feat(truapi): native bridge for funding and top-ups

.changeset/funding-native-bridge.md

@@ -0,0 +1,5 @@
+---
+"@parity/truapi": patch
+---
+
+Native hosts drive funding through `NativeTrUApiHostRuntime`: `set_funding_callbacks` installs the overlay, `set_top_up_callbacks` and `notify_top_up_status` the top-up engine, and `open_funding` and `funding_session` open and read sessions. Amounts cross the FFI as decimal strings.

rust/crates/truapi/RUNTIME.md

@@ -403,6 +403,10 @@ AutoSigning without approval. Legacy-account signing still asks the user.
   Balance card opens sessions with `open_funding`. The core owns the sessions,
   persists them, expires them, and answers Funding calls `Unsupported` while no
   overlay is installed.
+  Native hosts reach this through `NativeTrUApiHostRuntime`:
+  `set_funding_callbacks` (the overlay), `set_top_up_callbacks` with
+  `notify_top_up_status` (the top-up engine), `open_funding` and
+  `funding_session`. Amounts cross the FFI as decimal strings.
 - `TopUpPlatform`: claim a top-up source's funds into the user's balance and
   stream each top-up's status. Installed with `set_top_up_platform`. The core
   requires a session and checks the source keys; the host owns claiming,

rust/crates/truapi/src/host_core.rs

@@ -748,6 +748,15 @@ impl SigningHostRuntime {
         installed
     }
 
+    /// One funding session as the core holds it, for the host's own status
+    /// and history views.
+    pub fn funding_session(
+        &self,
+        intent: &str,
+    ) -> Option<crate::host_logic::funding::FundingSession> {
+        self.services.funding().get(intent)
+    }
+
     /// Open a funding session on the host's own behalf, as the Balance card's
     /// Add and Withdraw do, and show the overlay. Returns the session id, or
     /// `None` when the user dismissed the overlay without starting.

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

@@ -20,6 +20,10 @@ const SETTLED_HISTORY_LIMIT: usize = 50;
 
 /// What the core knows about one session, independent of any host surface.
 #[derive(Debug, Clone, PartialEq, Eq, Encode, Decode)]
+#[cfg_attr(
+    all(feature = "runtime", not(target_arch = "wasm32")),
+    derive(uniffi::Record)
+)]
 pub struct FundingSession {
     /// Identifier handed back to the caller and used to re-attach.
     pub intent: String,
@@ -41,6 +45,10 @@ pub struct FundingSession {
 
 /// Stage of a session, as the core persists it.
 #[derive(Debug, Clone, PartialEq, Eq, Encode, Decode)]
+#[cfg_attr(
+    all(feature = "runtime", not(target_arch = "wasm32")),
+    derive(uniffi::Enum)
+)]
 pub enum FundingStage {
     /// In flight.
     Open,

rust/crates/truapi/src/lib.rs

@@ -66,6 +66,26 @@ uniffi::custom_type!(Bytes32, Vec<u8>, {
     try_lift: |bytes| Ok(bytes.as_slice().try_into()?),
 });
 
+/// A 64-byte value, such as an sr25519 secret key, passed as plain bytes on
+/// FFI surfaces.
+pub type Bytes64 = [u8; 64];
+
+#[cfg(all(feature = "runtime", not(target_arch = "wasm32")))]
+uniffi::custom_type!(Bytes64, Vec<u8>, {
+    remote,
+    lower: |bytes| bytes.to_vec(),
+    try_lift: |bytes| Ok(bytes.as_slice().try_into()?),
+});
+
+// Swift and Kotlin have no 128-bit integer, so amounts cross FFI surfaces as
+// decimal strings.
+#[cfg(all(feature = "runtime", not(target_arch = "wasm32")))]
+uniffi::custom_type!(u128, String, {
+    remote,
+    lower: |amount| amount.to_string(),
+    try_lift: |amount| Ok(amount.parse()?),
+});
+
 /// Latest-version protocol payload types, unwrapped from their versioned
 /// envelopes. Runtime code should use these instead of per-version modules.
 pub mod latest {

rust/crates/truapi/src/native.rs

@@ -29,8 +29,8 @@ mod ws_bridge;
 pub use crate::host_internal::sso_messages::SsoRequestOutcome;
 pub use crate::host_logic::dotns::{NavigateDecision, PocketDeeplinkAction};
 pub use callbacks::{
-    HostCallbacks, NativeChatCallbacks, NativeContactsCallbacks, NativePocketCallbacks,
-    NativePocketRemoval,
+    HostCallbacks, NativeChatCallbacks, NativeContactsCallbacks, NativeFundingCallbacks,
+    NativePocketCallbacks, NativePocketRemoval, NativeTopUpCallbacks,
 };
 pub use config::{HostRuntimeConfig, NativeRuntimeConfigError, ProductExecutionConfig};
 pub use errors::{HostRejection, NativeCoreDatabaseError};

rust/crates/truapi/src/native/callbacks.rs

@@ -306,3 +306,54 @@ pub trait NativeContactsCallbacks: Send + Sync {
         product_id: String,
     ) -> Result<crate::platform::HostContactPick, HostRejection>;
 }
+
+/// Native funding overlay. A host with a funding modality passes an
+/// implementation to [`NativeTrUApiHostRuntime::set_funding_callbacks`];
+/// without one, funding requests answer `Unsupported`.
+///
+/// [`NativeTrUApiHostRuntime::set_funding_callbacks`]: super::NativeTrUApiHostRuntime::set_funding_callbacks
+#[uniffi::export(rust, foreign)]
+#[async_trait::async_trait]
+pub trait NativeFundingCallbacks: Send + Sync {
+    /// Show the funding overlay for session `intent`, which `product_id`
+    /// opened, or the host itself when `None`, on the screen `direction`
+    /// names, and report whether the user started or dismissed it. `amount`
+    /// is a decimal string of CASH units.
+    async fn present_funding(
+        &self,
+        product_id: Option<String>,
+        intent: String,
+        direction: v01::FundingDirection,
+        amount: Option<u128>,
+    ) -> Result<crate::platform::FundingPresentOutcome, HostRejection>;
+
+    /// A session's status changed, for host UI such as the in-flight pill.
+    fn funding_session_changed(&self, intent: String, status: v01::HostFundingStatusSubscribeItem);
+}
+
+/// Native top-up engine, which claims a source's funds into the user's
+/// balance. A host passes an implementation to
+/// [`NativeTrUApiHostRuntime::set_top_up_callbacks`] and reports each later
+/// status with [`NativeTrUApiHostRuntime::notify_top_up_status`].
+///
+/// [`NativeTrUApiHostRuntime::set_top_up_callbacks`]: super::NativeTrUApiHostRuntime::set_top_up_callbacks
+/// [`NativeTrUApiHostRuntime::notify_top_up_status`]: super::NativeTrUApiHostRuntime::notify_top_up_status
+#[uniffi::export(rust, foreign)]
+#[async_trait::async_trait]
+pub trait NativeTopUpCallbacks: Send + Sync {
+    /// Start top-up `request` for `product_id`, returning once the host has
+    /// accepted it. Its amount is a decimal string of CASH units.
+    async fn top_up(
+        &self,
+        product_id: String,
+        request: v01::HostPaymentTopUpRequest,
+    ) -> Result<(), v01::HostPaymentTopUpError>;
+
+    /// The current status of `product_id`'s top-up `id`, or `None` when the
+    /// host holds no such top-up.
+    fn top_up_status(
+        &self,
+        product_id: String,
+        id: crate::Bytes32,
+    ) -> Result<Option<v01::HostPaymentTopUpStatusSubscribeItem>, HostRejection>;
+}

rust/crates/truapi/src/native/errors.rs

@@ -50,6 +50,16 @@ impl From<uniffi::UnexpectedUniFFICallbackError> for v01::HostLocalStorageReadEr
     }
 }
 
+impl From<uniffi::UnexpectedUniFFICallbackError> for v01::HostPaymentTopUpError {
+    fn from(err: uniffi::UnexpectedUniFFICallbackError) -> Self {
+        tracing::warn!(
+            reason = %err.reason,
+            "host callback threw an undeclared error; reporting it as a rejection"
+        );
+        v01::HostPaymentTopUpError::Unknown { reason: err.reason }
+    }
+}
+
 impl From<uniffi::UnexpectedUniFFICallbackError> for v01::HostNavigateToError {
     fn from(err: uniffi::UnexpectedUniFFICallbackError) -> Self {
         tracing::warn!(