chore: establish local platform baseline

internal/orchestration/lease_cache.go

@@ -0,0 +1,82 @@
+package orchestration
+
+import (
+	"context"
+	"errors"
+	"strconv"
+	"time"
+
+	"github.com/redis/go-redis/v9"
+)
+
+type LeaseRecord struct {
+	ConversationID string
+	DeviceID       string
+	SequenceNo     int64
+	Status         string
+	ExpiresAt      time.Time
+	ObservedAt     time.Time
+}
+
+type LeaseCache interface {
+	Refresh(context.Context, LeaseRecord) error
+	End(context.Context, string, string, time.Time) error
+}
+
+type RedisLeaseCache struct {
+	client *redis.Client
+	prefix string
+}
+
+var refreshLeaseScript = redis.NewScript(`
+local current = redis.call('HGET', KEYS[1], 'sequence_no')
+if current and tonumber(current) >= tonumber(ARGV[1]) then
+  return 0
+end
+redis.call('HSET', KEYS[1],
+  'sequence_no', ARGV[1], 'status', ARGV[2], 'device_id', ARGV[3],
+  'lease_expires_at', ARGV[4], 'observed_at', ARGV[5])
+redis.call('PEXPIRE', KEYS[1], ARGV[6])
+redis.call('HSET', KEYS[2],
+  'online', 'true', 'conversation_id', ARGV[7], 'sequence_no', ARGV[1],
+  'last_seen_at', ARGV[5])
+redis.call('PEXPIRE', KEYS[2], ARGV[8])
+return 1
+`)
+
+func NewRedisLeaseCache(client *redis.Client, prefix string) (*RedisLeaseCache, error) {
+	if client == nil || prefix == "" {
+		return nil, errors.New("redis client and lease key prefix are required")
+	}
+	return &RedisLeaseCache{client: client, prefix: prefix}, nil
+}
+
+func (c *RedisLeaseCache) Refresh(ctx context.Context, record LeaseRecord) error {
+	ttl := time.Until(record.ExpiresAt)
+	if ttl <= 0 || record.SequenceNo < 1 || record.ConversationID == "" || record.DeviceID == "" {
+		return errors.New("active lease record is invalid or already expired")
+	}
+	presenceTTL := ttl * 2
+	_, err := refreshLeaseScript.Run(ctx, c.client, []string{
+		c.prefix + ":conversation:lease:" + record.ConversationID,
+		c.prefix + ":device:presence:" + record.DeviceID,
+	},
+		strconv.FormatInt(record.SequenceNo, 10), record.Status, record.DeviceID,
+		record.ExpiresAt.UTC().Format(time.RFC3339Nano), record.ObservedAt.UTC().Format(time.RFC3339Nano),
+		ttl.Milliseconds(), record.ConversationID, presenceTTL.Milliseconds(),
+	).Result()
+	return err
+}
+
+func (c *RedisLeaseCache) End(ctx context.Context, conversationID, deviceID string, observedAt time.Time) error {
+	if conversationID == "" || deviceID == "" {
+		return errors.New("conversation and device identifiers are required")
+	}
+	leaseKey := c.prefix + ":conversation:lease:" + conversationID
+	presenceKey := c.prefix + ":device:presence:" + deviceID
+	pipe := c.client.TxPipeline()
+	pipe.Del(ctx, leaseKey)
+	pipe.HSet(ctx, presenceKey, "conversation_id", "", "status", "idle", "last_seen_at", observedAt.UTC().Format(time.RFC3339Nano))
+	_, err := pipe.Exec(ctx)
+	return err
+}