package rqlite

import (
	"encoding/json"
	"fmt"
	"net"
	"os"
	"path/filepath"
	"sort"
	"strings"
	"time"

	"github.com/DeBrosOfficial/network/pkg/discovery"
	"go.uber.org/zap"
)

// MaxDefaultVoters is the maximum number of voter nodes in the default cluster.
// Additional nodes join as non-voters (read replicas). Voter election is
// deterministic: all peers sorted by the IP component of their raft address,
// and the first MaxDefaultVoters are voters.
const MaxDefaultVoters = 5

// collectPeerMetadata collects RQLite metadata from LibP2P peers
func (c *ClusterDiscoveryService) collectPeerMetadata() []*discovery.RQLiteNodeMetadata {
	connectedPeers := c.host.Network().Peers()
	var metadata []*discovery.RQLiteNodeMetadata

	c.mu.RLock()
	currentRaftAddr := c.raftAddress
	currentHTTPAddr := c.httpAddress
	c.mu.RUnlock()

	// Add ourselves
	ourMetadata := &discovery.RQLiteNodeMetadata{
		NodeID:         currentRaftAddr, // RQLite uses raft address as node ID
		RaftAddress:    currentRaftAddr,
		HTTPAddress:    currentHTTPAddr,
		NodeType:       c.nodeType,
		RaftLogIndex:   c.rqliteManager.getRaftLogIndex(),
		LastSeen:       time.Now(),
		ClusterVersion: "1.0",
		PeerID:         c.host.ID().String(),
		WireGuardIP:    c.wireGuardIP,
	}

	// Populate lifecycle state
	if c.lifecycle != nil {
		state, ttl := c.lifecycle.Snapshot()
		ourMetadata.LifecycleState = string(state)
		if state == "maintenance" {
			ourMetadata.MaintenanceTTL = ttl
		}
	}

	if c.adjustSelfAdvertisedAddresses(ourMetadata) {
		c.logger.Debug("Adjusted self-advertised RQLite addresses",
			zap.String("raft_address", ourMetadata.RaftAddress),
			zap.String("http_address", ourMetadata.HTTPAddress))
	}

	metadata = append(metadata, ourMetadata)

	staleNodeIDs := make([]string, 0)

	for _, peerID := range connectedPeers {
		if val, err := c.host.Peerstore().Get(peerID, "rqlite_metadata"); err == nil {
			if jsonData, ok := val.([]byte); ok {
				var peerMeta discovery.RQLiteNodeMetadata
				if err := json.Unmarshal(jsonData, &peerMeta); err == nil {
					if updated, stale := c.adjustPeerAdvertisedAddresses(peerID, &peerMeta); updated && stale != "" {
						staleNodeIDs = append(staleNodeIDs, stale)
					}
					peerMeta.LastSeen = time.Now()
					metadata = append(metadata, &peerMeta)
				}
			}
		}
	}

	if len(staleNodeIDs) > 0 {
		c.mu.Lock()
		for _, id := range staleNodeIDs {
			delete(c.knownPeers, id)
			delete(c.peerHealth, id)
		}
		c.mu.Unlock()
	}

	return metadata
}

type membershipUpdateResult struct {
	peersJSON []map[string]interface{}
	added     []string
	updated   []string
	changed   bool
}

func (c *ClusterDiscoveryService) updateClusterMembership() {
	metadata := c.collectPeerMetadata()

	c.mu.Lock()
	result := c.computeMembershipChangesLocked(metadata)
	c.mu.Unlock()

	if result.changed {
		if len(result.added) > 0 || len(result.updated) > 0 {
			c.logger.Info("Membership changed",
				zap.Int("added", len(result.added)),
				zap.Int("updated", len(result.updated)),
				zap.Strings("added", result.added),
				zap.Strings("updated", result.updated))
		}

		if err := c.writePeersJSONWithData(result.peersJSON); err != nil {
			c.logger.Error("Failed to write peers.json",
				zap.Error(err),
				zap.String("data_dir", c.dataDir),
				zap.Int("peers", len(result.peersJSON)))
		} else {
			c.logger.Debug("peers.json updated",
				zap.Int("peers", len(result.peersJSON)))
		}

		c.mu.Lock()
		c.lastUpdate = time.Now()
		c.mu.Unlock()
	}
}

func (c *ClusterDiscoveryService) computeMembershipChangesLocked(metadata []*discovery.RQLiteNodeMetadata) membershipUpdateResult {
	added := []string{}
	updated := []string{}

	for _, meta := range metadata {
		isSelf := meta.NodeID == c.raftAddress

		if existing, ok := c.knownPeers[meta.NodeID]; ok {
			if existing.RaftLogIndex != meta.RaftLogIndex ||
				existing.HTTPAddress != meta.HTTPAddress ||
				existing.RaftAddress != meta.RaftAddress {
				updated = append(updated, meta.NodeID)
			}
		} else {
			added = append(added, meta.NodeID)
			c.logger.Info("Node added",
				zap.String("node", meta.NodeID),
				zap.String("raft", meta.RaftAddress),
				zap.String("type", meta.NodeType),
				zap.Uint64("log_index", meta.RaftLogIndex))
		}

		c.knownPeers[meta.NodeID] = meta

		if !isSelf {
			if _, ok := c.peerHealth[meta.NodeID]; !ok {
				c.peerHealth[meta.NodeID] = &PeerHealth{
					LastSeen:       time.Now(),
					LastSuccessful: time.Now(),
					Status:         "active",
				}
			} else {
				c.peerHealth[meta.NodeID].LastSeen = time.Now()
				c.peerHealth[meta.NodeID].Status = "active"
				c.peerHealth[meta.NodeID].FailureCount = 0
			}
		}
	}

	remotePeerCount := 0
	for _, peer := range c.knownPeers {
		if peer.NodeID != c.raftAddress {
			remotePeerCount++
		}
	}

	peers := c.getPeersJSONUnlocked()
	shouldWrite := len(added) > 0 || len(updated) > 0 || c.lastUpdate.IsZero()

	if shouldWrite {
		if c.lastUpdate.IsZero() {
			requiredRemotePeers := c.minClusterSize - 1

			if remotePeerCount < requiredRemotePeers {
				c.logger.Info("Waiting for peers",
					zap.Int("have", remotePeerCount),
					zap.Int("need", requiredRemotePeers),
					zap.Int("min_size", c.minClusterSize))
				return membershipUpdateResult{
					changed: false,
				}
			}
		}

		if len(peers) == 0 && c.lastUpdate.IsZero() {
			c.logger.Info("No remote peers - waiting")
			return membershipUpdateResult{
				changed: false,
			}
		}

		if c.lastUpdate.IsZero() {
			c.logger.Info("Initial sync",
				zap.Int("total", len(c.knownPeers)),
				zap.Int("remote", remotePeerCount),
				zap.Int("in_json", len(peers)))
		}

		return membershipUpdateResult{
			peersJSON: peers,
			added:     added,
			updated:   updated,
			changed:   true,
		}
	}

	return membershipUpdateResult{
		changed: false,
	}
}

func (c *ClusterDiscoveryService) removeInactivePeers() {
	c.mu.Lock()
	defer c.mu.Unlock()

	now := time.Now()
	removed := []string{}

	for nodeID, health := range c.peerHealth {
		inactiveDuration := now.Sub(health.LastSeen)

		if inactiveDuration > c.inactivityLimit {
			c.logger.Warn("Node removed",
				zap.String("node", nodeID),
				zap.String("reason", "inactive"),
				zap.Duration("inactive_duration", inactiveDuration))

			delete(c.knownPeers, nodeID)
			delete(c.peerHealth, nodeID)
			removed = append(removed, nodeID)
		}
	}

	if len(removed) > 0 {
		c.logger.Info("Removed inactive",
			zap.Int("count", len(removed)),
			zap.Strings("nodes", removed))

		if err := c.writePeersJSON(); err != nil {
			c.logger.Error("Failed to write peers.json after cleanup", zap.Error(err))
		}
	}
}

func (c *ClusterDiscoveryService) getPeersJSON() []map[string]interface{} {
	c.mu.RLock()
	defer c.mu.RUnlock()
	return c.getPeersJSONUnlocked()
}

func (c *ClusterDiscoveryService) getPeersJSONUnlocked() []map[string]interface{} {
	// Collect all raft addresses
	raftAddrs := make([]string, 0, len(c.knownPeers))
	for _, peer := range c.knownPeers {
		raftAddrs = append(raftAddrs, peer.RaftAddress)
	}

	// Determine voter set
	voterSet := computeVoterSet(raftAddrs, MaxDefaultVoters)

	peers := make([]map[string]interface{}, 0, len(c.knownPeers))
	for _, peer := range c.knownPeers {
		_, isVoter := voterSet[peer.RaftAddress]
		peerEntry := map[string]interface{}{
			"id":        peer.RaftAddress,
			"address":   peer.RaftAddress,
			"non_voter": !isVoter,
		}
		peers = append(peers, peerEntry)
	}

	return peers
}

// computeVoterSet returns the set of raft addresses that should be voters.
// It sorts addresses by their numeric IP and selects the first maxVoters.
// This is deterministic — all nodes compute the same voter set from the same peer list.
func computeVoterSet(raftAddrs []string, maxVoters int) map[string]struct{} {
	sorted := make([]string, len(raftAddrs))
	copy(sorted, raftAddrs)

	sort.Slice(sorted, func(i, j int) bool {
		ipI := extractIPForSort(sorted[i])
		ipJ := extractIPForSort(sorted[j])
		return compareIPs(ipI, ipJ)
	})

	voters := make(map[string]struct{})
	for i, addr := range sorted {
		if i >= maxVoters {
			break
		}
		voters[addr] = struct{}{}
	}
	return voters
}

// extractIPForSort extracts the IP string from a raft address (host:port) for sorting.
func extractIPForSort(raftAddr string) string {
	host, _, err := net.SplitHostPort(raftAddr)
	if err != nil {
		return raftAddr
	}
	return host
}

// compareIPs compares two IP strings numerically (not alphabetically).
// Alphabetical sort gives wrong results: "10.0.0.10" < "10.0.0.2" alphabetically,
// but numerically 10.0.0.2 < 10.0.0.10. This was causing wrong nodes to be
// selected as voters (e.g., 10.0.0.1, 10.0.0.10, 10.0.0.11 instead of 10.0.0.1-5).
func compareIPs(a, b string) bool {
	ipA := net.ParseIP(a)
	ipB := net.ParseIP(b)

	// Fallback to string comparison if parsing fails
	if ipA == nil || ipB == nil {
		return a < b
	}

	// Normalize to 16-byte representation for consistent comparison
	ipA = ipA.To16()
	ipB = ipB.To16()

	for i := range ipA {
		if ipA[i] != ipB[i] {
			return ipA[i] < ipB[i]
		}
	}
	return false
}

// IsVoter returns true if the given raft address is in the voter set
// based on the current known peers. Must be called with c.mu held.
func (c *ClusterDiscoveryService) IsVoterLocked(raftAddress string) bool {
	// If we don't know enough peers yet, default to voter.
	// Non-voter demotion only kicks in once we see more than MaxDefaultVoters peers.
	if len(c.knownPeers) <= MaxDefaultVoters {
		return true
	}
	raftAddrs := make([]string, 0, len(c.knownPeers))
	for _, peer := range c.knownPeers {
		raftAddrs = append(raftAddrs, peer.RaftAddress)
	}
	voterSet := computeVoterSet(raftAddrs, MaxDefaultVoters)
	_, isVoter := voterSet[raftAddress]
	return isVoter
}

func (c *ClusterDiscoveryService) writePeersJSON() error {
	c.mu.RLock()
	peers := c.getPeersJSONUnlocked()
	c.mu.RUnlock()

	return c.writePeersJSONWithData(peers)
}

// writePeersJSONWithData writes the discovery peers file to a SAFE location
// outside the raft directory. This is critical: rqlite v8 treats any
// peers.json inside <dataDir>/raft/ as a recovery signal and RESETS
// the Raft configuration on startup. Writing there on every periodic sync
// caused split-brain on every node restart.
//
// Safe location: <dataDir>/rqlite/discovery-peers.json
// Dangerous location: <dataDir>/rqlite/raft/peers.json (only for explicit recovery)
func (c *ClusterDiscoveryService) writePeersJSONWithData(peers []map[string]interface{}) error {
	dataDir := os.ExpandEnv(c.dataDir)
	if strings.HasPrefix(dataDir, "~") {
		home, err := os.UserHomeDir()
		if err != nil {
			return fmt.Errorf("failed to determine home directory: %w", err)
		}
		dataDir = filepath.Join(home, dataDir[1:])
	}

	// Write to <dataDir>/rqlite/ — NOT inside raft/ subdirectory.
	// rqlite v8 auto-recovers from raft/peers.json on every startup,
	// which resets the Raft config and causes split-brain.
	rqliteDir := filepath.Join(dataDir, "rqlite")

	if err := os.MkdirAll(rqliteDir, 0755); err != nil {
		return fmt.Errorf("failed to create rqlite directory %s: %w", rqliteDir, err)
	}

	peersFile := filepath.Join(rqliteDir, "discovery-peers.json")

	data, err := json.MarshalIndent(peers, "", "  ")
	if err != nil {
		return fmt.Errorf("failed to marshal discovery-peers.json: %w", err)
	}

	tempFile := peersFile + ".tmp"
	if err := os.WriteFile(tempFile, data, 0644); err != nil {
		return fmt.Errorf("failed to write temp discovery-peers.json %s: %w", tempFile, err)
	}

	if err := os.Rename(tempFile, peersFile); err != nil {
		return fmt.Errorf("failed to rename %s to %s: %w", tempFile, peersFile, err)
	}

	nodeIDs := make([]string, 0, len(peers))
	for _, p := range peers {
		if id, ok := p["id"].(string); ok {
			nodeIDs = append(nodeIDs, id)
		}
	}

	c.logger.Debug("discovery-peers.json written",
		zap.Int("peers", len(peers)),
		zap.Strings("nodes", nodeIDs))

	return nil
}

// writeRecoveryPeersJSON writes peers.json to the raft directory for
// INTENTIONAL cluster recovery only. rqlite v8 will read this file on
// startup and reset the Raft configuration accordingly. Only call this
// when you explicitly want to trigger Raft recovery.
func (c *ClusterDiscoveryService) writeRecoveryPeersJSON(peers []map[string]interface{}) error {
	dataDir := os.ExpandEnv(c.dataDir)
	if strings.HasPrefix(dataDir, "~") {
		home, err := os.UserHomeDir()
		if err != nil {
			return fmt.Errorf("failed to determine home directory: %w", err)
		}
		dataDir = filepath.Join(home, dataDir[1:])
	}

	raftDir := filepath.Join(dataDir, "rqlite", "raft")

	if err := os.MkdirAll(raftDir, 0755); err != nil {
		return fmt.Errorf("failed to create raft directory %s: %w", raftDir, err)
	}

	peersFile := filepath.Join(raftDir, "peers.json")

	data, err := json.MarshalIndent(peers, "", "  ")
	if err != nil {
		return fmt.Errorf("failed to marshal recovery peers.json: %w", err)
	}

	tempFile := peersFile + ".tmp"
	if err := os.WriteFile(tempFile, data, 0644); err != nil {
		return fmt.Errorf("failed to write temp recovery peers.json %s: %w", tempFile, err)
	}

	if err := os.Rename(tempFile, peersFile); err != nil {
		return fmt.Errorf("failed to rename %s to %s: %w", tempFile, peersFile, err)
	}

	nodeIDs := make([]string, 0, len(peers))
	for _, p := range peers {
		if id, ok := p["id"].(string); ok {
			nodeIDs = append(nodeIDs, id)
		}
	}

	c.logger.Warn("RECOVERY peers.json written to raft directory — rqlited will reset Raft config on next startup",
		zap.Int("peers", len(peers)),
		zap.Strings("nodes", nodeIDs))

	return nil
}