package unified

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

	"github.com/vishvananda/netlink"
)

// Manager handles unified network operations for VMs and containers
type Manager struct {
	// State directory for leases and config
	stateDir string

	// Network configurations by name
	networks map[string]*NetworkConfig

	// IPAM state
	ipam *IPAM

	// Active interfaces by workload ID
	interfaces map[string]*Interface

	mu sync.RWMutex
}

// NewManager creates a new unified network manager
func NewManager(stateDir string) (*Manager, error) {
	if err := os.MkdirAll(stateDir, 0755); err != nil {
		return nil, fmt.Errorf("create state dir: %w", err)
	}

	m := &Manager{
		stateDir:   stateDir,
		networks:   make(map[string]*NetworkConfig),
		interfaces: make(map[string]*Interface),
	}

	// Initialize IPAM
	ipam, err := NewIPAM(filepath.Join(stateDir, "ipam"))
	if err != nil {
		return nil, fmt.Errorf("init IPAM: %w", err)
	}
	m.ipam = ipam

	// Load existing state
	if err := m.loadState(); err != nil {
		// Non-fatal, might be first run
		_ = err
	}

	return m, nil
}

// AddNetwork registers a network configuration
func (m *Manager) AddNetwork(config *NetworkConfig) error {
	m.mu.Lock()
	defer m.mu.Unlock()

	// Validate
	if config.Name == "" {
		return fmt.Errorf("network name required")
	}
	if config.Subnet == "" {
		return fmt.Errorf("subnet required")
	}

	_, subnet, err := net.ParseCIDR(config.Subnet)
	if err != nil {
		return fmt.Errorf("invalid subnet: %w", err)
	}

	// Set defaults
	if config.MTU == 0 {
		config.MTU = 1500
	}
	if config.Type == "" {
		config.Type = NetworkBridged
	}
	if config.Bridge == "" && config.Type == NetworkBridged {
		config.Bridge = config.Name
	}

	// Register with IPAM
	if config.IPAM != nil {
		var gateway net.IP
		if config.Gateway != "" {
			gateway = net.ParseIP(config.Gateway)
		}
		if err := m.ipam.AddPool(config.Name, subnet, gateway, nil); err != nil {
			return fmt.Errorf("register IPAM pool: %w", err)
		}
	}

	m.networks[config.Name] = config
	return m.saveState()
}

// EnsureBridge ensures the bridge exists and is configured
func (m *Manager) EnsureBridge(name string) (*BridgeInfo, error) {
	// Check if bridge exists
	link, err := netlink.LinkByName(name)
	if err != nil {
		// Bridge doesn't exist, create it
		bridge := &netlink.Bridge{
			LinkAttrs: netlink.LinkAttrs{
				Name: name,
				MTU:  1500,
			},
		}
		if err := netlink.LinkAdd(bridge); err != nil {
			return nil, fmt.Errorf("create bridge %s: %w", name, err)
		}
		link, err = netlink.LinkByName(name)
		if err != nil {
			return nil, fmt.Errorf("get created bridge: %w", err)
		}
	}

	// Ensure it's up
	if err := netlink.LinkSetUp(link); err != nil {
		return nil, fmt.Errorf("set bridge up: %w", err)
	}

	// Get bridge info
	info := &BridgeInfo{
		Name: name,
		MTU:  link.Attrs().MTU,
		Up:   link.Attrs().OperState == netlink.OperUp,
	}

	if link.Attrs().HardwareAddr != nil {
		info.MAC = link.Attrs().HardwareAddr
	}

	// Get IP addresses
	addrs, err := netlink.AddrList(link, netlink.FAMILY_V4)
	if err == nil && len(addrs) > 0 {
		info.IP = addrs[0].IP
		info.Subnet = addrs[0].IPNet
	}

	return info, nil
}

// CreateTAP creates a TAP device for a VM and attaches it to the bridge
func (m *Manager) CreateTAP(network, workloadID string) (*Interface, error) {
	m.mu.Lock()
	defer m.mu.Unlock()

	config, ok := m.networks[network]
	if !ok {
		return nil, fmt.Errorf("network %s not found", network)
	}

	// Generate TAP name (max 15 chars for Linux interface names)
	tapName := fmt.Sprintf("tap-%s", truncateID(workloadID, 10))

	// Create TAP device
	tap := &netlink.Tuntap{
		LinkAttrs: netlink.LinkAttrs{
			Name: tapName,
			MTU:  config.MTU,
		},
		Mode:   netlink.TUNTAP_MODE_TAP,
		Flags:  netlink.TUNTAP_NO_PI | netlink.TUNTAP_VNET_HDR,
		Queues: 1, // Can increase for multi-queue
	}

	if err := netlink.LinkAdd(tap); err != nil {
		return nil, fmt.Errorf("create TAP %s: %w", tapName, err)
	}

	// Get the created link to get FD
	link, err := netlink.LinkByName(tapName)
	if err != nil {
		_ = netlink.LinkDel(tap)
		return nil, fmt.Errorf("get TAP link: %w", err)
	}

	// Get the file descriptor from the TAP
	// This requires opening /dev/net/tun with the TAP name
	fd, err := openTAPFD(tapName)
	if err != nil {
		_ = netlink.LinkDel(tap)
		return nil, fmt.Errorf("open TAP fd: %w", err)
	}

	// Attach to bridge
	bridge, err := netlink.LinkByName(config.Bridge)
	if err != nil {
		_ = netlink.LinkDel(tap)
		return nil, fmt.Errorf("get bridge %s: %w", config.Bridge, err)
	}

	if err := netlink.LinkSetMaster(link, bridge); err != nil {
		_ = netlink.LinkDel(tap)
		return nil, fmt.Errorf("attach to bridge: %w", err)
	}

	// Set link up
	if err := netlink.LinkSetUp(link); err != nil {
		_ = netlink.LinkDel(tap)
		return nil, fmt.Errorf("set TAP up: %w", err)
	}

	// Generate MAC address
	mac := generateMAC(workloadID)

	// Allocate IP if IPAM enabled
	var ip net.IP
	var mask net.IPMask
	var gateway net.IP
	if config.IPAM != nil {
		lease, err := m.ipam.Allocate(network, workloadID, mac)
		if err != nil {
			_ = netlink.LinkDel(tap)
			return nil, fmt.Errorf("allocate IP: %w", err)
		}
		ip = lease.IP
		_, subnet, _ := net.ParseCIDR(config.Subnet)
		mask = subnet.Mask
		if config.Gateway != "" {
			gateway = net.ParseIP(config.Gateway)
		}
	}

	iface := &Interface{
		Name:         tapName,
		MAC:          mac,
		IP:           ip,
		Mask:         mask,
		Gateway:      gateway,
		Bridge:       config.Bridge,
		WorkloadID:   workloadID,
		WorkloadType: WorkloadVM,
		FD:           fd,
	}

	m.interfaces[workloadID] = iface
	_ = m.saveState()

	return iface, nil
}

// CreateVeth creates a veth pair for a container and attaches host end to bridge
func (m *Manager) CreateVeth(network, workloadID string) (*Interface, error) {
	m.mu.Lock()
	defer m.mu.Unlock()

	config, ok := m.networks[network]
	if !ok {
		return nil, fmt.Errorf("network %s not found", network)
	}

	// Generate veth names (max 15 chars)
	hostName := fmt.Sprintf("veth-%s-h", truncateID(workloadID, 7))
	peerName := fmt.Sprintf("veth-%s-c", truncateID(workloadID, 7))

	// Create veth pair
	veth := &netlink.Veth{
		LinkAttrs: netlink.LinkAttrs{
			Name: hostName,
			MTU:  config.MTU,
		},
		PeerName: peerName,
	}

	if err := netlink.LinkAdd(veth); err != nil {
		return nil, fmt.Errorf("create veth pair: %w", err)
	}

	// Get the created links
	hostLink, err := netlink.LinkByName(hostName)
	if err != nil {
		_ = netlink.LinkDel(veth)
		return nil, fmt.Errorf("get host veth: %w", err)
	}

	peerLink, err := netlink.LinkByName(peerName)
	if err != nil {
		_ = netlink.LinkDel(veth)
		return nil, fmt.Errorf("get peer veth: %w", err)
	}

	// Attach host end to bridge
	bridge, err := netlink.LinkByName(config.Bridge)
	if err != nil {
		_ = netlink.LinkDel(veth)
		return nil, fmt.Errorf("get bridge %s: %w", config.Bridge, err)
	}

	if err := netlink.LinkSetMaster(hostLink, bridge); err != nil {
		_ = netlink.LinkDel(veth)
		return nil, fmt.Errorf("attach to bridge: %w", err)
	}

	// Set host end up
	if err := netlink.LinkSetUp(hostLink); err != nil {
		_ = netlink.LinkDel(veth)
		return nil, fmt.Errorf("set host veth up: %w", err)
	}

	// Generate MAC address
	mac := generateMAC(workloadID)

	// Set MAC on peer (container) end
	if err := netlink.LinkSetHardwareAddr(peerLink, mac); err != nil {
		_ = netlink.LinkDel(veth)
		return nil, fmt.Errorf("set peer MAC: %w", err)
	}

	// Allocate IP if IPAM enabled
	var ip net.IP
	var mask net.IPMask
	var gateway net.IP
	if config.IPAM != nil {
		lease, err := m.ipam.Allocate(network, workloadID, mac)
		if err != nil {
			_ = netlink.LinkDel(veth)
			return nil, fmt.Errorf("allocate IP: %w", err)
		}
		ip = lease.IP
		_, subnet, _ := net.ParseCIDR(config.Subnet)
		mask = subnet.Mask
		if config.Gateway != "" {
			gateway = net.ParseIP(config.Gateway)
		}
	}

	iface := &Interface{
		Name:         hostName,
		PeerName:     peerName,
		MAC:          mac,
		IP:           ip,
		Mask:         mask,
		Gateway:      gateway,
		Bridge:       config.Bridge,
		WorkloadID:   workloadID,
		WorkloadType: WorkloadContainer,
	}

	m.interfaces[workloadID] = iface
	_ = m.saveState()

	return iface, nil
}

// MoveVethToNamespace moves the container end of a veth pair to a network namespace
func (m *Manager) MoveVethToNamespace(workloadID string, nsFD int) error {
	m.mu.RLock()
	iface, ok := m.interfaces[workloadID]
	m.mu.RUnlock()

	if !ok {
		return fmt.Errorf("interface for %s not found", workloadID)
	}

	if iface.PeerName == "" {
		return fmt.Errorf("not a veth pair interface")
	}

	// Get peer link
	peerLink, err := netlink.LinkByName(iface.PeerName)
	if err != nil {
		return fmt.Errorf("get peer veth: %w", err)
	}

	// Move to namespace
	if err := netlink.LinkSetNsFd(peerLink, nsFD); err != nil {
		return fmt.Errorf("move to namespace: %w", err)
	}

	return nil
}

// ConfigureContainerInterface configures the interface inside the container namespace
// This should be called from within the container's network namespace
func (m *Manager) ConfigureContainerInterface(workloadID string) error {
	m.mu.RLock()
	iface, ok := m.interfaces[workloadID]
	m.mu.RUnlock()

	if !ok {
		return fmt.Errorf("interface for %s not found", workloadID)
	}

	// Get the interface (should be the peer that was moved into this namespace)
	link, err := netlink.LinkByName(iface.PeerName)
	if err != nil {
		return fmt.Errorf("get interface: %w", err)
	}

	// Set link up
	if err := netlink.LinkSetUp(link); err != nil {
		return fmt.Errorf("set link up: %w", err)
	}

	// Add IP address if allocated
	if iface.IP != nil {
		addr := &netlink.Addr{
			IPNet: &net.IPNet{
				IP:   iface.IP,
				Mask: iface.Mask,
			},
		}
		if err := netlink.AddrAdd(link, addr); err != nil {
			return fmt.Errorf("add IP address: %w", err)
		}
	}

	// Add default route via gateway
	if iface.Gateway != nil {
		route := &netlink.Route{
			Gw: iface.Gateway,
		}
		if err := netlink.RouteAdd(route); err != nil {
			return fmt.Errorf("add default route: %w", err)
		}
	}

	return nil
}

// Release releases the network interface for a workload
func (m *Manager) Release(workloadID string) error {
	m.mu.Lock()
	defer m.mu.Unlock()

	iface, ok := m.interfaces[workloadID]
	if !ok {
		return nil // Already released
	}

	// Release IP from IPAM
	for network := range m.networks {
		_ = m.ipam.Release(network, workloadID)
	}

	// Delete the interface
	link, err := netlink.LinkByName(iface.Name)
	if err == nil {
		_ = netlink.LinkDel(link)
	}

	delete(m.interfaces, workloadID)
	return m.saveState()
}

// GetInterface returns the interface for a workload
func (m *Manager) GetInterface(workloadID string) (*Interface, error) {
	m.mu.RLock()
	defer m.mu.RUnlock()

	iface, ok := m.interfaces[workloadID]
	if !ok {
		return nil, fmt.Errorf("interface for %s not found", workloadID)
	}
	return iface, nil
}

// ListInterfaces returns all managed interfaces
func (m *Manager) ListInterfaces() []*Interface {
	m.mu.RLock()
	defer m.mu.RUnlock()

	result := make([]*Interface, 0, len(m.interfaces))
	for _, iface := range m.interfaces {
		result = append(result, iface)
	}
	return result
}

// saveState persists current state to disk
func (m *Manager) saveState() error {
	data, err := json.MarshalIndent(m.interfaces, "", "  ")
	if err != nil {
		return err
	}
	return os.WriteFile(filepath.Join(m.stateDir, "interfaces.json"), data, 0644)
}

// loadState loads state from disk
func (m *Manager) loadState() error {
	data, err := os.ReadFile(filepath.Join(m.stateDir, "interfaces.json"))
	if err != nil {
		return err
	}
	return json.Unmarshal(data, &m.interfaces)
}

// truncateID truncates a workload ID for use in interface names
func truncateID(id string, maxLen int) string {
	if len(id) <= maxLen {
		return id
	}
	return id[:maxLen]
}

// generateMAC generates a deterministic MAC address from workload ID
func generateMAC(workloadID string) net.HardwareAddr {
	// Use first 5 bytes of workload ID hash
	// Set local/unicast bits
	mac := make([]byte, 6)
	mac[0] = 0x52 // Local, unicast (Volt prefix)
	mac[1] = 0x54
	mac[2] = 0x00

	// Hash-based bytes
	h := 0
	for _, c := range workloadID {
		h = h*31 + int(c)
	}
	mac[3] = byte((h >> 16) & 0xFF)
	mac[4] = byte((h >> 8) & 0xFF)
	mac[5] = byte(h & 0xFF)

	return mac
}

// openTAPFD opens a TAP device and returns its file descriptor
func openTAPFD(name string) (int, error) {
	// This is a simplified version - in production, use proper ioctl
	// The netlink library handles TAP creation, but we need the FD for VMM use

	// For now, return -1 as placeholder
	// Real implementation would:
	// 1. Open /dev/net/tun
	// 2. ioctl TUNSETIFF with name and flags
	// 3. Return the fd
	return -1, fmt.Errorf("TAP FD extraction not yet implemented - use device fd from netlink")
}