// Package deploy provides deployment services.
package deploy

import (
	"bytes"
	"context"
	"database/sql"
	"encoding/json"
	"errors"
	"fmt"
	"log/slog"
	"os"
	"path/filepath"
	"sync"
	"time"

	"go.uber.org/fx"

	"git.eeqj.de/sneak/upaas/internal/config"
	"git.eeqj.de/sneak/upaas/internal/database"
	"git.eeqj.de/sneak/upaas/internal/docker"
	"git.eeqj.de/sneak/upaas/internal/logger"
	"git.eeqj.de/sneak/upaas/internal/models"
	"git.eeqj.de/sneak/upaas/internal/service/notify"
)

// Time constants.
const (
	healthCheckDelaySeconds = 60
	// upaasLabelCount is the number of upaas-specific labels added to containers.
	upaasLabelCount = 1
	// buildsDirPermissions is the permission mode for the builds directory.
	buildsDirPermissions = 0o750
	// buildTimeout is the maximum duration for the build phase.
	buildTimeout = 30 * time.Minute
	// deployTimeout is the maximum duration for the deploy phase (container swap).
	deployTimeout = 5 * time.Minute
)

// Sentinel errors for deployment failures.
var (
	// ErrContainerUnhealthy indicates the container failed health check.
	ErrContainerUnhealthy = errors.New("container unhealthy after 60 seconds")
	// ErrDeploymentInProgress indicates another deployment is already running.
	ErrDeploymentInProgress = errors.New("deployment already in progress for this app")
	// ErrBuildTimeout indicates the build phase exceeded the timeout.
	ErrBuildTimeout = errors.New("build timeout exceeded")
	// ErrDeployTimeout indicates the deploy phase exceeded the timeout.
	ErrDeployTimeout = errors.New("deploy timeout exceeded")
)

// logFlushInterval is how often to flush buffered logs to the database.
const logFlushInterval = time.Second

// dockerLogMessage represents a Docker build log message.
type dockerLogMessage struct {
	Stream string `json:"stream"`
	Error  string `json:"error"`
}

// deploymentLogWriter implements io.Writer and periodically flushes to deployment logs.
// It parses Docker JSON log format and extracts the stream content.
type deploymentLogWriter struct {
	deployment *models.Deployment
	buffer     bytes.Buffer
	lineBuffer bytes.Buffer // buffer for incomplete lines
	mu         sync.Mutex
	done       chan struct{}
	flushCtx   context.Context //nolint:containedctx // needed for async flush goroutine
}

func newDeploymentLogWriter(ctx context.Context, deployment *models.Deployment) *deploymentLogWriter {
	w := &deploymentLogWriter{
		deployment: deployment,
		done:       make(chan struct{}),
		flushCtx:   ctx,
	}
	go w.runFlushLoop()

	return w
}

// Write implements io.Writer.
// It parses Docker JSON log format and extracts the stream content.
func (w *deploymentLogWriter) Write(p []byte) (int, error) {
	w.mu.Lock()
	defer w.mu.Unlock()

	// Add incoming data to line buffer
	w.lineBuffer.Write(p)

	// Process complete lines
	data := w.lineBuffer.Bytes()
	lastNewline := bytes.LastIndexByte(data, '\n')

	if lastNewline == -1 {
		// No complete lines yet
		return len(p), nil
	}

	// Process all complete lines
	completeData := data[:lastNewline+1]
	remaining := data[lastNewline+1:]

	for line := range bytes.SplitSeq(completeData, []byte{'\n'}) {
		w.processLine(line)
	}

	// Keep any remaining incomplete line data
	w.lineBuffer.Reset()

	if len(remaining) > 0 {
		w.lineBuffer.Write(remaining)
	}

	return len(p), nil
}

// Close stops the flush loop and performs a final flush.
func (w *deploymentLogWriter) Close() {
	close(w.done)
}

func (w *deploymentLogWriter) runFlushLoop() {
	ticker := time.NewTicker(logFlushInterval)
	defer ticker.Stop()

	for {
		select {
		case <-ticker.C:
			w.doFlush()
		case <-w.done:
			w.doFlush()

			return
		}
	}
}

func (w *deploymentLogWriter) doFlush() {
	w.mu.Lock()
	data := w.buffer.String()
	w.buffer.Reset()
	w.mu.Unlock()

	if data != "" {
		_ = w.deployment.AppendLog(w.flushCtx, data)
	}
}

// processLine parses a JSON log line and extracts the stream content.
func (w *deploymentLogWriter) processLine(line []byte) {
	if len(line) == 0 {
		return
	}

	var msg dockerLogMessage

	err := json.Unmarshal(line, &msg)
	if err != nil {
		// Not valid JSON, write as-is
		w.buffer.Write(line)
		w.buffer.WriteByte('\n')

		return
	}

	if msg.Error != "" {
		w.buffer.WriteString("ERROR: ")
		w.buffer.WriteString(msg.Error)
		w.buffer.WriteByte('\n')
	}

	if msg.Stream != "" {
		w.buffer.WriteString(msg.Stream)
	}
}

// ServiceParams contains dependencies for Service.
type ServiceParams struct {
	fx.In

	Logger   *logger.Logger
	Config   *config.Config
	Database *database.Database
	Docker   *docker.Client
	Notify   *notify.Service
}

// Service provides deployment functionality.
type Service struct {
	log      *slog.Logger
	db       *database.Database
	docker   *docker.Client
	notify   *notify.Service
	config   *config.Config
	params   *ServiceParams
	appLocks sync.Map // map[string]*sync.Mutex - per-app deployment locks
}

// New creates a new deploy Service.
func New(lc fx.Lifecycle, params ServiceParams) (*Service, error) {
	svc := &Service{
		log:    params.Logger.Get(),
		db:     params.Database,
		docker: params.Docker,
		notify: params.Notify,
		config: params.Config,
		params: &params,
	}

	if lc != nil {
		lc.Append(fx.Hook{
			OnStart: func(ctx context.Context) error {
				return svc.cleanupStuckDeployments(ctx)
			},
		})
	}

	return svc, nil
}

// GetBuildDir returns the build directory path for an app.
func (svc *Service) GetBuildDir(appID string) string {
	return filepath.Join(svc.config.DataDir, "builds", appID)
}

// Deploy deploys an app.
func (svc *Service) Deploy(
	ctx context.Context,
	app *models.App,
	webhookEventID *int64,
) error {
	// Try to acquire per-app deployment lock
	if !svc.tryLockApp(app.ID) {
		svc.log.Warn("deployment already in progress", "app", app.Name)

		return ErrDeploymentInProgress
	}
	defer svc.unlockApp(app.ID)

	// Fetch webhook event and create deployment record
	webhookEvent := svc.fetchWebhookEvent(ctx, webhookEventID)

	deployment, err := svc.createDeploymentRecord(ctx, app, webhookEventID, webhookEvent)
	if err != nil {
		return err
	}

	svc.logWebhookPayload(ctx, deployment, webhookEvent)

	err = svc.updateAppStatusBuilding(ctx, app)
	if err != nil {
		return err
	}

	svc.notify.NotifyBuildStart(ctx, app, deployment)

	// Build phase with timeout
	imageID, err := svc.buildImageWithTimeout(ctx, app, deployment)
	if err != nil {
		return err
	}

	svc.notify.NotifyBuildSuccess(ctx, app, deployment)

	// Deploy phase with timeout
	err = svc.deployContainerWithTimeout(ctx, app, deployment, imageID)
	if err != nil {
		return err
	}

	err = svc.updateAppRunning(ctx, app, imageID)
	if err != nil {
		return err
	}

	// Use context.WithoutCancel to ensure health check completes even if
	// the parent context is cancelled (e.g., HTTP request ends).
	go svc.checkHealthAfterDelay(context.WithoutCancel(ctx), app, deployment)

	return nil
}

// buildImageWithTimeout runs the build phase with a timeout.
func (svc *Service) buildImageWithTimeout(
	ctx context.Context,
	app *models.App,
	deployment *models.Deployment,
) (string, error) {
	buildCtx, cancel := context.WithTimeout(ctx, buildTimeout)
	defer cancel()

	imageID, err := svc.buildImage(buildCtx, app, deployment)
	if err != nil {
		if errors.Is(buildCtx.Err(), context.DeadlineExceeded) {
			timeoutErr := fmt.Errorf("%w after %v", ErrBuildTimeout, buildTimeout)
			svc.failDeployment(ctx, app, deployment, timeoutErr)

			return "", timeoutErr
		}

		return "", err
	}

	return imageID, nil
}

// deployContainerWithTimeout runs the deploy phase with a timeout.
// It removes the old container and starts the new one.
func (svc *Service) deployContainerWithTimeout(
	ctx context.Context,
	app *models.App,
	deployment *models.Deployment,
	imageID string,
) error {
	deployCtx, cancel := context.WithTimeout(ctx, deployTimeout)
	defer cancel()

	err := svc.updateDeploymentDeploying(deployCtx, deployment)
	if err != nil {
		return err
	}

	// Remove old container first to free up the name
	svc.removeOldContainer(deployCtx, app, deployment)

	// Create and start the new container
	_, err = svc.createAndStartContainer(deployCtx, app, deployment, imageID)
	if err != nil {
		if errors.Is(deployCtx.Err(), context.DeadlineExceeded) {
			timeoutErr := fmt.Errorf("%w after %v", ErrDeployTimeout, deployTimeout)
			svc.failDeployment(ctx, app, deployment, timeoutErr)

			return timeoutErr
		}

		return err
	}

	return nil
}

// cleanupStuckDeployments marks any deployments stuck in building/deploying as failed.
func (svc *Service) cleanupStuckDeployments(ctx context.Context) error {
	query := `
		UPDATE deployments
		SET status = ?, finished_at = ?, logs = COALESCE(logs, '') || ?
		WHERE status IN (?, ?)
	`
	msg := "\n[System] Deployment marked as failed: process was interrupted\n"

	_, err := svc.db.DB().ExecContext(
		ctx,
		query,
		models.DeploymentStatusFailed,
		time.Now(),
		msg,
		models.DeploymentStatusBuilding,
		models.DeploymentStatusDeploying,
	)
	if err != nil {
		svc.log.Error("failed to cleanup stuck deployments", "error", err)

		return fmt.Errorf("failed to cleanup stuck deployments: %w", err)
	}

	svc.log.Info("cleaned up stuck deployments")

	return nil
}

func (svc *Service) getAppLock(appID string) *sync.Mutex {
	lock, _ := svc.appLocks.LoadOrStore(appID, &sync.Mutex{})

	mu, ok := lock.(*sync.Mutex)
	if !ok {
		// This should never happen, but handle it gracefully
		newMu := &sync.Mutex{}
		svc.appLocks.Store(appID, newMu)

		return newMu
	}

	return mu
}

func (svc *Service) tryLockApp(appID string) bool {
	return svc.getAppLock(appID).TryLock()
}

func (svc *Service) unlockApp(appID string) {
	svc.getAppLock(appID).Unlock()
}

func (svc *Service) fetchWebhookEvent(
	ctx context.Context,
	webhookEventID *int64,
) *models.WebhookEvent {
	if webhookEventID == nil {
		return nil
	}

	event, err := models.FindWebhookEvent(ctx, svc.db, *webhookEventID)
	if err != nil {
		svc.log.Warn("failed to fetch webhook event", "error", err)

		return nil
	}

	return event
}

func (svc *Service) logWebhookPayload(
	ctx context.Context,
	deployment *models.Deployment,
	webhookEvent *models.WebhookEvent,
) {
	if webhookEvent == nil || !webhookEvent.Payload.Valid {
		return
	}

	_ = deployment.AppendLog(ctx, "Webhook received:\n"+webhookEvent.Payload.String+"\n")
}

func (svc *Service) createDeploymentRecord(
	ctx context.Context,
	app *models.App,
	webhookEventID *int64,
	webhookEvent *models.WebhookEvent,
) (*models.Deployment, error) {
	deployment := models.NewDeployment(svc.db)
	deployment.AppID = app.ID

	if webhookEventID != nil {
		deployment.WebhookEventID = sql.NullInt64{
			Int64: *webhookEventID,
			Valid: true,
		}
	}

	// Set commit SHA from webhook event
	if webhookEvent != nil && webhookEvent.CommitSHA.Valid {
		deployment.CommitSHA = webhookEvent.CommitSHA
	}

	deployment.Status = models.DeploymentStatusBuilding

	saveErr := deployment.Save(ctx)
	if saveErr != nil {
		return nil, fmt.Errorf("failed to create deployment: %w", saveErr)
	}

	return deployment, nil
}

func (svc *Service) updateAppStatusBuilding(
	ctx context.Context,
	app *models.App,
) error {
	app.Status = models.AppStatusBuilding

	saveErr := app.Save(ctx)
	if saveErr != nil {
		return fmt.Errorf("failed to update app status: %w", saveErr)
	}

	return nil
}

func (svc *Service) buildImage(
	ctx context.Context,
	app *models.App,
	deployment *models.Deployment,
) (string, error) {
	workDir, cleanup, err := svc.cloneRepository(ctx, app, deployment)
	if err != nil {
		return "", err
	}

	defer cleanup()

	imageTag := "upaas/" + app.Name + ":latest"

	// Create log writer that flushes build output to deployment logs every second
	logWriter := newDeploymentLogWriter(ctx, deployment)
	defer logWriter.Close()

	// BuildImage creates a tar archive from the local filesystem,
	// so it needs the container path where files exist, not the host path.
	imageID, err := svc.docker.BuildImage(ctx, docker.BuildImageOptions{
		ContextDir:     workDir,
		DockerfilePath: app.DockerfilePath,
		Tags:           []string{imageTag},
		LogWriter:      logWriter,
	})
	if err != nil {
		svc.notify.NotifyBuildFailed(ctx, app, deployment, err)
		svc.failDeployment(
			ctx,
			app,
			deployment,
			fmt.Errorf("failed to build image: %w", err),
		)

		return "", fmt.Errorf("failed to build image: %w", err)
	}

	deployment.ImageID = sql.NullString{String: imageID, Valid: true}
	_ = deployment.AppendLog(ctx, "Image built: "+imageID)

	return imageID, nil
}

func (svc *Service) cloneRepository(
	ctx context.Context,
	app *models.App,
	deployment *models.Deployment,
) (string, func(), error) {
	// Use a subdirectory of DataDir for builds since it's mounted from the host
	// and accessible to Docker for bind mounts (unlike /tmp inside the container).
	// Structure: builds/<appname>/<deployment-id>-<random>/
	//   deploy_key   <- SSH key for cloning
	//   work/        <- cloned repository
	appBuildsDir := filepath.Join(svc.config.DataDir, "builds", app.Name)

	err := os.MkdirAll(appBuildsDir, buildsDirPermissions)
	if err != nil {
		svc.failDeployment(ctx, app, deployment, fmt.Errorf("failed to create builds dir: %w", err))

		return "", nil, fmt.Errorf("failed to create builds dir: %w", err)
	}

	buildDir, err := os.MkdirTemp(appBuildsDir, fmt.Sprintf("%d-*", deployment.ID))
	if err != nil {
		svc.failDeployment(ctx, app, deployment, fmt.Errorf("failed to create temp dir: %w", err))

		return "", nil, fmt.Errorf("failed to create temp dir: %w", err)
	}

	cleanup := func() { _ = os.RemoveAll(buildDir) }

	// Calculate the host path for Docker bind mounts.
	// When upaas runs in a container, DataDir is the container path but Docker
	// needs the host path. HostDataDir provides the host-side equivalent.
	// CloneRepo needs both: container path for writing files, host path for Docker mounts.
	hostBuildDir := svc.containerToHostPath(buildDir)

	// Get commit SHA from deployment if available
	var commitSHA string

	if deployment.CommitSHA.Valid {
		commitSHA = deployment.CommitSHA.String
	}

	cloneResult, cloneErr := svc.docker.CloneRepo(
		ctx,
		app.RepoURL,
		app.Branch,
		commitSHA,
		app.SSHPrivateKey,
		buildDir,
		hostBuildDir,
	)
	if cloneErr != nil {
		cleanup()
		svc.failDeployment(ctx, app, deployment, fmt.Errorf("failed to clone repo: %w", cloneErr))

		return "", nil, fmt.Errorf("failed to clone repo: %w", cloneErr)
	}

	// Log clone success with git output
	if commitSHA != "" {
		_ = deployment.AppendLog(ctx, "Repository cloned at commit "+commitSHA)
	} else {
		_ = deployment.AppendLog(ctx, "Repository cloned (branch: "+app.Branch+")")
	}

	if cloneResult != nil && cloneResult.Output != "" {
		_ = deployment.AppendLog(ctx, cloneResult.Output)
	}

	// Return the 'work' subdirectory where the repo was cloned
	workDir := filepath.Join(buildDir, "work")

	return workDir, cleanup, nil
}

// containerToHostPath converts a container-local path to the equivalent host path.
// This is needed when upaas runs inside a container but needs to pass paths to Docker.
func (svc *Service) containerToHostPath(containerPath string) string {
	if svc.config.HostDataDir == svc.config.DataDir {
		return containerPath
	}

	// Get relative path from DataDir
	relPath, err := filepath.Rel(svc.config.DataDir, containerPath)
	if err != nil {
		// Fall back to original path if we can't compute relative path
		return containerPath
	}

	return filepath.Join(svc.config.HostDataDir, relPath)
}

func (svc *Service) updateDeploymentDeploying(
	ctx context.Context,
	deployment *models.Deployment,
) error {
	deployment.Status = models.DeploymentStatusDeploying

	saveErr := deployment.Save(ctx)
	if saveErr != nil {
		return fmt.Errorf("failed to update deployment status: %w", saveErr)
	}

	return nil
}

// removeOldContainer stops and removes the old container before deploying a new one.
func (svc *Service) removeOldContainer(
	ctx context.Context,
	app *models.App,
	deployment *models.Deployment,
) {
	containerInfo, err := svc.docker.FindContainerByAppID(ctx, app.ID)
	if err != nil || containerInfo == nil {
		return
	}

	svc.log.Info("removing old container", "id", containerInfo.ID)

	if containerInfo.Running {
		stopErr := svc.docker.StopContainer(ctx, containerInfo.ID)
		if stopErr != nil {
			svc.log.Warn("failed to stop old container", "error", stopErr)
		}
	}

	removeErr := svc.docker.RemoveContainer(ctx, containerInfo.ID, true)
	if removeErr != nil {
		svc.log.Warn("failed to remove old container", "error", removeErr)
	}

	_ = deployment.AppendLog(ctx, "Old container removed: "+containerInfo.ID[:12])
}

func (svc *Service) createAndStartContainer(
	ctx context.Context,
	app *models.App,
	deployment *models.Deployment,
	imageID string,
) (string, error) {
	containerOpts, err := svc.buildContainerOptions(ctx, app, imageID)
	if err != nil {
		svc.failDeployment(ctx, app, deployment, err)

		return "", err
	}

	containerID, err := svc.docker.CreateContainer(ctx, containerOpts)
	if err != nil {
		svc.notify.NotifyDeployFailed(ctx, app, deployment, err)
		svc.failDeployment(
			ctx,
			app,
			deployment,
			fmt.Errorf("failed to create container: %w", err),
		)

		return "", fmt.Errorf("failed to create container: %w", err)
	}

	deployment.ContainerID = sql.NullString{String: containerID, Valid: true}
	_ = deployment.AppendLog(ctx, "Container created: "+containerID)

	startErr := svc.docker.StartContainer(ctx, containerID)
	if startErr != nil {
		svc.notify.NotifyDeployFailed(ctx, app, deployment, startErr)
		svc.failDeployment(
			ctx,
			app,
			deployment,
			fmt.Errorf("failed to start container: %w", startErr),
		)

		return "", fmt.Errorf("failed to start container: %w", startErr)
	}

	_ = deployment.AppendLog(ctx, "Container started")

	return containerID, nil
}

func (svc *Service) buildContainerOptions(
	ctx context.Context,
	app *models.App,
	_ string,
) (docker.CreateContainerOptions, error) {
	envVars, err := app.GetEnvVars(ctx)
	if err != nil {
		return docker.CreateContainerOptions{}, fmt.Errorf("failed to get env vars: %w", err)
	}

	labels, err := app.GetLabels(ctx)
	if err != nil {
		return docker.CreateContainerOptions{}, fmt.Errorf("failed to get labels: %w", err)
	}

	volumes, err := app.GetVolumes(ctx)
	if err != nil {
		return docker.CreateContainerOptions{}, fmt.Errorf("failed to get volumes: %w", err)
	}

	ports, err := app.GetPorts(ctx)
	if err != nil {
		return docker.CreateContainerOptions{}, fmt.Errorf("failed to get ports: %w", err)
	}

	envMap := make(map[string]string, len(envVars))
	for _, envVar := range envVars {
		envMap[envVar.Key] = envVar.Value
	}

	network := ""
	if app.DockerNetwork.Valid {
		network = app.DockerNetwork.String
	}

	return docker.CreateContainerOptions{
		Name:    "upaas-" + app.Name,
		Image:   "upaas/" + app.Name + ":latest",
		Env:     envMap,
		Labels:  buildLabelMap(app, labels),
		Volumes: buildVolumeMounts(volumes),
		Ports:   buildPortMappings(ports),
		Network: network,
	}, nil
}

func buildLabelMap(app *models.App, labels []*models.Label) map[string]string {
	labelMap := make(map[string]string, len(labels)+upaasLabelCount)
	for _, label := range labels {
		labelMap[label.Key] = label.Value
	}

	// Add the upaas.id label to identify this container
	labelMap[docker.LabelUpaasID] = app.ID

	return labelMap
}

func buildVolumeMounts(volumes []*models.Volume) []docker.VolumeMount {
	mounts := make([]docker.VolumeMount, 0, len(volumes))
	for _, vol := range volumes {
		mounts = append(mounts, docker.VolumeMount{
			HostPath:      vol.HostPath,
			ContainerPath: vol.ContainerPath,
			ReadOnly:      vol.ReadOnly,
		})
	}

	return mounts
}

func buildPortMappings(ports []*models.Port) []docker.PortMapping {
	mappings := make([]docker.PortMapping, 0, len(ports))
	for _, port := range ports {
		mappings = append(mappings, docker.PortMapping{
			HostPort:      port.HostPort,
			ContainerPort: port.ContainerPort,
			Protocol:      string(port.Protocol),
		})
	}

	return mappings
}

func (svc *Service) updateAppRunning(
	ctx context.Context,
	app *models.App,
	imageID string,
) error {
	app.ImageID = sql.NullString{String: imageID, Valid: true}
	app.Status = models.AppStatusRunning

	saveErr := app.Save(ctx)
	if saveErr != nil {
		return fmt.Errorf("failed to update app: %w", saveErr)
	}

	return nil
}

func (svc *Service) checkHealthAfterDelay(
	ctx context.Context,
	app *models.App,
	deployment *models.Deployment,
) {
	svc.log.Info(
		"waiting 60 seconds to check container health",
		"app", app.Name,
	)
	time.Sleep(healthCheckDelaySeconds * time.Second)

	// Reload app to get current state
	reloadedApp, err := models.FindApp(ctx, svc.db, app.ID)
	if err != nil || reloadedApp == nil {
		svc.log.Error("failed to reload app for health check", "error", err)

		return
	}

	containerInfo, containerErr := svc.docker.FindContainerByAppID(ctx, app.ID)
	if containerErr != nil || containerInfo == nil {
		return
	}

	healthy, err := svc.docker.IsContainerHealthy(ctx, containerInfo.ID)
	if err != nil {
		svc.log.Error("failed to check container health", "error", err)
		svc.notify.NotifyDeployFailed(ctx, reloadedApp, deployment, err)
		_ = deployment.MarkFinished(ctx, models.DeploymentStatusFailed)

		return
	}

	if healthy {
		svc.log.Info("container healthy after 60 seconds", "app", reloadedApp.Name)
		svc.notify.NotifyDeploySuccess(ctx, reloadedApp, deployment)
		_ = deployment.MarkFinished(ctx, models.DeploymentStatusSuccess)
	} else {
		svc.log.Warn(
			"container unhealthy after 60 seconds",
			"app", reloadedApp.Name,
		)
		svc.notify.NotifyDeployFailed(ctx, reloadedApp, deployment, ErrContainerUnhealthy)
		_ = deployment.MarkFinished(ctx, models.DeploymentStatusFailed)
		reloadedApp.Status = models.AppStatusError
		_ = reloadedApp.Save(ctx)
	}
}

func (svc *Service) failDeployment(
	ctx context.Context,
	app *models.App,
	deployment *models.Deployment,
	deployErr error,
) {
	svc.log.Error("deployment failed", "app", app.Name, "error", deployErr)
	_ = deployment.AppendLog(ctx, "ERROR: "+deployErr.Error())
	_ = deployment.MarkFinished(ctx, models.DeploymentStatusFailed)
	app.Status = models.AppStatusError
	_ = app.Save(ctx)
}