From 4dac4d4df7c4720f13dff5e0b5b413f975fce1b9 Mon Sep 17 00:00:00 2001
From: Alfredo Garcia <oxarbitrage@gmail.com>
Date: Tue, 18 Aug 2020 10:33:40 -0300
Subject: [PATCH] move `is_coinbase_first` from chain to consensus

---
 zebra-chain/src/block.rs            | 23 -----------------------
 zebra-consensus/src/block.rs        |  5 ++++-
 zebra-consensus/src/block/checks.rs | 27 +++++++++++++++++++++++++++
 3 files changed, 31 insertions(+), 24 deletions(-)
 create mode 100644 zebra-consensus/src/block/checks.rs

diff --git a/zebra-chain/src/block.rs b/zebra-chain/src/block.rs
index 6f144ad1..6ce2fb24 100644
--- a/zebra-chain/src/block.rs
+++ b/zebra-chain/src/block.rs
@@ -50,29 +50,6 @@ impl Block {
             })
     }
 
-    /// Check that there is exactly one coinbase transaction in `Block`, and that
-    /// the coinbase transaction is the first transaction in the block.
-    ///
-    /// "The first (and only the first) transaction in a block is a coinbase
-    /// transaction, which collects and spends any miner subsidy and transaction
-    /// fees paid by transactions included in this block." [§3.10][3.10]
-    ///
-    /// [3.10]: https://zips.z.cash/protocol/protocol.pdf#coinbasetransactions
-    pub fn is_coinbase_first(&self) -> Result<(), Error> {
-        let first = self
-            .transactions
-            .get(0)
-            .ok_or_else(|| "block has no transactions")?;
-        let mut rest = self.transactions.iter().skip(1);
-        if !first.is_coinbase() {
-            return Err("first transaction must be coinbase".into());
-        }
-        if rest.any(|tx| tx.contains_coinbase_input()) {
-            return Err("coinbase input found in non-coinbase transaction".into());
-        }
-        Ok(())
-    }
-
     /// Get the hash for the current block
     pub fn hash(&self) -> Hash {
         Hash::from(self)
diff --git a/zebra-consensus/src/block.rs b/zebra-consensus/src/block.rs
index f22fc793..7f88b8a0 100644
--- a/zebra-consensus/src/block.rs
+++ b/zebra-consensus/src/block.rs
@@ -8,9 +8,12 @@
 //! Verification is provided via a `tower::Service`, to support backpressure and batch
 //! verification.
 
+mod checks;
+
 #[cfg(test)]
 mod tests;
 
+use checks::*;
 use chrono::Utc;
 use color_eyre::eyre::{eyre, Report};
 use futures_util::FutureExt;
@@ -106,7 +109,7 @@ where
             // Field validity and structure checks
             let now = Utc::now();
             block.header.is_time_valid_at(now)?;
-            block.is_coinbase_first()?;
+            is_coinbase_first(&block)?;
 
             // TODO:
             //   - context-free header verification: merkle root
diff --git a/zebra-consensus/src/block/checks.rs b/zebra-consensus/src/block/checks.rs
new file mode 100644
index 00000000..aa4cfdb7
--- /dev/null
+++ b/zebra-consensus/src/block/checks.rs
@@ -0,0 +1,27 @@
+//! Consensus check functions
+
+use super::*;
+use zebra_chain::block::Block;
+
+/// Check that there is exactly one coinbase transaction in `Block`, and that
+/// the coinbase transaction is the first transaction in the block.
+///
+/// "The first (and only the first) transaction in a block is a coinbase
+/// transaction, which collects and spends any miner subsidy and transaction
+/// fees paid by transactions included in this block." [§3.10][3.10]
+///
+/// [3.10]: https://zips.z.cash/protocol/protocol.pdf#coinbasetransactions
+pub fn is_coinbase_first(block: &Block) -> Result<(), Error> {
+    let first = block
+        .transactions
+        .get(0)
+        .ok_or_else(|| "block has no transactions")?;
+    let mut rest = block.transactions.iter().skip(1);
+    if !first.is_coinbase() {
+        return Err("first transaction must be coinbase".into());
+    }
+    if rest.any(|tx| tx.contains_coinbase_input()) {
+        return Err("coinbase input found in non-coinbase transaction".into());
+    }
+    Ok(())
+}