package shell

import (
	"context"
	"log/slog"
	"sync"
	"time"

	"git.t-juice.club/torjus/oubliette/internal/storage"
)

// EventRecorder buffers I/O events in memory and periodically flushes them to
// a storage.Store. It is designed to be registered as a RecordingChannel
// callback so that SSH I/O is never blocked by database writes.
type EventRecorder struct {
	sessionID string
	store     storage.Store
	logger    *slog.Logger

	mu     sync.Mutex
	buf    []storage.SessionEvent
	cancel context.CancelFunc
	done   chan struct{}
}

// NewEventRecorder creates a recorder that will persist events for the given session.
func NewEventRecorder(sessionID string, store storage.Store, logger *slog.Logger) *EventRecorder {
	return &EventRecorder{
		sessionID: sessionID,
		store:     store,
		logger:    logger,
		done:      make(chan struct{}),
	}
}

// RecordEvent implements the EventCallback signature and appends an event to
// the in-memory buffer. It is safe to call concurrently.
func (er *EventRecorder) RecordEvent(ts time.Time, direction int, data []byte) {
	er.mu.Lock()
	defer er.mu.Unlock()
	er.buf = append(er.buf, storage.SessionEvent{
		SessionID: er.sessionID,
		Timestamp: ts,
		Direction: direction,
		Data:      data,
	})
}

// Start begins the background flush goroutine that drains the buffer every 2 seconds.
func (er *EventRecorder) Start(ctx context.Context) {
	ctx, er.cancel = context.WithCancel(ctx)
	go er.run(ctx)
}

// Close cancels the background goroutine and performs a final flush.
func (er *EventRecorder) Close() {
	if er.cancel != nil {
		er.cancel()
	}
	<-er.done
}

func (er *EventRecorder) run(ctx context.Context) {
	defer close(er.done)
	ticker := time.NewTicker(2 * time.Second)
	defer ticker.Stop()

	for {
		select {
		case <-ctx.Done():
			er.flush()
			return
		case <-ticker.C:
			er.flush()
		}
	}
}

func (er *EventRecorder) flush() {
	er.mu.Lock()
	if len(er.buf) == 0 {
		er.mu.Unlock()
		return
	}
	events := er.buf
	er.buf = nil
	er.mu.Unlock()

	if err := er.store.AppendSessionEvents(context.Background(), events); err != nil {
		er.logger.Error("failed to flush session events", "err", err, "session_id", er.sessionID)
	}
}