From 1d6a2426180703802ff932c3bf2cde88cb90fc92 Mon Sep 17 00:00:00 2001
From: Casey Rodarmor <casey@rodarmor.com>
Date: Sun, 15 Oct 2023 13:41:26 -0700
Subject: [PATCH] Delta encode Rune IDs in edicts (#2532)

---
 src/runes/runestone.rs | 68 +++++++++++++++++++++++++++++++++++-------
 1 file changed, 57 insertions(+), 11 deletions(-)

diff --git a/src/runes/runestone.rs b/src/runes/runestone.rs
index 8f6ebad0c0..6640c91dd9 100644
--- a/src/runes/runestone.rs
+++ b/src/runes/runestone.rs
@@ -27,10 +27,13 @@ impl Runestone {
 
     let mut edicts = Vec::new();
     let mut etching = None;
-
+    let mut id = 0u128;
     for chunk in integers.chunks(3) {
       match *chunk {
-        [id, amount, output] => edicts.push(Edict { id, amount, output }),
+        [id_delta, amount, output] => {
+          id = id.saturating_add(id_delta);
+          edicts.push(Edict { id, amount, output });
+        }
         [rune] => {
           etching = Some(Etching {
             divisibility: 0,
@@ -56,10 +59,15 @@ impl Runestone {
   pub(crate) fn encipher(&self) -> ScriptBuf {
     let mut payload = Vec::new();
 
-    for edict in &self.edicts {
-      varint::encode_to_vec(edict.id, &mut payload);
+    let mut edicts = self.edicts.clone();
+    edicts.sort_by_key(|edict| edict.id);
+
+    let mut id = 0;
+    for edict in edicts {
+      varint::encode_to_vec(edict.id - id, &mut payload);
       varint::encode_to_vec(edict.amount, &mut payload);
       varint::encode_to_vec(edict.output, &mut payload);
+      id = edict.id;
     }
 
     if let Some(etching) = self.etching {
@@ -529,7 +537,7 @@ mod tests {
 
   #[test]
   fn runestone_may_contain_multiple_edicts() {
-    let payload = payload(&[1, 2, 3, 4, 5, 6]);
+    let payload = payload(&[1, 2, 3, 3, 5, 6]);
 
     let payload: &PushBytes = payload.as_slice().try_into().unwrap();
 
@@ -565,6 +573,44 @@ mod tests {
     );
   }
 
+  #[test]
+  fn id_deltas_saturate_to_max() {
+    let payload = payload(&[1, 2, 3, u128::max_value(), 5, 6]);
+
+    let payload: &PushBytes = payload.as_slice().try_into().unwrap();
+
+    assert_eq!(
+      Runestone::decipher(&Transaction {
+        input: Vec::new(),
+        output: vec![TxOut {
+          script_pubkey: script::Builder::new()
+            .push_opcode(opcodes::all::OP_RETURN)
+            .push_slice(b"RUNE_TEST")
+            .push_slice(payload)
+            .into_script(),
+          value: 0
+        }],
+        lock_time: locktime::absolute::LockTime::ZERO,
+        version: 0,
+      }),
+      Ok(Some(Runestone {
+        edicts: vec![
+          Edict {
+            id: 1,
+            amount: 2,
+            output: 3,
+          },
+          Edict {
+            id: u128::max_value(),
+            amount: 5,
+            output: 6,
+          },
+        ],
+        etching: None,
+      }))
+    );
+  }
+
   #[test]
   fn payload_pushes_are_concatenated() {
     assert_eq!(
@@ -768,7 +814,7 @@ mod tests {
         },
       ],
       None,
-      54,
+      49,
     );
 
     case(
@@ -802,7 +848,7 @@ mod tests {
         },
       ],
       None,
-      81,
+      70,
     );
 
     case(
@@ -819,7 +865,7 @@ mod tests {
         4
       ],
       None,
-      70,
+      55,
     );
 
     case(
@@ -836,7 +882,7 @@ mod tests {
         5
       ],
       None,
-      88,
+      67,
     );
 
     case(
@@ -853,7 +899,7 @@ mod tests {
         5
       ],
       None,
-      72,
+      64,
     );
 
     case(
@@ -870,7 +916,7 @@ mod tests {
         5
       ],
       None,
-      83,
+      62,
     );
   }
 }