package main

import (
	"fmt"
	"sync"
	"time"
)

// generateNumbers sends numbers from start to start+count to the output channel.
func generateNumbers(name string, start, count int, out chan<- int) {
	for i := 0; i < count; i++ {
		num := start + i
		fmt.Printf("%s: Sending %d
", name, num)
		out <- num
		time.Sleep(time.Millisecond * time.Duration(100+num%50))
	}
}

// fanIn merges multiple input channels into a single output channel.
func fanIn(done <-chan struct{}, channels ...<-chan int) <-chan int {
	var wg sync.WaitGroup
	out := make(chan int)

	output := func(c <-chan int) {
		defer wg.Done()
		for n := range c {
			select {
			case out <- n:
			case <-done:
				return
			}
		}
	}

	wg.Add(len(channels))
	for _, c := range channels {
		go output(c)
	}

	go func() {
		wg.Wait()
		close(out)
	}()

	return out
}

func main() {
	gen1 := make(chan int)
	gen2 := make(chan int)
	gen3 := make(chan int)

	done := make(chan struct{}) // Signal to stop fanIn if needed

	go func() { defer close(gen1); generateNumbers("Gen1", 0, 5, gen1) }()
	go func() { defer close(gen2); generateNumbers("Gen2", 100, 4, gen2) }()
	go func() { defer close(gen3); generateNumbers("Gen3", 200, 6, gen3) }()

	// Merge the output of all generators into a single channel
	merged := fanIn(done, gen1, gen2, gen3)

	fmt.Println("
--- Merged Results ---")
	for num := range merged {
		fmt.Printf("Received: %d
", num)
	}
	fmt.Println("All data merged and processed.")
}