package cluster

import (
	"time"
)

// Default configuration values
const (
	// DefaultNumShards defines the default total number of shards in the cluster
	DefaultNumShards = 1024
	// DefaultVirtualNodes defines the default number of virtual nodes per physical node
	DefaultVirtualNodes = 150
	// Leadership election constants
	LeaderLeaseTimeout = 10 * time.Second // How long a leader lease lasts
	HeartbeatInterval  = 3 * time.Second  // How often leader sends heartbeats
	ElectionTimeout    = 2 * time.Second  // How long to wait for election
)

// HashRingConfig holds configuration for the consistent hash ring
type HashRingConfig struct {
	// VirtualNodes is the number of virtual nodes per physical node (default: 150)
	VirtualNodes int
}

// DefaultHashRingConfig returns the default hash ring configuration
func DefaultHashRingConfig() HashRingConfig {
	return HashRingConfig{
		VirtualNodes: DefaultVirtualNodes,
	}
}

// ShardConfig holds configuration for shard management
type ShardConfig struct {
	// ShardCount is the total number of shards (default: 1024)
	ShardCount int
	// ReplicationFactor is the number of replicas per shard (default: 1)
	ReplicationFactor int
}

// DefaultShardConfig returns the default shard configuration
func DefaultShardConfig() ShardConfig {
	return ShardConfig{
		ShardCount:        DefaultNumShards,
		ReplicationFactor: 1,
	}
}

// NodeStatus represents the health status of a node
type NodeStatus string

const (
	NodeStatusActive   NodeStatus = "active"
	NodeStatusDraining NodeStatus = "draining"
	NodeStatusFailed   NodeStatus = "failed"
)

// NodeInfo represents information about a cluster node
type NodeInfo struct {
	ID        string            `json:"id"`
	Address   string            `json:"address"`
	Port      int               `json:"port"`
	Status    NodeStatus        `json:"status"`
	Capacity  float64           `json:"capacity"` // Maximum load capacity
	Load      float64           `json:"load"`     // Current CPU/memory load
	LastSeen  time.Time         `json:"lastSeen"` // Last heartbeat timestamp
	Timestamp time.Time         `json:"timestamp"`
	Metadata  map[string]string `json:"metadata"`
	IsLeader  bool              `json:"isLeader"`
	VMCount   int               `json:"vmCount"`  // Number of VMs on this node
	ShardIDs  []int             `json:"shardIds"` // Shards assigned to this node
}

// NodeUpdateType represents the type of node update
type NodeUpdateType string

const (
	NodeJoined  NodeUpdateType = "joined"
	NodeLeft    NodeUpdateType = "left"
	NodeUpdated NodeUpdateType = "updated"
)

// NodeUpdate represents a node status update
type NodeUpdate struct {
	Type NodeUpdateType `json:"type"`
	Node *NodeInfo      `json:"node"`
}

// ShardMap represents the distribution of shards across cluster nodes
type ShardMap struct {
	Version    uint64              `json:"version"` // Incremented on each change
	Shards     map[int][]string    `json:"shards"`  // shard ID -> [primary, replica1, replica2]
	Nodes      map[string]NodeInfo `json:"nodes"`   // node ID -> node info
	UpdateTime time.Time           `json:"updateTime"`
}

// ClusterMessage represents inter-node communication
type ClusterMessage struct {
	Type      string      `json:"type"`
	From      string      `json:"from"`
	To        string      `json:"to"`
	Payload   interface{} `json:"payload"`
	Timestamp time.Time   `json:"timestamp"`
}

// RebalanceRequest represents a request to rebalance shards
type RebalanceRequest struct {
	RequestID  string           `json:"requestId"`
	FromNode   string           `json:"fromNode"`
	ToNode     string           `json:"toNode"`
	ShardIDs   []int            `json:"shardIds"`
	Reason     string           `json:"reason"`
	Migrations []ActorMigration `json:"migrations"`
}

// ActorMigration represents the migration of an actor between nodes
type ActorMigration struct {
	ActorID  string                 `json:"actorId"`
	FromNode string                 `json:"fromNode"`
	ToNode   string                 `json:"toNode"`
	ShardID  int                    `json:"shardId"`
	State    map[string]interface{} `json:"state"`
	Version  int64                  `json:"version"`
	Status   string                 `json:"status"` // "pending", "in_progress", "completed", "failed"
}

// LeaderElectionCallbacks defines callbacks for leadership changes
type LeaderElectionCallbacks struct {
	OnBecameLeader func()
	OnLostLeader   func()
	OnNewLeader    func(leaderID string)
}

// LeadershipLease represents a leadership lease in the cluster
type LeadershipLease struct {
	LeaderID  string    `json:"leaderId"`
	Term      uint64    `json:"term"`
	ExpiresAt time.Time `json:"expiresAt"`
	StartedAt time.Time `json:"startedAt"`
}