package client

import (
	"crypto/tls"
	"fmt"
	"log"
	"net/http"
	"net/url"
	"strings"
	"sync"
	"time"

	consul "github.com/hashicorp/consul/api"
	"github.com/hashicorp/go-multierror"
	"github.com/hashicorp/nomad/nomad/structs"
)

const (
	syncInterval = 5 * time.Second
)

// consulApi is the interface which wraps the actual consul api client
type consulApi interface {
	CheckRegister(check *consul.AgentCheckRegistration) error
	CheckDeregister(checkID string) error
	ServiceRegister(service *consul.AgentServiceRegistration) error
	ServiceDeregister(ServiceID string) error
	Services() (map[string]*consul.AgentService, error)
	Checks() (map[string]*consul.AgentCheck, error)
}

// consulApiClient is the actual implementation of the consulApi which
// talks to the consul agent
type consulApiClient struct {
	client *consul.Client
}

func (a *consulApiClient) CheckRegister(check *consul.AgentCheckRegistration) error {
	return a.client.Agent().CheckRegister(check)
}

func (a *consulApiClient) CheckDeregister(checkID string) error {
	return a.client.Agent().CheckDeregister(checkID)
}

func (a *consulApiClient) ServiceRegister(service *consul.AgentServiceRegistration) error {
	return a.client.Agent().ServiceRegister(service)
}

func (a *consulApiClient) ServiceDeregister(serviceID string) error {
	return a.client.Agent().ServiceDeregister(serviceID)
}

func (a *consulApiClient) Services() (map[string]*consul.AgentService, error) {
	return a.client.Agent().Services()
}

func (a *consulApiClient) Checks() (map[string]*consul.AgentCheck, error) {
	return a.client.Agent().Checks()
}

// trackedTask is a Task that we are tracking for changes in service and check
// definitions and keep them sycned with Consul Agent
type trackedTask struct {
	task  *structs.Task
	alloc *structs.Allocation
}

// ConsulService is the service which tracks tasks and syncs the services and
// checks defined in them with Consul Agent
type ConsulService struct {
	client     consulApi
	logger     *log.Logger
	shutdownCh chan struct{}
	node       *structs.Node

	trackedTasks   map[string]*trackedTask
	serviceStates  map[string]string
	trackedTskLock sync.Mutex
}

type consulServiceConfig struct {
	logger     *log.Logger
	consulAddr string
	token      string
	auth       string
	enableSSL  bool
	verifySSL  bool
	node       *structs.Node
}

// A factory method to create new consul service
func NewConsulService(config *consulServiceConfig) (*ConsulService, error) {
	var err error
	var c *consul.Client
	cfg := consul.DefaultConfig()
	cfg.Address = config.consulAddr
	if config.token != "" {
		cfg.Token = config.token
	}

	if config.auth != "" {
		var username, password string
		if strings.Contains(config.auth, ":") {
			split := strings.SplitN(config.auth, ":", 2)
			username = split[0]
			password = split[1]
		} else {
			username = config.auth
		}

		cfg.HttpAuth = &consul.HttpBasicAuth{
			Username: username,
			Password: password,
		}
	}
	if config.enableSSL {
		cfg.Scheme = "https"
	}
	if config.enableSSL && !config.verifySSL {
		cfg.HttpClient.Transport = &http.Transport{
			TLSClientConfig: &tls.Config{
				InsecureSkipVerify: true,
			},
		}

	}
	if c, err = consul.NewClient(cfg); err != nil {
		return nil, err
	}

	consulService := ConsulService{
		client:        &consulApiClient{client: c},
		logger:        config.logger,
		node:          config.node,
		trackedTasks:  make(map[string]*trackedTask),
		serviceStates: make(map[string]string),
		shutdownCh:    make(chan struct{}),
	}

	return &consulService, nil
}

// Register starts tracking a task for changes to it's services and tasks and
// adds/removes services and checks associated with it.
func (c *ConsulService) Register(task *structs.Task, alloc *structs.Allocation) error {
	var mErr multierror.Error
	c.trackedTskLock.Lock()
	tt := &trackedTask{task: task, alloc: alloc}
	c.trackedTasks[fmt.Sprintf("%s-%s", alloc.ID, task.Name)] = tt
	c.trackedTskLock.Unlock()
	for _, service := range task.Services {
		c.logger.Printf("[INFO] consul: registering service %s with consul.", service.Name)
		if err := c.registerService(service, task, alloc); err != nil {
			mErr.Errors = append(mErr.Errors, err)
		}
	}

	return mErr.ErrorOrNil()
}

// Deregister stops tracking a task for changes to it's services and checks and
// removes all the services and checks associated with the Task
func (c *ConsulService) Deregister(task *structs.Task, alloc *structs.Allocation) error {
	var mErr multierror.Error
	c.trackedTskLock.Lock()
	delete(c.trackedTasks, fmt.Sprintf("%s-%s", alloc.ID, task.Name))
	c.trackedTskLock.Unlock()
	for _, service := range task.Services {
		serviceID := alloc.Services[service.Name]
		if serviceID == "" {
			continue
		}
		c.logger.Printf("[INFO] consul: deregistering service %v with consul", service.Name)
		if err := c.deregisterService(serviceID); err != nil {
			c.printLogMessage("[DEBUG] consul: error in deregistering service %v from consul", service.Name)
			mErr.Errors = append(mErr.Errors, err)
		}
	}
	return mErr.ErrorOrNil()
}

func (c *ConsulService) ShutDown() {
	close(c.shutdownCh)
}

// SyncWithConsul is a long lived function that performs calls to sync
// checks and services periodically with Consul Agent
func (c *ConsulService) SyncWithConsul() {
	sync := time.After(syncInterval)

	for {
		select {
		case <-sync:
			c.performSync()
			sync = time.After(syncInterval)
		case <-c.shutdownCh:
			c.logger.Printf("[INFO] consul: shutting down consul service")
			return
		}
	}
}

// performSync syncs checks and services with Consul and removed tracked
// services which are no longer present in tasks
func (c *ConsulService) performSync() {
	// Get the list of the services and that Consul knows about
	srvcs, err := c.client.Services()
	if err != nil {
		return
	}
	chks, err := c.client.Checks()
	if err != nil {
		return
	}

	// Filter the services and checks that isn't managed by consul
	consulServices := c.filterConsulServices(srvcs)
	consulChecks := c.filterConsulChecks(chks)

	knownChecks := make(map[string]struct{})
	knownServices := make(map[string]struct{})

	// Add services and checks which Consul doesn't know about
	for _, trackedTask := range c.trackedTasks {
		for _, service := range trackedTask.task.Services {
			serviceID := trackedTask.alloc.Services[service.Name]

			// Add new services which Consul agent isn't aware of
			knownServices[serviceID] = struct{}{}
			if _, ok := consulServices[serviceID]; !ok {
				c.printLogMessage("[INFO] consul: registering service %s with consul.", service.Name)
				c.registerService(service, trackedTask.task, trackedTask.alloc)
				continue
			}

			// If a service has changed, re-register it with Consul agent
			if service.Hash() != c.serviceStates[serviceID] {
				c.printLogMessage("[INFO] consul: reregistering service %s with consul.", service.Name)
				c.registerService(service, trackedTask.task, trackedTask.alloc)
				continue
			}

			// Add new checks that Consul isn't aware of
			for _, check := range service.Checks {
				checkID := check.Hash(serviceID)
				knownChecks[checkID] = struct{}{}
				if _, ok := consulChecks[checkID]; !ok {
					host, port := trackedTask.task.FindHostAndPortFor(service.PortLabel)
					cr := c.makeCheck(serviceID, check, host, port)
					if err := c.registerCheck(cr); err != nil {
						c.printLogMessage("[DEBUG] consul: error registering check %q: %v", cr.ID, err)
					}

				}
			}
		}
	}

	// Remove services from the service tracker which no longer exists
	for serviceID := range c.serviceStates {
		if _, ok := knownServices[serviceID]; !ok {
			delete(c.serviceStates, serviceID)
		}
	}

	// Remove services that are not present anymore
	for _, consulService := range consulServices {
		if _, ok := knownServices[consulService.ID]; !ok {
			delete(c.serviceStates, consulService.ID)
			c.printLogMessage("[INFO] consul: deregistering service %v with consul", consulService.Service)
			c.deregisterService(consulService.ID)
		}
	}

	// Remove checks that are not present anymore
	for _, consulCheck := range consulChecks {
		if _, ok := knownChecks[consulCheck.CheckID]; !ok {
			c.deregisterCheck(consulCheck.CheckID)
		}
	}
}

// registerService registers a Service with Consul
func (c *ConsulService) registerService(service *structs.Service, task *structs.Task, alloc *structs.Allocation) error {
	var mErr multierror.Error
	host, port := task.FindHostAndPortFor(service.PortLabel)
	if host == "" || port == 0 {
		return fmt.Errorf("consul: the port:%q marked for registration of service: %q couldn't be found", service.PortLabel, service.Name)
	}
	serviceID := alloc.Services[service.Name]
	c.serviceStates[serviceID] = service.Hash()

	asr := &consul.AgentServiceRegistration{
		ID:      serviceID,
		Name:    service.Name,
		Tags:    service.Tags,
		Port:    port,
		Address: host,
	}

	if err := c.client.ServiceRegister(asr); err != nil {
		c.printLogMessage("[DEBUG] consul: error while registering service %v with consul: %v", service.Name, err)
		mErr.Errors = append(mErr.Errors, err)
	}
	for _, check := range service.Checks {
		cr := c.makeCheck(serviceID, check, host, port)
		if err := c.registerCheck(cr); err != nil {
			c.printLogMessage("[DEBUG] consul: error while registerting check %v with consul: %v", check.Name, err)
			mErr.Errors = append(mErr.Errors, err)
		}

	}
	return mErr.ErrorOrNil()
}

// registerCheck registers a check with Consul
func (c *ConsulService) registerCheck(check *consul.AgentCheckRegistration) error {
	c.printLogMessage("[INFO] consul: registering check with ID: %s for service: %s", check.ID, check.ServiceID)
	return c.client.CheckRegister(check)
}

// deregisterCheck de-registers a check with a specific ID from Consul
func (c *ConsulService) deregisterCheck(checkID string) error {
	c.printLogMessage("[INFO] consul: removing check with ID: %v", checkID)
	return c.client.CheckDeregister(checkID)
}

// deregisterService de-registers a Service with a specific id from Consul
func (c *ConsulService) deregisterService(serviceID string) error {
	delete(c.serviceStates, serviceID)
	if err := c.client.ServiceDeregister(serviceID); err != nil {
		return err
	}
	return nil
}

// makeCheck creates a Consul Check Registration struct
func (c *ConsulService) makeCheck(serviceID string, check *structs.ServiceCheck, ip string, port int) *consul.AgentCheckRegistration {
	checkID := check.Hash(serviceID)
	cr := &consul.AgentCheckRegistration{
		ID:        checkID,
		Name:      check.Name,
		ServiceID: serviceID,
	}
	cr.Interval = check.Interval.String()
	cr.Timeout = check.Timeout.String()

	switch check.Type {
	case structs.ServiceCheckHTTP:
		if check.Protocol == "" {
			check.Protocol = "http"
		}
		url := url.URL{
			Scheme: check.Protocol,
			Host:   fmt.Sprintf("%s:%d", ip, port),
			Path:   check.Path,
		}
		cr.HTTP = url.String()
	case structs.ServiceCheckTCP:
		cr.TCP = fmt.Sprintf("%s:%d", ip, port)
	case structs.ServiceCheckScript:
		cr.Script = check.Script // TODO This needs to include the path of the alloc dir and based on driver types
	}
	return cr
}

// filterConsulServices prunes out all the service whose ids are not prefixed
// with nomad-
func (c *ConsulService) filterConsulServices(srvcs map[string]*consul.AgentService) map[string]*consul.AgentService {
	nomadServices := make(map[string]*consul.AgentService)
	delete(srvcs, "consul")
	for _, srv := range srvcs {
		if strings.HasPrefix(srv.ID, structs.NomadConsulPrefix) {
			nomadServices[srv.ID] = srv
		}
	}
	return nomadServices

}

// filterConsulChecks prunes out all the consul checks which do not have
// services with id prefixed with noamd-
func (c *ConsulService) filterConsulChecks(chks map[string]*consul.AgentCheck) map[string]*consul.AgentCheck {
	nomadChecks := make(map[string]*consul.AgentCheck)
	for _, chk := range chks {
		if strings.HasPrefix(chk.ServiceID, structs.NomadConsulPrefix) {
			nomadChecks[chk.CheckID] = chk
		}
	}
	return nomadChecks

}

// printLogMessage prints log messages only when the node attributes have consul
// related information
func (c *ConsulService) printLogMessage(message string, v ...interface{}) {
	if _, ok := c.node.Attributes["consul.version"]; ok {
		c.logger.Println(fmt.Sprintf(message, v...))
	}
}