package manager

import (
	"math/rand"
	"testing"
	"time"

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

// creating, starting and stopping tests

// newManager is a helper for creating new managers for tests
func newManager(conn int, want error, t *testing.T) *Manager {
	var manager *Manager
	var err error
	assert := assert.New(t)

	manager, err = New(conn)

	if err != want {
		t.Fatalf(
			`New(%d) = %v, %v, %d max connections failed`,
			conn,
			manager,
			err,
			conn,
		)
	}

	assert.Equal(manager.IsActive(), Inactive, "manager should start inactive")

	return manager
}

// TestEmptyManager creates a new manager with 0 max connections
func TestEmptyManager(t *testing.T) {
	conn := 0
	newManager(conn, nil, t)
}

// TestPostiveManager creates a new manager with valid max connections
func TestPositiveManager(t *testing.T) {
	conn := rand.Intn(MaxConnAttempts)
	newManager(conn, nil, t)
}

// TestNegativeManager creates a new manager with negative max connections
func TestNegativeManager(t *testing.T) {
	conn := -1 * rand.Intn(MaxConnAttempts)
	newManager(conn, ErrInvalidMaxConn, t)
}

// TestInvalidManager creates a new manager with large max connections
func TestInvalidManager(t *testing.T) {
	conn := MaxConnAttempts + 0xf
	newManager(conn, ErrInvalidMaxConn, t)
}

// TestManagerLifeCycle tests that a manager can start and exit several times
func TestManagerLifeCycle(t *testing.T) {

	var manager *Manager
	assert := assert.New(t)

	conn := rand.Intn(MaxConnAttempts)
	manager = newManager(conn, nil, t)

	cycles := 10

	// starting and stopping sequentially
	for i := 0; i < cycles; i++ {

		assert.NoError(manager.Start(), "starting manager failed")
		assert.Equal(manager.IsActive(), Active, "manager inactive after start")

		assert.NoError(manager.Stop(), "stopping manager failed")
		assert.Equal(manager.IsActive(), Inactive, "manager active after stop")
	}
}

// TestManagerStopFail tests that stopping an inactive manager will error
func TestManagerStopFail(t *testing.T) {

	var manager *Manager
	assert := assert.New(t)

	conn := rand.Intn(MaxConnAttempts)
	manager = newManager(conn, nil, t)

	assert.NoError(manager.Start(), "starting manager failed")

	// stopping sequentially
	assert.NoError(manager.Stop(), "stopping manager failed")
	assert.Error(manager.Stop(), "stopping inactive manager should fail")
}

// TestManagerStartFail tests that starting an active manager will error
func TestManagerStartFail(t *testing.T) {

	var manager *Manager
	assert := assert.New(t)

	conn := rand.Intn(MaxConnAttempts)
	manager = newManager(conn, nil, t)

	// starting sequentially
	assert.NoError(manager.Start(), "starting manager failed")
	assert.Error(manager.Start(), "starting active manager should fail")
}

// auxiliary tests

// TestManagerTimeout checks that timeouts exponentially backoff
func TestManagerTimeout(t *testing.T) {
	var manager *Manager
	assert := assert.New(t)

	conn := 10
	manager = newManager(conn, nil, t)

	assert.NoError(manager.Start(), "starting manager failed")
	assert.Equal(manager.IsActive(), Active, "manager is inactive")

	prevTimeout, err := manager.Timeout()

	for i := 1; i <= conn; i++ {
		assert.NoError(err, "generating timeout failed")
		assert.True(prevTimeout > 0, "invalid timeout")

		timeout, err := manager.Timeout()

		if i == conn {
			assert.Error(err, "allowed exceeding max attempts")
		} else {
			assert.NoError(err, "generating timeout failed")
			assert.True(
				timeout == 2*prevTimeout,
				"incorrect timeout %d, expected %d",
				timeout, 2*prevTimeout,
			)
		}

		prevTimeout = timeout
	}
}

// TestManagerHB tests the heartbeat channel opens and closes
func TestManagerHB(t *testing.T) {

	var manager *Manager
	assert := assert.New(t)

	conn := rand.Intn(MaxConnAttempts)
	manager = newManager(conn, nil, t)

	assert.NoError(manager.Start(), "starting manager failed")
	assert.Equal(manager.IsActive(), Active, "manager is inactive")

	ch := make(chan struct{})

	go manager.HeartBeat(ch, 10, 0, time.Millisecond)

	for range ch {
		// close on first ping
		assert.NoError(manager.Stop(), "stopping manager failed")
	}

	assert.Equal(manager.IsActive(), Inactive, "manager is active")
}

// TestManagerHBTiming tests the heartbeat channel timing is correct
func TestManagerHBTiming(t *testing.T) {

	var manager *Manager
	assert := assert.New(t)

	conn := rand.Intn(MaxConnAttempts)
	manager = newManager(conn, nil, t)

	assert.NoError(manager.Start(), "starting manager failed")
	assert.Equal(manager.IsActive(), Active, "manager is inactive")

	ch := make(chan struct{})
	hb := 100
	pings := 10

	// expected time with tolerance for other logic and worst case rand timeout
	expected := time.Duration(pings*hb+15) * time.Millisecond

	go manager.HeartBeat(ch, hb, 1, time.Millisecond)

	iter := 0
	start := time.Now()
	for range ch {
		// close after 10 pings
		iter += 1
		if iter >= pings {
			assert.NoError(manager.Stop(), "stopping manager failed")
		}
	}
	end := time.Now()

	assert.Equal(manager.IsActive(), Inactive, "manager is active")
	assert.WithinDuration(start, end, expected, "inaccurate heartbeat")
}