fetch_ml/internal/queue/event_store.go

package queue

import (
	"context"
	"encoding/json"
	"fmt"
	"strconv"
	"time"

	"github.com/jfraeys/fetch_ml/internal/domain"
	"github.com/redis/go-redis/v9"
)

// EventStore provides append-only event storage using Redis Streams.
// Events are stored chronologically and can be queried for audit trails.
type EventStore struct {
	client        *redis.Client
	ctx           context.Context
	retentionDays int
	maxStreamLen  int64
}

// EventStoreConfig holds configuration for the event store.
type EventStoreConfig struct {
	RedisAddr     string
	RedisPassword string
	RedisDB       int
	RetentionDays int   // How long to keep events (default: 7)
	MaxStreamLen  int64 // Max events per task stream (default: 1000)
}

// NewEventStore creates a new event store instance.
func NewEventStore(cfg EventStoreConfig) (*EventStore, error) {
	retentionDays := cfg.RetentionDays
	if retentionDays == 0 {
		retentionDays = 7
	}

	maxStreamLen := cfg.MaxStreamLen
	if maxStreamLen == 0 {
		maxStreamLen = 1000
	}

	opts := &redis.Options{
		Addr:     cfg.RedisAddr,
		Password: cfg.RedisPassword,
		DB:       cfg.RedisDB,
		PoolSize: 50,
	}

	client := redis.NewClient(opts)
	ctx := context.Background()

	// Test connection
	if err := client.Ping(ctx).Err(); err != nil {
		return nil, fmt.Errorf("failed to connect to redis: %w", err)
	}

	return &EventStore{
		client:        client,
		ctx:           ctx,
		retentionDays: retentionDays,
		maxStreamLen:  maxStreamLen,
	}, nil
}

// Close closes the event store.
func (es *EventStore) Close() error {
	return es.client.Close()
}

// RecordEvent records a task event to the append-only stream.
func (es *EventStore) RecordEvent(event domain.TaskEvent) error {
	streamKey := fmt.Sprintf("task_events:%s", event.TaskID)

	data, err := json.Marshal(event.Data)
	if err != nil {
		return fmt.Errorf("failed to marshal event data: %w", err)
	}

	values := map[string]interface{}{
		"type": event.EventType,
		"who":  event.Who,
		"ts":   event.Timestamp.Unix(),
	}

	if len(data) > 0 {
		values["data"] = string(data)
	}

	// Add to stream with approximate max length trimming
	_, err = es.client.XAdd(es.ctx, &redis.XAddArgs{
		Stream: streamKey,
		MaxLen: es.maxStreamLen,
		Approx: true, // Allow approximate trimming for performance
		Values: values,
	}).Result()

	if err != nil {
		return fmt.Errorf("failed to record event: %w", err)
	}

	// Set expiration on the stream
	es.client.Expire(es.ctx, streamKey, time.Duration(es.retentionDays)*24*time.Hour)

	return nil
}

// GetEvents retrieves all events for a task, ordered chronologically.
func (es *EventStore) GetEvents(taskID string) ([]domain.TaskEvent, error) {
	streamKey := fmt.Sprintf("task_events:%s", taskID)

	// Read all events from the stream
	messages, err := es.client.XRange(es.ctx, streamKey, "-", "+").Result()
	if err != nil {
		return nil, fmt.Errorf("failed to get events: %w", err)
	}

	var events []domain.TaskEvent
	for _, msg := range messages {
		event, err := es.parseEvent(taskID, msg)
		if err != nil {
			continue // Skip malformed events
		}
		events = append(events, event)
	}

	return events, nil
}

// GetEventsSince retrieves events for a task since a specific time.
func (es *EventStore) GetEventsSince(taskID string, since time.Time) ([]domain.TaskEvent, error) {
	streamKey := fmt.Sprintf("task_events:%s", taskID)

	// Use XRANGEBYTIME equivalent - scan from timestamp
	start := fmt.Sprintf("%d-0", since.Unix()*1000) // Redis stream IDs are ms-based

	messages, err := es.client.XRange(es.ctx, streamKey, start, "+").Result()
	if err != nil {
		return nil, fmt.Errorf("failed to get events: %w", err)
	}

	var events []domain.TaskEvent
	for _, msg := range messages {
		event, err := es.parseEvent(taskID, msg)
		if err != nil {
			continue
		}
		// Filter by actual timestamp
		if event.Timestamp.After(since) {
			events = append(events, event)
		}
	}

	return events, nil
}

// parseEvent converts a Redis stream message to a TaskEvent.
func (es *EventStore) parseEvent(taskID string, msg redis.XMessage) (domain.TaskEvent, error) {
	var event domain.TaskEvent
	event.TaskID = taskID

	// Parse event type
	if v, ok := msg.Values["type"]; ok {
		event.EventType = domain.TaskEventType(v.(string))
	}

	// Parse who
	if v, ok := msg.Values["who"]; ok {
		event.Who = v.(string)
	}

	// Parse timestamp
	if v, ok := msg.Values["ts"]; ok {
		ts, err := strconv.ParseInt(v.(string), 10, 64)
		if err == nil {
			event.Timestamp = time.Unix(ts, 0).UTC()
		}
	}

	// Parse data
	if v, ok := msg.Values["data"]; ok {
		event.Data = json.RawMessage(v.(string))
	}

	return event, nil
}

// DeleteOldEvents manually deletes events older than retention period.
// This is normally handled by Redis TTL, but can be called for cleanup.
func (es *EventStore) DeleteOldEvents(taskID string) error {
	streamKey := fmt.Sprintf("task_events:%s", taskID)
	return es.client.Del(es.ctx, streamKey).Err()
}