package graph

import (
	"sync/atomic"
	"testing"
	"time"

	"github.com/stretchr/testify/assert"
	"github.com/stretchr/testify/require"
)

func TestDebouncer_Coalesces(t *testing.T) {
	d := NewDebouncer(50 * time.Millisecond)
	var calls atomic.Int32

	// Fire 10 rapid calls for the same key — only the last should execute.
	for range 10 {
		d.Debounce("key1", func() {
			calls.Add(1)
		})
	}

	// Wait for the debounce delay plus some margin.
	time.Sleep(150 * time.Millisecond)

	assert.Equal(t, int32(1), calls.Load(), "rapid calls should coalesce into a single execution")
}

func TestDebouncer_DifferentKeys(t *testing.T) {
	d := NewDebouncer(50 * time.Millisecond)
	var calls atomic.Int32

	d.Debounce("key-a", func() { calls.Add(1) })
	d.Debounce("key-b", func() { calls.Add(1) })
	d.Debounce("key-c", func() { calls.Add(1) })

	time.Sleep(150 * time.Millisecond)

	assert.Equal(t, int32(3), calls.Load(), "different keys should fire independently")
}

func TestDebouncer_TimerReset(t *testing.T) {
	d := NewDebouncer(100 * time.Millisecond)
	var value atomic.Int32

	// First call sets value to 1.
	d.Debounce("key", func() { value.Store(1) })

	// Wait 60ms (less than the 100ms delay), then replace with value 2.
	time.Sleep(60 * time.Millisecond)
	d.Debounce("key", func() { value.Store(2) })

	// At 60ms the first timer hasn't fired yet. Wait for the second timer.
	time.Sleep(150 * time.Millisecond)

	require.Equal(t, int32(2), value.Load(), "later call should replace the earlier one")
}