package gostream

import "errors"

type StreamOption struct {
	WaterMark int // buffer len
}

type IReadAble[T any] interface {
	StartRead() chan T
}

type IReadStream[T any] interface {
	OnData(func(T)) error
	Read() (T, error)
	Pipe(w IWriteStream[T]) error
}

type IWriteAble[T any] interface {
	StartWrite() chan T
}

type IWriteStream[T any] interface {
	Write(T)
}
type WriteStream[T any] struct {
	IWriteAble[T]
	IWriteStream[T]
	writeChan chan T
	// isSync    bool
}

func (w *WriteStream[T]) Write(t T) {
	if w.writeChan == nil {
		w.writeChan = w.StartWrite()
	}
	w.writeChan <- t
}

type ReadStream[T any] struct {
	IReadAble[T]
	IReadStream[T]
	readChan chan T
	isSync   bool
}

//	func (r *ReadStream[T]) StartRead() <-chan T {
//		return nil
//	}
func (r *ReadStream[T]) OnData(cb func(T)) error {
	if r.readChan != nil {
		return errors.New("already has reader")
	}
	r.readChan = r.StartRead()

	go func() {
		for t := range r.readChan {
			cb(t)
		}
	}()
	return nil
}

func (r *ReadStream[T]) Read() (T, error) {
	if r.readChan != nil && !r.isSync {
		return *new(T), errors.New("already has reader")
	}
	if r.readChan == nil {
		r.readChan = r.StartRead()
		r.isSync = true
	}

	return <-r.readChan, nil
}

func (r *ReadStream[T]) Pipe(w IWriteStream[T]) error {
	if r.readChan != nil {
		return errors.New("already has reader")
	}
	r.readChan = r.StartRead()
	go func() {
		for t := range r.readChan {
			w.Write(t)
		}
	}()
	return nil
}

type ITransformer[T any, K any] interface {
	Transform(t T) K
}

type TransformStream[T any, K any] struct {
	Options StreamOption
	IWriteAble[T]
	WriteStream[T]
	IReadAble[K]
	ReadStream[K]
	ITransformer[T, K]
	writer chan T
	reader chan K
}

func (tr *TransformStream[T, K]) StartRead() chan K {
	if tr.reader != nil {
		return tr.reader
	}
	return make(chan K, tr.Options.WaterMark)
}

func (tr *TransformStream[T, K]) StartWrite() chan T {
	if tr.writer != nil {
		return tr.writer
	}
	return make(chan T, tr.Options.WaterMark)
}

func (tr *TransformStream[T, K]) OnData(cb func(K)) error {
	err := tr.ReadStream.OnData(cb)
	if err == nil {
		if tr.writer == nil {
			tr.writer = tr.StartWrite()
		}
		go func() {
			for k := range tr.writer {
				transfered := tr.ITransformer.Transform(k)
				tr.reader <- transfered
			}
		}()
	}
	return err
}

func NewTransform[T any, K any](t ITransformer[T, K], options StreamOption) *TransformStream[T, K] {
	ret := &TransformStream[T, K]{
		Options:      options,
		ITransformer: t,
		ReadStream:   ReadStream[K]{},
		WriteStream:  WriteStream[T]{},
	}
	ret.ReadStream.IReadAble = ret
	ret.WriteStream.IWriteAble = ret
	return ret
}

func NewReadStream[T any](reader IReadAble[T]) *ReadStream[T] {
	ret := &ReadStream[T]{
		IReadAble: reader,
	}
	return ret
}

func NewWriteStream[T any](writer IWriteAble[T]) *WriteStream[T] {
	ret := &WriteStream[T]{
		IWriteAble: writer,
	}
	return ret
}