feat(truapi): convert native and unserved stablecoin deposits through the pools

.changeset/funding-pool-route.md

@@ -0,0 +1,5 @@
+---
+"@parity/truapi": patch
+---
+
+Funding deposits in the native token, and in a stablecoin the PSM cannot serve, convert through the asset-conversion pools: one XCM program swaps them into CASH (through the native token for a stablecoin) and teleports it to People, as getcash does. `funding-check` accepts `--asset dot`.

rust/crates/truapi-host-cli/src/funding_check.rs

@@ -32,6 +32,8 @@ const MISSING_POLLS: u32 = 5;
 /// The asset a provider pays the deposit in.
 #[derive(Debug, Clone, Copy, PartialEq, Eq, ValueEnum)]
 pub enum FundingAsset {
+    /// The native token, swapped into CASH through the pools.
+    Dot,
     /// dotUSD, which is CASH already: teleported to People.
     Cash,
     /// Minted into CASH through the PSM, then teleported.
@@ -60,12 +62,13 @@ impl FundingAssets {
         }
     }
 
-    /// The asset id and the getcash source id for `asset`.
-    fn source(&self, asset: FundingAsset) -> (u32, &'static str) {
+    /// The deposit asset and the getcash source id for `asset`.
+    fn source(&self, asset: FundingAsset) -> (DepositAsset, &'static str) {
         match asset {
-            FundingAsset::Cash => (self.cash, "dotusd-assethub"),
-            FundingAsset::Usdt => (self.usdt, "usdt-assethub"),
-            FundingAsset::Usdc => (self.usdc, "usdc-assethub"),
+            FundingAsset::Dot => (DepositAsset::Native, "dot-assethub"),
+            FundingAsset::Cash => (DepositAsset::Asset(self.cash), "dotusd-assethub"),
+            FundingAsset::Usdt => (DepositAsset::Asset(self.usdt), "usdt-assethub"),
+            FundingAsset::Usdc => (DepositAsset::Asset(self.usdc), "usdc-assethub"),
         }
     }
 }
@@ -139,29 +142,29 @@ async fn open_and_assign(
     asset: FundingAsset,
     amount: u128,
 ) -> Result<String> {
-    let (asset_id, source_id) = assets.source(asset);
+    let (deposit_asset, source_id) = assets.source(asset);
     let intent = runtime
         .open_funding(FundingDirection::In, Some(amount))
         .await
         .map_err(|error| anyhow::anyhow!("opening a session failed: {}", error.reason))?
         .context("the session was dismissed")?;
     let expected = runtime
-        .quote_funding_deposit(&intent, DepositAsset::Asset(asset_id))
+        .quote_funding_deposit(&intent, deposit_asset)
         .await
         .map_err(|error| anyhow::anyhow!("quoting the deposit failed: {}", error.reason))?;
     let account = runtime
         .assign_funding_deposit(
             &intent,
             DepositRequest {
                 source_id: source_id.to_string(),
-                asset: DepositAsset::Asset(asset_id),
+                asset: deposit_asset,
                 expected,
             },
         )
         .await
         .map_err(|error| anyhow::anyhow!("assigning a deposit account failed: {}", error.reason))?;
     println!("session  {intent}, crediting {amount} CASH units");
-    println!("pay      {expected} of asset {asset_id} ({source_id}) on Asset Hub to");
+    println!("pay      {expected} of {deposit_asset:?} ({source_id}) on Asset Hub to");
     println!(
         "         {}",
         truapi::host_logic::product_account::product_public_key_to_address(account)

rust/crates/truapi/src/host_logic/funding.rs

@@ -97,6 +97,8 @@ pub struct FundingDeposit {
     pub expected: u128,
     /// How the deposit becomes CASH on People.
     pub route: ConversionRoute,
+    /// CASH the session asks to credit, which a swap must not land below.
+    pub target: Option<u128>,
 }
 
 /// How a deposit becomes CASH on People, fixed when its account is assigned
@@ -111,6 +113,10 @@ pub enum ConversionRoute {
         /// Minting fee the route was chosen at, in parts per million.
         fee_ppm: u32,
     },
+    /// The deposit is the native token, or a stablecoin the PSM cannot
+    /// serve: swap it to CASH through the asset-conversion pools, then
+    /// teleport.
+    Pool,
 }
 
 /// A conversion transaction handed to Asset Hub, with what tells whether it
@@ -812,6 +818,7 @@ mod tests {
                 account: [1; 32],
                 expected: 50,
                 route: ConversionRoute::Teleport,
+                target: None,
             }),
             ..session(FundingDirection::In)
         }

rust/crates/truapi/src/runtime/funding.rs

@@ -251,9 +251,10 @@ impl FundingRegistry {
         plan: DepositPlan,
         derive: impl Fn(u32) -> Result<[u8; 32], GenericError>,
     ) -> Result<[u8; 32], AssignDepositError> {
-        self.get(intent)
+        let target = self
+            .get(intent)
             .ok_or(AssignDepositError::NotFound)
-            .and_then(|session| assignable(&session))?;
+            .and_then(|session| assignable(&session).map(|()| session.amount))?;
         let DepositPlan { request, route } = plan;
         for _ in 0..MAX_USED_ACCOUNTS {
             let number = self
@@ -274,6 +275,7 @@ impl FundingRegistry {
                 account,
                 expected: request.expected,
                 route,
+                target,
             };
             let intent = intent.to_string();
             return self
@@ -1300,6 +1302,7 @@ mod tests {
                     account: account(3),
                     expected: 50,
                     route: ConversionRoute::Teleport,
+                    target: Some(100),
                 })
             )
         );
@@ -1532,6 +1535,7 @@ mod tests {
             account: keypair(1).public.to_bytes(),
             expected: 50,
             route: ConversionRoute::Teleport,
+            target: None,
         }
     }