package wireguard

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

	"gitea.perlbach24.de/scripte/wireguard-ui-multi/internal/server"
)

// ConfigDir is where per-interface wgX.conf files are written, e.g. /etc/wireguard.
var ConfigDir = "/etc/wireguard"

// RenderConfig builds the wg-quick compatible config text for a server and its peers.
func RenderConfig(srv *server.Server, peers []*server.Peer) string {
	var b strings.Builder

	fmt.Fprintf(&b, "[Interface]\n")
	fmt.Fprintf(&b, "PrivateKey = %s\n", srv.PrivateKey)
	fmt.Fprintf(&b, "Address = %s\n", srv.AddressRange)
	fmt.Fprintf(&b, "ListenPort = %d\n", srv.ListenPort)
	if srv.MTU > 0 {
		fmt.Fprintf(&b, "MTU = %d\n", srv.MTU)
	}
	if srv.DNS != "" {
		fmt.Fprintf(&b, "DNS = %s\n", srv.DNS)
	}

	for _, p := range peers {
		if !p.Enabled {
			continue
		}
		b.WriteString("\n[Peer]\n")
		fmt.Fprintf(&b, "# %s\n", p.Name)
		fmt.Fprintf(&b, "PublicKey = %s\n", p.PublicKey)
		if p.PresharedKey != "" {
			fmt.Fprintf(&b, "PresharedKey = %s\n", p.PresharedKey)
		}
		fmt.Fprintf(&b, "AllowedIPs = %s\n", p.AllowedIPs)
		if p.PersistentKeepalive > 0 {
			fmt.Fprintf(&b, "PersistentKeepalive = %d\n", p.PersistentKeepalive)
		}
	}

	return b.String()
}

// RenderClientConfig builds the config a peer/client would use to connect to srv.
func RenderClientConfig(srv *server.Server, p *server.Peer, endpointHost string) string {
	var b strings.Builder

	b.WriteString("[Interface]\n")
	fmt.Fprintf(&b, "PrivateKey = %s\n", p.PrivateKey)
	fmt.Fprintf(&b, "Address = %s\n", p.AllowedIPs)
	if srv.DNS != "" {
		fmt.Fprintf(&b, "DNS = %s\n", srv.DNS)
	}

	b.WriteString("\n[Peer]\n")
	fmt.Fprintf(&b, "PublicKey = %s\n", srv.PublicKey)
	if p.PresharedKey != "" {
		fmt.Fprintf(&b, "PresharedKey = %s\n", p.PresharedKey)
	}
	fmt.Fprintf(&b, "Endpoint = %s:%d\n", endpointHost, srv.ListenPort)
	fmt.Fprintf(&b, "AllowedIPs = 0.0.0.0/0, ::/0\n")
	if p.PersistentKeepalive > 0 {
		fmt.Fprintf(&b, "PersistentKeepalive = %d\n", p.PersistentKeepalive)
	}

	return b.String()
}

// WriteConfig writes the rendered server config to ConfigDir/<interface>.conf with 0600 perms.
func WriteConfig(srv *server.Server, peers []*server.Peer) error {
	if err := os.MkdirAll(ConfigDir, 0700); err != nil {
		return err
	}
	path := filepath.Join(ConfigDir, srv.InterfaceName+".conf")
	return os.WriteFile(path, []byte(RenderConfig(srv, peers)), 0600)
}

// ConfigPath returns the on-disk path for a server's config file.
func ConfigPath(srv *server.Server) string {
	return filepath.Join(ConfigDir, srv.InterfaceName+".conf")
}