package orchestrator

import (
	"context"
	"log"
	"time"

	"vetting/internal/model"
	"vetting/internal/store"
)

// Dispatcher picks Queued runs off the DB and drives them through
// WaitingWoL (sending a WoL packet). Concurrency is capped at Max.
//
// For Phase 2 the dispatcher's job ends at WaitingWoL; further
// transitions are driven by iPXE and agent callbacks. Phase 4+ will
// return here and shepherd each run through stage execution.
type Dispatcher struct {
	Max    int
	Runs   *store.Runs
	Hosts  *store.Hosts
	Runner *Runner

	active chan struct{}
	stop   chan struct{}
}

func NewDispatcher(max int, runs *store.Runs, hosts *store.Hosts, runner *Runner) *Dispatcher {
	if max < 1 {
		max = 1
	}
	return &Dispatcher{
		Max:    max,
		Runs:   runs,
		Hosts:  hosts,
		Runner: runner,
		active: make(chan struct{}, max),
		stop:   make(chan struct{}),
	}
}

func (d *Dispatcher) Start(ctx context.Context) {
	go d.loop(ctx)
}

func (d *Dispatcher) Stop() {
	close(d.stop)
}

func (d *Dispatcher) loop(ctx context.Context) {
	t := time.NewTicker(2 * time.Second)
	defer t.Stop()
	for {
		select {
		case <-ctx.Done():
			return
		case <-d.stop:
			return
		case <-t.C:
			d.pickNext(ctx)
		}
	}
}

func (d *Dispatcher) pickNext(ctx context.Context) {
	select {
	case d.active <- struct{}{}:
	default:
		return // at capacity
	}
	released := false
	defer func() {
		if !released {
			<-d.active
		}
	}()

	runs, err := d.Runs.Active(ctx)
	if err != nil {
		log.Printf("dispatcher: list active: %v", err)
		return
	}

	var queued *model.Run
	inFlight := 0
	for i := range runs {
		switch runs[i].State {
		case model.StateQueued:
			if queued == nil {
				queued = &runs[i]
			}
		case model.StateWaitingWoL, model.StateBooting, model.StateInventoryCheck,
			model.StateSpecValidate, model.StateSMART, model.StateCPUStress,
			model.StateStorage, model.StateNetwork, model.StateGPU,
			model.StatePSU, model.StateReporting:
			inFlight++
		}
	}

	if inFlight >= d.Max || queued == nil {
		return
	}

	host, err := d.Hosts.Get(ctx, queued.HostID)
	if err != nil {
		log.Printf("dispatcher: get host %d: %v", queued.HostID, err)
		return
	}
	if _, err := d.Runner.Transition(ctx, queued.ID, TriggerDispatched); err != nil {
		log.Printf("dispatcher: transition run %d: %v", queued.ID, err)
		return
	}
	if err := SendWoL(host.MAC, host.WoLBroadcastIP, host.WoLPort); err != nil {
		log.Printf("dispatcher: WoL run %d host %s: %v", queued.ID, host.Name, err)
		// Stay in WaitingWoL; operator can retry or investigate.
		return
	}
	log.Printf("dispatcher: WoL sent for run %d (host=%s mac=%s)", queued.ID, host.Name, host.MAC)

	// Slot stays reserved until the run leaves active (Phase 4+).
	// Phase 2 lets the loop observe inFlight via DB state.
	released = true
	<-d.active
}