package client

import (
	"fmt"
	"os"
	"path/filepath"
	"strings"
	"sync"
	"time"

	ctconf "github.com/hashicorp/consul-template/config"
	"github.com/hashicorp/consul-template/manager"
	"github.com/hashicorp/consul-template/signals"
	"github.com/hashicorp/consul-template/watch"
	multierror "github.com/hashicorp/go-multierror"
	"github.com/hashicorp/nomad/client/config"
	"github.com/hashicorp/nomad/client/driver/env"
	"github.com/hashicorp/nomad/nomad/structs"
)

var (
	// testRetryRate is used to speed up tests by setting consul-templates retry
	// rate to something low
	testRetryRate time.Duration = 0
)

// TaskHooks is an interface which provides hooks into the tasks life-cycle
type TaskHooks interface {
	// Restart is used to restart the task
	Restart(source, reason string)

	// Signal is used to signal the task
	Signal(source, reason string, s os.Signal) error

	// UnblockStart is used to unblock the starting of the task. This should be
	// called after prestart work is completed
	UnblockStart(source string)

	// Kill is used to kill the task because of the passed error. If fail is set
	// to true, the task is marked as failed
	Kill(source, reason string, fail bool)
}

// TaskTemplateManager is used to run a set of templates for a given task
type TaskTemplateManager struct {
	// templates is the set of templates we are managing
	templates []*structs.Template

	// lookup allows looking up the set of Nomad templates by their consul-template ID
	lookup map[string][]*structs.Template

	// allRendered marks whether all the templates have been rendered
	allRendered bool

	// hooks is used to signal/restart the task as templates are rendered
	hook TaskHooks

	// runner is the consul-template runner
	runner *manager.Runner

	// signals is a lookup map from the string representation of a signal to its
	// actual signal
	signals map[string]os.Signal

	// shutdownCh is used to signal and started goroutine to shutdown
	shutdownCh chan struct{}

	// shutdown marks whether the manager has been shutdown
	shutdown     bool
	shutdownLock sync.Mutex
}

func NewTaskTemplateManager(hook TaskHooks, tmpls []*structs.Template,
	allRendered bool, config *config.Config, vaultToken, taskDir string,
	taskEnv *env.TaskEnvironment) (*TaskTemplateManager, error) {

	// Check pre-conditions
	if hook == nil {
		return nil, fmt.Errorf("Invalid task hook given")
	} else if config == nil {
		return nil, fmt.Errorf("Invalid config given")
	} else if taskDir == "" {
		return nil, fmt.Errorf("Invalid task directory given")
	} else if taskEnv == nil {
		return nil, fmt.Errorf("Invalid task environment given")
	}

	tm := &TaskTemplateManager{
		templates:   tmpls,
		allRendered: allRendered,
		hook:        hook,
		shutdownCh:  make(chan struct{}),
	}

	// Parse the signals that we need
	for _, tmpl := range tmpls {
		if tmpl.ChangeSignal == "" {
			continue
		}

		sig, err := signals.Parse(tmpl.ChangeSignal)
		if err != nil {
			return nil, fmt.Errorf("Failed to parse signal %q", tmpl.ChangeSignal)
		}

		if tm.signals == nil {
			tm.signals = make(map[string]os.Signal)
		}

		tm.signals[tmpl.ChangeSignal] = sig
	}

	// Build the consul-template runner
	runner, lookup, err := templateRunner(tmpls, config, vaultToken, taskDir, taskEnv)
	if err != nil {
		return nil, err
	}
	tm.runner = runner
	tm.lookup = lookup

	go tm.run()
	return tm, nil
}

// Stop is used to stop the consul-template runner
func (tm *TaskTemplateManager) Stop() {
	tm.shutdownLock.Lock()
	defer tm.shutdownLock.Unlock()

	if tm.shutdown {
		return
	}

	close(tm.shutdownCh)
	tm.shutdown = true

	// Stop the consul-template runner
	if tm.runner != nil {
		tm.runner.Stop()
	}
}

// run is the long lived loop that handles errors and templates being rendered
func (tm *TaskTemplateManager) run() {
	// Runner is nil if there is no templates
	if tm.runner == nil {
		// Unblock the start if there is nothing to do
		if !tm.allRendered {
			tm.hook.UnblockStart("consul-template")
		}

		return
	}

	// Start the runner
	go tm.runner.Start()

	// Track when they have all been rendered so we don't signal the task for
	// any render event before hand
	var allRenderedTime time.Time

	// Handle the first rendering
	if !tm.allRendered {
		// Wait till all the templates have been rendered
	WAIT:
		for {
			select {
			case <-tm.shutdownCh:
				return
			case err, ok := <-tm.runner.ErrCh:
				if !ok {
					continue
				}

				tm.hook.Kill("consul-template", err.Error(), true)
			case <-tm.runner.TemplateRenderedCh():
				// A template has been rendered, figure out what to do
				events := tm.runner.RenderEvents()

				// Not all templates have been rendered yet
				if len(events) < len(tm.lookup) {
					continue
				}

				for _, event := range events {
					// This template hasn't been rendered
					if event.LastDidRender.IsZero() {
						continue WAIT
					}
				}

				break WAIT
			}

			// TODO Thinking, I believe we could check every 30 seconds and if
			// they are all would be rendered we should start anyways. That is
			// the reattach mechanism when they have all been rendered
		}

		allRenderedTime = time.Now()
		tm.hook.UnblockStart("consul-template")
	}

	// If all our templates are change mode no-op, then we can exit here
	if tm.allTemplatesNoop() {
		return
	}

	// A lookup for the last time the template was handled
	numTemplates := len(tm.templates)
	handledRenders := make(map[string]time.Time, numTemplates)

	for {
		select {
		case <-tm.shutdownCh:
			return
		case err, ok := <-tm.runner.ErrCh:
			if !ok {
				continue
			}

			tm.hook.Kill("consul-template", err.Error(), true)
		case <-tm.runner.TemplateRenderedCh():
			// A template has been rendered, figure out what to do
			var handling []string
			signals := make(map[string]struct{})
			restart := false
			var splay time.Duration

			now := time.Now()
			for id, event := range tm.runner.RenderEvents() {

				// First time through
				if allRenderedTime.After(event.LastDidRender) {
					handledRenders[id] = now
					continue
				}

				// We have already handled this one
				if htime := handledRenders[id]; htime.After(event.LastDidRender) {
					continue
				}

				// Lookup the template and determine what to do
				tmpls, ok := tm.lookup[id]
				if !ok {
					tm.hook.Kill("consul-template", fmt.Sprintf("consul-template runner returned unknown template id %q", id), true)
					return
				}

				for _, tmpl := range tmpls {
					switch tmpl.ChangeMode {
					case structs.TemplateChangeModeSignal:
						signals[tmpl.ChangeSignal] = struct{}{}
					case structs.TemplateChangeModeRestart:
						restart = true
					case structs.TemplateChangeModeNoop:
						continue
					}

					if tmpl.Splay > splay {
						splay = tmpl.Splay
					}
				}

				handling = append(handling, id)
			}

			if restart || len(signals) != 0 {
				if splay != 0 {
					select {
					case <-time.After(time.Duration(splay)):
					case <-tm.shutdownCh:
						return
					}
				}

				// Update handle time
				now = time.Now()
				for _, id := range handling {
					handledRenders[id] = now
				}

				if restart {
					tm.hook.Restart("consul-template", "template with change_mode restart re-rendered")
				} else if len(signals) != 0 {
					var mErr multierror.Error
					for signal := range signals {
						err := tm.hook.Signal("consul-template", "template re-rendered", tm.signals[signal])
						if err != nil {
							multierror.Append(&mErr, err)
						}
					}

					if err := mErr.ErrorOrNil(); err != nil {
						flat := make([]os.Signal, 0, len(signals))
						for signal := range signals {
							flat = append(flat, tm.signals[signal])
						}
						tm.hook.Kill("consul-template", fmt.Sprintf("Sending signals %v failed: %v", flat, err), true)
					}
				}
			}
		}
	}
}

// allTemplatesNoop returns whether all the managed templates have change mode noop.
func (tm *TaskTemplateManager) allTemplatesNoop() bool {
	for _, tmpl := range tm.templates {
		if tmpl.ChangeMode != structs.TemplateChangeModeNoop {
			return false
		}
	}

	return true
}

// templateRunner returns a consul-template runner for the given templates and a
// lookup by destination to the template. If no templates are given, a nil
// template runner and lookup is returned.
func templateRunner(tmpls []*structs.Template, config *config.Config,
	vaultToken, taskDir string, taskEnv *env.TaskEnvironment) (
	*manager.Runner, map[string][]*structs.Template, error) {

	if len(tmpls) == 0 {
		return nil, nil, nil
	}

	runnerConfig, err := runnerConfig(config, vaultToken)
	if err != nil {
		return nil, nil, err
	}

	// Parse the templates
	ctmplMapping := parseTemplateConfigs(tmpls, taskDir, taskEnv)

	// Set the config
	flat := make([]*ctconf.ConfigTemplate, 0, len(ctmplMapping))
	for ctmpl := range ctmplMapping {
		local := ctmpl
		flat = append(flat, &local)
	}
	runnerConfig.ConfigTemplates = flat

	runner, err := manager.NewRunner(runnerConfig, false, false)
	if err != nil {
		return nil, nil, err
	}

	// Build the lookup
	idMap := runner.ConfigTemplateMapping()
	lookup := make(map[string][]*structs.Template, len(idMap))
	for id, ctmpls := range idMap {
		for _, ctmpl := range ctmpls {
			templates := lookup[id]
			templates = append(templates, ctmplMapping[ctmpl])
			lookup[id] = templates
		}
	}

	return runner, lookup, nil
}

// parseTemplateConfigs converts the tasks templates into consul-templates
func parseTemplateConfigs(tmpls []*structs.Template, taskDir string, taskEnv *env.TaskEnvironment) map[ctconf.ConfigTemplate]*structs.Template {
	// Build the task environment
	// TODO Should be able to inject the Nomad env vars into Consul-template for
	// rendering
	taskEnv.Build()

	ctmpls := make(map[ctconf.ConfigTemplate]*structs.Template, len(tmpls))
	for _, tmpl := range tmpls {
		var src, dest string
		if tmpl.SourcePath != "" {
			src = filepath.Join(taskDir, taskEnv.ReplaceEnv(tmpl.SourcePath))
		}
		if tmpl.DestPath != "" {
			dest = filepath.Join(taskDir, taskEnv.ReplaceEnv(tmpl.DestPath))
		}

		ct := ctconf.ConfigTemplate{
			Source:           src,
			Destination:      dest,
			EmbeddedTemplate: tmpl.EmbeddedTmpl,
			Perms:            ctconf.DefaultFilePerms,
			Wait:             &watch.Wait{},
		}

		ctmpls[ct] = tmpl
	}

	return ctmpls
}

// runnerConfig returns a consul-template runner configuration, setting the
// Vault and Consul configurations based on the clients configs.
func runnerConfig(config *config.Config, vaultToken string) (*ctconf.Config, error) {
	conf := &ctconf.Config{}

	set := func(keys []string) {
		for _, k := range keys {
			conf.Set(k)
		}
	}

	if testRetryRate != 0 {
		conf.Retry = testRetryRate
		conf.Set("retry")
	}

	// Setup the Consul config
	if config.ConsulConfig != nil {
		conf.Consul = config.ConsulConfig.Addr
		conf.Token = config.ConsulConfig.Token
		set([]string{"consul", "token"})

		if config.ConsulConfig.EnableSSL {
			conf.SSL = &ctconf.SSLConfig{
				Enabled: true,
				Verify:  config.ConsulConfig.VerifySSL,
				Cert:    config.ConsulConfig.CertFile,
				Key:     config.ConsulConfig.KeyFile,
				CaCert:  config.ConsulConfig.CAFile,
			}
			set([]string{"ssl", "ssl.enabled", "ssl.verify", "ssl.cert", "ssl.key", "ssl.ca_cert"})
		}

		if config.ConsulConfig.Auth != "" {
			parts := strings.SplitN(config.ConsulConfig.Auth, ":", 2)
			if len(parts) != 2 {
				return nil, fmt.Errorf("Failed to parse Consul Auth config")
			}

			conf.Auth = &ctconf.AuthConfig{
				Enabled:  true,
				Username: parts[0],
				Password: parts[1],
			}

			set([]string{"auth", "auth.username", "auth.password", "auth.enabled"})
		}
	}

	// Setup the Vault config
	if config.VaultConfig != nil && config.VaultConfig.IsEnabled() {
		conf.Vault = &ctconf.VaultConfig{
			Address:    config.VaultConfig.Addr,
			Token:      vaultToken,
			RenewToken: false,
		}
		set([]string{"vault", "vault.address", "vault.token", "vault.renew_token"})

		if strings.HasPrefix(config.VaultConfig.Addr, "https") || config.VaultConfig.TLSCertFile != "" {
			verify := config.VaultConfig.TLSSkipVerify == nil || !*config.VaultConfig.TLSSkipVerify
			conf.Vault.SSL = &ctconf.SSLConfig{
				Enabled: true,
				Verify:  !verify,
				Cert:    config.VaultConfig.TLSCertFile,
				Key:     config.VaultConfig.TLSKeyFile,
				CaCert:  config.VaultConfig.TLSCaFile,
				CaPath:  config.VaultConfig.TLSCaPath,
			}

			set([]string{"vault.ssl", "vault.ssl.enabled", "vault.ssl.verify",
				"vault.ssl.cert", "vault.ssl.key", "vault.ssl.ca_cert"})
		}
	}

	return conf, nil
}