package js

import (
	"errors"
	"io/ioutil"
	"os"
	"path/filepath"
	"strings"
	"sync"
	"time"

	"src.dualinventive.com/go/devsim/simulator"
	"src.dualinventive.com/go/devsim/simulator/js/console"
	"src.dualinventive.com/go/dinet"

	"github.com/dop251/goja"
	"github.com/dop251/goja_nodejs/require"
)

const (
	// Entrypoint is the javascript entrypoint file
	Entrypoint = "devsim.js"
)

// ErrEntrypoint when the Entrypoint is non-existing or unable to be loaded
var ErrEntrypoint = errors.New("entrypoint could not be loaded")

// ErrPathInvalid when the javascript file is an invalid path
var ErrPathInvalid = errors.New("path is invalid")

// Simulator is a simulator vm with a JavaScript engine
type Simulator struct {
	simulator.Info
	wg              sync.WaitGroup
	intervalsWg     sync.WaitGroup
	requestHandlers requestHandlers
	m               simulator.Model
	entrypoint      string
	dispatchC       chan func()
	intervals       []*interval
	vm              *goja.Runtime
}

func isFilePathInBaseDir(baseDir, filePath string) bool {
	absPath, err := filepath.Abs(filePath)
	if err != nil {
		return false
	}
	return strings.HasPrefix(absPath, baseDir)
}

func newSourceLoader(cwd string) require.SourceLoader {
	return func(path string) ([]byte, error) {
		jsPath := filepath.Join(cwd, path) + ".js"
		if !isFilePathInBaseDir(cwd, jsPath) {
			return nil, ErrPathInvalid
		}
		// #nosec we allow running arbitrary javascript files
		return ioutil.ReadFile(jsPath)
	}
}

func vmSleep(call goja.FunctionCall) goja.Value {
	delayMs := call.Argument(0).ToInteger()
	time.Sleep(time.Duration(delayMs) * time.Millisecond)
	return nil
}

// newSimulator creates a new javascript Simulator
func newSimulator(m simulator.Model, info simulator.Info) (*Simulator, error) {
	entrypoint := filepath.Join(info.Path(), Entrypoint)
	if _, err := os.Stat(entrypoint); os.IsNotExist(err) {
		return nil, ErrEntrypoint
	}

	s := &Simulator{m: m, vm: goja.New(), entrypoint: entrypoint, Info: info}

	cwd, err := filepath.Abs(info.Path())
	if err != nil {
		return nil, err
	}

	r := require.NewRegistryWithLoader(newSourceLoader(cwd))
	r.Enable(s.vm)

	console.Enable(s.vm, m)

	s.vm.Set("sleep", vmSleep)

	o := s.vm.NewObject()

	err = o.Set("request", s.request)
	if err != nil {
		return nil, err
	}

	err = o.Set("publish", s.publish)
	if err != nil {
		return nil, err
	}

	err = o.Set("info", s.info)
	if err != nil {
		return nil, err
	}

	err = o.Set("set", s.storageSet)
	if err != nil {
		return nil, err
	}

	err = o.Set("get", s.storageGet)
	if err != nil {
		return nil, err
	}

	err = o.Set("del", s.storageDel)
	if err != nil {
		return nil, err
	}

	err = o.Set("setInterval", s.setInterval)
	if err != nil {
		return nil, err
	}

	s.vm.Set("devsim", o)
	return s, nil
}

// Start loads the libdir bootstrap file and executes the simulator bootstrap js file
func (s *Simulator) Start() error {
	if err := s.m.Connect(); err != nil {
		return err
	}

	s.dispatchC = make(chan func())

	if err := s.runFile(s.entrypoint); err != nil {
		return err
	}

	// VM call dispatcher
	s.wg.Add(1)
	go func() {
		defer s.wg.Done()
		for fn := range s.dispatchC {
			fn()
		}
	}()

	// Recv
	s.wg.Add(1)
	go func() {
		defer s.wg.Done()
		for {
			msg, err := s.m.Recv()
			if err != nil && err == dinet.ErrClosed {
				return
			}
			if msg == nil {
				continue
			}
			s.requestHandleMsg(msg)
		}
	}()

	return nil
}

// Stop interrupts the vm and waits until it is stopped
func (s *Simulator) Stop() error {
	err := s.m.Close()
	if err != nil {
		return err
	}

	err = s.m.Disconnect()
	for _, interval := range s.intervals {
		interval.stopChan <- 0
	}
	s.intervalsWg.Wait()
	s.vm.Interrupt("stop")
	close(s.dispatchC)
	s.wg.Wait()
	return err
}

// runFile reads and runs the content in the Simulator
func (s *Simulator) runFile(file string) error {
	// #nosec we allow running arbitrary javascript files
	js, err := ioutil.ReadFile(file)
	if err != nil {
		return err
	}
	_, err = s.vm.RunString(string(js[:]))
	return err
}

func (s *Simulator) info(call goja.FunctionCall) goja.Value {
	return nil
}