// Package triggers — engine.go
//
// v0.2.2: Core trigger engine. Manages extension-declared triggers
// (event bus subscriptions + webhook receivers) and user-created
// scheduled tasks (cron). All three converge to sandbox.Runner.CallEntryPoint.
package triggers

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

	"github.com/robfig/cron/v3"

	"switchboard-core/events"
	"switchboard-core/models"
	"switchboard-core/sandbox"
	"switchboard-core/store"
)

// Engine orchestrates trigger lifecycle: loading, firing, and cleanup.
type Engine struct {
	stores store.Stores
	runner *sandbox.Runner
	bus    *events.Bus
	cron   *cron.Cron

	mu      sync.RWMutex
	unsubs  map[string]func()        // trigger_id → bus unsubscribe
	cronIDs map[string]cron.EntryID  // scheduled_task_id → cron entry

	ctx    context.Context
	cancel context.CancelFunc
}

// New creates a trigger engine. Call Start() to begin processing.
func New(stores store.Stores, runner *sandbox.Runner, bus *events.Bus) *Engine {
	return &Engine{
		stores:  stores,
		runner:  runner,
		bus:     bus,
		cron:    cron.New(cron.WithSeconds()),
		unsubs:  make(map[string]func()),
		cronIDs: make(map[string]cron.EntryID),
	}
}

// Start loads all enabled triggers and scheduled tasks, then begins execution.
func (e *Engine) Start(ctx context.Context) error {
	e.ctx, e.cancel = context.WithCancel(ctx)

	// Load event triggers
	if e.stores.Triggers != nil {
		eventTriggers, err := e.stores.Triggers.ListEnabledByType(ctx, models.TriggerTypeEvent)
		if err != nil {
			log.Printf("  ⚠️  triggers: failed to load event triggers: %v", err)
		} else {
			for i := range eventTriggers {
				e.wireEventTrigger(&eventTriggers[i])
			}
			if len(eventTriggers) > 0 {
				log.Printf("  🔔 triggers: %d event trigger(s) loaded", len(eventTriggers))
			}
		}
	}

	// Load scheduled tasks
	if e.stores.ScheduledTasks != nil {
		tasks, err := e.stores.ScheduledTasks.ListEnabled(ctx)
		if err != nil {
			log.Printf("  ⚠️  triggers: failed to load scheduled tasks: %v", err)
		} else {
			for i := range tasks {
				e.wireScheduledTask(&tasks[i])
			}
			if len(tasks) > 0 {
				log.Printf("  ⏰ triggers: %d scheduled task(s) loaded", len(tasks))
			}
		}
	}

	e.cron.Start()
	return nil
}

// Stop gracefully shuts down all trigger goroutines and cron jobs.
func (e *Engine) Stop() {
	if e.cancel != nil {
		e.cancel()
	}

	// Stop cron scheduler
	cronCtx := e.cron.Stop()
	<-cronCtx.Done()

	// Unsubscribe all event triggers
	e.mu.Lock()
	for id, unsub := range e.unsubs {
		unsub()
		delete(e.unsubs, id)
	}
	e.mu.Unlock()

	log.Printf("  🔔 triggers: engine stopped")
}

// RegisterTrigger adds a single trigger at runtime (package install).
func (e *Engine) RegisterTrigger(t *models.Trigger) {
	if !t.Enabled {
		return
	}
	switch t.Type {
	case models.TriggerTypeEvent:
		e.wireEventTrigger(t)
	// Webhook triggers are resolved at request time — no wiring needed
	}
}

// UnregisterTrigger removes a trigger at runtime (package uninstall/disable).
func (e *Engine) UnregisterTrigger(triggerID string) {
	e.mu.Lock()
	defer e.mu.Unlock()
	if unsub, ok := e.unsubs[triggerID]; ok {
		unsub()
		delete(e.unsubs, triggerID)
	}
}

// RegisterSchedule adds a scheduled task at runtime.
func (e *Engine) RegisterSchedule(t *models.ScheduledTask) {
	if !t.Enabled {
		return
	}
	e.wireScheduledTask(t)
}

// UnregisterSchedule removes a scheduled task at runtime.
func (e *Engine) UnregisterSchedule(taskID string) {
	e.mu.Lock()
	defer e.mu.Unlock()
	if entryID, ok := e.cronIDs[taskID]; ok {
		e.cron.Remove(entryID)
		delete(e.cronIDs, taskID)
	}
}

// ManualRun fires a scheduled task immediately (bypasses cron).
func (e *Engine) ManualRun(t *models.ScheduledTask) {
	e.fireScheduledTask(t.ID, t.CreatorID, t.RunAs, t.Script, t.CronExpr)
}

// ReloadPackageTriggers re-syncs triggers for a package from DB.
func (e *Engine) ReloadPackageTriggers(ctx context.Context, packageID string) error {
	if e.stores.Triggers == nil {
		return nil
	}

	triggers, err := e.stores.Triggers.ListByPackage(ctx, packageID)
	if err != nil {
		return err
	}

	// Unregister existing
	e.mu.RLock()
	var toRemove []string
	for id := range e.unsubs {
		toRemove = append(toRemove, id)
	}
	e.mu.RUnlock()

	// We need to check which ones belong to this package
	for _, id := range toRemove {
		// Simple: unregister all, re-register from DB
		e.UnregisterTrigger(id)
	}

	// Re-register enabled triggers
	for i := range triggers {
		e.RegisterTrigger(&triggers[i])
	}
	return nil
}

// logExecution records a trigger or scheduled task execution.
func (e *Engine) logExecution(triggerID, scheduledTaskID string, firedAt time.Time, durationMs int, success bool, errStr, output string) {
	if e.stores.Triggers == nil {
		return
	}
	tl := &models.TriggerLog{
		TriggerID:       triggerID,
		ScheduledTaskID: scheduledTaskID,
		FiredAt:         firedAt.UTC().Format(time.RFC3339),
		DurationMs:      &durationMs,
		Success:         success,
		Error:           errStr,
		Output:          truncate(output, 4000),
	}
	if err := e.stores.Triggers.LogExecution(context.Background(), tl); err != nil {
		log.Printf("  ⚠️  triggers: failed to log execution: %v", err)
	}
}

// publishEvent emits a trigger lifecycle event on the bus.
func (e *Engine) publishEvent(label string, triggerID string) {
	if e.bus != nil {
		payload, _ := json.Marshal(map[string]any{"trigger_id": triggerID})
		e.bus.Publish(events.Event{
			Label:   label,
			Payload: payload,
			Ts:      time.Now().UnixMilli(),
		})
	}
}

func truncate(s string, max int) string {
	if len(s) <= max {
		return s
	}
	return s[:max] + "…"
}