From 7b39f643abed643c00a683e20a3bb23a6d6e05b1 Mon Sep 17 00:00:00 2001
From: Alejandro Mery <amery@jpi.io>
Date: Tue, 28 May 2024 02:29:34 +0000
Subject: [PATCH] rings: DecodeAddress() [WIP]

Signed-off-by: Alejandro Mery <amery@jpi.io>
---
 pkg/rings/decode.go | 62 +++++++++++++++++++++++++++++++++++++++++++++
 pkg/rings/rings.go  | 14 ++++++++++
 2 files changed, 76 insertions(+)
 create mode 100644 pkg/rings/decode.go

diff --git a/pkg/rings/decode.go b/pkg/rings/decode.go
new file mode 100644
index 0000000..6c91442
--- /dev/null
+++ b/pkg/rings/decode.go
@@ -0,0 +1,62 @@
+package rings
+
+import (
+	"net/netip"
+
+	"darvaza.org/core"
+)
+
+// DecodeAddress ... TODO
+//
+// revive:disable:function-result-limit
+func DecodeAddress(addr netip.Addr) (RingID, RegionID, ZoneID, uint) {
+	// revive:enable:function-result-limit
+	if addr.IsValid() {
+		if addr.Is4In6() {
+			addr = addr.Unmap()
+		}
+
+		if addr.Is4() {
+			a4 := addr.As4()
+			return unsafeDecodeAddress(a4[0], a4[1], a4[2], a4[3])
+		}
+	}
+
+	return InvalidRing, 0, 0, 0
+}
+
+// revive:disable:function-result-limit
+func unsafeDecodeAddress(a, b, c, d byte) (RingID, RegionID, ZoneID, uint) {
+	// revive:enable:function-result-limit
+	switch {
+	case a != 10:
+		return InvalidRing, 0, 0, 0
+	case b&0xf0 != 0:
+		k := RingThree
+		r := RegionID(b >> 4)
+
+		n2 := uint(b & 0x0f)
+		n1 := uint(c)
+		n0 := uint(d)
+		n := n0 + n1<<8 + n2<<16
+
+		return k, r, 0, n
+	case b&0x0f != 0:
+		r := RegionID(b)
+		z := ZoneID(c >> 4)
+		k := core.IIf(z == 0, RingTwo, RingOne)
+
+		n1 := uint(c & 0x0f)
+		n0 := uint(d)
+		n := n0 + n1<<8
+
+		return k, r, z, n
+	default: // b == 0
+		k := RingZero
+		r := RegionID(c >> 4)
+		z := ZoneID(c & 0xf)
+		n := uint(d)
+
+		return k, r, z, n
+	}
+}
diff --git a/pkg/rings/rings.go b/pkg/rings/rings.go
index 646014d..b816db7 100644
--- a/pkg/rings/rings.go
+++ b/pkg/rings/rings.go
@@ -8,7 +8,21 @@ import (
 	"darvaza.org/core"
 )
 
+// RingID ... TODO
+type RingID int
+
 const (
+	// InvalidRing ... TODO
+	InvalidRing RingID = iota - 1
+	// RingZero ... TODO
+	RingZero
+	// RingOne ... TODO
+	RingOne
+	// RingTwo ... TODO
+	RingTwo
+	// RingThree ... TODO
+	RingThree
+
 	// 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].