package network

import (
	"fmt"
	"os"
	"path/filepath"
	"strings"
	"time"
)

const (
	DebianInterfacesPath = "/etc/network/interfaces"
	DebianVlansCfgPath   = "/etc/network/interfaces.d/vlans.cfg"
	DebianIfacesCfgPath  = "/etc/network/interfaces.d/interfaces.cfg"
)

// PersistenceManager handles writing Debian network configuration files.
type PersistenceManager struct {
	netMgr *Manager
}

func NewPersistenceManager(netMgr *Manager) *PersistenceManager {
	return &PersistenceManager{netMgr: netMgr}
}

// GenerateDebianConfig creates the contents of the /etc/network/interfaces.d/vlans.cfg file.
func (p *PersistenceManager) GenerateDebianConfig() (string, error) {
	vlans, err := p.netMgr.ListVLANs()
	if err != nil {
		return "", err
	}

	var sb strings.Builder
	sb.WriteString(fmt.Sprintf("# ====================================================\n"))
	sb.WriteString(fmt.Sprintf("# Proxmox Router Appliance - VLANs Configuration\n"))
	sb.WriteString(fmt.Sprintf("# Generated: %s\n", time.Now().Format(time.RFC1123)))
	sb.WriteString(fmt.Sprintf("# DO NOT EDIT MANUALLY - Managed via Router Web UI\n"))
	sb.WriteString(fmt.Sprintf("# ====================================================\n\n"))

	if len(vlans) == 0 {
		sb.WriteString("# No VLAN sub-interfaces configured.\n")
		return sb.String(), nil
	}

	for _, v := range vlans {
		sb.WriteString(fmt.Sprintf("# --- VLAN ID %d (%s) ---\n", v.VlanID, v.Name))
		if v.Description != "" {
			sb.WriteString(fmt.Sprintf("# Description: %s\n", v.Description))
		}
		if v.Role != "" {
			sb.WriteString(fmt.Sprintf("# Role: %s\n", v.Role))
		}

		sb.WriteString(fmt.Sprintf("auto %s\n", v.Name))

		if len(v.IPv4) > 0 {
			sb.WriteString(fmt.Sprintf("iface %s inet static\n", v.Name))
			sb.WriteString(fmt.Sprintf("    address %s\n", v.IPv4[0]))
			if v.ParentName != "" {
				sb.WriteString(fmt.Sprintf("    vlan-raw-device %s\n", v.ParentName))
			}
			if v.MTU > 0 && v.MTU != 1500 {
				sb.WriteString(fmt.Sprintf("    mtu %d\n", v.MTU))
			}
			// additional secondary IPv4 addresses
			for i := 1; i < len(v.IPv4); i++ {
				sb.WriteString(fmt.Sprintf("    up ip addr add %s dev %s\n", v.IPv4[i], v.Name))
				sb.WriteString(fmt.Sprintf("    down ip addr del %s dev %s\n", v.IPv4[i], v.Name))
			}
		} else {
			sb.WriteString(fmt.Sprintf("iface %s inet manual\n", v.Name))
			if v.ParentName != "" {
				sb.WriteString(fmt.Sprintf("    vlan-raw-device %s\n", v.ParentName))
			}
		}

		sb.WriteString("\n")
	}

	return sb.String(), nil
}

// EnsureSourceInclude ensures that /etc/network/interfaces contains loopback and "source /etc/network/interfaces.d/*"
// while removing duplicate interface stanzas that are managed inside interfaces.d/.
func (p *PersistenceManager) EnsureSourceInclude() error {
	cleanContent := `# The loopback network interface
auto lo
iface lo inet loopback

# Include extra interface configurations managed by DebTik / Proxmox Router
source /etc/network/interfaces.d/*
`
	return os.WriteFile(DebianInterfacesPath, []byte(cleanContent), 0644)
}

// GenerateInterfacesConfig creates /etc/network/interfaces.d/interfaces.cfg for regular interfaces
func (p *PersistenceManager) GenerateInterfacesConfig() (string, error) {
	ifacesWithIPs := p.netMgr.metadata.GetAllWithIPs()
	var sb strings.Builder
	sb.WriteString("# ====================================================\n")
	sb.WriteString("# Proxmox Router Appliance - Interface IP Configuration\n")
	sb.WriteString(fmt.Sprintf("# Generated: %s\n", time.Now().Format(time.RFC1123)))
	sb.WriteString("# DO NOT EDIT MANUALLY - Managed via Router Web UI\n")
	sb.WriteString("# ====================================================\n\n")

	if len(ifacesWithIPs) == 0 {
		sb.WriteString("# No persistent physical interface IPs configured.\n")
		return sb.String(), nil
	}

	for ifaceName, ips := range ifacesWithIPs {
		if len(ips) == 0 || strings.HasPrefix(ifaceName, "vlan") || strings.Contains(ifaceName, ".") {
			continue // Skip VLANs (handled in vlans.cfg)
		}
		sb.WriteString(fmt.Sprintf("# --- Interface %s ---\n", ifaceName))
		sb.WriteString(fmt.Sprintf("auto %s\n", ifaceName))
		sb.WriteString(fmt.Sprintf("iface %s inet static\n", ifaceName))
		sb.WriteString(fmt.Sprintf("    address %s\n", ips[0]))
		for i := 1; i < len(ips); i++ {
			sb.WriteString(fmt.Sprintf("    up ip addr add %s dev %s || true\n", ips[i], ifaceName))
			sb.WriteString(fmt.Sprintf("    down ip addr del %s dev %s || true\n", ips[i], ifaceName))
		}
		sb.WriteString("\n")
	}

	return sb.String(), nil
}

// SaveDebianConfig writes the configuration to disk.
func (p *PersistenceManager) SaveDebianConfig() (string, error) {
	cfg, err := p.GenerateDebianConfig()
	if err != nil {
		return "", err
	}

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

	if err := os.WriteFile(DebianVlansCfgPath, []byte(cfg), 0644); err != nil {
		return "", fmt.Errorf("failed to write %s: %w", DebianVlansCfgPath, err)
	}

	ifaceCfg, err := p.GenerateInterfacesConfig()
	if err == nil {
		_ = os.WriteFile(DebianIfacesCfgPath, []byte(ifaceCfg), 0644)
	}

	_ = p.EnsureSourceInclude()
	return cfg, nil
}