interface StreamInterface
{
	method close {}
	method next {}     // if readable
	method nextPut: item {} // if writable
	method atEnd {}
	method contents {}
	method isReadable {}
	method isWritable {}
}

class FileStream(Object) [StreamInterface]
{
	| accessor |

	method(#class) on: path for: flags
	{
		| stream |
		stream := self basicNew.
		stream accessor: (FileAccessor on: path for: flags).
		^stream
	}

	method close
	{
		ifnot (self.accessor isNil)
		{
			self.accessor close.
			self.accessor := nil.
		}.
	}

	method next
	{
		
	}
}

class Stream(Object)
{
	method(#class) new
	{
		// you must use dedicated class methods for instantiation
		self messageProhibited: #new.
	}

	method(#class) on: object
	{
		^self subclassResponsibility: #on:.
	}

	method contents
	{
		^self subclassResponsibility: #contents.
	}

	method next
	{
		// return the next object in the receiver
		^self subclassResponsibility: #next.
	}

	method nextPut: object
	{
		// insert an object at the next position in the receiver
		^self subclassResponsibility: #next.
	}

	method nextPutAll: collection
	{
		collection do: [:elem | self nextPut: elem ].
		^collection.
	}

	method atEnd
	{
		^self subclassResponsibility: #next.
	}

	method print: object
	{
		object printOn: self.
	}
}

class PositionableStream(Stream)
{
	var collection.
	var(#get) position.
	var readLimit.

	method(#class) on: collection
	{
		^self new __on collection.
	}

	method initialize
	{
		super initialize.
		self.position := 0.
		self.readLimit := collection size.
	}

	method __on: collection
	{
		self.collection := collection.
	}

	method contents
	{
		^self.collection copyFrom: 0 to: self.readLimit
	}

	method next: count
	{
		| newobj i |
		newobj := self contents class new: count.
		while (i < count)
		{
			newobj at: i put: self next.
			i := i + 1.
		}.
	}

	method peek
	{
	}

	method atEnd
	{
		^self.position >= self.readLimit.
	}

	method isEmpty
	{
		^self.position == 0.
	}

	method position: pos
	{
		//if (pos >= 0 and 
	}

	method reset
	{
		self.position := 0.
	}

	method setToEnd
	{
		self.position := self.readLimit.
	}
}

class ReadWriteStream(PositionableStream)
{
	method next
	{
	}
}

class ExternalStream(ReadWriteStream)
{
}

class ByteStreamAdapter(Object) //# [ByteStreamable, ByteXXX]
{
	var bsobj.
	var inbuf.
	var inpos.
	var inlen.
	var indown.

	var outbuf.
	var outlen.
	var outdown.

	method(#class) new
	{
		self messageProhibited: #new.
	}

	method(#class) new: obj
	{
		self messageProhibited: #new:.
	}

	method initialize
	{
		super initialize.
		self.bsobj := nil.

		self.inbuf := ByteArray new: 1024.
		self.inpos := 0.
		self.inlen := 0.
		self.indown := false.

		self.outbuf := ByteArray new: 1024.
		self.outlen := 0.
		self.outdown := false.
	}

	method(#class) on: bsobj
	{
		^super new __on: bsobj.
	}

	method __on: bsobj
	{
		self.bsobj := bsobj.
	}

	method __fill_inbuf
	{
		| v |
		v := self.bsobj readBytesInto: self.inbuf.
		// if the streamable object is not blocking, it may return an 
		// error object when data is not ready. 
		if (v isError) { ^v }. 
		if (v == 0) 
		{
			// end of input
			self.indown := true.
			^v
		}.

		self.inlen := v.
		self.inpos := 0.
		^v.
	}

	method next
	{
		| v |

		if (self.indown) { ^nil }.
		if (self.inpos >= self.inlen)
		{ 
			v := self __fill_inbuf.
			if (v isError) { ^v }. // TODO: change error handling
			if (v <= 0) { ^nil }.
			////if (self.inpos >= self.inlen) { ^nil }.
		}.
		
		v := self.inbuf at: self.inpos.
		self.inpos := self.inpos + 1.
		^v.
	}

	method next: count into: byte_array startingAt: pos
	{
		// return the count bytes
		| taken avail needed v incapa |

		if (self.indown) { ^0 }.

		// i assume the given byte array is large enough
		// to store as many as count bytes starting at the pos position.
		// if the parameters cannot meet this assumption, you will get
		// into various system exceptions.
		needed := count.
		incapa := self.inbuf size.

		while (needed > 0)
		{
			avail := self.inlen - self.inpos.
			if (avail <= 0)
			{
				if (needed >= incapa)
				{
					// don't rely on the internal buffer if the number of bytes 
					// needed are equal to or greater than the capacity of the
					// buffer.
					v := self.bsobj readBytesInto: byte_array at: pos for: needed.
					if (v isError or v <= 0) { break }.  // <<< TODO: change the error handling
					pos := pos + v.
					needed := needed - v.
					continue.
				}
				else
				{
					v := self __fill_inbuf.
					if (v isError or v <= 0) { break }. // <<< TODO: change the error handling
				}.
			}.

			taken := if (avail <= needed) { avail } else { needed }.
			byte_array replaceFrom: pos count: taken with: self.inbuf startingAt: self.inpos. 
			self.inpos := self.inpos + taken.
			pos := pos + taken.
			needed := needed - taken.
		}.

		^count - needed.
	}

	method nextPut: count from: byte_array startingAt: pos
	{
		| consumed free rem outcapa |

		if (self.outdown) { ^0 }.

		rem := count.
		outcapa := self.outbuf size.

		while (rem > 0)
		{
			free := outcapa - self.outlen.
			if (free <= 0)
			{
				self flush. // TODO: error handling...
			}.

			if (self.outlen <= 0 and rem >= outcapa)
			{
				consumed := self.bsobj writeBytesFrom: byte_array at: pos for: rem.
				if (consumed <= 0) { break }. // TODO: error handling. also handle exceptions
			}
			else
			{
				consumed := if (free <= rem) { free } else { rem }.
				self.outbuf replaceFrom: self.outlen count: consumed with: byte_array startingAt: pos.
				self.outlen := self.outlen + consumed.
			}.

			pos := pos + consumed.
			rem := rem - consumed.
		}.

		^count - rem.
	}

	method flush
	{
		| v pos |

		pos := 0.
		while (pos < self.outlen)
		{
			v := self.bsobj writeBytesFrom: self.outbuf at: pos for: (self.outlen - pos).
			if (v <= 0) { break }. // TODO: error handling. also handle exceptions
			pos := pos + v.
		}.

		self.outlen := 0.
	}
}

class ByteStream(ByteStreamAdapter)
{
	method close
	{
		if (self.bsobj notNil)
		{
			self.bsobj close.
			self.bsobj := nil.
		}.
	}
}

/*
class TextStream(ByteStream)
{
	method initialize
	{
		super initialize.
		self.
	}

	method next
	{
	}

	method __utf8_to_uc
	{
		if (self.seq at: 0) bitAnd: 
	}
}*/