v0.2.12-pre.008

crates/ksp-app-wallet-desk/src/wallet_balance.rs

@@ -1,5 +1,5 @@
 // file: crates/ksp-app-wallet-desk/src/wallet_balance.rs
-// version: 1
+// version: 2
 
 //! Safe Wallet balance projection produced by the typed HTTP Transport path.
 
@@ -18,6 +18,8 @@ pub(crate) struct WalletBalanceDto {
     pub(crate) slot: u64,
     /// Exact decimal SOL presentation derived from lamports without floating point.
     pub(crate) sol: String,
+    /// Arithmetic mean of successful SOL/USD observations produced by this refresh, or unavailable when no provider returned one.
+    pub(crate) sol_usd_average: std::option::Option<String>,
     /// Composite-selected Transport profile used for the RPC.
     pub(crate) transport_profile: String,
     /// Logical Transport role used for the RPC.
@@ -34,6 +36,98 @@ pub(crate) fn format_lamports_as_sol(lamports: u64) -> String {
     return format!("{whole}.{fractional:09}");
 }
 
+/// Computes a deterministic SOL/USD arithmetic mean without IEEE-754 conversion.
+///
+/// The output is rounded half-up to at most eight fractional digits and trailing zeroes are removed. Arithmetic overflow degrades to `None`, which Wallet Desk
+/// renders as `N.A.` without affecting the authoritative SOL balance.
+#[must_use]
+pub(crate) fn average_sol_usd_prices(prices: &[ksp_offchain_transport_lib::MarketPriceDecimal]) -> std::option::Option<String> {
+    const OUTPUT_SCALE: u8 = 8;
+    if prices.is_empty() {
+        return std::option::Option::None;
+    }
+    let max_scale = prices.iter().map(ksp_offchain_transport_lib::MarketPriceDecimal::scale).max();
+    let max_scale = match max_scale {
+        std::option::Option::Some(value) => value,
+        std::option::Option::None => return std::option::Option::None,
+    };
+    let mut sum = 0_u128;
+    for price in prices {
+        let exponent = u32::from(max_scale.saturating_sub(price.scale()));
+        let factor = 10_u128.checked_pow(exponent);
+        let factor = match factor {
+            std::option::Option::Some(value) => value,
+            std::option::Option::None => return std::option::Option::None,
+        };
+        let coefficient = price.coefficient().checked_mul(factor);
+        let coefficient = match coefficient {
+            std::option::Option::Some(value) => value,
+            std::option::Option::None => return std::option::Option::None,
+        };
+        sum = match sum.checked_add(coefficient) {
+            std::option::Option::Some(value) => value,
+            std::option::Option::None => return std::option::Option::None,
+        };
+    }
+    let count = match u128::try_from(prices.len()) {
+        std::result::Result::Ok(value) if value > 0 => value,
+        _ => return std::option::Option::None,
+    };
+    let target_scale = OUTPUT_SCALE;
+    let (numerator, denominator) = if max_scale <= target_scale {
+        let factor = 10_u128.checked_pow(u32::from(target_scale - max_scale));
+        let factor = match factor {
+            std::option::Option::Some(value) => value,
+            std::option::Option::None => return std::option::Option::None,
+        };
+        let numerator = match sum.checked_mul(factor) {
+            std::option::Option::Some(value) => value,
+            std::option::Option::None => return std::option::Option::None,
+        };
+        (numerator, count)
+    } else {
+        let factor = 10_u128.checked_pow(u32::from(max_scale - target_scale));
+        let factor = match factor {
+            std::option::Option::Some(value) => value,
+            std::option::Option::None => return std::option::Option::None,
+        };
+        let denominator = match count.checked_mul(factor) {
+            std::option::Option::Some(value) => value,
+            std::option::Option::None => return std::option::Option::None,
+        };
+        (sum, denominator)
+    };
+    let quotient = numerator / denominator;
+    let remainder = numerator % denominator;
+    let round_up = remainder >= denominator.div_ceil(2);
+    let coefficient = if round_up {
+        match quotient.checked_add(1) {
+            std::option::Option::Some(value) => value,
+            std::option::Option::None => return std::option::Option::None,
+        }
+    } else {
+        quotient
+    };
+    return std::option::Option::Some(format_scaled_decimal(coefficient, target_scale));
+}
+
+fn format_scaled_decimal(mut coefficient: u128, mut scale: u8) -> String {
+    while scale > 0 && coefficient % 10 == 0 {
+        coefficient /= 10;
+        scale -= 1;
+    }
+    let digits = coefficient.to_string();
+    if scale == 0 {
+        return digits;
+    }
+    let scale = usize::from(scale);
+    if digits.len() > scale {
+        let split = digits.len() - scale;
+        return format!("{}.{}", &digits[..split], &digits[split..]);
+    }
+    return format!("0.{}{}", "0".repeat(scale - digits.len()), digits);
+}
+
 #[cfg(test)]
 #[path = "../unit_tests/wallet_balance.rs"]
 mod tests;