package ci

import (
	"context"
	"encoding/json"
	"log"

	"xorm.io/xorm"

	"github.com/forgeo/forgebucket/internal/config"
	"github.com/forgeo/forgebucket/internal/events"
)

// RunnerManager subscribes to job.queued events and dispatches them to the
// local Docker executor. A semaphore limits concurrent executions.
type RunnerManager struct {
	db  *xorm.Engine
	bus events.EventBus
	cfg *config.Config
	sem chan struct{}
}

func NewRunnerManager(db *xorm.Engine, bus events.EventBus, cfg *config.Config, maxConcurrent int) *RunnerManager {
	if maxConcurrent <= 0 {
		maxConcurrent = 4
	}
	return &RunnerManager{
		db:  db,
		bus: bus,
		cfg: cfg,
		sem: make(chan struct{}, maxConcurrent),
	}
}

// Start subscribes to job.queued and dispatches executions until ctx is cancelled.
func (m *RunnerManager) Start(ctx context.Context) {
	if !IsDockerAvailable() {
		log.Printf("runner: Docker not available — CI execution disabled")
		<-ctx.Done()
		return
	}
	log.Printf("runner: started (max concurrent jobs: %d)", cap(m.sem))

	wsDir := workspaceDir(m.cfg.ArtifactRoot)

	unsub, err := m.bus.Subscribe(events.SubjectJobQueued, func(_ string, data []byte) {
		var evt events.JobEvent
		if err := json.Unmarshal(data, &evt); err != nil {
			log.Printf("runner: bad job.queued payload: %v", err)
			return
		}

		jc, ok := buildJobContext(m.db, evt.JobID, m.cfg.SessionSecret)
		if !ok {
			log.Printf("runner: could not build job context for job %d", evt.JobID)
			return
		}

		// Acquire semaphore slot — blocks if at capacity.
		select {
		case m.sem <- struct{}{}:
		case <-ctx.Done():
			return
		}

		go func() {
			defer func() { <-m.sem }()
			// Sanitize the Docker image name before execution.
			jc.Job.Image = sanitizeImage(jc.Job.Image)
			ExecuteJob(ctx, m.db, m.bus, jc, wsDir)
		}()
	})
	if err != nil {
		log.Printf("runner: subscribe job.queued: %v", err)
		<-ctx.Done()
		return
	}
	defer unsub()

	<-ctx.Done()
	log.Printf("runner: stopping — draining %d active jobs", len(m.sem))
	// Wait for all running jobs to finish by filling the semaphore.
	for i := 0; i < cap(m.sem); i++ {
		m.sem <- struct{}{}
	}
}