package election

import (
	"context"
	"encoding/json"
	"fmt"
	"log"
	"math/rand"
	"sync"
	"time"

	"github.com/anthonyrawlins/bzzz/pkg/config"
	"github.com/anthonyrawlins/bzzz/pubsub"
	libp2p "github.com/libp2p/go-libp2p/core/host"
	"github.com/libp2p/go-libp2p/core/peer"
)

// ElectionTrigger represents why an election was triggered
type ElectionTrigger string

const (
	TriggerHeartbeatTimeout  ElectionTrigger = "admin_heartbeat_timeout"
	TriggerDiscoveryFailure  ElectionTrigger = "no_admin_discovered"
	TriggerSplitBrain       ElectionTrigger = "split_brain_detected"
	TriggerQuorumRestored   ElectionTrigger = "quorum_restored"
	TriggerManual           ElectionTrigger = "manual_trigger"
)

// ElectionState represents the current election state
type ElectionState string

const (
	StateIdle        ElectionState = "idle"
	StateDiscovering ElectionState = "discovering"
	StateElecting    ElectionState = "electing"
	StateReconstructing ElectionState = "reconstructing_keys"
	StateComplete    ElectionState = "complete"
)

// AdminCandidate represents a node candidate for admin role
type AdminCandidate struct {
	NodeID      string                 `json:"node_id"`
	PeerID      peer.ID               `json:"peer_id"`
	Capabilities []string              `json:"capabilities"`
	Uptime      time.Duration         `json:"uptime"`
	Resources   ResourceMetrics       `json:"resources"`
	Experience  time.Duration         `json:"experience"`
	Score       float64               `json:"score"`
	Metadata    map[string]interface{} `json:"metadata,omitempty"`
}

// ResourceMetrics holds node resource information for election scoring
type ResourceMetrics struct {
	CPUUsage    float64 `json:"cpu_usage"`
	MemoryUsage float64 `json:"memory_usage"`
	DiskUsage   float64 `json:"disk_usage"`
	NetworkQuality float64 `json:"network_quality"`
}

// ElectionMessage represents election-related messages
type ElectionMessage struct {
	Type      string      `json:"type"`
	NodeID    string      `json:"node_id"`
	Timestamp time.Time   `json:"timestamp"`
	Term      int         `json:"term"`
	Data      interface{} `json:"data,omitempty"`
}

// ElectionManager handles admin election coordination
type ElectionManager struct {
	ctx        context.Context
	cancel     context.CancelFunc
	config     *config.Config
	host       libp2p.Host
	pubsub     *pubsub.PubSub
	nodeID     string
	
	// Election state
	mu              sync.RWMutex
	state           ElectionState
	currentTerm     int
	lastHeartbeat   time.Time
	currentAdmin    string
	candidates      map[string]*AdminCandidate
	votes           map[string]string // voter -> candidate
	
	// Timers and channels
	heartbeatTimer    *time.Timer
	discoveryTimer    *time.Timer
	electionTimer     *time.Timer
	electionTrigger   chan ElectionTrigger
	
	// Callbacks
	onAdminChanged    func(oldAdmin, newAdmin string)
	onElectionComplete func(winner string)
	
	startTime time.Time
}

// NewElectionManager creates a new election manager
func NewElectionManager(
	ctx context.Context,
	cfg *config.Config,
	host libp2p.Host,
	ps *pubsub.PubSub,
	nodeID string,
) *ElectionManager {
	electionCtx, cancel := context.WithCancel(ctx)
	
	em := &ElectionManager{
		ctx:             electionCtx,
		cancel:          cancel,
		config:          cfg,
		host:            host,
		pubsub:          ps,
		nodeID:          nodeID,
		state:           StateIdle,
		candidates:      make(map[string]*AdminCandidate),
		votes:           make(map[string]string),
		electionTrigger: make(chan ElectionTrigger, 10),
		startTime:       time.Now(),
	}
	
	return em
}

// Start begins the election management system
func (em *ElectionManager) Start() error {
	log.Printf("🗳️ Starting election manager for node %s", em.nodeID)
	
	// Subscribe to election-related messages
	if err := em.pubsub.Subscribe("bzzz/election/v1", em.handleElectionMessage); err != nil {
		return fmt.Errorf("failed to subscribe to election messages: %w", err)
	}
	
	if err := em.pubsub.Subscribe("bzzz/admin/heartbeat/v1", em.handleAdminHeartbeat); err != nil {
		return fmt.Errorf("failed to subscribe to admin heartbeat: %w", err)
	}
	
	// Start discovery process
	go em.startDiscoveryLoop()
	
	// Start election coordinator
	go em.electionCoordinator()
	
	log.Printf("✅ Election manager started")
	return nil
}

// Stop shuts down the election manager
func (em *ElectionManager) Stop() {
	log.Printf("🛑 Stopping election manager")
	em.cancel()
	
	em.mu.Lock()
	defer em.mu.Unlock()
	
	if em.heartbeatTimer != nil {
		em.heartbeatTimer.Stop()
	}
	if em.discoveryTimer != nil {
		em.discoveryTimer.Stop()
	}
	if em.electionTimer != nil {
		em.electionTimer.Stop()
	}
}

// TriggerElection manually triggers an election
func (em *ElectionManager) TriggerElection(trigger ElectionTrigger) {
	select {
	case em.electionTrigger <- trigger:
		log.Printf("🗳️ Election triggered: %s", trigger)
	default:
		log.Printf("⚠️ Election trigger buffer full, ignoring: %s", trigger)
	}
}

// GetCurrentAdmin returns the current admin node ID
func (em *ElectionManager) GetCurrentAdmin() string {
	em.mu.RLock()
	defer em.mu.RUnlock()
	return em.currentAdmin
}

// IsCurrentAdmin checks if this node is the current admin
func (em *ElectionManager) IsCurrentAdmin() bool {
	return em.GetCurrentAdmin() == em.nodeID
}

// GetElectionState returns the current election state
func (em *ElectionManager) GetElectionState() ElectionState {
	em.mu.RLock()
	defer em.mu.RUnlock()
	return em.state
}

// SetCallbacks sets election event callbacks
func (em *ElectionManager) SetCallbacks(
	onAdminChanged func(oldAdmin, newAdmin string),
	onElectionComplete func(winner string),
) {
	em.onAdminChanged = onAdminChanged
	em.onElectionComplete = onElectionComplete
}

// startDiscoveryLoop starts the admin discovery loop
func (em *ElectionManager) startDiscoveryLoop() {
	log.Printf("🔍 Starting admin discovery loop")
	
	for {
		select {
		case <-em.ctx.Done():
			return
		case <-time.After(em.config.Security.ElectionConfig.DiscoveryTimeout):
			em.performAdminDiscovery()
		}
	}
}

// performAdminDiscovery attempts to discover existing admin
func (em *ElectionManager) performAdminDiscovery() {
	em.mu.Lock()
	currentState := em.state
	lastHeartbeat := em.lastHeartbeat
	em.mu.Unlock()
	
	// Only discover if we're idle or the heartbeat is stale
	if currentState != StateIdle {
		return
	}
	
	// Check if admin heartbeat has timed out
	if !lastHeartbeat.IsZero() && time.Since(lastHeartbeat) > em.config.Security.ElectionConfig.HeartbeatTimeout {
		log.Printf("⚰️ Admin heartbeat timeout detected (last: %v)", lastHeartbeat)
		em.TriggerElection(TriggerHeartbeatTimeout)
		return
	}
	
	// If we haven't heard from an admin recently, try to discover one
	if lastHeartbeat.IsZero() || time.Since(lastHeartbeat) > em.config.Security.ElectionConfig.DiscoveryTimeout/2 {
		em.sendDiscoveryRequest()
	}
}

// sendDiscoveryRequest broadcasts admin discovery request
func (em *ElectionManager) sendDiscoveryRequest() {
	discoveryMsg := ElectionMessage{
		Type:      "admin_discovery_request",
		NodeID:    em.nodeID,
		Timestamp: time.Now(),
	}
	
	if err := em.publishElectionMessage(discoveryMsg); err != nil {
		log.Printf("❌ Failed to send admin discovery request: %v", err)
	}
}

// electionCoordinator handles the main election logic
func (em *ElectionManager) electionCoordinator() {
	log.Printf("🎯 Election coordinator started")
	
	for {
		select {
		case <-em.ctx.Done():
			return
		case trigger := <-em.electionTrigger:
			em.handleElectionTrigger(trigger)
		}
	}
}

// handleElectionTrigger processes election triggers
func (em *ElectionManager) handleElectionTrigger(trigger ElectionTrigger) {
	log.Printf("🔥 Processing election trigger: %s", trigger)
	
	em.mu.Lock()
	currentState := em.state
	em.mu.Unlock()
	
	// Ignore triggers if we're already in an election
	if currentState != StateIdle {
		log.Printf("⏸️ Ignoring election trigger, current state: %s", currentState)
		return
	}
	
	// Begin election process
	em.beginElection(trigger)
}

// beginElection starts a new election
func (em *ElectionManager) beginElection(trigger ElectionTrigger) {
	log.Printf("🗳️ Beginning election due to: %s", trigger)
	
	em.mu.Lock()
	em.state = StateElecting
	em.currentTerm++
	term := em.currentTerm
	em.candidates = make(map[string]*AdminCandidate)
	em.votes = make(map[string]string)
	em.mu.Unlock()
	
	// Announce candidacy if this node can be admin
	if em.canBeAdmin() {
		em.announceCandidacy(term)
	}
	
	// Send election announcement
	electionMsg := ElectionMessage{
		Type:      "election_started",
		NodeID:    em.nodeID,
		Timestamp: time.Now(),
		Term:      term,
		Data: map[string]interface{}{
			"trigger": string(trigger),
		},
	}
	
	if err := em.publishElectionMessage(electionMsg); err != nil {
		log.Printf("❌ Failed to announce election start: %v", err)
	}
	
	// Start election timeout
	em.startElectionTimeout(term)
}

// canBeAdmin checks if this node can become admin
func (em *ElectionManager) canBeAdmin() bool {
	// Check if node has admin capabilities
	for _, cap := range em.config.Agent.Capabilities {
		if cap == "admin_election" || cap == "context_curation" || cap == "project_manager" {
			return true
		}
	}
	return false
}

// announceCandidacy announces this node as an election candidate
func (em *ElectionManager) announceCandidacy(term int) {
	uptime := time.Since(em.startTime)
	
	candidate := &AdminCandidate{
		NodeID:       em.nodeID,
		PeerID:       em.host.ID(),
		Capabilities: em.config.Agent.Capabilities,
		Uptime:       uptime,
		Resources:    em.getResourceMetrics(),
		Experience:   uptime, // For now, use uptime as experience
		Metadata: map[string]interface{}{
			"specialization": em.config.Agent.Specialization,
			"models":        em.config.Agent.Models,
		},
	}
	
	// Calculate candidate score
	candidate.Score = em.calculateCandidateScore(candidate)
	
	candidacyMsg := ElectionMessage{
		Type:      "candidacy_announcement",
		NodeID:    em.nodeID,
		Timestamp: time.Now(),
		Term:      term,
		Data:      candidate,
	}
	
	log.Printf("📢 Announcing candidacy (score: %.2f)", candidate.Score)
	
	if err := em.publishElectionMessage(candidacyMsg); err != nil {
		log.Printf("❌ Failed to announce candidacy: %v", err)
	}
}

// getResourceMetrics collects current node resource metrics
func (em *ElectionManager) getResourceMetrics() ResourceMetrics {
	// TODO: Implement actual resource collection
	// For now, return simulated values
	return ResourceMetrics{
		CPUUsage:       rand.Float64() * 0.5,  // 0-50% CPU
		MemoryUsage:    rand.Float64() * 0.7,  // 0-70% Memory
		DiskUsage:      rand.Float64() * 0.6,  // 0-60% Disk
		NetworkQuality: 0.8 + rand.Float64()*0.2, // 80-100% Network Quality
	}
}

// calculateCandidateScore calculates election score for a candidate
func (em *ElectionManager) calculateCandidateScore(candidate *AdminCandidate) float64 {
	scoring := em.config.Security.ElectionConfig.LeadershipScoring
	
	// Normalize metrics to 0-1 range
	uptimeScore := min(1.0, candidate.Uptime.Hours()/24.0) // Up to 24 hours gets full score
	
	// Capability score - higher for admin/coordination capabilities
	capabilityScore := 0.0
	adminCapabilities := []string{"admin_election", "context_curation", "key_reconstruction", "semantic_analysis", "project_manager"}
	for _, cap := range candidate.Capabilities {
		for _, adminCap := range adminCapabilities {
			if cap == adminCap {
				weight := 0.25 // Default weight
				// Project manager capabilities get higher weight
				if adminCap == "project_manager" || adminCap == "context_curation" {
					weight = 0.35
				}
				capabilityScore += weight
			}
		}
	}
	capabilityScore = min(1.0, capabilityScore)
	
	// Resource score - lower usage is better
	resourceScore := (1.0 - candidate.Resources.CPUUsage) * 0.3 +
		(1.0 - candidate.Resources.MemoryUsage) * 0.3 +
		(1.0 - candidate.Resources.DiskUsage) * 0.2 +
		candidate.Resources.NetworkQuality * 0.2
	
	experienceScore := min(1.0, candidate.Experience.Hours()/168.0) // Up to 1 week gets full score
	
	// Weighted final score
	finalScore := uptimeScore*scoring.UptimeWeight +
		capabilityScore*scoring.CapabilityWeight +
		resourceScore*scoring.ResourceWeight +
		candidate.Resources.NetworkQuality*scoring.NetworkWeight +
		experienceScore*scoring.ExperienceWeight
	
	return finalScore
}

// startElectionTimeout starts the election timeout timer
func (em *ElectionManager) startElectionTimeout(term int) {
	em.mu.Lock()
	defer em.mu.Unlock()
	
	if em.electionTimer != nil {
		em.electionTimer.Stop()
	}
	
	em.electionTimer = time.AfterFunc(em.config.Security.ElectionConfig.ElectionTimeout, func() {
		em.completeElection(term)
	})
}

// completeElection completes the election and announces winner
func (em *ElectionManager) completeElection(term int) {
	em.mu.Lock()
	defer em.mu.Unlock()
	
	// Verify this is still the current term
	if term != em.currentTerm {
		log.Printf("⏰ Election timeout for old term %d, ignoring", term)
		return
	}
	
	log.Printf("⏰ Election timeout reached, tallying votes")
	
	// Find the winning candidate
	winner := em.findElectionWinner()
	if winner == nil {
		log.Printf("❌ No winner found in election")
		em.state = StateIdle
		// Trigger another election after a delay
		go func() {
			time.Sleep(em.config.Security.ElectionConfig.DiscoveryBackoff)
			em.TriggerElection(TriggerDiscoveryFailure)
		}()
		return
	}
	
	log.Printf("🏆 Election winner: %s (score: %.2f)", winner.NodeID, winner.Score)
	
	// Update admin
	oldAdmin := em.currentAdmin
	em.currentAdmin = winner.NodeID
	em.state = StateComplete
	
	// Announce the winner
	winnerMsg := ElectionMessage{
		Type:      "election_winner",
		NodeID:    em.nodeID,
		Timestamp: time.Now(),
		Term:      term,
		Data:      winner,
	}
	
	em.mu.Unlock() // Unlock before publishing
	
	if err := em.publishElectionMessage(winnerMsg); err != nil {
		log.Printf("❌ Failed to announce election winner: %v", err)
	}
	
	// Trigger callbacks
	if em.onAdminChanged != nil {
		em.onAdminChanged(oldAdmin, winner.NodeID)
	}
	if em.onElectionComplete != nil {
		em.onElectionComplete(winner.NodeID)
	}
	
	em.mu.Lock()
	em.state = StateIdle // Reset state for next election
}

// findElectionWinner determines the election winner based on votes and scores
func (em *ElectionManager) findElectionWinner() *AdminCandidate {
	if len(em.candidates) == 0 {
		return nil
	}
	
	// Count votes for each candidate
	voteCounts := make(map[string]int)
	totalVotes := 0
	
	// Initialize vote counts for all candidates
	for candidateID := range em.candidates {
		voteCounts[candidateID] = 0
	}
	
	// Tally actual votes
	for _, candidateID := range em.votes {
		if _, exists := em.candidates[candidateID]; exists {
			voteCounts[candidateID]++
			totalVotes++
		}
	}
	
	// If no votes cast, fall back to highest scoring candidate
	if totalVotes == 0 {
		var winner *AdminCandidate
		highestScore := -1.0
		
		for _, candidate := range em.candidates {
			if candidate.Score > highestScore {
				highestScore = candidate.Score
				winner = candidate
			}
		}
		return winner
	}
	
	// Find candidate with most votes
	var winner *AdminCandidate
	maxVotes := -1
	highestScore := -1.0
	
	for candidateID, voteCount := range voteCounts {
		candidate := em.candidates[candidateID]
		if voteCount > maxVotes || (voteCount == maxVotes && candidate.Score > highestScore) {
			maxVotes = voteCount
			highestScore = candidate.Score
			winner = candidate
		}
	}
	
	log.Printf("🗳️ Election results: %d total votes, winner: %s with %d votes (score: %.2f)", 
		totalVotes, winner.NodeID, maxVotes, winner.Score)
	
	return winner
}

// handleElectionMessage processes incoming election messages
func (em *ElectionManager) handleElectionMessage(data []byte) {
	var msg ElectionMessage
	if err := json.Unmarshal(data, &msg); err != nil {
		log.Printf("❌ Failed to unmarshal election message: %v", err)
		return
	}
	
	// Ignore messages from ourselves
	if msg.NodeID == em.nodeID {
		return
	}
	
	switch msg.Type {
	case "admin_discovery_request":
		em.handleAdminDiscoveryRequest(msg)
	case "admin_discovery_response":
		em.handleAdminDiscoveryResponse(msg)
	case "election_started":
		em.handleElectionStarted(msg)
	case "candidacy_announcement":
		em.handleCandidacyAnnouncement(msg)
	case "election_vote":
		em.handleElectionVote(msg)
	case "election_winner":
		em.handleElectionWinner(msg)
	}
}

// handleAdminDiscoveryRequest responds to admin discovery requests
func (em *ElectionManager) handleAdminDiscoveryRequest(msg ElectionMessage) {
	em.mu.RLock()
	currentAdmin := em.currentAdmin
	state := em.state
	em.mu.RUnlock()
	
	// Only respond if we know who the current admin is and we're idle
	if currentAdmin != "" && state == StateIdle {
		responseMsg := ElectionMessage{
			Type:      "admin_discovery_response",
			NodeID:    em.nodeID,
			Timestamp: time.Now(),
			Data: map[string]interface{}{
				"current_admin": currentAdmin,
			},
		}
		
		if err := em.publishElectionMessage(responseMsg); err != nil {
			log.Printf("❌ Failed to send admin discovery response: %v", err)
		}
	}
}

// handleAdminDiscoveryResponse processes admin discovery responses
func (em *ElectionManager) handleAdminDiscoveryResponse(msg ElectionMessage) {
	if data, ok := msg.Data.(map[string]interface{}); ok {
		if admin, ok := data["current_admin"].(string); ok && admin != "" {
			em.mu.Lock()
			if em.currentAdmin == "" {
				log.Printf("📡 Discovered admin: %s", admin)
				em.currentAdmin = admin
			}
			em.mu.Unlock()
		}
	}
}

// handleElectionStarted processes election start announcements
func (em *ElectionManager) handleElectionStarted(msg ElectionMessage) {
	em.mu.Lock()
	defer em.mu.Unlock()
	
	// If we receive an election start with a higher term, join the election
	if msg.Term > em.currentTerm {
		log.Printf("🔄 Joining election with term %d", msg.Term)
		em.currentTerm = msg.Term
		em.state = StateElecting
		em.candidates = make(map[string]*AdminCandidate)
		em.votes = make(map[string]string)
		
		// Announce candidacy if eligible
		if em.canBeAdmin() {
			go em.announceCandidacy(msg.Term)
		}
	}
}

// handleCandidacyAnnouncement processes candidacy announcements
func (em *ElectionManager) handleCandidacyAnnouncement(msg ElectionMessage) {
	em.mu.Lock()
	defer em.mu.Unlock()
	
	// Only process if it's for the current term
	if msg.Term != em.currentTerm {
		return
	}
	
	// Convert data to candidate struct
	candidateData, err := json.Marshal(msg.Data)
	if err != nil {
		log.Printf("❌ Failed to marshal candidate data: %v", err)
		return
	}
	
	var candidate AdminCandidate
	if err := json.Unmarshal(candidateData, &candidate); err != nil {
		log.Printf("❌ Failed to unmarshal candidate: %v", err)
		return
	}
	
	log.Printf("📝 Received candidacy from %s (score: %.2f)", candidate.NodeID, candidate.Score)
	em.candidates[candidate.NodeID] = &candidate
}

// handleElectionVote processes election votes
func (em *ElectionManager) handleElectionVote(msg ElectionMessage) {
	em.mu.Lock()
	defer em.mu.Unlock()
	
	// Extract vote data
	voteData, ok := msg.Data.(map[string]interface{})
	if !ok {
		log.Printf("❌ Invalid vote data format from %s", msg.NodeID)
		return
	}
	
	candidateID, ok := voteData["candidate"].(string)
	if !ok {
		log.Printf("❌ Invalid candidate ID in vote from %s", msg.NodeID)
		return
	}
	
	// Validate candidate exists
	if _, exists := em.candidates[candidateID]; !exists {
		log.Printf("❌ Vote for unknown candidate %s from %s", candidateID, msg.NodeID)
		return
	}
	
	// Prevent duplicate voting
	if existingVote, exists := em.votes[msg.NodeID]; exists {
		log.Printf("⚠️ Node %s already voted for %s, updating to %s", msg.NodeID, existingVote, candidateID)
	}
	
	// Record the vote
	em.votes[msg.NodeID] = candidateID
	log.Printf("🗳️ Recorded vote from %s for candidate %s", msg.NodeID, candidateID)
}

// handleElectionWinner processes election winner announcements
func (em *ElectionManager) handleElectionWinner(msg ElectionMessage) {
	candidateData, err := json.Marshal(msg.Data)
	if err != nil {
		log.Printf("❌ Failed to marshal winner data: %v", err)
		return
	}
	
	var winner AdminCandidate
	if err := json.Unmarshal(candidateData, &winner); err != nil {
		log.Printf("❌ Failed to unmarshal winner: %v", err)
		return
	}
	
	em.mu.Lock()
	oldAdmin := em.currentAdmin
	em.currentAdmin = winner.NodeID
	em.state = StateIdle
	em.mu.Unlock()
	
	log.Printf("👑 New admin elected: %s", winner.NodeID)
	
	// Trigger callback
	if em.onAdminChanged != nil {
		em.onAdminChanged(oldAdmin, winner.NodeID)
	}
}

// handleAdminHeartbeat processes admin heartbeat messages
func (em *ElectionManager) handleAdminHeartbeat(data []byte) {
	var heartbeat struct {
		NodeID    string    `json:"node_id"`
		Timestamp time.Time `json:"timestamp"`
	}
	
	if err := json.Unmarshal(data, &heartbeat); err != nil {
		log.Printf("❌ Failed to unmarshal heartbeat: %v", err)
		return
	}
	
	em.mu.Lock()
	defer em.mu.Unlock()
	
	// Update admin and heartbeat timestamp
	if em.currentAdmin == "" || em.currentAdmin == heartbeat.NodeID {
		em.currentAdmin = heartbeat.NodeID
		em.lastHeartbeat = heartbeat.Timestamp
	}
}

// publishElectionMessage publishes an election message
func (em *ElectionManager) publishElectionMessage(msg ElectionMessage) error {
	data, err := json.Marshal(msg)
	if err != nil {
		return fmt.Errorf("failed to marshal election message: %w", err)
	}
	
	return em.pubsub.Publish("bzzz/election/v1", data)
}

// SendAdminHeartbeat sends admin heartbeat (only if this node is admin)
func (em *ElectionManager) SendAdminHeartbeat() error {
	if !em.IsCurrentAdmin() {
		return fmt.Errorf("not current admin")
	}
	
	heartbeat := struct {
		NodeID    string    `json:"node_id"`
		Timestamp time.Time `json:"timestamp"`
	}{
		NodeID:    em.nodeID,
		Timestamp: time.Now(),
	}
	
	data, err := json.Marshal(heartbeat)
	if err != nil {
		return fmt.Errorf("failed to marshal heartbeat: %w", err)
	}
	
	return em.pubsub.Publish("bzzz/admin/heartbeat/v1", data)
}

// min returns the minimum of two float64 values
func min(a, b float64) float64 {
	if a < b {
		return a
	}
	return b
}