package app

import (
	"context"
	"math/rand"
	"sync"

	"github.com/dop251/goja"
	"github.com/dop251/goja_nodejs/eventloop"
	"github.com/pkg/errors"
	"gitlab.com/wpetit/goweb/logger"
)

var (
	ErrFuncDoesNotExist = errors.New("function does not exist")
	ErrUnknownError     = errors.New("unknown error")
)

type Server struct {
	loop      *eventloop.EventLoop
	factories []ServerModuleFactory
	modules   []ServerModule
}

func (s *Server) Load(name string, src string) error {
	var err error

	s.loop.RunOnLoop(func(rt *goja.Runtime) {
		_, err = rt.RunScript(name, src)
		if err != nil {
			err = errors.Wrap(err, "could not run js script")
		}
	})
	if err != nil {
		return errors.WithStack(err)
	}

	return nil
}

func (s *Server) ExecFuncByName(ctx context.Context, funcName string, args ...interface{}) (goja.Value, error) {
	ctx = logger.With(ctx, logger.F("function", funcName), logger.F("args", args))

	ret, err := s.Exec(ctx, funcName, args...)
	if err != nil {
		return nil, errors.WithStack(err)
	}

	return ret, nil
}

func (s *Server) Exec(ctx context.Context, callableOrFuncname any, args ...interface{}) (goja.Value, error) {
	var (
		wg    sync.WaitGroup
		value goja.Value
		err   error
	)

	wg.Add(1)

	s.loop.RunOnLoop(func(rt *goja.Runtime) {
		var callable goja.Callable
		switch typ := callableOrFuncname.(type) {
		case goja.Callable:
			callable = typ

		case string:
			call, ok := goja.AssertFunction(rt.Get(typ))
			if !ok {
				err = errors.WithStack(ErrFuncDoesNotExist)

				return
			}

			callable = call

		default:
			err = errors.Errorf("callableOrFuncname: expected callable or function name, got '%T'", callableOrFuncname)

			return
		}

		logger.Debug(ctx, "executing callable")

		defer wg.Done()

		defer func() {
			if recovered := recover(); recovered != nil {
				revoveredErr, ok := recovered.(error)
				if ok {
					logger.Error(ctx, "recovered runtime error", logger.E(errors.WithStack(revoveredErr)))

					err = errors.WithStack(ErrUnknownError)

					return
				}

				panic(recovered)
			}
		}()

		jsArgs := make([]goja.Value, 0, len(args))
		for _, a := range args {
			jsArgs = append(jsArgs, rt.ToValue(a))
		}

		value, err = callable(nil, jsArgs...)
		if err != nil {
			err = errors.WithStack(err)
		}
	})

	wg.Wait()

	if err != nil {
		return nil, errors.WithStack(err)
	}

	return value, nil
}

func (s *Server) WaitForPromise(promise *goja.Promise) goja.Value {
	var (
		wg    sync.WaitGroup
		value goja.Value
	)

	wg.Add(1)

	// Wait for promise completion
	go func() {
		for {
			var loopWait sync.WaitGroup
			loopWait.Add(1)

			breakLoop := false

			s.loop.RunOnLoop(func(vm *goja.Runtime) {
				defer loopWait.Done()

				if promise.State() == goja.PromiseStatePending {
					return
				}

				value = promise.Result()

				breakLoop = true
			})

			loopWait.Wait()

			if breakLoop {
				wg.Done()

				return
			}
		}
	}()

	wg.Wait()

	return value
}

func (s *Server) Start(ctx context.Context) error {
	s.loop.Start()

	var err error

	s.loop.RunOnLoop(func(rt *goja.Runtime) {
		rt.SetFieldNameMapper(goja.TagFieldNameMapper("goja", true))
		rt.SetRandSource(createRandomSource())

		if err = s.initModules(ctx, rt); err != nil {
			err = errors.WithStack(err)
		}
	})
	if err != nil {
		return errors.WithStack(err)
	}

	return nil
}

func (s *Server) Stop() {
	s.loop.Stop()
}

func (s *Server) initModules(ctx context.Context, rt *goja.Runtime) error {
	modules := make([]ServerModule, 0, len(s.factories))

	for _, moduleFactory := range s.factories {
		mod := moduleFactory(s)

		export := rt.NewObject()
		mod.Export(export)

		rt.Set(mod.Name(), export)

		modules = append(modules, mod)
	}

	for _, mod := range modules {
		initMod, ok := mod.(InitializableModule)
		if !ok {
			continue
		}

		logger.Debug(ctx, "initializing module", logger.F("module", initMod.Name()))

		if err := initMod.OnInit(ctx, rt); err != nil {
			return errors.WithStack(err)
		}
	}

	s.modules = modules

	return nil
}

func NewServer(factories ...ServerModuleFactory) *Server {
	server := &Server{
		factories: factories,
		loop: eventloop.NewEventLoop(
			eventloop.EnableConsole(false),
		),
	}

	return server
}

func createRandomSource() goja.RandSource {
	rnd := rand.New(&cryptoSource{})

	return rnd.Float64
}