package allocrunner

import (
	"sync"
	"time"

	log "github.com/hashicorp/go-hclog"
	"github.com/hashicorp/nomad/client/allocrunner/interfaces"
	"github.com/hashicorp/nomad/client/consul"
	"github.com/hashicorp/nomad/client/taskenv"
	agentconsul "github.com/hashicorp/nomad/command/agent/consul"
	"github.com/hashicorp/nomad/nomad/structs"
	"github.com/hashicorp/nomad/plugins/drivers"
)

// groupServiceHook manages task group Consul service registration and
// deregistration.
type groupServiceHook struct {
	allocID      string
	group        string
	restarter    agentconsul.WorkloadRestarter
	consulClient consul.ConsulServiceAPI
	prerun       bool
	delay        time.Duration
	deregistered bool

	logger log.Logger

	// The following fields may be updated
	canary         bool
	services       []*structs.Service
	networks       structs.Networks
	taskEnvBuilder *taskenv.Builder

	// Since Update() may be called concurrently with any other hook all
	// hook methods must be fully serialized
	mu sync.Mutex
}

type groupServiceHookConfig struct {
	alloc          *structs.Allocation
	consul         consul.ConsulServiceAPI
	restarter      agentconsul.WorkloadRestarter
	taskEnvBuilder *taskenv.Builder
	logger         log.Logger
}

func newGroupServiceHook(cfg groupServiceHookConfig) *groupServiceHook {
	var shutdownDelay time.Duration
	tg := cfg.alloc.Job.LookupTaskGroup(cfg.alloc.TaskGroup)

	if tg.ShutdownDelay != nil {
		shutdownDelay = *tg.ShutdownDelay
	}

	h := &groupServiceHook{
		allocID:        cfg.alloc.ID,
		group:          cfg.alloc.TaskGroup,
		restarter:      cfg.restarter,
		consulClient:   cfg.consul,
		taskEnvBuilder: cfg.taskEnvBuilder,
		delay:          shutdownDelay,
	}
	h.logger = cfg.logger.Named(h.Name())
	h.services = cfg.alloc.Job.LookupTaskGroup(h.group).Services

	if cfg.alloc.AllocatedResources != nil {
		h.networks = cfg.alloc.AllocatedResources.Shared.Networks
	}

	if cfg.alloc.DeploymentStatus != nil {
		h.canary = cfg.alloc.DeploymentStatus.Canary
	}
	return h
}

func (*groupServiceHook) Name() string {
	return "group_services"
}

func (h *groupServiceHook) Prerun() error {
	h.mu.Lock()
	defer func() {
		// Mark prerun as true to unblock Updates
		h.prerun = true
		h.mu.Unlock()
	}()

	if len(h.services) == 0 {
		return nil
	}

	services := h.getWorkloadServices()
	return h.consulClient.RegisterWorkload(services)
}

func (h *groupServiceHook) Update(req *interfaces.RunnerUpdateRequest) error {
	h.mu.Lock()
	defer h.mu.Unlock()

	oldWorkloadServices := h.getWorkloadServices()

	// Store new updated values out of request
	canary := false
	if req.Alloc.DeploymentStatus != nil {
		canary = req.Alloc.DeploymentStatus.Canary
	}

	var networks structs.Networks
	if req.Alloc.AllocatedResources != nil {
		networks = req.Alloc.AllocatedResources.Shared.Networks
	}

	// Update group service hook fields
	tg := req.Alloc.Job.LookupTaskGroup(h.group)
	h.networks = networks
	h.services = tg.Services
	h.canary = canary
	h.taskEnvBuilder.UpdateTask(req.Alloc, nil)

	// Update shutdown delay
	var shutdown time.Duration
	if tg.ShutdownDelay != nil {
		shutdown = *tg.ShutdownDelay
	}
	h.delay = shutdown

	// Create new task services struct with those new values
	newWorkloadServices := h.getWorkloadServices()

	if !h.prerun {
		// Update called before Prerun. Update alloc and exit to allow
		// Prerun to do initial registration.
		return nil
	}

	return h.consulClient.UpdateWorkload(oldWorkloadServices, newWorkloadServices)
}

func (h *groupServiceHook) PreKill() {
	h.mu.Lock()
	defer h.mu.Unlock()

	// If we have a shutdown delay deregister
	// group services and then wait
	// before continuing to kill tasks
	h.deregister()
	h.deregistered = true

	if h.delay == 0 {
		return
	}

	h.logger.Debug("waiting before removing group service", "shutdown_delay", h.delay)

	// Wait for specified shutdown_delay
	// this will block an agent from shutting down
	<-time.After(h.delay)
}

func (h *groupServiceHook) Postrun() error {
	h.mu.Lock()
	defer h.mu.Unlock()

	if !h.deregistered {
		h.deregister()
	}
	return nil
}

func (h *groupServiceHook) driverNet() *drivers.DriverNetwork {
	if len(h.networks) == 0 {
		return nil
	}

	//TODO(schmichael) only support one network for now
	net := h.networks[0]
	//TODO(schmichael) there's probably a better way than hacking driver network
	return &drivers.DriverNetwork{
		AutoAdvertise: true,
		IP:            net.IP,
		// Copy PortLabels from group network
		PortMap: net.PortLabels(),
	}
}

// deregister services from Consul.
func (h *groupServiceHook) deregister() {
	if len(h.services) > 0 {
		workloadServices := h.getWorkloadServices()
		h.consulClient.RemoveWorkload(workloadServices)

		// Canary flag may be getting flipped when the alloc is being
		// destroyed, so remove both variations of the service
		workloadServices.Canary = !workloadServices.Canary
		h.consulClient.RemoveWorkload(workloadServices)
	}
}

func (h *groupServiceHook) getWorkloadServices() *agentconsul.WorkloadServices {
	// Interpolate with the task's environment
	interpolatedServices := taskenv.InterpolateServices(h.taskEnvBuilder.Build(), h.services)

	// Create task services struct with request's driver metadata
	return &agentconsul.WorkloadServices{
		AllocID:       h.allocID,
		Group:         h.group,
		Restarter:     h.restarter,
		Services:      interpolatedServices,
		DriverNetwork: h.driverNet(),
		Networks:      h.networks,
		Canary:        h.canary,
	}
}