// Package rings provides logic to work with the four rings
// of a cluster
package rings

import (
	"syscall"

	"darvaza.org/core"
)

const (
	// RegionMax indicates the highest number that can be used for a [RegionID].
	RegionMax = (1 << 4) - 1
	// ZoneMax indicates the highest number that can be used for a [ZoneID].
	ZoneMax = (1 << 4) - 1
	// NodeMax indicates the highest number that can be used for a [NodeID].
	NodeMax = (1 << 12) - 1
	// NodeZeroMax indicates the highest number that can be used for a [NodeID]
	// when its a gateway connected to Ring 0 (backbone).
	NodeZeroMax = (1 << 8) - 1

	// RingZeroBits indicates the size of the prefix on the ring 0 (backbone) network.
	RingZeroBits = 16
	// RingOneBits indicates the size of the prefix on the ring 1 (lan) network.
	RingOneBits = 20
	// RingThreeBits indicates the size of the prefix on the ring 3 (pods) network
	// of the kubernetes cluster of a region.
	RingThreeBits = 12
)

// RegionID is the identifier of a region, valid between 1 and [RegionMax].
type RegionID int

// Valid tells a [RegionID] is within the valid range.
func (n RegionID) Valid() bool { return n > 0 && n <= RegionMax }

// ZoneID is the identifier of a zone within a region, valid between 1 and [ZoneMax].
type ZoneID int

// Valid tells a [ZoneID] is within the valid range.
func (n ZoneID) Valid() bool { return n > 0 && n <= ZoneMax }

// NodeID is the identifier of a machine within a zone of a region, valid between
// 1 and [NodeMax], but between 1 and [NodeZeroMax] if it will be a zone gateway.
type NodeID int

// Valid tells a [NodeID] is within the valid range.
func (n NodeID) Valid() bool { return n > 0 && n <= NodeMax }

// ValidZero tells a [NodeID] is within the valid range for a gateway.
func (n NodeID) ValidZero() bool { return n > 0 && n <= NodeZeroMax }

// ErrOutOfRange is an error indicating the value of a field
// is out of range.
func ErrOutOfRange[T ~int | ~uint32](value T, field string) error {
	return core.Wrap(syscall.EINVAL, "%s out of range (%v)", field, value)
}