package deployer

import (
	"context"
	"encoding/json"
	"fmt"
	"log/slog"
	"path/filepath"
	"sort"
	"sync"
	"sync/atomic"

	"github.com/alexei/docker-watcher/internal/crypto"
	"github.com/alexei/docker-watcher/internal/docker"
	"github.com/alexei/docker-watcher/internal/events"
	"github.com/alexei/docker-watcher/internal/health"
	"github.com/alexei/docker-watcher/internal/notify"
	"github.com/alexei/docker-watcher/internal/npm"
	"github.com/alexei/docker-watcher/internal/store"
	"github.com/moby/moby/api/types/mount"
	"github.com/google/uuid"
)

// Deployer orchestrates the full deployment flow: pull image, create container,
// start, configure proxy, health check, and handle rollback on failure.
// It implements both webhook.DeployTriggerer and registry.DeployTriggerer.
type Deployer struct {
	docker   *docker.Client
	npm      *npm.Client
	store    *store.Store
	health   *health.Checker
	notifier *notify.Notifier
	eventBus EventPublisher
	encKey   [32]byte

	// Graceful shutdown: tracks in-progress deploys.
	activeWg     sync.WaitGroup
	shuttingDown atomic.Bool
}

// EventPublisher is the interface for publishing events to the event bus.
type EventPublisher interface {
	Publish(evt events.Event)
}

// New creates a new Deployer with all required dependencies.
func New(
	dockerClient *docker.Client,
	npmClient *npm.Client,
	st *store.Store,
	checker *health.Checker,
	notifier *notify.Notifier,
	eventBus EventPublisher,
	encKey [32]byte,
) *Deployer {
	return &Deployer{
		docker:   dockerClient,
		npm:      npmClient,
		store:    st,
		health:   checker,
		notifier: notifier,
		eventBus: eventBus,
		encKey:   encKey,
	}
}

// Drain waits for all in-progress deploys to complete. Call this during graceful shutdown.
func (d *Deployer) Drain() {
	d.shuttingDown.Store(true)
	slog.Info("deployer: draining in-progress deploys")
	d.activeWg.Wait()
	slog.Info("deployer: all deploys drained")
}

// AsyncTriggerDeploy creates a deploy record and returns the deploy ID immediately,
// then runs the full deploy pipeline in a background goroutine. Use this from HTTP handlers
// to avoid blocking the request. Progress is streamed via SSE.
func (d *Deployer) AsyncTriggerDeploy(ctx context.Context, projectID, stageID, imageTag string) (string, error) {
	if d.shuttingDown.Load() {
		return "", fmt.Errorf("deployer is shutting down, rejecting new deploy")
	}

	// Validate inputs synchronously so the caller gets immediate feedback.
	project, err := d.store.GetProjectByID(projectID)
	if err != nil {
		return "", fmt.Errorf("get project: %w", err)
	}
	stage, err := d.store.GetStageByID(stageID)
	if err != nil {
		return "", fmt.Errorf("get stage: %w", err)
	}
	if err := d.validatePromoteFrom(stage, imageTag); err != nil {
		return "", fmt.Errorf("promote validation: %w", err)
	}

	// Create deploy record synchronously so caller gets the ID.
	deploy, err := d.store.CreateDeploy(store.Deploy{
		ProjectID: projectID,
		StageID:   stageID,
		ImageTag:  imageTag,
		Status:    "pending",
	})
	if err != nil {
		return "", fmt.Errorf("create deploy record: %w", err)
	}

	// Run the actual deploy in the background.
	d.activeWg.Add(1)
	go func() {
		defer d.activeWg.Done()
		// Use a detached context so client disconnect doesn't abort the deploy.
		bgCtx := context.Background()
		if err := d.runDeploy(bgCtx, project, stage, deploy.ID, imageTag); err != nil {
			slog.Error("async deploy failed", "deploy_id", deploy.ID, "error", err)
		}
	}()

	return deploy.ID, nil
}

// runDeploy is the internal deploy pipeline used by AsyncTriggerDeploy.
// It assumes the deploy record already exists and project/stage are validated.
func (d *Deployer) runDeploy(ctx context.Context, project store.Project, stage store.Stage, deployID string, imageTag string) error {
	settings, err := d.store.GetSettings()
	if err != nil {
		if updateErr := d.store.UpdateDeployStatus(deployID, "failed", err.Error()); updateErr != nil {
			slog.Warn("update deploy status", "error", updateErr)
		}
		return fmt.Errorf("get settings: %w", err)
	}

	slog.Info("starting deploy",
		"deploy_id", deployID,
		"project", project.Name,
		"stage", stage.Name,
		"tag", imageTag,
	)
	d.logDeploy(deployID, fmt.Sprintf("Starting deploy of %s:%s for project %s, stage %s", project.Image, imageTag, project.Name, stage.Name), "info")

	// Enforce max_instances before deploying.
	if err := d.enforceMaxInstances(ctx, stage, deployID, settings); err != nil {
		d.logDeploy(deployID, fmt.Sprintf("Failed to enforce max instances: %v", err), "error")
	}

	var containerID string
	var npmProxyID int
	var instanceID string
	var deployErr error

	if stage.MaxInstances == 1 {
		containerID, npmProxyID, instanceID, deployErr = d.blueGreenDeploy(ctx, project, stage, settings, deployID, imageTag)
	} else {
		containerID, npmProxyID, instanceID, deployErr = d.executeDeploy(ctx, project, stage, settings, deployID, imageTag)
	}

	if deployErr != nil {
		d.logDeploy(deployID, fmt.Sprintf("Deploy failed: %v", deployErr), "error")
		d.publishDeployStatus(deployID, project.ID, stage.ID, imageTag, "failed", deployErr.Error())
		d.rollback(ctx, deployID, containerID, npmProxyID, instanceID)

		d.notifier.Send(settings.NotificationURL, notify.Event{
			Type:     "deploy_failure",
			Project:  project.Name,
			Stage:    stage.Name,
			ImageTag: imageTag,
			Error:    deployErr.Error(),
		})

		return fmt.Errorf("deploy failed: %w", deployErr)
	}

	if err := d.store.UpdateDeployStatus(deployID, "success", ""); err != nil {
		slog.Warn("update deploy status to success", "error", err)
	}
	d.publishDeployStatus(deployID, project.ID, stage.ID, imageTag, "success", "")

	subdomain := d.buildSubdomain(project, stage, settings, imageTag)
	fullURL := fmt.Sprintf("https://%s.%s", subdomain, settings.Domain)

	d.logDeploy(deployID, fmt.Sprintf("Deploy successful: %s", fullURL), "info")

	d.notifier.Send(settings.NotificationURL, notify.Event{
		Type:      "deploy_success",
		Project:   project.Name,
		Stage:     stage.Name,
		ImageTag:  imageTag,
		Subdomain: subdomain,
		URL:       fullURL,
	})

	return nil
}

// TriggerDeploy is the synchronous entry point for deployments (used by poller and webhook).
// It validates inputs, creates a deploy record, and delegates to runDeploy.
func (d *Deployer) TriggerDeploy(ctx context.Context, projectID, stageID, imageTag string) error {
	if d.shuttingDown.Load() {
		return fmt.Errorf("deployer is shutting down, rejecting new deploy")
	}

	d.activeWg.Add(1)
	defer d.activeWg.Done()

	project, err := d.store.GetProjectByID(projectID)
	if err != nil {
		return fmt.Errorf("get project: %w", err)
	}

	stage, err := d.store.GetStageByID(stageID)
	if err != nil {
		return fmt.Errorf("get stage: %w", err)
	}

	if err := d.validatePromoteFrom(stage, imageTag); err != nil {
		return fmt.Errorf("promote validation: %w", err)
	}

	deploy, err := d.store.CreateDeploy(store.Deploy{
		ProjectID: projectID,
		StageID:   stageID,
		ImageTag:  imageTag,
		Status:    "pending",
	})
	if err != nil {
		return fmt.Errorf("create deploy record: %w", err)
	}

	if err := d.runDeploy(ctx, project, stage, deploy.ID, imageTag); err != nil {
		return err
	}
	return nil
}

// executeDeploy runs the deploy pipeline steps and returns rollback-relevant state.
// It returns (containerID, npmProxyID, instanceID, error).
func (d *Deployer) executeDeploy(
	ctx context.Context,
	project store.Project,
	stage store.Stage,
	settings store.Settings,
	deployID string,
	imageTag string,
) (string, int, string, error) {
	var containerID string
	var npmProxyID int
	var instanceID string

	// Step 1: Pull image.
	if err := d.store.UpdateDeployStatus(deployID, "pulling", ""); err != nil {
		slog.Warn("update deploy status", "error", err)
	}
	d.publishDeployStatus(deployID, project.ID, stage.ID, imageTag, "pulling", "")
	d.logDeploy(deployID, fmt.Sprintf("Pulling image %s:%s", project.Image, imageTag), "info")

	authConfig, err := d.buildRegistryAuth(project)
	if err != nil {
		return containerID, npmProxyID, instanceID, fmt.Errorf("build registry auth: %w", err)
	}

	if err := d.docker.PullImage(ctx, project.Image, imageTag, authConfig); err != nil {
		return containerID, npmProxyID, instanceID, fmt.Errorf("pull image: %w", err)
	}
	d.logDeploy(deployID, "Image pulled successfully", "info")

	// Step 2: Ensure network exists.
	networkID, err := d.docker.EnsureNetwork(ctx, settings.Network)
	if err != nil {
		return containerID, npmProxyID, instanceID, fmt.Errorf("ensure network: %w", err)
	}
	d.logDeploy(deployID, fmt.Sprintf("Network %s ready (ID: %s)", settings.Network, truncateID(networkID)), "info")

	// Step 3: Create and start container.
	if err := d.store.UpdateDeployStatus(deployID, "starting", ""); err != nil {
		slog.Warn("update deploy status", "error", err)
	}
	d.publishDeployStatus(deployID, project.ID, stage.ID, imageTag, "starting", "")

	// Pre-generate instance ID so it can be set as a container label.
	instanceID = uuid.New().String()
	subdomain := d.buildSubdomain(project, stage, settings, imageTag)

	containerName := docker.ContainerName(project.Name, stage.Name, imageTag)
	portStr := fmt.Sprintf("%d/tcp", project.Port)
	envVars := d.mergeEnvVars(project, stage.ID)
	mounts := d.computeVolumeMounts(project.ID, stage.Name, imageTag, settings.BaseVolumePath)

	containerCfg := docker.ContainerConfig{
		Name:         containerName,
		Image:        project.Image + ":" + imageTag,
		Env:          envVars,
		ExposedPorts: []string{portStr},
		NetworkName:  settings.Network,
		NetworkID:    networkID,
		Project:      project.Name,
		Stage:        stage.Name,
		InstanceID:   instanceID,
		Mounts:       mounts,
	}

	d.logDeploy(deployID, fmt.Sprintf("Creating container %s", containerName), "info")
	containerID, err = d.docker.CreateContainer(ctx, containerCfg)
	if err != nil {
		return containerID, npmProxyID, instanceID, fmt.Errorf("create container: %w", err)
	}
	d.logDeploy(deployID, fmt.Sprintf("Container created (ID: %s)", truncateID(containerID)), "info")

	// Create instance record in store with the pre-generated ID.
	inst, err := d.store.CreateInstanceWithID(store.Instance{
		ID:          instanceID,
		StageID:     stage.ID,
		ProjectID:   project.ID,
		ContainerID: containerID,
		ImageTag:    imageTag,
		Subdomain:   subdomain,
		Status:      "stopped",
		Port:        project.Port,
	})
	if err != nil {
		return containerID, npmProxyID, instanceID, fmt.Errorf("create instance record: %w", err)
	}
	instanceID = inst.ID

	// Link deploy to instance.
	if err := d.store.SetDeployInstanceID(deployID, instanceID); err != nil {
		slog.Warn("link deploy to instance", "error", err)
	}

	d.logDeploy(deployID, fmt.Sprintf("Starting container %s", containerName), "info")
	if err := d.docker.StartContainer(ctx, containerID); err != nil {
		return containerID, npmProxyID, instanceID, fmt.Errorf("start container: %w", err)
	}

	if err := d.store.UpdateInstanceStatus(instanceID, "running"); err != nil {
		slog.Warn("update instance status to running", "error", err)
	}
	d.publishInstanceStatus(instanceID, project.ID, stage.ID, "running")
	d.logDeploy(deployID, "Container started", "info")

	// Step 4: Configure NPM proxy.
	if err := d.store.UpdateDeployStatus(deployID, "configuring_proxy", ""); err != nil {
		slog.Warn("update deploy status", "error", err)
	}
	d.publishDeployStatus(deployID, project.ID, stage.ID, imageTag, "configuring_proxy", "")

	npmProxyID, err = d.configureProxy(ctx, deployID, settings, containerName, project.Port, subdomain)
	if err != nil {
		return containerID, npmProxyID, instanceID, fmt.Errorf("configure proxy: %w", err)
	}

	// Update instance with NPM proxy ID.
	inst.NpmProxyID = npmProxyID
	inst.Subdomain = subdomain
	if err := d.store.UpdateInstance(inst); err != nil {
		slog.Warn("update instance with proxy ID", "error", err)
	}

	// Step 5: Health check.
	if project.Healthcheck != "" {
		if err := d.store.UpdateDeployStatus(deployID, "health_checking", ""); err != nil {
			slog.Warn("update deploy status", "error", err)
		}
		d.publishDeployStatus(deployID, project.ID, stage.ID, imageTag, "health_checking", "")

		healthURL := fmt.Sprintf("http://%s:%d%s", containerName, project.Port, project.Healthcheck)
		d.logDeploy(deployID, fmt.Sprintf("Running health check: %s", healthURL), "info")

		if err := d.health.Check(ctx, healthURL); err != nil {
			return containerID, npmProxyID, instanceID, fmt.Errorf("health check: %w", err)
		}
		d.logDeploy(deployID, "Health check passed", "info")
	} else {
		d.logDeploy(deployID, "No health check configured, skipping", "info")
	}

	return containerID, npmProxyID, instanceID, nil
}

// configureProxy creates or updates an NPM proxy host for the deployed container.
// It authenticates to NPM using credentials from settings, then creates the proxy.
// Returns the NPM proxy host ID.
func (d *Deployer) configureProxy(
	ctx context.Context,
	deployID string,
	settings store.Settings,
	containerName string,
	containerPort int,
	subdomain string,
) (int, error) {
	// Authenticate to NPM.
	npmPassword, err := d.decryptNpmPassword(settings.NpmPassword)
	if err != nil {
		return 0, fmt.Errorf("decrypt npm password: %w", err)
	}

	if err := d.npm.Authenticate(ctx, settings.NpmEmail, npmPassword); err != nil {
		return 0, fmt.Errorf("authenticate to npm: %w", err)
	}

	fqdn := subdomain + "." + settings.Domain
	d.logDeploy(deployID, fmt.Sprintf("Configuring proxy: %s -> %s:%d", fqdn, containerName, containerPort), "info")

	// Check if a proxy host already exists for this domain.
	existing, found, err := d.npm.FindProxyHostByDomain(ctx, fqdn)
	if err != nil {
		return 0, fmt.Errorf("find existing proxy host: %w", err)
	}

	proxyConfig := npm.ProxyHostConfig{
		DomainNames:    []string{fqdn},
		ForwardScheme:  "http",
		ForwardHost:    containerName,
		ForwardPort:    containerPort,
		BlockExploits:  true,
		AllowWebsocket: true,
		HTTP2Support:   true,
		Meta:           npm.Meta{},
		Locations:      []any{},
	}

	if found {
		d.logDeploy(deployID, fmt.Sprintf("Updating existing proxy host %d for %s", existing.ID, fqdn), "info")
		host, err := d.npm.UpdateProxyHost(ctx, existing.ID, proxyConfig)
		if err != nil {
			return 0, fmt.Errorf("update proxy host: %w", err)
		}
		d.logDeploy(deployID, "Proxy host updated", "info")
		return host.ID, nil
	}

	d.logDeploy(deployID, fmt.Sprintf("Creating new proxy host for %s", fqdn), "info")
	host, err := d.npm.CreateProxyHost(ctx, proxyConfig)
	if err != nil {
		return 0, fmt.Errorf("create proxy host: %w", err)
	}
	d.logDeploy(deployID, fmt.Sprintf("Proxy host created (ID: %d)", host.ID), "info")
	return host.ID, nil
}

// enforceMaxInstances removes the oldest instances when the stage has reached its limit.
// This makes room for the new deployment.
func (d *Deployer) enforceMaxInstances(ctx context.Context, stage store.Stage, deployID string, settings store.Settings) error {
	if stage.MaxInstances <= 0 {
		return nil
	}

	instances, err := d.store.GetInstancesByStageID(stage.ID)
	if err != nil {
		return fmt.Errorf("get instances for stage: %w", err)
	}

	// Filter to running/stopped instances (not already failed/removing).
	var active []store.Instance
	for _, inst := range instances {
		if inst.Status == "running" || inst.Status == "stopped" {
			active = append(active, inst)
		}
	}

	// We need room for one more instance, so remove oldest when at limit.
	removeCount := len(active) - stage.MaxInstances + 1
	if removeCount <= 0 {
		return nil
	}

	// Sort by created_at ascending (oldest first).
	sort.Slice(active, func(i, j int) bool {
		return active[i].CreatedAt < active[j].CreatedAt
	})

	for i := 0; i < removeCount && i < len(active); i++ {
		inst := active[i]
		d.logDeploy(deployID, fmt.Sprintf("Removing oldest instance %s (tag: %s) to enforce max_instances=%d", inst.ID, inst.ImageTag, stage.MaxInstances), "info")

		if err := d.removeInstance(ctx, inst, settings); err != nil {
			d.logDeploy(deployID, fmt.Sprintf("Failed to remove instance %s: %v", inst.ID, err), "warn")
			continue
		}
		d.logDeploy(deployID, fmt.Sprintf("Removed instance %s", inst.ID), "info")
	}

	return nil
}

// removeInstance stops and removes a container, deletes its NPM proxy host,
// and removes the instance record from the store.
func (d *Deployer) removeInstance(ctx context.Context, inst store.Instance, settings store.Settings) error {
	// Mark as removing.
	if err := d.store.UpdateInstanceStatus(inst.ID, "removing"); err != nil {
		slog.Warn("update instance status to removing", "instance_id", inst.ID, "error", err)
	}

	// Remove Docker container.
	if inst.ContainerID != "" {
		if err := d.docker.RemoveContainer(ctx, inst.ContainerID, true); err != nil {
			slog.Warn("remove container", "container_id", inst.ContainerID, "error", err)
		}
	}

	// Delete NPM proxy host.
	if inst.NpmProxyID > 0 {
		npmPassword, err := d.decryptNpmPassword(settings.NpmPassword)
		if err != nil {
			slog.Warn("decrypt npm password for proxy cleanup", "error", err)
		} else if authErr := d.npm.Authenticate(ctx, settings.NpmEmail, npmPassword); authErr != nil {
			slog.Warn("authenticate npm for proxy cleanup", "error", authErr)
		} else if delErr := d.npm.DeleteProxyHost(ctx, inst.NpmProxyID); delErr != nil {
			slog.Warn("delete proxy host", "proxy_id", inst.NpmProxyID, "error", delErr)
		}
	}

	// Delete instance record.
	if err := d.store.DeleteInstance(inst.ID); err != nil {
		return fmt.Errorf("delete instance record: %w", err)
	}

	return nil
}

// buildSubdomain generates the subdomain for an instance based on settings and stage config.
func (d *Deployer) buildSubdomain(project store.Project, stage store.Stage, settings store.Settings, imageTag string) string {
	return GenerateTaggedSubdomain(settings.SubdomainPattern, project.Name, stage.Name, imageTag, stage.Subdomain)
}

// buildRegistryAuth constructs the Docker registry auth string for pulling images.
// If the project has a registry configured, it looks up the registry token.
func (d *Deployer) buildRegistryAuth(project store.Project) (string, error) {
	if project.Registry == "" {
		return "", nil
	}

	reg, err := d.store.GetRegistryByName(project.Registry)
	if err != nil {
		return "", fmt.Errorf("get registry %s: %w", project.Registry, err)
	}

	if reg.Token != "" {
		decrypted, err := crypto.Decrypt(d.encKey, reg.Token)
		if err != nil {
			return "", fmt.Errorf("decrypt registry token: %w", err)
		}
		return docker.EncodeRegistryAuth(decrypted, decrypted, reg.URL)
	}
	return "", nil
}

// decryptNpmPassword decrypts the NPM password from settings.
// Returns empty string if the encrypted password is empty.
func (d *Deployer) decryptNpmPassword(encryptedPassword string) (string, error) {
	if encryptedPassword == "" {
		return "", nil
	}
	return crypto.Decrypt(d.encKey, encryptedPassword)
}

// mergeEnvVars builds the final environment variable list for a container:
// 1. Parse project-level env JSON
// 2. Overlay with stage-level env overrides (stage wins on key conflict)
// 3. Decrypt any encrypted (secret) values
// Returns a []string of KEY=VALUE pairs.
func (d *Deployer) mergeEnvVars(project store.Project, stageID string) []string {
	// Step 1: Parse project-level env.
	envMap := make(map[string]string)
	if project.Env != "" && project.Env != "{}" {
		var projectEnv map[string]string
		if err := json.Unmarshal([]byte(project.Env), &projectEnv); err != nil {
			slog.Warn("parse project env vars", "error", err)
		} else {
			for k, v := range projectEnv {
				envMap[k] = v
			}
		}
	}

	// Step 2: Overlay with stage-level overrides.
	stageEnvs, err := d.store.GetStageEnvByStageID(stageID)
	if err != nil {
		slog.Warn("get stage env overrides", "stage_id", stageID, "error", err)
	} else {
		for _, se := range stageEnvs {
			value := se.Value
			if se.Encrypted {
				// Step 3: Decrypt secret values.
				decrypted, err := crypto.Decrypt(d.encKey, se.Value)
				if err != nil {
					slog.Warn("decrypt stage env value", "key", se.Key, "error", err)
					continue
				}
				value = decrypted
			}
			envMap[se.Key] = value
		}
	}

	vars := make([]string, 0, len(envMap))
	for k, v := range envMap {
		vars = append(vars, k+"="+v)
	}
	return vars
}

// computeVolumeMounts builds Docker mount specifications from the project's volume config.
// For shared mode, source is used as-is.
// For isolated mode, source gets /{stage}-{tag}/ appended.
func (d *Deployer) computeVolumeMounts(projectID, stageName, imageTag, basePath string) []mount.Mount {
	vols, err := d.store.GetVolumesByProjectID(projectID)
	if err != nil {
		slog.Warn("get project volumes", "project_id", projectID, "error", err)
		return nil
	}

	if len(vols) == 0 {
		return nil
	}

	mounts := make([]mount.Mount, 0, len(vols))
	for _, vol := range vols {
		source := vol.Source
		// Prepend base path if source is relative (doesn't start with /).
		if basePath != "" && !filepath.IsAbs(source) {
			source = filepath.Join(basePath, source)
		}
		if vol.Mode == "isolated" {
			source = filepath.Join(source, fmt.Sprintf("%s-%s", stageName, imageTag))
		}
		mounts = append(mounts, mount.Mount{
			Type:   mount.TypeBind,
			Source: source,
			Target: vol.Target,
		})
	}
	return mounts
}

// logDeploy appends a log entry for a deploy and publishes it on the event bus.
// Errors are logged to stderr but not propagated.
func (d *Deployer) logDeploy(deployID, message, level string) {
	if err := d.store.AppendDeployLog(deployID, message, level); err != nil {
		slog.Warn("append deploy log", "error", err)
	}
	if d.eventBus != nil {
		d.eventBus.Publish(events.Event{
			Type: events.EventDeployLog,
			Payload: events.DeployLogPayload{
				DeployID: deployID,
				Message:  message,
				Level:    level,
			},
		})
	}
}

// publishDeployStatus publishes a deploy status change event on the bus.
func (d *Deployer) publishDeployStatus(deployID, projectID, stageID, imageTag, status, deployErr string) {
	if d.eventBus != nil {
		d.eventBus.Publish(events.Event{
			Type: events.EventDeployStatus,
			Payload: events.DeployStatusPayload{
				DeployID:  deployID,
				ProjectID: projectID,
				StageID:   stageID,
				ImageTag:  imageTag,
				Status:    status,
				Error:     deployErr,
			},
		})
	}
}

// publishInstanceStatus publishes an instance status change event on the bus.
func (d *Deployer) publishInstanceStatus(instanceID, projectID, stageID, status string) {
	if d.eventBus != nil {
		d.eventBus.Publish(events.Event{
			Type: events.EventInstanceStatus,
			Payload: events.InstanceStatusPayload{
				InstanceID: instanceID,
				ProjectID:  projectID,
				StageID:    stageID,
				Status:     status,
			},
		})
	}
}

// truncateID safely truncates a Docker ID to 12 characters for display.
func truncateID(id string) string {
	if len(id) > 12 {
		return id[:12]
	}
	return id
}