// Package pipeline provides composable, type-safe stream processing with backpressure.
package pipeline

import "context"

// Stage transforms an input channel into an output channel.
// The stage owns the output channel and closes it when the input
// is exhausted or the context is cancelled.
type Stage[T any] func(ctx context.Context, in <-chan T) <-chan T

// Run connects stages into a pipeline and returns the final output channel.
func Run[T any](ctx context.Context, input <-chan T, stages ...Stage[T]) <-chan T {
	if input == nil {
		panic("pipeline: input channel must not be nil")
	}
	ch := input
	for _, stage := range stages {
		ch = stage(ctx, ch)
	}
	return ch
}