package rings

import (
	"net/netip"
)

// DecodeAddress extracts ring address fields from a given 10.0.0.0/8
// address.
//
// revive:disable:function-result-limit
func DecodeAddress[T ~uint | NodeID](addr netip.Addr) (RingID, RegionID, ZoneID, T) {
	// revive:enable:function-result-limit
	if addr.IsValid() {
		if addr.Is4In6() {
			addr = addr.Unmap()
		}

		if addr.Is4() {
			a4 := addr.As4()
			return unsafeDecodeAddress[T](a4[0], a4[1], a4[2], a4[3])
		}
	}

	return UnspecifiedRingID, 0, 0, 0
}

// revive:disable:function-result-limit
func unsafeDecodeAddress[T ~uint | NodeID](a, b, c, d byte) (RingID, RegionID, ZoneID, T) {
	// revive:enable:function-result-limit
	switch {
	case a != 10:
		return UnspecifiedRingID, 0, 0, 0
	case b == 0x00:
		// 10.00.RZ.dd
		k := RingZeroID
		r := RegionID(c >> 4)
		z := ZoneID(c & 0xf)
		n := T(d)

		return k, r, z, n
	case b&0xf0 != 0:
		// 10.Rb.cc.dd
		k := RingThreeID
		r := RegionID(b >> 4)

		n2 := T(b & 0x0f)
		n1 := T(c)
		n0 := T(d)
		n := n0 + n1<<8 + n2<<16

		return k, r, 0, n
	case c&0xf0 != 0:
		// 10.0R.Zc.dd
		k := RingOneID
		r := RegionID(b)
		z := ZoneID(c >> 4)

		n1 := T(c & 0x0f)
		n0 := T(d)
		n := n0 + n1<<8

		return k, r, z, n
	default:
		// 10.0R.0c.dd
		k := RingTwoID
		r := RegionID(b)

		n1 := T(c & 0x0f)
		n0 := T(d)
		n := n0 + n1<<8

		return k, r, 0, n
	}
}