package main

import (
	"fmt"
	"time"
)

func main() {
	// Unbuffered channel
	messageChannel := make(chan string)
	// Buffered channel
	bufferedChannel := make(chan int, 2)

	fmt.Println("--- Non-blocking read from unbuffered channel ---")
	select {
	case msg := <-messageChannel:
		fmt.Printf("Received message: %s
", msg)
	default:
		fmt.Println("No message available immediately (unbuffered channel).")
	}

	fmt.Println("
--- Non-blocking write to unbuffered channel ---")
	select {
	case messageChannel <- "hello":
		fmt.Println("Sent message: hello")
	default:
		fmt.Println("Could not send message immediately (unbuffered channel, no receiver).")
	}

	// Start a receiver for the unbuffered channel
	go func() {
		time.Sleep(100 * time.Millisecond) // Simulate some delay
		msg := <-messageChannel
		fmt.Printf("Goroutine received: %s
", msg)
	}()

	// Try sending again after a short delay (receiver might be ready)
	time.Sleep(50 * time.Millisecond)
	fmt.Println("
--- Non-blocking write to unbuffered channel (retry with receiver) ---")
	select {
	case messageChannel <- "world":
		fmt.Println("Sent message: world")
	default:
		fmt.Println("Could not send message immediately (unbuffered channel, receiver not ready yet).")
	}
	// Give time for the receiver goroutine to finish
	time.Sleep(100 * time.Millisecond)

	fmt.Println("
--- Non-blocking write to buffered channel ---")
	select {
	case bufferedChannel <- 1:
		fmt.Println("Sent 1 to buffered channel.")
	default:
		fmt.Println("Buffered channel is full, could not send 1.")
	}
	select {
	case bufferedChannel <- 2:
		fmt.Println("Sent 2 to buffered channel.")
	default:
		fmt.Println("Buffered channel is full, could not send 2.")
	}
	select {
	case bufferedChannel <- 3: // This will fail as capacity is 2
		fmt.Println("Sent 3 to buffered channel.")
	default:
		fmt.Println("Buffered channel is full, could not send 3 (expected).")
	}

	fmt.Println("
--- Non-blocking read from buffered channel ---")
	select {
	case val := <-bufferedChannel:
		fmt.Printf("Read %d from buffered channel.
", val)
	default:
		fmt.Println("Buffered channel is empty, no value to read.")
	}

	select {
	case val := <-bufferedChannel:
		fmt.Printf("Read %d from buffered channel.
", val)
	default:
		fmt.Println("Buffered channel is empty, no value to read.")
	}

	select { // This will now hit default
	case val := <-bufferedChannel:
		fmt.Printf("Read %d from buffered channel.
", val)
	default:
		fmt.Println("Buffered channel is empty, no value to read (expected).
")
	}

	close(messageChannel)
	close(bufferedChannel)
	fmt.Println("Main: Exiting.")
}