// Copyright © 2019 The Things Network Foundation, The Things Industries B.V.

//

// Licensed under the Apache License, Version 2.0 (the "License");

// you may not use this file except in compliance with the License.

// You may obtain a copy of the License at

//

// http://www.apache.org/licenses/LICENSE-2.0

//

// Unless required by applicable law or agreed to in writing, software

// distributed under the License is distributed on an "AS IS" BASIS,

// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.

// See the License for the specific language governing permissions and

// limitations under the License.

// Package javascript implements a Javascript scripting engine.

package javascript

import (

"context"

"runtime/trace"

"time"

"github.com/robertkrimen/otto"

"go.thethings.network/lorawan-stack/pkg/errors"

"go.thethings.network/lorawan-stack/pkg/scripting"

)

type js struct {

options scripting.Options

}

// New returns a new Javascript scripting engine.

func New(options scripting.Options) scripting.Engine {

return &js{options}

}

var errRuntime = errors.Define("runtime", "runtime error")

// Run executes the Javascript script in the environment env and returns the output.

func (j *js) Run(ctx context.Context, script string, env map[string]interface{}) (val interface{}, err error) {

defer trace.StartRegion(ctx, "run javascript").End()

start := time.Now()

defer func() {

runLatency.Observe(time.Since(start).Seconds())

if err != nil {

runs.WithLabelValues("error").Inc()

} else {

runs.WithLabelValues("ok").Inc()

}

}()

vm := otto.New()

vm.SetStackDepthLimit(j.options.StackDepthLimit)

err = vm.Set("env", env)

if err != nil {

return

}

defer func() {

if caught := recover(); caught != nil {

switch val := caught.(type) {

case error:

err = errRuntime.WithCause(val)

default:

err = errRuntime

}

return

}

}()

vm.Interrupt = make(chan func(), 1)

ctx, cancel := context.WithTimeout(ctx, j.options.Timeout)

defer cancel()

go func() {

<-ctx.Done()

vm.Interrupt <- func() {

panic(context.DeadlineExceeded)

}

}()

output, err := vm.Run(script)

if err != nil {

return nil, errRuntime.WithCause(err)

}

return output.Export()

}