package argvpb

import (
	"fmt"
	"time"
)

// RunIfTakesLonger schedules a function `f` to run after a duration `d`.
// It returns a "cancel" function. If the cancel function is called before
// the duration `d` has passed, the scheduled function `f` will not be executed.
//
// This is designed to be used with defer, like so:
//
//	func myFunc() {
//		cancel := RunIfTakesLonger(time.Second, func() {
//			fmt.Println("myFunc took more than a second!")
//		})
//		defer cancel()
//
//		// ... rest of the function
//	}
func RunIfTakesLonger(d time.Duration, f func()) (cancel func()) {
	// time.AfterFunc executes a function in its own goroutine after the
	// specified duration. It returns a Timer that can be used to cancel it.
	timer := time.AfterFunc(d, f)

	// We return a function that stops the timer.
	// The caller is expected to call this function using `defer`.
	return func() {
		// The Stop method returns true if it successfully prevented the
		// timer from firing. We don't need the return value here, but it's
		// useful for understanding.
		timer.Stop()
	}
}

// A task that takes less time than the timeout.
func shortTask() {
	fmt.Println("--- Running shortTask (will take 500ms) ---")
	cancel := RunIfTakesLonger(time.Second, func() {
		fmt.Println("!!! This should NOT be printed !!!")
	})
	defer cancel()

	fmt.Println("shortTask: working...")
	time.Sleep(500 * time.Millisecond)
	fmt.Println("shortTask: finished.")
}

// A task that takes more time than the timeout.
func longTask() {
	fmt.Println("\n--- Running longTask (will take 2 seconds) ---")
	cancel := RunIfTakesLonger(time.Second, func() {
		fmt.Println(">>> longTask took more than 1 second! Clean-up function executed. <<<")
	})
	defer cancel()

	fmt.Println("longTask: working...")
	time.Sleep(2 * time.Second)
	fmt.Println("longTask: finished.")
}

func main() {
	shortTask()
	longTask()
}