package resolver

import (
	"context"
	"fmt"
	"net"

	"git.zb-server.de/Sebi/ssh-netbox-wrapper/internal/netbox"
)

// ManagementSubnetStrategy finds the first IP of a host that falls within
// one of the configured management subnets.
type ManagementSubnetStrategy struct {
	subnets []*net.IPNet
}

func NewManagementSubnetStrategy(cidrs []string) (*ManagementSubnetStrategy, error) {
	nets := make([]*net.IPNet, 0, len(cidrs))
	for _, cidr := range cidrs {
		_, ipNet, err := net.ParseCIDR(cidr)
		if err != nil {
			return nil, fmt.Errorf("invalid CIDR %q: %w", cidr, err)
		}
		nets = append(nets, ipNet)
	}
	return &ManagementSubnetStrategy{subnets: nets}, nil
}

func (s *ManagementSubnetStrategy) Name() string { return "management_subnet" }

func (s *ManagementSubnetStrategy) Resolve(ctx context.Context, entry *netbox.HostEntry, client *netbox.Client) (string, error) {
	if len(s.subnets) == 0 {
		return "", ErrNoIP
	}

	ips, err := client.GetIPs(ctx, *entry)
	if err != nil {
		return "", fmt.Errorf("fetching IPs: %w", err)
	}

	for _, rawIP := range ips {
		ip := net.ParseIP(rawIP)
		if ip == nil {
			continue
		}
		for _, subnet := range s.subnets {
			if subnet.Contains(ip) {
				return rawIP, nil
			}
		}
	}
	return "", ErrNoIP
}