package runner

import (
	"context"
	"errors"
	"fmt"
	"os"
	"strings"
	"time"

	"github.com/easyai/easyai-ai-gateway/apps/api/internal/auth"
	"github.com/easyai/easyai-ai-gateway/apps/api/internal/store"
	"github.com/google/uuid"
	"github.com/jackc/pgx/v5"
	"github.com/riverqueue/river"
	"github.com/riverqueue/river/riverdriver/riverpgxv5"
	"github.com/riverqueue/river/rivermigrate"
	"github.com/riverqueue/river/rivertype"
)

const asyncTaskQueueName = "gateway_tasks"

type asyncTaskArgs struct {
	TaskID string `json:"task_id" river:"unique"`
}

type asyncExecutionClient interface {
	Start(context.Context) error
	Stop(context.Context) error
	StopAndCancel(context.Context) error
}

func (asyncTaskArgs) Kind() string { return "gateway_task_run" }

type asyncTaskWorker struct {
	river.WorkerDefaults[asyncTaskArgs]

	service *Service
}

func (w *asyncTaskWorker) Work(ctx context.Context, job *river.Job[asyncTaskArgs]) error {
	task, err := w.service.store.GetTask(ctx, job.Args.TaskID)
	if err != nil {
		return err
	}
	if task.Status == "succeeded" || task.Status == "failed" || task.Status == "cancelled" {
		return nil
	}
	executionToken := uuid.NewString()
	result, runErr := w.service.executeWithToken(ctx, task, authUserFromTask(task), nil, executionToken)
	if runErr == nil {
		w.service.logger.Debug("river async task completed", "taskID", task.ID, "status", result.Task.Status, "riverJobID", job.ID)
		return nil
	}
	if errors.Is(runErr, store.ErrTaskExecutionLeaseUnavailable) {
		w.service.logger.Debug("river async task execution lease already held", "taskID", task.ID, "riverJobID", job.ID)
		return nil
	}
	if errors.Is(runErr, store.ErrTaskExecutionManualReview) {
		w.service.logger.Warn("river async task moved to manual review after ambiguous upstream submission", "taskID", task.ID, "riverJobID", job.ID)
		return nil
	}
	var queuedErr *TaskQueuedError
	if errors.As(runErr, &queuedErr) {
		return river.JobSnooze(queuedErr.Delay)
	}
	if ctx.Err() != nil {
		task.ExecutionToken = executionToken
		queued, queueErr := w.service.requeueInterruptedAsyncTask(context.WithoutCancel(ctx), task)
		if queueErr != nil {
			return queueErr
		}
		w.service.logger.Debug("river async task interrupted and requeued", "taskID", task.ID, "status", queued.Status, "riverJobID", job.ID)
		return river.JobSnooze(0)
	}
	w.service.logger.Warn("river async task completed with failure", "taskID", task.ID, "error", runErr, "riverJobID", job.ID)
	return nil
}

func (s *Service) StartAsyncQueueWorker(ctx context.Context) {
	if err := s.startRiverQueue(ctx); err != nil {
		s.logger.Error("start river async queue failed", "error", err)
		panic(err)
	}
}

func (s *Service) startRiverQueue(ctx context.Context) error {
	driver := riverpgxv5.New(s.store.Pool())
	migrator, err := rivermigrate.New(driver, nil)
	if err != nil {
		return err
	}
	if _, err := migrator.Migrate(ctx, rivermigrate.DirectionUp, nil); err != nil {
		return err
	}

	controlClient, err := river.NewClient(driver, &river.Config{
		ID:       asyncWorkerID() + "-control",
		Logger:   s.logger,
		TestOnly: s.cfg.AppEnv == "test",
	})
	if err != nil {
		return err
	}
	snapshot, err := s.loadAsyncWorkerCapacity(ctx)
	if err != nil {
		return fmt.Errorf("calculate initial async worker capacity: %w", err)
	}
	executionClient, err := s.makeAsyncExecutionClient(snapshot.Capacity)
	if err != nil {
		return err
	}
	if err := executionClient.Start(ctx); err != nil {
		cleanupCtx, cancel := context.WithTimeout(context.Background(), 10*time.Second)
		_ = executionClient.StopAndCancel(cleanupCtx)
		cancel()
		return err
	}
	s.riverMu.Lock()
	s.riverControlClient = controlClient
	s.riverExecutionClient = executionClient
	s.riverWorkerCapacity = snapshot.Capacity
	s.riverDrainingClients = make(map[asyncExecutionClient]struct{})
	s.riverMu.Unlock()
	s.observeAsyncWorkerCapacity(snapshot)
	s.logger.Info("async worker capacity initialized",
		"capacity", snapshot.Capacity,
		"desiredCapacity", snapshot.Desired,
		"hardLimit", snapshot.HardLimit,
		"enabledModels", snapshot.EnabledModels,
		"unlimitedModels", snapshot.UnlimitedModels,
		"modelDesired", snapshot.ModelDesired,
		"enabledGroups", snapshot.EnabledGroups,
		"unlimitedGroups", snapshot.UnlimitedGroups,
		"groupDesired", snapshot.GroupDesired,
		"capped", snapshot.Capped,
	)
	if err := s.recoverAsyncRiverJobs(ctx); err != nil {
		cleanupCtx, cancel := context.WithTimeout(context.Background(), 10*time.Second)
		_ = executionClient.StopAndCancel(cleanupCtx)
		cancel()
		return err
	}
	go s.refreshAsyncWorkerCapacity(ctx)
	go s.stopAsyncWorkersOnShutdown(ctx)
	return nil
}

func (s *Service) newRiverAsyncExecutionClient(capacity int) (*river.Client[pgx.Tx], error) {
	workers := river.NewWorkers()
	if err := river.AddWorkerSafely(workers, &asyncTaskWorker{service: s}); err != nil {
		return nil, err
	}
	return river.NewClient(riverpgxv5.New(s.store.Pool()), &river.Config{
		ID:                          fmt.Sprintf("%s-exec-%d-%d", asyncWorkerID(), capacity, time.Now().UnixNano()),
		JobTimeout:                  -1,
		Logger:                      s.logger,
		CompletedJobRetentionPeriod: 24 * time.Hour,
		Queues: map[string]river.QueueConfig{
			asyncTaskQueueName: {MaxWorkers: capacity},
		},
		// Provider-backed media jobs commonly poll for 10-20 minutes. River may
		// execute a still-running job again once this window elapses, so keep the
		// rescue horizon above the longest configured provider poll timeout.
		RescueStuckJobsAfter: time.Hour,
		TestOnly:             s.cfg.AppEnv == "test",
		Workers:              workers,
	})
}

func (s *Service) makeAsyncExecutionClient(capacity int) (asyncExecutionClient, error) {
	if s.asyncClientFactory != nil {
		return s.asyncClientFactory(capacity)
	}
	return s.newRiverAsyncExecutionClient(capacity)
}

func (s *Service) loadAsyncWorkerCapacity(ctx context.Context) (store.AsyncWorkerCapacitySnapshot, error) {
	if s.asyncCapacityLoader != nil {
		return s.asyncCapacityLoader(ctx, s.cfg.AsyncWorkerHardLimit)
	}
	return s.store.AsyncWorkerCapacity(ctx, s.cfg.AsyncWorkerHardLimit)
}

func (s *Service) refreshAsyncWorkerCapacity(ctx context.Context) {
	ticker := time.NewTicker(time.Duration(s.cfg.AsyncWorkerRefreshIntervalSeconds) * time.Second)
	defer ticker.Stop()
	for {
		select {
		case <-ctx.Done():
			return
		case <-ticker.C:
			s.resizeAsyncWorkerCapacity(ctx)
		}
	}
}

func (s *Service) resizeAsyncWorkerCapacity(ctx context.Context) {
	snapshot, err := s.loadAsyncWorkerCapacity(ctx)
	if err != nil {
		s.observeAsyncWorkerResize("refresh_failed")
		s.logger.Warn("refresh async worker capacity failed; keeping current client", "error", err)
		return
	}
	s.riverMu.RLock()
	currentCapacity := s.riverWorkerCapacity
	s.riverMu.RUnlock()
	s.observeAsyncWorkerCapacity(snapshot)
	if snapshot.Capacity == currentCapacity {
		return
	}
	newClient, err := s.makeAsyncExecutionClient(snapshot.Capacity)
	if err != nil {
		s.observeAsyncWorkerResize("create_failed")
		s.logger.Warn("create replacement async worker client failed; keeping current client",
			"error", err, "currentCapacity", currentCapacity, "desiredCapacity", snapshot.Capacity)
		return
	}
	if err := newClient.Start(ctx); err != nil {
		cleanupCtx, cancel := context.WithTimeout(context.Background(), 10*time.Second)
		_ = newClient.StopAndCancel(cleanupCtx)
		cancel()
		s.observeAsyncWorkerResize("start_failed")
		s.logger.Warn("start replacement async worker client failed; keeping current client",
			"error", err, "currentCapacity", currentCapacity, "desiredCapacity", snapshot.Capacity)
		return
	}
	if ctx.Err() != nil {
		cleanupCtx, cancel := context.WithTimeout(context.Background(), 10*time.Second)
		_ = newClient.StopAndCancel(cleanupCtx)
		cancel()
		return
	}
	s.riverMu.Lock()
	oldClient := s.riverExecutionClient
	s.riverExecutionClient = newClient
	s.riverWorkerCapacity = snapshot.Capacity
	if oldClient != nil {
		if s.riverDrainingClients == nil {
			s.riverDrainingClients = make(map[asyncExecutionClient]struct{})
		}
		s.riverDrainingClients[oldClient] = struct{}{}
	}
	s.riverMu.Unlock()
	s.observeAsyncWorkerResize("success")
	s.logger.Info("async worker capacity resized",
		"previousCapacity", currentCapacity,
		"capacity", snapshot.Capacity,
		"desiredCapacity", snapshot.Desired,
		"hardLimit", snapshot.HardLimit,
		"modelDesired", snapshot.ModelDesired,
		"groupDesired", snapshot.GroupDesired,
		"capped", snapshot.Capped,
	)
	if oldClient != nil {
		go s.drainAsyncWorkerClient(oldClient)
	}
}

func (s *Service) drainAsyncWorkerClient(client asyncExecutionClient) {
	stopCtx, cancel := context.WithTimeout(context.Background(), time.Hour)
	defer cancel()
	if err := client.Stop(stopCtx); err != nil {
		s.logger.Warn("gracefully drain previous async worker client failed", "error", err)
	}
	s.riverMu.Lock()
	delete(s.riverDrainingClients, client)
	s.riverMu.Unlock()
}

func (s *Service) stopAsyncWorkersOnShutdown(ctx context.Context) {
	<-ctx.Done()
	s.riverMu.Lock()
	clients := make([]asyncExecutionClient, 0, 1+len(s.riverDrainingClients))
	if s.riverExecutionClient != nil {
		clients = append(clients, s.riverExecutionClient)
	}
	for client := range s.riverDrainingClients {
		clients = append(clients, client)
	}
	s.riverExecutionClient = nil
	s.riverDrainingClients = nil
	s.riverMu.Unlock()
	for _, client := range clients {
		stopCtx, cancel := context.WithTimeout(context.Background(), 10*time.Second)
		if err := client.StopAndCancel(stopCtx); err != nil {
			s.logger.Warn("stop river async queue failed", "error", err)
		}
		cancel()
	}
}

func (s *Service) asyncControlClient() *river.Client[pgx.Tx] {
	s.riverMu.RLock()
	defer s.riverMu.RUnlock()
	return s.riverControlClient
}

func (s *Service) observeAsyncWorkerCapacity(snapshot store.AsyncWorkerCapacitySnapshot) {
	observer, ok := s.billingMetrics.(interface {
		SetAsyncWorkerCapacity(current, desired, hardLimit int, capped bool)
	})
	if ok {
		observer.SetAsyncWorkerCapacity(snapshot.Capacity, snapshot.Desired, snapshot.HardLimit, snapshot.Capped)
	}
}

func (s *Service) observeAsyncWorkerResize(outcome string) {
	observer, ok := s.billingMetrics.(interface {
		ObserveAsyncWorkerResize(string)
	})
	if ok {
		observer.ObserveAsyncWorkerResize(outcome)
	}
}

func (s *Service) EnqueueAsyncTask(ctx context.Context, task store.GatewayTask) error {
	riverClient := s.asyncControlClient()
	if riverClient == nil {
		return errors.New("river async queue is not started")
	}
	result, err := riverClient.Insert(ctx, asyncTaskArgs{TaskID: task.ID}, asyncTaskInsertOpts(task))
	if err != nil {
		return err
	}
	if result.Job != nil {
		return s.store.SetTaskRiverJobID(ctx, task.ID, result.Job.ID)
	}
	return nil
}

func (s *Service) WakeAsyncQueueAfter(ctx context.Context, delay time.Duration) {
}

func (s *Service) RunAsyncTask(ctx context.Context, task store.GatewayTask, user *auth.User) {
	if err := s.EnqueueAsyncTask(ctx, task); err != nil {
		s.logger.Warn("enqueue river async task failed", "taskID", task.ID, "error", err)
	}
}

func (s *Service) recoverAsyncRiverJobs(ctx context.Context) error {
	riverClient := s.asyncControlClient()
	if riverClient == nil {
		return errors.New("river async queue is not started")
	}
	items, err := s.store.ListRecoverableAsyncTasks(ctx, 1000)
	if err != nil {
		return err
	}
	for _, item := range items {
		result, err := riverClient.Insert(ctx, asyncTaskArgs{TaskID: item.ID}, asyncTaskRecoveryInsertOpts(item, time.Now()))
		if err != nil {
			return err
		}
		if result.Job != nil {
			if err := s.store.SetTaskRiverJobID(ctx, item.ID, result.Job.ID); err != nil {
				return err
			}
		}
	}
	if len(items) > 0 {
		s.logger.Info("river async queue recovered persisted tasks", "count", len(items))
	}
	return nil
}

func asyncTaskInsertOpts(task store.GatewayTask) *river.InsertOpts {
	priority := 2
	if task.ID == "" {
		priority = 3
	}
	return &river.InsertOpts{
		MaxAttempts: 1000,
		Priority:    priority,
		Queue:       asyncTaskQueueName,
		Tags:        []string{"gateway-task"},
		UniqueOpts: river.UniqueOpts{
			ByArgs:  true,
			ByQueue: true,
			ByState: []rivertype.JobState{
				rivertype.JobStateAvailable,
				rivertype.JobStatePending,
				rivertype.JobStateRetryable,
				rivertype.JobStateRunning,
				rivertype.JobStateScheduled,
			},
		},
	}
}

func asyncTaskRecoveryInsertOpts(item store.AsyncTaskQueueItem, now time.Time) *river.InsertOpts {
	opts := asyncTaskInsertOpts(store.GatewayTask{ID: item.ID})
	if item.NextRunAt.After(now) {
		opts.ScheduledAt = item.NextRunAt
	}
	// A replacement process must not be blocked by a River row that the dead
	// process left in running state. PostgreSQL execution leases still ensure
	// that only one recovery job can call the upstream provider.
	opts.UniqueOpts = river.UniqueOpts{}
	return opts
}

func authUserFromTask(task store.GatewayTask) *auth.User {
	roles := []string{"user"}
	if strings.TrimSpace(task.UserID) == "" {
		roles = nil
	}
	return &auth.User{
		ID:              firstNonEmptyString(task.GatewayUserID, task.UserID),
		Roles:           roles,
		TenantID:        task.TenantID,
		GatewayTenantID: task.GatewayTenantID,
		TenantKey:       task.TenantKey,
		Source:          firstNonEmptyString(task.UserSource, "gateway"),
		GatewayUserID:   task.GatewayUserID,
		UserGroupID:     task.UserGroupID,
		UserGroupKey:    task.UserGroupKey,
		APIKeyID:        task.APIKeyID,
		APIKeyName:      task.APIKeyName,
		APIKeyPrefix:    task.APIKeyPrefix,
	}
}

func asyncWorkerID() string {
	host, _ := os.Hostname()
	host = strings.TrimSpace(host)
	if host == "" {
		host = "localhost"
	}
	return fmt.Sprintf("%s:%d:%d", host, os.Getpid(), time.Now().UnixNano())
}

var _ river.Worker[asyncTaskArgs] = (*asyncTaskWorker)(nil)