glkvm-cloud/internal/server/command.go

/*
 * MIT License
 *
 * Copyright (c) 2019 Jianhui Zhao <zhaojh329@gmail.com>
 *
 * Permission is hereby granted, free of charge, to any person obtaining a copy
 * of this software and associated documentation files (the "Software"), to deal
 * in the Software without restriction, including without limitation the rights
 * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
 * copies of the Software, and to permit persons to whom the Software is
 * furnished to do so, subject to the following conditions:
 *
 * The above copyright notice and this permission notice shall be included in all
 * copies or substantial portions of the Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
 * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
 * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
 * SOFTWARE.
 */

package server

import (
	"context"
	"encoding/json"
	"net/http"
	"rttys/utils"
	"strconv"
	"sync"
	"time"

	"github.com/gin-gonic/gin"
	"github.com/rs/zerolog/log"
	"github.com/valyala/bytebufferpool"
)

type CommandReq struct {
	cancel context.CancelFunc
	acked  bool
	c      *gin.Context
	// respondOnce guarantees the HTTP response body is written exactly once.
	// Both the device-response path (handleCmdMsg) and the timeout/offline paths
	// here race to respond; without this a timeout used to write the error twice
	// (timeout + offline), producing a malformed, concatenated JSON body.
	respondOnce sync.Once
}

type CommandReqInfo struct {
	Cmd      string   `json:"cmd"`
	Username string   `json:"username"`
	Params   []string `json:"params"`
}

type CommandRespInfo struct {
	Token string          `json:"token"`
	Attrs json.RawMessage `json:"attrs"`
}

const (
	rttyCmdErrInvalid   = 1001
	rttyCmdErrOffline   = 1002
	rttyCmdErrTimeout   = 1003
	rttyCmdErrForbidden = 1004
)

var cmdErrMsg = map[int]string{
	rttyCmdErrInvalid:   "invalid format",
	rttyCmdErrOffline:   "device offline",
	rttyCmdErrTimeout:   "timeout",
	rttyCmdErrForbidden: "permission denied",
}

func (dev *Device) handleCmdReq(c *gin.Context, info *CommandReqInfo) {
	ctx, cancel := context.WithCancel(dev.ctx)
	defer cancel()

	req := &CommandReq{
		cancel: cancel,
		c:      c,
	}

	token := utils.GenUniqueID()

	msg := bytebufferpool.Get()
	defer bytebufferpool.Put(msg)

	BpWriteCString(msg, info.Username)
	BpWriteCString(msg, info.Cmd)
	BpWriteCString(msg, token)

	msg.WriteByte(byte(len(info.Params)))

	for _, param := range info.Params {
		BpWriteCString(msg, param)
	}

	log.Debug().Msgf("send cmd request for device '%s', token '%s'", dev.id, token)

	err := dev.WriteMsg(msgTypeCmd, "", msg.Bytes())
	if err != nil {
		cmdErrResp(c, rttyCmdErrOffline)
		return
	}

	waitTime := CommandTimeout

	wait := c.Query("wait")
	if wait != "" {
		waitTime, _ = strconv.Atoi(wait)
	}

	if waitTime == 0 {
		c.Status(http.StatusOK)
		return
	}

	dev.commands.Store(token, req)

	if waitTime < 0 || waitTime > CommandTimeout {
		waitTime = CommandTimeout
	}

	tmr := time.NewTimer(time.Second * time.Duration(waitTime))

	log.Debug().Msgf("wait for cmd response for device '%s', token '%s', waitTime %ds", dev.id, token, waitTime)

	select {
	case <-tmr.C:
		req.respondOnce.Do(func() {
			cmdErrResp(c, rttyCmdErrTimeout)
		})
	case <-ctx.Done():
	}

	dev.commands.Delete(token)

	// Only writes when neither the device response nor the timeout has responded
	// yet (i.e. the device/connection went away before acking).
	req.respondOnce.Do(func() {
		cmdErrResp(c, rttyCmdErrOffline)
	})

	log.Debug().Msgf("handle cmd request for device '%s', token '%s' done", dev.id, token)
}

func cmdErrResp(c *gin.Context, err int) {
	c.JSON(http.StatusOK, gin.H{
		"err": err,
		"msg": cmdErrMsg[err],
	})
}

func BpWriteCString(bb *bytebufferpool.ByteBuffer, s string) {
	bb.WriteString(s)
	bb.WriteByte(0)
}