package main

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

const maxConcurrent = 3 // Limit to 3 concurrent operations

// simulate an operation that needs to be limited
func limitedOperation(id int) {
	fmt.Printf("Worker %d: Starting operation...
", id)
	time.Sleep(time.Duration(2+id) * 200 * time.Millisecond) // Simulate work
	fmt.Printf("Worker %d: Operation finished.
", id)
}

func main() {
	semaphore := make(chan struct{}, maxConcurrent) // Buffered channel acts as a semaphore
	var wg sync.WaitGroup
	numWorkers := 10

	fmt.Println("Starting workers, limited to", maxConcurrent, "concurrent operations.")

	for i := 1; i <= numWorkers; i++ {
		wg.Add(1)
		go func(workerID int) {
			defer wg.Done()
			
			semaphore <- struct{}{} // Acquire a slot (block if semaphore is full)
			fmt.Printf("Worker %d: Acquired slot.
", workerID)
			
			limitedOperation(workerID)
			
			<-semaphore // Release the slot
			fmt.Printf("Worker %d: Released slot.
", workerID)
		}(i)
	}

	wg.Wait()
	fmt.Println("All workers finished.")
}