package cluster

import (
	"time"
)

const (
	// NumShards defines the total number of shards in the cluster
	NumShards = 1024
	// VirtualNodes defines the number of virtual nodes per physical node for consistent hashing
	VirtualNodes = 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
)

// 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"`
}

// VirtualMachine defines the interface for a virtual machine instance.
// This interface provides the minimal contract needed by the cluster package
// to interact with VMs without creating import cycles with the runtime package.
type VirtualMachine interface {
	// GetID returns the unique identifier for this VM
	GetID() string
	// GetActorID returns the actor ID this VM represents
	GetActorID() string
	// GetState returns the current state of the VM
	GetState() VMState
}

// VMState represents the state of a virtual machine
type VMState string

const (
	VMStateIdle    VMState = "idle"
	VMStateRunning VMState = "running"
	VMStatePaused  VMState = "paused"
	VMStateStopped VMState = "stopped"
)

// RuntimeModel defines the interface for an EventStorming model that can be loaded into a runtime.
// This decouples the cluster package from the specific eventstorming package.
type RuntimeModel interface {
	// GetID returns the unique identifier for this model
	GetID() string
	// GetName returns the name of this model
	GetName() string
}

// RuntimeMessage defines the interface for messages that can be sent through the runtime.
// This provides type safety for inter-actor communication without creating import cycles.
type RuntimeMessage interface {
	// GetTargetActorID returns the ID of the actor this message is addressed to
	GetTargetActorID() string
	// GetType returns the message type identifier
	GetType() string
}