From 32976af62afa5b9c44393d0cb54f9e0dc02ad46f Mon Sep 17 00:00:00 2001
From: Jack Grigg <jack@electriccoin.co>
Date: Wed, 6 Dec 2023 14:43:59 +0000
Subject: [PATCH] Add `AccountId::{zero, next}` convenience methods

---
 src/lib.rs | 22 +++++++++++++++++++++-
 1 file changed, 21 insertions(+), 1 deletion(-)

diff --git a/src/lib.rs b/src/lib.rs
index 18f8825..68aed68 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -59,6 +59,16 @@ impl ConditionallySelectable for AccountId {
     }
 }
 
+impl AccountId {
+    /// The ID for account zero (the first account).
+    pub const ZERO: Self = Self(0);
+
+    /// Returns the next account ID in sequence, or `None` on overflow.
+    pub fn next(&self) -> Option<Self> {
+        Self::try_from(self.0 + 1).ok()
+    }
+}
+
 /// The error type returned when a checked integral type conversion fails.
 #[derive(Clone, Copy, Debug)]
 pub struct TryFromIntError(());
@@ -264,9 +274,19 @@ memuse::impl_no_dynamic_usage!(Scope);
 
 #[cfg(test)]
 mod tests {
-    use super::DiversifierIndex;
+    use super::{AccountId, DiversifierIndex};
+
     use assert_matches::assert_matches;
 
+    #[test]
+    fn account_id_next() {
+        let zero = AccountId::ZERO;
+        assert_eq!(zero.next(), AccountId::try_from(1).ok());
+
+        let max_id = AccountId::try_from((1 << 31) - 1).unwrap();
+        assert_eq!(max_id.next(), None);
+    }
+
     #[test]
     fn diversifier_index_to_u32() {
         let two = DiversifierIndex([