package cluster

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

	"github.com/nats-io/nats.go"
)

// NodeDiscovery manages cluster membership using NATS
type NodeDiscovery struct {
	nodeID    string
	nodeInfo  *NodeInfo
	natsConn  *nats.Conn
	heartbeat time.Duration
	timeout   time.Duration
	updates   chan NodeUpdate
	ctx       context.Context
}

// NewNodeDiscovery creates a node discovery service
func NewNodeDiscovery(nodeID string, natsConn *nats.Conn, ctx context.Context) *NodeDiscovery {
	nodeInfo := &NodeInfo{
		ID:       nodeID,
		Status:   NodeStatusActive,
		Capacity: 1000, // Default capacity
		Load:     0,
		LastSeen: time.Now(),
		Metadata: make(map[string]string),
	}

	return &NodeDiscovery{
		nodeID:    nodeID,
		nodeInfo:  nodeInfo,
		natsConn:  natsConn,
		heartbeat: 30 * time.Second,
		timeout:   90 * time.Second,
		updates:   make(chan NodeUpdate, 100),
		ctx:       ctx,
	}
}

// Start begins node discovery and heartbeating
func (nd *NodeDiscovery) Start() {
	// Announce this node joining
	nd.announceNode(NodeJoined)

	// Start heartbeat
	ticker := time.NewTicker(nd.heartbeat)
	defer ticker.Stop()

	// Subscribe to node announcements
	nd.natsConn.Subscribe("aether.discovery", func(msg *nats.Msg) {
		var update NodeUpdate
		if err := json.Unmarshal(msg.Data, &update); err != nil {
			return
		}

		select {
		case nd.updates <- update:
		case <-nd.ctx.Done():
		}
	})

	for {
		select {
		case <-ticker.C:
			nd.announceNode(NodeUpdated)

		case <-nd.ctx.Done():
			nd.announceNode(NodeLeft)
			return
		}
	}
}

// GetUpdates returns the channel for receiving node updates
func (nd *NodeDiscovery) GetUpdates() <-chan NodeUpdate {
	return nd.updates
}

// GetNodeInfo returns the current node information
func (nd *NodeDiscovery) GetNodeInfo() *NodeInfo {
	return nd.nodeInfo
}

// UpdateLoad updates the node's current load
func (nd *NodeDiscovery) UpdateLoad(load float64) {
	nd.nodeInfo.Load = load
}

// UpdateVMCount updates the number of VMs on this node
func (nd *NodeDiscovery) UpdateVMCount(count int) {
	nd.nodeInfo.VMCount = count
}

// announceNode publishes node status to the cluster
func (nd *NodeDiscovery) announceNode(updateType NodeUpdateType) {
	nd.nodeInfo.LastSeen = time.Now()

	update := NodeUpdate{
		Type: updateType,
		Node: nd.nodeInfo,
	}

	data, err := json.Marshal(update)
	if err != nil {
		return
	}

	nd.natsConn.Publish("aether.discovery", data)
}

// Stop gracefully stops the node discovery service
func (nd *NodeDiscovery) Stop() {
	nd.announceNode(NodeLeft)
}