package main // import "ciena.com/envoyd"

import (
	"os"
	"os/exec"
	"fmt"
	"log"
	"strconv"
	"time"
	"net"
	"io/ioutil"
	"io"
	"text/template"
	"encoding/json"
	"sync"
	"flag"
	"bufio"
	consulapi "github.com/hashicorp/consul/api"
)

// DATA STRUCTURES

//Client provides an interface for getting data out of Consul
type Client interface {
// Get a Service from consulapi
	Service(string, string) ([]string, error)
// Register a service with local agent
	Register(string, int) error
// Deregister a service with local agent
	DeRegister(string) error
}

type client struct {
	consulapi *consulapi.Client
}

type EnvoyConfigVars struct {
	VolthaVip string
	VolthaRR []string
}

type VolthaClusterEntry struct {
	Prefix string
	Id string
	Host string
}

// This struct is not used yet
// TODO: Update the daemon to use this structure to for a
// more object oriented implementation
type EnvoyControl struct {
	// Command line parameters
	assignmentKey string
	envoyConfigTemplate string
	envoyConfig string
	vcoreSvcName  string
	consulSvcName  string
	vcorePort string
	consulPort string
	retries int
	waitTime int
	// Runtime variables
	consul * consulapi.Client
	vcoreHostIpName string
	vcoreIdName string
	vc []VolthaClusterEntry
	ipAddrs map[string][]string
	restartEpoch int
	reLock sync.Mutex // Exclusive access to the restartEpoch
}


func NewEnvoyControl() (ec * EnvoyControl) {
	var envCtrl EnvoyControl = EnvoyControl { // Default values
		// Command line parameters
		assignmentKey: "service/voltha/data/core/assignment",
		envoyConfigTemplate: "/envoy/voltha-grpc-proxy.template.json",
		envoyConfig: "/envoy/voltha-grpc-proxy.json",
		//envoyLogFile: "/envoy/voltha_access_log.log",
		vcoreSvcName: "vcore",
		consulSvcName: "consul",
		vcorePort: "50556",
		consulPort: "8500",
		retries: 10,
		waitTime: 2,
		// Runtime variables
		vcoreHostIpName: "host",
		vcoreIdName: "id",
		ipAddrs: make(map[string][]string),
		restartEpoch: 0,
	}
	ec = &envCtrl
	return
}

func (ec * EnvoyControl) resolveServiceAddress(serviceName string) (err error) {
	for i := 0; i < ec.retries; i++ {
		ec.ipAddrs[serviceName], err = net.LookupHost(serviceName)
		if err != nil {
			log.Printf("%s name resolution failed %d time(s) retrying...", serviceName, i+1)
		} else {
			//fmt.Printf("%s address = %s\n",serviceName, addrs[0])
			break
		}
		time.Sleep(time.Duration(ec.waitTime) * time.Second)
	}
	if err != nil {
		log.Printf("%s name resolution failed %d times gving up", serviceName, ec.retries)
	}
	return
}

func (ec * EnvoyControl) consulConnect(serviceName string, port string) (err error) {
	// Fire up a consul client and get the kv store
	cConfig := consulapi.DefaultNonPooledConfig()
	cConfig.Address = ec.ipAddrs[serviceName][0] + ":" + port
	ec.consul, err = consulapi.NewClient(cConfig)
	if err != nil {
		log.Fatal("error creating consul client aborting")
		return
	}
	return
}


//NewConsul returns a Client interface for given consulapi address
func NewConsulClient(addr string) (*client, error) {
	config := consulapi.DefaultConfig()
	config.Address = addr
	c, err := consulapi.NewClient(config)
	if err != nil {
		return nil, err
	}
	return &client{consulapi: c}, nil
}

// Register a service with consulapi local agent
func (c *client) Register(name string, port int) error {
	reg := &consulapi.AgentServiceRegistration{
		ID:   name,
		Name: name,
		Port: port,
	}
	return c.consulapi.Agent().ServiceRegister(reg)
}

// DeRegister a service with consulapi local agent
func (c *client) DeRegister(id string) error {
	return c.consulapi.Agent().ServiceDeregister(id)
}

// Service return a service 
func (c *client) Service(service, tag string) ([]*consulapi.ServiceEntry, *consulapi.QueryMeta, error) {
	passingOnly := true
	addrs, meta, err := c.consulapi.Health().Service(service, tag, passingOnly, nil)
	if len(addrs) == 0 && err == nil {
		return nil, nil, fmt.Errorf("service ( %s ) was not found", service)
	}
	if err != nil {
		return nil, nil, err
	}
	return addrs, meta, nil
}

// Starts envoy with the current restartEpoch
func (ec * EnvoyControl) startEnvoy() {
	var curEpoch int
	var err error
	var count int

	ec.reLock.Lock() // Make sure we've got exclusive access to the variable
	cmd := exec.Command("/usr/local/bin/envoy", "--restart-epoch", strconv.Itoa(ec.restartEpoch),
			    "--config-path", ec.envoyConfig, "--parent-shutdown-time-s", "10")

	curEpoch = ec.restartEpoch
	ec.restartEpoch += 1
	ec.reLock.Unlock() // Done, release the lock.

	stderr, err := cmd.StderrPipe()
	if err != nil {
		log.Printf("Couldn't attach to stderr running envoy command")
		panic(err)
	}
	stdout, err := cmd.StdoutPipe()
	if err != nil {
		log.Printf("Couldn't attach to stdout running envoy command")
		panic(err)
	}
	so := bufio.NewReader(stdout)
	se := bufio.NewReader(stderr)

	if err = cmd.Start(); err != nil {
		log.Fatal("Error starting envoy")
		panic(err)
	}
	log.Printf("Envoy(%d) started", curEpoch)
	soEof := false
	seEof := false

	data := make([]byte, 80)
	log.Printf("Log forwarding for envoy(%d) started", curEpoch)
	for {
		data = make([]byte, 80)
		count, err = so.Read(data)
		log.Printf("ENVOY_LOG(%d): %s", curEpoch, string(data))
		if err == io.EOF {
			if seEof == true {
				break
			} else {
				soEof = true
			}
		} else if err != nil {
			log.Printf("Attempt to read envoy standard out failed")
			panic(err)
		} else if count > 0 {
			log.Printf("ENVOY_LOG(%d)(%d): %s",curEpoch,count,string(data))
		}
		data = make([]byte, 80)
		count, err = se.Read(data)
		if err == io.EOF {
			if soEof == true {
				break
			} else {
				seEof = true
			}
		} else if err != nil {
			log.Fatal("Attempt to read envoy standard err failed")
			panic(err)
		} else if count > 0 {
			log.Printf("ENVOY_LOG(%d)(%d): %s",curEpoch,count,string(data))
		}
	}
	log.Printf("Waiting on envoy %d to exit", curEpoch)
	if err = cmd.Wait(); err != nil {
		log.Printf("Envoy %d exited with an unexpected exit code", curEpoch)
		panic(err)
	}
	log.Printf("Envoy %d exited", curEpoch)
	// Check if this was the primary envoy, if so
	// something went terribly wrong, panic to force
	// forcefully exit.
	ec.reLock.Lock()
	if ec.restartEpoch == (curEpoch + 1) {
		ec.reLock.Unlock()
		log.Fatal("Last running envoy exited, aborting!")
		panic("This should never happen")
	}
	ec.reLock.Unlock()

}

// This function will use the provided templete file to generate
// the targetfile substituting 
func (ec * EnvoyControl) updateEnvoyConfig(ecv * EnvoyConfigVars) (err error) {
	var firstRun bool = true
	f := func() (bool) {
		var rtrn bool = firstRun
		firstRun = false
		return rtrn
	}
	var funcs = template.FuncMap{"isFirst": f}
	// Slurp up the template file.
	tplt, err := ioutil.ReadFile(ec.envoyConfigTemplate)
	if err != nil {
		log.Fatal("ERROR reading the template file, aborting")
		panic(err)
	}
	//fmt.Println(string(tplt))
	configTemplate, err := template.New("config").Funcs(funcs).Parse(string(tplt));
	if err != nil {
		log.Fatal("Unexpected error loading the Envoy template, aborting")
		panic(err)
	}
	outFile,err := os.Create(ec.envoyConfig)
	if err != nil {
		log.Fatal("Unexpected error opening the Envoy config file for write, aborting")
		panic(err)
	}
	if err = configTemplate.Execute(outFile, ecv); err != nil {
		log.Fatal("Unexpected error executing the Envoy config template, aborting")
		panic(err)
	}
	//cfgFile, err := ioutil.ReadFile(ec.envoyConfig)
	//if err != nil {
	//	log.Fatal("ERROR reading the config file, aborting")
	//	panic(err)
	//}
	//fmt.Println(string(cfgFile))
	return
}

func (ec * EnvoyControl) parseAssignment(jsonString []byte) (vCluster []VolthaClusterEntry, err error) {
	var f interface{}
	var vc VolthaClusterEntry
	//var isErr bool

	log.Printf("Parsing %s", string(jsonString))
	//err = json.Unmarshal(jsonString, &f)
	err = json.Unmarshal(jsonString, &f)
	if err != nil {
			log.Fatal("Unable to parse json record %s", jsonString)
			panic(err)
	} else {
		m := f.(map[string]interface{})
		for k, v := range m {
			isErr := false
			vc.Prefix = k
			//log.Printf("Processing key %s\n", k)
			switch vv := v.(type) {
			case map[string]interface{}:
				for i, u := range vv {
					//log.Printf("Processing key %sn", i)
					switch uu := u.(type) {
					case string:
						if i == ec.vcoreHostIpName {
							vc.Host = uu
						} else if i == ec.vcoreIdName {
							vc.Id = uu
						} else {
							log.Printf("WARNING: unexpected descriptor,%s", i)
							isErr = true
						}
					default:
						log.Printf("WARNING: unexpected type, ")
						log.Println(i, u)
						isErr = true
					}
				}
			default:
				log.Printf("WARNING: unexpected type, ")
				log.Println(k, v)
				isErr = true
			}
			if ! isErr {
				vCluster = append(vCluster, vc)
			}
		}
	}
	log.Println("Parsing complete")
	return
}

func (ec * EnvoyControl) prepareEnvoyConfig(kvp * consulapi.KVPair, ecv * EnvoyConfigVars) (err error) {
	var vCluster []VolthaClusterEntry

	ecv.VolthaVip = ec.ipAddrs[ec.vcoreSvcName][0] + ":" + ec.vcorePort

	// Extract all values from the KV record
	// In the future, the values should all be compared to what we currently have 
	vCluster, err = ec.parseAssignment([]byte(kvp.Value))
	if err == nil {
		ec.vc = vCluster // For future use to determine if there's been a real change
		//templateValues["VolthaRR"] = []string{}
		ecv.VolthaRR = []string{}
		for i := range vCluster {
			//log.Printf("Processing %s\n", vCluster[i].Host)
			//templateValues["VolthaRR"] = append(templateValues["VolthaRR"].([]string), vCluster[i].Host)
			ecv.VolthaRR = append(ecv.VolthaRR, vCluster[i].Host + ":" + ec.vcorePort)
		}
	} else {
		log.Fatal("Couldn't parse the KV record %s", string(kvp.Value))
		panic(err)
	}
	return
}

func (ec * EnvoyControl) runEnvoy(kvp * consulapi.KVPair) {
	var err error
	var ecv EnvoyConfigVars

	if err = ec.prepareEnvoyConfig(kvp, &ecv); err != nil {
		log.Fatal("Error preparing envoy config variables, aborting")
		panic(err)
	}

	// Now that we have the data loaded, update the envoy config and start envoy
	ec.updateEnvoyConfig(&ecv)
	go ec.startEnvoy()
}

func (ec * EnvoyControl) readConsulKey(key string, qo * consulapi.QueryOptions) (kvp * consulapi.KVPair, meta * consulapi.QueryMeta, err error) {

	kv := ec.consul.KV()
	// Get the initial values of the assignment key which contains individual
	// voltha core IP addresses. This may be empty until voltha populates it
	// so it must be checked
	kvp, meta, err = kv.Get(ec.assignmentKey, qo)
	for i := 0; i < ec.retries; i++ {
		if err != nil {
			fmt.Println(err)
			log.Printf("Unable to read assignment consul key, retry %d", i+1)
			time.Sleep(time.Duration(ec.waitTime) * time.Second)
			kvp, meta, err = kv.Get(ec.assignmentKey, qo)
		} else if kvp != nil && len(string(kvp.Value)) > 10 {
			// A valid read, return
			break
		} else {
			log.Printf("Voltha assignment key invalid, retry %d", i+1)
			time.Sleep(time.Duration(ec.waitTime) * time.Second)
			kvp, meta, err = kv.Get(ec.assignmentKey, qo)
		}
		if i == ec.retries {
			log.Printf("Failed to read the assignment key after %d retries, aborting", ec.retries)
			panic(err)
		}
	}
	return
}

func (ec * EnvoyControl) runMonitorEnvoy() {
	var err error
	var qo consulapi.QueryOptions

	// Get the initial values of the assignment key which contains individual
	// voltha core IP addresses. This may be empty until voltha populates it
	// so it must be checked
	kvp, meta, err := ec.readConsulKey(ec.assignmentKey, nil)
	log.Printf("Starting Envoy")
	ec.runEnvoy(kvp)

	for {
		qo.WaitIndex = meta.LastIndex
		qo.RequireConsistent = true
		for {
			if qo.WaitIndex != meta.LastIndex {
				break
			}
			kvp, meta, err = ec.readConsulKey(ec.assignmentKey, &qo)
			if err != nil {
				log.Printf("Unable to read assignment consul key")
				panic(err)
			} else {
				log.Println(string(kvp.Value))
				log.Printf("meta.LastIndex = %d", meta.LastIndex)
			}
		}
		// Fell through, the index has changed thus the key has changed

		log.Printf("Starting Envoy")
		ec.runEnvoy(kvp)
		log.Printf("meta.LastIndex = %d", meta.LastIndex)
	}
}

func (ec * EnvoyControl) ParseCommandArguments() {
	flag.StringVar(&(ec.assignmentKey), "assignment-key", ec.assignmentKey,
				"The key for the voltha assignment value in consul")

	flag.StringVar(&( ec.envoyConfigTemplate),"envoy-cfg-template", ec.envoyConfigTemplate,
					"The path to envoy's configuration template")

	flag.StringVar(&(ec.envoyConfig), "envoy-config", ec.envoyConfig,
				"The path to envoy's configuration file" )

	flag.StringVar(&(ec.vcoreSvcName), "vcore-svc-name", ec.vcoreSvcName,
				"The service name of the voltha core service")

	flag.StringVar(&(ec.consulSvcName),"consul-svc-nme", ec.consulSvcName,
				"The service name of the consul service")

	flag.StringVar(&(ec.vcorePort), "vcore-port", ec.vcorePort,
				"The port where the vcore's GRPC service can be found")

	flag.StringVar(&(ec.consulPort), "consul-port", ec.consulPort,
				"The port where the consul service api can be found")

	flag.IntVar(&(ec.retries), "retries", ec.retries,
			"The number of times to retry name lookups and connect requests before failing")

	flag.IntVar(&(ec.waitTime), "wait-time", ec.waitTime,
			"The number of seconds to wait between retries")

	flag.Parse()
}

func (ec * EnvoyControl) Initialize() (err error) {
	// Resolve consul's virtual ip address
	if err = ec.resolveServiceAddress(ec.consulSvcName); err != nil {
		log.Fatal("Can't proceed without consul's vIP address")
		panic(err)
	}

	// Resolve voltha's virtual ip address
	if err = ec.resolveServiceAddress(ec.vcoreSvcName); err != nil {
		log.Fatal("Can't proceed without voltha's vIP address")
		panic(err)
	}

	if err = ec.consulConnect(ec.consulSvcName, ec.consulPort); err != nil {
		log.Fatal("error creating consul client aborting")
		panic(err)
	}

	return
}

func main() {

	var err error
	var ec * EnvoyControl

	ec = NewEnvoyControl()
	ec.ParseCommandArguments()
	if err = ec.Initialize(); err != nil {
		log.Fatal("Envoy control initialization failed, aboring")
		panic(err)
	}


	// Start envoy and monitor changes to the KV store to reload
	// consul's config. This never returns unless somethign crashes.
	ec.runMonitorEnvoy()
	log.Fatal("Monitor returned, this shouldn't happen")
}