package aerotun

import (
	"encoding/json"
	"fmt"
	"log"
	"os"
	"path/filepath"
	"sort"
	"sync"
	"time"
)

type Manager struct {
	mu        sync.RWMutex
	instances map[string]TunnelInstance
	runners   map[string]*TunnelRunner
	errors    map[string]string
	filePath  string
	health    *healthMonitor
}

func NewManager() *Manager { return NewManagerWithPath(StoragePath) }
func NewManagerWithPath(path string) *Manager {
	m := &Manager{
		instances: make(map[string]TunnelInstance),
		runners:   make(map[string]*TunnelRunner),
		errors:    make(map[string]string),
		filePath:  path,
	}

	_ = os.MkdirAll(filepath.Dir(m.filePath), 0755)
	if err := m.load(); err != nil {
		log.Printf("[AeroTUN] Error loading saved instances: %v", err)
	}

	// Auto-start enabled tunnels
	for id, inst := range m.instances {
		if !inst.Disabled {
			if err := m.startRunnerLocked(id); err != nil {
				m.errors[id] = err.Error()
				log.Printf("[AeroTUN] Failed to auto-start tunnel %s (%s): %v", inst.Name, id, err)
			}
		}
	}
	m.health = newHealthMonitor(filepath.Join(filepath.Dir(path), "aerotun_health.json"))
	go m.monitorHealth()

	return m
}

func (m *Manager) load() error {
	m.mu.Lock()
	defer m.mu.Unlock()

	data, err := os.ReadFile(m.filePath)
	if err != nil {
		if os.IsNotExist(err) {
			return nil
		}
		return err
	}

	var list []TunnelInstance
	if err := json.Unmarshal(data, &list); err != nil {
		return err
	}

	for _, inst := range list {
		m.instances[inst.ID] = inst
	}
	return nil
}

func (m *Manager) saveLocked() error {
	list := make([]TunnelInstance, 0, len(m.instances))
	for _, inst := range m.instances {
		// Do not persist volatile runtime counters
		copyInst := inst
		copyInst.Running = false
		copyInst.Handshakes = 0
		copyInst.Backend = ""
		copyInst.ConfiguredMTU = 0
		copyInst.DropBreakdown = nil
		copyInst.HasPSK = false
		copyInst.HasPrivateKey = false
		copyInst.Connected = false
		copyInst.LastError = ""
		copyInst.DroppedPackets = 0
		copyInst.AuthFailures = 0
		copyInst.ReplayDrops = 0
		copyInst.ActivePeerEndpoint = ""
		copyInst.LastHandshake = ""
		copyInst.RxBytes = 0
		copyInst.TxBytes = 0
		copyInst.RawBytesIn = 0
		copyInst.RawBytesOut = 0
		copyInst.WireBytesIn = 0
		copyInst.WireBytesOut = 0
		copyInst.SavedBytes = 0
		copyInst.CompressionRatio = ""
		copyInst.PacketsRx = 0
		copyInst.PacketsTx = 0
		copyInst.CompressedPackets = 0
		copyInst.RawPackets = 0
		list = append(list, copyInst)
	}

	data, err := json.MarshalIndent(list, "", "  ")
	if err != nil {
		return err
	}

	f, err := os.CreateTemp(filepath.Dir(m.filePath), ".aerotun-*.json")
	if err != nil {
		return err
	}
	defer os.Remove(f.Name())
	if err = f.Chmod(0600); err != nil {
		f.Close()
		return err
	}
	if _, err = f.Write(data); err != nil {
		f.Close()
		return err
	}
	if err = f.Sync(); err != nil {
		f.Close()
		return err
	}
	if err = f.Close(); err != nil {
		return err
	}
	return os.Rename(f.Name(), m.filePath)
}

func (m *Manager) List() []TunnelInstance {
	m.mu.RLock()
	defer m.mu.RUnlock()

	result := make([]TunnelInstance, 0, len(m.instances))
	for id, inst := range m.instances {
		if runner, ok := m.runners[id]; ok && runner != nil {
			tele := runner.GetTelemetry()
			tele.Disabled = inst.Disabled
			tele.Comment = inst.Comment
			result = append(result, tele)
		} else {
			inst.Running = false
			inst.Connected = false
			inst.LastError = m.errors[id]
			result = append(result, inst)
		}
	}

	sort.Slice(result, func(i, j int) bool {
		return result[i].Name < result[j].Name
	})

	return result
}

func (m *Manager) Get(id string) (TunnelInstance, bool) {
	m.mu.RLock()
	defer m.mu.RUnlock()

	inst, exists := m.instances[id]
	if !exists {
		return TunnelInstance{}, false
	}

	if runner, ok := m.runners[id]; ok && runner != nil {
		tele := runner.GetTelemetry()
		tele.Disabled = inst.Disabled
		tele.Comment = inst.Comment
		return tele, true
	}
	inst.Running = false
	inst.Connected = false
	inst.LastError = m.errors[id]
	return inst, true
}

func (m *Manager) Save(inst TunnelInstance) (TunnelInstance, error) {
	m.mu.Lock()
	defer m.mu.Unlock()

	if inst.ID == "" {
		inst.ID = fmt.Sprintf("aerotun-%d", time.Now().UnixNano())
	}
	if inst.Name == "" {
		inst.Name = fmt.Sprintf("aerotun%d", len(m.instances))
	}
	if inst.MTU == 0 {
		inst.MTU = DefaultMTU
	}
	if inst.Mode == "server" && inst.ListenPort == 0 {
		inst.ListenPort = DefaultPort
	}
	if inst.CreatedAt.IsZero() {
		inst.CreatedAt = time.Now()
	}

	if old, ok := m.instances[inst.ID]; ok {
		if inst.PSK == "" {
			inst.PSK = old.PSK
		}
		if inst.PrivateKey == "" {
			inst.PrivateKey = old.PrivateKey
			inst.PublicKey = old.PublicKey
		}
	}
	if inst.Protocol == 3 && inst.PrivateKey == "" {
		var err error
		inst.PrivateKey, inst.PublicKey, err = GenerateIdentity()
		if err != nil {
			return inst, err
		}
	}
	if err := validateConfig(&inst); err != nil {
		return inst, err
	}
	for id, existing := range m.instances {
		if id != inst.ID && existing.Name == inst.Name {
			return inst, fmt.Errorf("interface name already configured: %s", inst.Name)
		}
	}
	previous, existed := m.instances[inst.ID]
	m.instances[inst.ID] = inst
	if err := m.saveLocked(); err != nil {
		if existed {
			m.instances[inst.ID] = previous
		} else {
			delete(m.instances, inst.ID)
		}
		return inst, fmt.Errorf("failed to save configuration: %w", err)
	}
	if runner := m.runners[inst.ID]; runner != nil {
		runner.Stop()
		delete(m.runners, inst.ID)
	}
	delete(m.errors, inst.ID)

	// Restart if not disabled
	if !inst.Disabled {
		if err := m.startRunnerLocked(inst.ID); err != nil {
			m.errors[inst.ID] = err.Error()
			return inst, fmt.Errorf("configuration saved but tunnel failed to start: %w", err)
		}
	}

	if runner, ok := m.runners[inst.ID]; ok && runner != nil {
		return runner.GetTelemetry(), nil
	}
	return inst, nil
}

func (m *Manager) Delete(id string) error {
	m.mu.Lock()
	defer m.mu.Unlock()

	if runner, exists := m.runners[id]; exists && runner != nil {
		runner.Stop()
		delete(m.runners, id)
	}

	delete(m.instances, id)
	delete(m.errors, id)
	return m.saveLocked()
}

func (m *Manager) StartTunnel(id string) error {
	m.mu.Lock()
	defer m.mu.Unlock()

	return m.toggleStateLocked(id, false)
}

func (m *Manager) StopTunnel(id string) error {
	m.mu.Lock()
	defer m.mu.Unlock()

	if runner, exists := m.runners[id]; exists && runner != nil {
		runner.Stop()
		delete(m.runners, id)
	}
	return nil
}

func (m *Manager) ToggleState(id string, disabled bool) error {
	m.mu.Lock()
	defer m.mu.Unlock()

	return m.toggleStateLocked(id, disabled)
}
func (m *Manager) toggleStateLocked(id string, disabled bool) error {
	inst, exists := m.instances[id]
	if !exists {
		return fmt.Errorf("tunnel not found: %s", id)
	}
	previous := inst
	inst.Disabled = disabled
	m.instances[id] = inst
	if err := m.saveLocked(); err != nil {
		m.instances[id] = previous
		return err
	}
	if disabled {
		if runner := m.runners[id]; runner != nil {
			runner.Stop()
			delete(m.runners, id)
		}
		delete(m.errors, id)
		return nil
	}
	return m.startRunnerLocked(id)
}

func (m *Manager) startRunnerLocked(id string) error {
	inst, exists := m.instances[id]
	if !exists {
		return fmt.Errorf("tunnel not found: %s", id)
	}

	if runner, exists := m.runners[id]; exists && runner != nil {
		runner.Stop()
		delete(m.runners, id)
	}

	delete(m.errors, id)
	runner, err := NewTunnelRunner(inst)
	if err != nil {
		m.errors[id] = err.Error()
		return err
	}

	if err := runner.Start(); err != nil {
		runner.Stop()
		m.errors[id] = err.Error()
		return err
	}
	m.runners[id] = runner
	return nil
}

func (m *Manager) StopAll() {
	if m.health != nil {
		m.health.stop()
	}
	m.mu.Lock()
	defer m.mu.Unlock()

	for id, runner := range m.runners {
		if runner != nil {
			runner.Stop()
		}
		delete(m.runners, id)
	}
}

func (m *Manager) GetSummaryStats() SummaryStats {
	tunnels := m.List()
	stats := SummaryStats{
		TotalTunnels:      len(tunnels),
		AlgorithmCrypto:   "XChaCha20-Poly1305 AEAD (v3: Noise IKpsk2)",
		AlgorithmCompress: "Adaptive LZ4 (Dynamic Threshold)",
	}

	var totalRawOut, totalWireOut uint64
	for _, t := range tunnels {
		if t.Connected {
			stats.ActiveTunnels++
		}
		stats.TotalRxBytes += t.RxBytes
		stats.TotalTxBytes += t.TxBytes
		stats.TotalSavedBytes += t.SavedBytes
		totalRawOut += t.RawBytesOut
		totalWireOut += t.WireBytesOut
	}

	if totalRawOut > 0 && totalWireOut > 0 {
		ratio := float64(totalRawOut) / float64(totalWireOut)
		if ratio > 1.0 {
			savedPct := (1.0 - (float64(totalWireOut) / float64(totalRawOut))) * 100.0
			stats.AverageRatio = fmt.Sprintf("%.2fx (%.1f%% saved)", ratio, savedPct)
		} else {
			stats.AverageRatio = "1.00x (0% saved)"
		}
	} else {
		stats.AverageRatio = "1.00x (0% saved)"
	}

	return stats
}