stages

type AggregateStage[T any] struct {
	Name   string
	Buffer uint
}

type BatchStage[T any] struct {
	Name      string
	Buffer    uint
	BatchSize uint
}

type ExpandStage[In any, Out any] struct {
	Name     string
	Buffer   uint
	Expander Expander[In, Out]
}

type Expander[In any, Out any] func(context.Context, In) iter.Seq2[Out, error]

type FanInStage[T any] struct {
	Name   string
	Buffer uint
}

type FanOutRoundRobinStage[T any] struct {
	Name        string
	OutputCount uint
	Buffer      uint
}

type FanOutStage[T any] struct {
	Name        string
	OutputCount uint
	Buffer      uint
}

type Filter[T any] func(context.Context, T) (bool, error)

type FilterStage[T any] struct {
	Name   string
	Buffer uint
	Filter Filter[T]
}

type FlattenStage[T any] struct {
	Name   string
	Buffer uint
}

type LimitStage[T any] struct {
	Name   string
	Buffer uint
	Limit  uint
}

type ParallelTransformStage[In any, Out any] struct {
	Name        string
	Buffer      uint
	Workers     uint
	Transformer Transformer[In, Out]
}

type ReduceStage[T any, Acc any] struct {
	Name    string
	Buffer  uint
	Initial Acc
	Reducer Reducer[T, Acc]
}

type Reducer[T any, Acc any] func(context.Context, Acc, T) (Acc, error)

type Selector[T any] func(context.Context, T) int

type SplitStage[T any] struct {
	Name        string
	OutputCount uint
	Buffer      uint
	Selector    Selector[T]
}

type TransformStage[In any, Out any] struct {
	Name        string
	Buffer      uint
	Transformer Transformer[In, Out]
}

type Transformer[In any, Out any] func(context.Context, In) (Out, error)

type WindowedReduceStage[T any, Acc any] struct {
	Name    string
	Buffer  uint
	Initial Acc
	Reducer WindowedReducer[T, Acc]
}

type WindowedReducer[T any, Acc any] func(context.Context, Acc, T) (nextAcc Acc, output Acc, emit bool, err error)