add support for mixed transactions, including those with SCIs in them

Cargo.toml

@@ -161,6 +161,7 @@ members = [
     "util/telemetry",
     "util/test-helper",
     "util/test-vector",
+    "util/u64-ratio",
     "util/uri",
     "util/vec-map",
     "util/zip-exact",

mobilecoind/api/proto/mobilecoind_api.proto

@@ -108,11 +108,20 @@ enum TxStatus {
 }
 
 // Structure used in specifying the list of outputs when generating a transaction.
+// Here the token id is implied from context, and matches the fee token id.
 message Outlay {
     uint64 value = 1;
     external.PublicAddress receiver = 2;
 }
 
+// Structure used in specifying the list of outputs in a transaction.
+// Here the token id is explicit.
+message OutlayV2 {
+    uint64 value = 1;
+    external.PublicAddress receiver = 2;
+    uint64 token_id = 3;
+}
+
 // Structure used to refer to a TxOut in the ledger that is presumed to be spendable.
 // The structure is annotated with extra information needed to spend the TxOut in a payment, calculated using the private keys that control the TxOut.
 message UnspentTxOut {
@@ -142,14 +151,24 @@ message UnspentTxOut {
     bytes monitor_id = 10;
 }
 
+// Structure used to refer to an SCI that we want to add to a transaction.
+// The structure has additional information -- if it's a partial fill SCI, we need to know the partial fill amount.
+message SciForTx {
+    /// The signed input we want to add
+    external.SignedContingentInput sci = 1;
+
+    /// If it's a partial fill SCI, the value we wish to fill it for
+    uint64 partial_fill_value = 2;
+}
+
 // Structure used to refer to a prepared transaction
 message TxProposal {
     // List of inputs being spent.
     repeated UnspentTxOut input_list = 1;
 
     // List of outputs being created.
     // This excludes the fee output.
-    repeated Outlay outlay_list = 2;
+    repeated OutlayV2 outlay_list = 2;
 
     // The actual transaction object.
     // Together with the private view/spend keys, this structure contains all information in existence about the transaction.
@@ -493,12 +512,55 @@ message GenerateTxRequest {
 
     // Token id to use for the transaction.
     uint64 token_id = 7;
+
+    // List of SCIs to be added to the transaction
+    repeated SciForTx scis = 8;
 }
 
 message GenerateTxResponse {
     TxProposal tx_proposal = 1;
 }
 
+// Generate a transaction proposal object with mixed token types.
+// Notes:
+// - Sum of inputs needs to be greater than sum of outlays and fee.
+// - The set of inputs to use would be chosen automatically by mobilecoind.
+// - The fee field could be set to zero, in which case mobilecoind would choose a fee.
+// Right now that fee is hardcoded.
+message GenerateMixedTxRequest {
+    // Monitor id sending the funds.
+    bytes sender_monitor_id = 1;
+
+    // Subaddress to return change to.
+    uint64 change_subaddress = 2;
+
+    // List of UnspentTxOuts to be spent by the transaction.
+    // All UnspentTxOuts must belong to the same sender_monitor_id.
+    // mobilecoind would choose a subset of these inputs to construct the transaction.
+    // Total input amount must be >= sum of outlays + fees.
+    repeated UnspentTxOut input_list = 3;
+
+    // List of SCIs to be added to the transaction
+    repeated SciForTx scis = 4;
+
+    // Outputs to be generated by the transaction. This excludes change and fee.
+    repeated OutlayV2 outlay_list = 5;
+
+    // Fee in picoMOB (setting to 0 causes mobilecoind to choose a value).
+    // The value used can be checked (but not changed) in tx_proposal.tx.prefix.fee
+    uint64 fee = 6;
+
+    // Token id to use for the transaction.
+    uint64 fee_token_id = 7;
+
+    // Tombstone block (setting to 0 causes mobilecoind to choose a value).
+    // The value used can be checked (but not changed) in tx_proposal.tx.prefix.tombstone_block
+    uint64 tombstone = 8;
+}
+
+message GenerateMixedTxResponse {
+    TxProposal tx_proposal = 1;
+}
 // Generate a transaction that merges a few UnspentTxOuts into one, in order to reduce wallet fragmentation.
 message GenerateOptimizationTxRequest {
     // Monitor Id to operate on.

mobilecoind/src/conversions.rs

@@ -4,7 +4,7 @@
 //! types.
 
 use crate::{
-    payments::{Outlay, TxProposal},
+    payments::{Outlay, SciForTx, TxProposal},
     utxo_store::UnspentTxOut,
 };
 use mc_account_keys::PublicAddress;
@@ -171,6 +171,29 @@ impl TryFrom<&api::TxProposal> for TxProposal {
     }
 }
 
+impl From<&SciForTx> for api::SciForTx {
+    fn from(src: &SciForTx) -> Self {
+        let mut dst = Self::new();
+        dst.set_sci((&src.sci).into());
+        dst.set_partial_fill_value(src.partial_fill_value);
+        dst
+    }
+}
+
+impl TryFrom<&api::SciForTx> for SciForTx {
+    type Error = ConversionError;
+
+    fn try_from(src: &api::SciForTx) -> Result<Self, Self::Error> {
+        let sci = src.get_sci().try_into()?;
+        let partial_fill_value = src.partial_fill_value;
+
+        Ok(Self {
+            sci,
+            partial_fill_value,
+        })
+    }
+}
+
 #[cfg(test)]
 mod test {
     use super::*;