package iptools

import (
	"fmt"
	"net/netip"
)

const (
	DefaultMaskBits = 24
)

type Range struct {
	Start   netip.Addr   `yaml:"start"`
	End     netip.Addr   `yaml:"end"`
	Network netip.Prefix `yaml:"network"`
}

func (r *Range) Validate() error {
	if !r.Start.Is4() {
		return fmt.Errorf("range start %s is not a valid IPv4 address", r.Start)
	}

	if !r.End.Is4() {
		return fmt.Errorf("range end %s is not a valid IPv4 address", r.End)
	}

	// Compare returns -1 if lhs < rhs, 0 if lhs == rhs, and 1 if lhs > rhs.
	if r.End.Compare(r.Start) != 1 {
		return fmt.Errorf("start address %s is not before end address %s", r.Start, r.End)
	}

	var err error
	if !r.Network.IsValid() {
		r.Network, err = r.Start.Prefix(DefaultMaskBits)
		if err != nil {
			return err
		}
	}

	if !r.Network.Contains(r.Start) {
		return fmt.Errorf("prefix %s does not contain start address %s", r.Network, r.Start)
	}

	if !r.Network.Contains(r.End) {
		return fmt.Errorf("prefix %s does not contain end address %s", r.Network, r.End)
	}

	return nil
}

// this is probably dumb, but it's a one-time cost upfront on pool instantiation.
func (r *Range) numHosts() int {
	cur := r.Start
	hosts := 0
	for cur.Compare(r.End) < 1 {
		hosts++
		cur.Next()
	}

	return hosts
}