Introduce FeeMetadata

ledger/block/src/transaction/fee/metadata.rs

@@ -0,0 +1,43 @@
+// Copyright (C) 2019-2023 Aleo Systems Inc.
+// This file is part of the snarkVM library.
+
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at:
+// http://www.apache.org/licenses/LICENSE-2.0
+
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+use super::*;
+
+use std::marker::PhantomData;
+
+#[derive(Copy, Clone, Debug)]
+pub struct FeeMetadata<N: Network> {
+    /// The number of blocks after the current block that the fee is valid for.
+    expires_in: Option<u16>,
+    /// PhantomData.
+    _phantom: PhantomData<N>,
+}
+
+impl<N: Network> FeeMetadata<N> {
+    /// Specifies the number of blocks until expiration.
+    const EXPIRES_IN: u16 = 21600 / N::BLOCK_TIME;
+
+    // 21000 blocks / 10 seconds per block = ~6 hours
+
+    /// Initializes a new `FeeMetadata` instance with the given expiration.
+    pub fn new(expires_in: Option<u16>) -> Result<Self> {
+        if let Some(num_blocks) = &expires_in {
+            if *num_blocks > Self::EXPIRES_IN {
+                bail!("Fee expiration is too far in the future")
+            }
+        }
+
+        Ok(Self { expires_in, _phantom: PhantomData })
+    }
+}

ledger/block/src/transaction/fee/mod.rs

@@ -12,6 +12,8 @@
 // See the License for the specific language governing permissions and
 // limitations under the License.
 
+pub mod metadata;
+
 mod bytes;
 mod serialize;
 mod string;