From f93e67977a0f05b2cb44df061d224fc08c40b98f Mon Sep 17 00:00:00 2001
From: yancy <yancy@yancy.lol>
Date: Tue, 13 Jun 2023 10:55:04 +0200
Subject: [PATCH 1/2] Add from_int_btc function to Amount

---
 bitcoin/src/amount.rs | 32 ++++++++++++++++++++++++++++++++
 1 file changed, 32 insertions(+)

diff --git a/bitcoin/src/amount.rs b/bitcoin/src/amount.rs
index a8895d59..f1e62f03 100644
--- a/bitcoin/src/amount.rs
+++ b/bitcoin/src/amount.rs
@@ -529,6 +529,28 @@ impl Amount {
         Amount::from_float_in(btc, Denomination::Bitcoin)
     }
 
+    /// Convert from a value expressing integer values of bitcoins to an [Amount]
+    /// in const context.
+    ///
+    /// ## Panics
+    ///
+    /// The function panics if the argument multiplied by the number of sats
+    /// per bitcoin overflows a u64 type.
+    pub const fn from_int_btc(btc: u64) -> Amount {
+        // TODO replace whith unwrap() when available in const context.
+        match btc.checked_mul(100_000_000) {
+            Some(amount) => Amount::from_sat(amount),
+            None => {
+                // TODO replace with panic!() when MSRV = 1.57+
+                #[allow(unconditional_panic)]
+                // disabling this lint until panic!() can be used.
+                #[allow(clippy::let_unit_value)]
+                let _int_overflow_converting_btc_to_sats = [(); 0][1];
+                Amount(0)
+            }
+        }
+    }
+
     /// Parse a decimal string as a value in the given denomination.
     ///
     /// Note: This only parses the value string.  If you want to parse a value
@@ -1589,6 +1611,16 @@ mod tests {
         }
     }
 
+    #[test]
+    fn from_int_btc() {
+        let amt = Amount::from_int_btc(2);
+        assert_eq!(Amount::from_sat(200_000_000), amt);
+    }
+
+    #[should_panic]
+    #[test]
+    fn from_int_btc_panic() { Amount::from_int_btc(u64::MAX); }
+
     #[test]
     fn mul_div() {
         let sat = Amount::from_sat;

From 9f7449b57299e550bae1107f96d21a95c7c684af Mon Sep 17 00:00:00 2001
From: yancy <yancy@yancy.lol>
Date: Tue, 13 Jun 2023 11:05:08 +0200
Subject: [PATCH 2/2] Use from_int_btc function for const context

---
 bitcoin/examples/taproot-psbt.rs | 6 +++---
 bitcoin/src/amount.rs            | 4 ++--
 2 files changed, 5 insertions(+), 5 deletions(-)

diff --git a/bitcoin/examples/taproot-psbt.rs b/bitcoin/examples/taproot-psbt.rs
index 0ad84de0..3794688d 100644
--- a/bitcoin/examples/taproot-psbt.rs
+++ b/bitcoin/examples/taproot-psbt.rs
@@ -49,7 +49,7 @@ const UTXO_1: P2trUtxo = P2trUtxo {
     script_pubkey: UTXO_SCRIPT_PUBKEY,
     pubkey: UTXO_PUBKEY,
     master_fingerprint: UTXO_MASTER_FINGERPRINT,
-    amount_in_sats: Amount::from_sat(50 * 100_000_000), // 50 BTC
+    amount_in_sats: Amount::from_int_btc(50),
     derivation_path: BIP86_DERIVATION_PATH,
 };
 
@@ -60,7 +60,7 @@ const UTXO_2: P2trUtxo = P2trUtxo {
     script_pubkey: UTXO_SCRIPT_PUBKEY,
     pubkey: UTXO_PUBKEY,
     master_fingerprint: UTXO_MASTER_FINGERPRINT,
-    amount_in_sats: Amount::from_sat(50 * 100_000_000), // 50 BTC
+    amount_in_sats: Amount::from_int_btc(50),
     derivation_path: BIP86_DERIVATION_PATH,
 };
 
@@ -71,7 +71,7 @@ const UTXO_3: P2trUtxo = P2trUtxo {
     script_pubkey: UTXO_SCRIPT_PUBKEY,
     pubkey: UTXO_PUBKEY,
     master_fingerprint: UTXO_MASTER_FINGERPRINT,
-    amount_in_sats: Amount::from_sat(50 * 100_000_000), // 50 BTC
+    amount_in_sats: Amount::from_int_btc(50),
     derivation_path: BIP86_DERIVATION_PATH,
 };
 
diff --git a/bitcoin/src/amount.rs b/bitcoin/src/amount.rs
index f1e62f03..aa008b44 100644
--- a/bitcoin/src/amount.rs
+++ b/bitcoin/src/amount.rs
@@ -502,9 +502,9 @@ impl Amount {
     /// Exactly one satoshi.
     pub const ONE_SAT: Amount = Amount(1);
     /// Exactly one bitcoin.
-    pub const ONE_BTC: Amount = Amount(100_000_000);
+    pub const ONE_BTC: Amount = Self::from_int_btc(1);
     /// The maximum value allowed as an amount. Useful for sanity checking.
-    pub const MAX_MONEY: Amount = Amount(21_000_000 * 100_000_000);
+    pub const MAX_MONEY: Amount = Self::from_int_btc(21_000_000);
     /// The minimum value of an amount.
     pub const MIN: Amount = Amount::ZERO;
     /// The maximum value of an amount.