s: State, config: LoadBuildConfiguration): BuildLoader =
	{
		def makeMulti[S <: Info, T](base: S => Option[T]) = new MultiHandler[S,T](base, None, Nil, _.uri, _.config.log)
		new BuildLoader(fail, s, config, makeMulti(base.resolver), makeMulti(base.builder), base.transformer, makeMulti(base.full), base.transformAll)
	}

	def componentLoader: Loader = (info: LoadInfo) => {
		import info.{components, config, staging, state, uri}
		val cs = info.components
		for {
			resolve <- cs.resolver(new ResolveInfo(uri, staging, config, state))
			val base = resolve()
			build <- cs.builder(new BuildInfo(uri, base, config, state))
		} yield () => {
			val unit = build()
			cs.transformer(new TransformInfo(uri, base, unit, config, state))
		}
	}
}

final class BuildLoader(
	val fail: URI => Nothing,
	val state: State,
	val config: LoadBuildConfiguration,
	val resolvers: MultiHandler[ResolveInfo, ()=>File],
	val builders: MultiHandler[BuildInfo, ()=>BuildUnit],
	val transformer: Transformer,
	val full: MultiHandler[LoadInfo, ()=>BuildUnit],
	val transformAll: TransformAll)
{
	def addNonRoot(uri: URI, loaders: Components): BuildLoader =
		new BuildLoader(fail, state, config,
			resolvers.addNonRoot(uri, loaders.resolver),
			builders.addNonRoot(uri, loaders.builder),
			seq(transformer, loaders.transformer),
			full.addNonRoot(uri, loaders.full),
			transformAll andThen loaders.transformAll
		)
	def setRoot(loaders: Components): BuildLoader =
		new BuildLoader(fail, state, config,
			resolvers.setRoot(loaders.resolver),
			builders.setRoot(loaders.builder),
			seq(loaders.transformer, transformer),
			full.setRoot(loaders.full),
			loaders.transformAll andThen transformAll
		)
	def updatePluginManagement(overrides: Set[ModuleID]): BuildLoader =
	{
		val mgmt = config.pluginManagement
		val newConfig = config.copy(pluginManagement = mgmt.copy(overrides = mgmt.overrides ++ overrides))
		new BuildLoader(fail, state, newConfig, resolvers, builders, transformer, full, transformAll)
	}
	def components = new Components(resolvers.applyFun, builders.applyFun, transformer, full.applyFun, transformAll)
	def apply(uri: URI): BuildUnit =
	{
		val info = new LoadInfo(uri, config.stagingDirectory, config, state, components)
		val load = full(info) getOrElse fail(uri)
		load()
	}
}