package dispatch

import (
	"errors"
	"runtime"
	"testing"
	"time"

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

var (
	errTest      = errors.New("test error")
	nonEmptyUUID = [uuid.Size]byte{108, 105, 99, 107, 77, 121, 72, 97, 105, 114, 121, 66, 97, 108, 108, 115}
)

func TestGlobalDispatcher(t *testing.T) {
	err := Start(0, 0)
	require.NoError(t, err, "Start should not error")
	assert.True(t, IsRunning(), "IsRunning should return true")

	err = Stop()
	assert.NoError(t, err, "Stop should not error")
	assert.False(t, IsRunning(), "IsRunning should return false")
}

func TestStartStop(t *testing.T) {
	t.Parallel()
	var d *Dispatcher

	assert.False(t, d.isRunning(), "IsRunning should return false")

	err := d.stop()
	assert.ErrorIs(t, err, errDispatcherNotInitialized, "stop should error correctly")

	err = d.start(10, 0)
	assert.ErrorIs(t, err, errDispatcherNotInitialized, "start should error correctly")

	d = NewDispatcher()

	err = d.stop()
	assert.ErrorIs(t, err, ErrNotRunning, "stop should error correctly")
	assert.False(t, d.isRunning(), "IsRunning should return false")

	err = d.start(1, 100)
	assert.NoError(t, err, "start should not error")
	assert.True(t, d.isRunning(), "IsRunning should return true")

	err = d.start(0, 0)
	assert.ErrorIs(t, err, errDispatcherAlreadyRunning, "start should error correctly")

	// Add route option
	id, err := d.getNewID(uuid.NewV4)
	assert.NoError(t, err, "getNewID should not error")

	// Add pipe
	_, err = d.subscribe(id)
	assert.NoError(t, err, "subscribe should not error")

	// Max out jobs channel
	for x := 0; x < 99; x++ {
		err = d.publish(id, "woah-nelly")
		assert.NoError(t, err, "publish should not error")
	}

	err = d.stop()
	assert.NoError(t, err, "stop should not error")
	assert.False(t, d.isRunning(), "IsRunning should return false")
}

func TestSubscribe(t *testing.T) {
	t.Parallel()
	var d *Dispatcher
	_, err := d.subscribe(uuid.Nil)
	assert.ErrorIs(t, err, errDispatcherNotInitialized, "subscribe should error correctly")

	d = NewDispatcher()

	_, err = d.subscribe(uuid.Nil)
	assert.ErrorIs(t, err, errIDNotSet, "subscribe should error correctly")

	_, err = d.subscribe(nonEmptyUUID)
	assert.ErrorIs(t, err, ErrNotRunning, "subscribe should error correctly")

	err = d.start(0, 0)
	require.NoError(t, err, "start should not error")

	id, err := d.getNewID(uuid.NewV4)
	require.NoError(t, err, "getNewID should not error")

	_, err = d.subscribe(nonEmptyUUID)
	assert.ErrorIs(t, err, errDispatcherUUIDNotFoundInRouteList, "subscribe should error correctly")

	d.outbound.New = func() interface{} { return "omg" }
	_, err = d.subscribe(id)
	assert.ErrorIs(t, err, errTypeAssertionFailure, "subscribe should error correctly")

	d.outbound.New = getChan
	ch, err := d.subscribe(id)
	assert.NoError(t, err, "subscribe should not error")
	assert.NotNil(t, ch, "Channel should not be nil")
}

func TestUnsubscribe(t *testing.T) {
	t.Parallel()
	var d *Dispatcher

	err := d.unsubscribe(uuid.Nil, nil)
	assert.ErrorIs(t, err, errDispatcherNotInitialized, "unsubscribe should error correctly")

	d = NewDispatcher()

	err = d.unsubscribe(uuid.Nil, nil)
	assert.ErrorIs(t, err, errIDNotSet, "unsubscribe should error correctly")

	err = d.unsubscribe(nonEmptyUUID, nil)
	assert.ErrorIs(t, err, errChannelIsNil, "unsubscribe should error correctly")

	// will return nil if not running
	err = d.unsubscribe(nonEmptyUUID, make(chan interface{}))
	assert.NoError(t, err, "unsubscribe should not error")

	err = d.start(0, 0)
	require.NoError(t, err, "start should not error")

	err = d.unsubscribe(nonEmptyUUID, make(chan interface{}))
	assert.ErrorIs(t, err, errDispatcherUUIDNotFoundInRouteList, "unsubscribe should error correctly")

	id, err := d.getNewID(uuid.NewV4)
	require.NoError(t, err, "getNewID should not error")

	err = d.unsubscribe(id, make(chan interface{}))
	assert.ErrorIs(t, err, errChannelNotFoundInUUIDRef, "unsubscribe should error correctly")

	ch, err := d.subscribe(id)
	require.NoError(t, err, "subscribe should not error")

	err = d.unsubscribe(id, ch)
	assert.NoError(t, err, "unsubscribe should not error")

	ch2, err := d.subscribe(id)
	require.NoError(t, err, "subscribe should not error")

	err = d.unsubscribe(id, ch2)
	assert.NoError(t, err, "unsubscribe should not error")
}

func TestPublish(t *testing.T) {
	t.Parallel()
	var d *Dispatcher

	err := d.publish(uuid.Nil, nil)
	assert.ErrorIs(t, err, errDispatcherNotInitialized, "publish should error correctly")

	d = NewDispatcher()

	err = d.publish(nonEmptyUUID, "test")
	assert.NoError(t, err, "publish should not error")

	err = d.start(2, 10)
	require.NoError(t, err, "start should not error")

	err = d.publish(uuid.Nil, nil)
	assert.ErrorIs(t, err, errIDNotSet, "publish should error correctly")

	err = d.publish(nonEmptyUUID, nil)
	assert.ErrorIs(t, err, errNoData, "publish should error correctly")

	// demonstrate job limit error
	d.routes[nonEmptyUUID] = []chan interface{}{
		make(chan interface{}),
	}
	for x := 0; x < 200; x++ {
		if err = d.publish(nonEmptyUUID, "test"); err != nil {
			break
		}
	}
	assert.ErrorIs(t, err, errDispatcherJobsAtLimit, "publish should eventually error at limit")
}

func TestPublishReceive(t *testing.T) {
	t.Parallel()
	d := NewDispatcher()
	err := d.start(0, 0)
	require.NoError(t, err, "start should not error")

	id, err := d.getNewID(uuid.NewV4)
	require.NoError(t, err, "getNewID should not error")

	incoming, err := d.subscribe(id)
	require.NoError(t, err, "subscribe should not error")

	go func(d *Dispatcher, id uuid.UUID) {
		for x := 0; x < 10; x++ {
			err := d.publish(id, "WOW")
			assert.NoError(t, err, "publish should not error")
		}
	}(d, id)

	data, ok := (<-incoming).(string)
	assert.True(t, ok, "Should get a string type from the pipe")
	assert.Equal(t, "WOW", data, "Should get correct value from the pipe")
}

func TestGetNewID(t *testing.T) {
	t.Parallel()
	var d *Dispatcher

	_, err := d.getNewID(uuid.NewV4)
	assert.ErrorIs(t, err, errDispatcherNotInitialized, "getNewID should error correctly")

	d = NewDispatcher()

	err = d.start(0, 0)
	require.NoError(t, err, "start should not error")

	_, err = d.getNewID(nil)
	assert.ErrorIs(t, err, errUUIDGeneratorFunctionIsNil, "getNewID should error correctly")

	_, err = d.getNewID(func() (uuid.UUID, error) { return uuid.Nil, errTest })
	assert.ErrorIs(t, err, errTest, "getNewID should error correctly")

	_, err = d.getNewID(func() (uuid.UUID, error) { return [uuid.Size]byte{254}, nil })
	assert.NoError(t, err, "getNewID should not error")

	_, err = d.getNewID(func() (uuid.UUID, error) { return [uuid.Size]byte{254}, nil })
	assert.ErrorIs(t, err, errUUIDCollision, "getNewID should error correctly")
}

func TestMux(t *testing.T) {
	t.Parallel()
	var mux *Mux
	_, err := mux.Subscribe(uuid.Nil)
	assert.ErrorIs(t, err, errMuxIsNil, "Subscribe should error correctly")

	err = mux.Unsubscribe(uuid.Nil, nil)
	assert.ErrorIs(t, err, errMuxIsNil, "Unsubscribe should error correctly")

	err = mux.Publish(nil)
	assert.ErrorIs(t, err, errMuxIsNil, "Publish should error correctly")

	_, err = mux.GetID()
	assert.ErrorIs(t, err, errMuxIsNil, "GetID should error correctly")

	d := NewDispatcher()
	err = d.start(0, 0)
	require.NoError(t, err, "start should not error")

	mux = GetNewMux(d)

	err = mux.Publish(nil)
	assert.ErrorIs(t, err, errNoData, "Publish should error correctly")

	err = mux.Publish("lol")
	assert.ErrorIs(t, err, errNoIDs, "Publish should error correctly")

	id, err := mux.GetID()
	require.NoError(t, err, "GetID should not error")

	_, err = mux.Subscribe(uuid.Nil)
	assert.ErrorIs(t, err, errIDNotSet, "Subscribe should error correctly")

	pipe, err := mux.Subscribe(id)
	require.NoError(t, err, "Subscribe should not error")

	var ready = make(chan bool)

	payload := "string"

	go func() {
		close(ready)
		response, ok := (<-pipe.c).(string)
		assert.True(t, ok, "Should get a string type value from Publish")
		assert.Equal(t, payload, response, "Should get correct value from Publish")
	}()

	<-ready

	err = mux.Publish(payload, id)
	assert.NoError(t, err, "Publish should not error")

	err = pipe.Release()
	assert.NoError(t, err, "Release should not error")
}

func TestMuxSubscribe(t *testing.T) {
	t.Parallel()
	d := NewDispatcher()
	err := d.start(0, 0)
	require.NoError(t, err, "start should not error")
	mux := GetNewMux(d)
	itemID, err := mux.GetID()
	require.NoError(t, err, "GetID should not error")

	var pipes []Pipe
	for i := 0; i < 1000; i++ {
		newPipe, err := mux.Subscribe(itemID)
		assert.NoError(t, err, "Subscribe should not error")
		pipes = append(pipes, newPipe)
	}

	for i := range pipes {
		err := pipes[i].Release()
		assert.NoError(t, err, "Release should not error")
	}
}

func TestMuxPublish(t *testing.T) {
	t.Parallel()
	d := NewDispatcher()
	err := d.start(0, 0)
	require.NoError(t, err, "start should not error")

	mux := GetNewMux(d)
	itemID, err := mux.GetID()
	require.NoError(t, err, "GetID should not error")

	overloadCeiling := DefaultMaxWorkers * DefaultJobsLimit * 2

	for i := 0; i < overloadCeiling; i++ {
		err = mux.Publish("test", itemID)
		if !assert.NoError(t, err, "Publish should not error when over limit but no listeners") {
			break
		}
	}

	ready := make(chan any)
	demux := make(chan any, 1)
	pipe, err := mux.Subscribe(itemID)
	require.NoError(t, err, "Subscribe should not error")

	// Subscribers must be actively selecting in order to receive anything
	go func() {
		close(ready)
		i := <-pipe.c
		demux <- i
		close(demux)
	}()

	go func() {
		<-ready // Ensure listener is ready before starting
		for i := 0; i < 100; i++ {
			errMux := mux.Publish(i, itemID)
			if !assert.NoError(t, errMux, "Publish should not error within limits") {
				return
			}
		}
	}()

	assert.Eventually(t, func() bool { return len(demux) >= 1 }, time.Second, time.Millisecond*10, "Subscriber should eventually get at least one message")

	// demonstrate that jobs can be limited when subscribed
	// Published data gets consumed from .jobs to the worker channels, so we're looking to push more than it's consumed and prevent the select reading them too quickly
	runtime.LockOSThread()
	for i := 0; i < overloadCeiling; i++ {
		if err = mux.Publish("test", itemID); err != nil {
			break
		}
	}
	assert.ErrorIs(t, err, errDispatcherJobsAtLimit, "Publish should error when more published than expected")
	runtime.UnlockOSThread()

	err = mux.Unsubscribe(itemID, pipe.c)
	assert.NoError(t, err, "Unsubscribe should not error")

	for i := 0; i < overloadCeiling; i++ {
		if err = mux.Publish("test", itemID); err != nil {
			break
		}
	}
	assert.NoError(t, err, "Publish should not error after Unsubscribe when over limit")

	// Shut down dispatch system
	err = d.stop()
	assert.NoError(t, err, "stop should not error")
}

// 13636467	        84.26 ns/op	     141 B/op	       1 allocs/op
func BenchmarkSubscribe(b *testing.B) {
	d := NewDispatcher()
	err := d.start(0, 0)
	require.NoError(b, err, "start should not error")
	mux := GetNewMux(d)
	newID, err := mux.GetID()
	require.NoError(b, err, "GetID should not error")

	for n := 0; n < b.N; n++ {
		_, err := mux.Subscribe(newID)
		if err != nil {
			b.Error(err)
		}
	}
}