feat: add transaction building core infrastructure

Implements the core transaction building functionality using Solana SDK:

- types.rs: TransactionIntent, Nonce (blockhash/durable), Instruction variants
- build.rs: Transaction builder using solana-sdk 3.x types
- Uses SDK instruction builders: system_ix::transfer(), advance_nonce_account(), etc.
- Uses ComputeBudgetInstruction for priority fees

Supported instructions:
- Transfer, CreateAccount, NonceAdvance, NonceInitialize
- Allocate, Assign, Memo, ComputeBudget

Ticket: BTC-2955

Author: lcovar

packages/wasm-solana/Cargo.lock

@@ -14,20 +14,22 @@ wasm-bindgen = "0.2"
 js-sys = "0.3"
 serde = { version = "1.0", features = ["derive"] }
 serde_json = "1.0"
-# Solana SDK crates
+# Solana 3.x crates (for transaction building)
+solana-sdk = { version = "3.0", default-features = false, features = ["full"] }
+solana-transaction = { version = "3.0", features = ["serde", "bincode"] }
+solana-system-interface = { version = "3.0", features = ["bincode"] }
+solana-compute-budget-interface = { version = "3.0", features = ["borsh"] }
+# Solana 2.x crates (no 3.x available yet for these)
+solana-stake-interface = { version = "2.0", features = ["bincode"] }
 solana-pubkey = { version = "2.0", features = ["curve25519"] }
 solana-keypair = "2.0"
 solana-signer = "2.0"
-solana-transaction = { version = "3.0", features = ["serde", "bincode"] }
-# Instruction decoder interfaces (official Solana crates)
-solana-system-interface = { version = "2.0", features = ["bincode"] }
-solana-stake-interface = { version = "2.0", features = ["bincode"] }
-solana-compute-budget-interface = { version = "2.0", features = ["borsh"] }
 # Serialization
 bincode = "1.3"
 borsh = "1.5"
 base64 = "0.22"
 serde-wasm-bindgen = "0.6"
+# SPL Stake Pool for Jito decoding
 spl-stake-pool = { version = "2.0.3", features = ["no-entrypoint"] }
 
 [dev-dependencies]

packages/wasm-solana/Cargo.toml

@@ -0,0 +1,207 @@
+/**
+ * Transaction building from high-level intents.
+ *
+ * Provides types and functions for building Solana transactions from a
+ * declarative intent structure, without requiring the full @solana/web3.js dependency.
+ */
+
+import { BuilderNamespace } from "./wasm/wasm_solana.js";
+
+// =============================================================================
+// Nonce Types
+// =============================================================================
+
+/** Use a recent blockhash for the transaction */
+export interface BlockhashNonceSource {
+  type: "blockhash";
+  /** The recent blockhash value (base58) */
+  value: string;
+}
+
+/** Use a durable nonce account for the transaction */
+export interface DurableNonceSource {
+  type: "durable";
+  /** The nonce account address (base58) */
+  address: string;
+  /** The nonce authority address (base58) */
+  authority: string;
+  /** The nonce value stored in the account (base58) - this becomes the blockhash */
+  value: string;
+}
+
+/** Nonce source for the transaction */
+export type NonceSource = BlockhashNonceSource | DurableNonceSource;
+
+// =============================================================================
+// Instruction Types
+// =============================================================================
+
+/** SOL transfer instruction */
+export interface TransferInstruction {
+  type: "transfer";
+  /** Source account (base58) */
+  from: string;
+  /** Destination account (base58) */
+  to: string;
+  /** Amount in lamports (as string for BigInt compatibility) */
+  lamports: string;
+}
+
+/** Create new account instruction */
+export interface CreateAccountInstruction {
+  type: "createAccount";
+  /** Funding account (base58) */
+  from: string;
+  /** New account address (base58) */
+  newAccount: string;
+  /** Lamports to transfer (as string) */
+  lamports: string;
+  /** Space to allocate in bytes */
+  space: number;
+  /** Owner program (base58) */
+  owner: string;
+}
+
+/** Advance durable nonce instruction */
+export interface NonceAdvanceInstruction {
+  type: "nonceAdvance";
+  /** Nonce account address (base58) */
+  nonce: string;
+  /** Nonce authority (base58) */
+  authority: string;
+}
+
+/** Initialize nonce account instruction */
+export interface NonceInitializeInstruction {
+  type: "nonceInitialize";
+  /** Nonce account address (base58) */
+  nonce: string;
+  /** Nonce authority (base58) */
+  authority: string;
+}
+
+/** Allocate space instruction */
+export interface AllocateInstruction {
+  type: "allocate";
+  /** Account to allocate (base58) */
+  account: string;
+  /** Space to allocate in bytes */
+  space: number;
+}
+
+/** Assign account to program instruction */
+export interface AssignInstruction {
+  type: "assign";
+  /** Account to assign (base58) */
+  account: string;
+  /** New owner program (base58) */
+  owner: string;
+}
+
+/** Memo instruction */
+export interface MemoInstruction {
+  type: "memo";
+  /** The memo message */
+  message: string;
+}
+
+/** Compute budget instruction */
+export interface ComputeBudgetInstruction {
+  type: "computeBudget";
+  /** Compute unit limit (optional) */
+  unitLimit?: number;
+  /** Compute unit price in micro-lamports (optional) */
+  unitPrice?: number;
+}
+
+/** Union of all instruction types */
+export type Instruction =
+  | TransferInstruction
+  | CreateAccountInstruction
+  | NonceAdvanceInstruction
+  | NonceInitializeInstruction
+  | AllocateInstruction
+  | AssignInstruction
+  | MemoInstruction
+  | ComputeBudgetInstruction;
+
+// =============================================================================
+// TransactionIntent
+// =============================================================================
+
+/**
+ * A declarative intent to build a Solana transaction.
+ *
+ * @example
+ * ```typescript
+ * const intent: TransactionIntent = {
+ *   feePayer: 'DgT9qyYwYKBRDyDw3EfR12LHQCQjtNrKu2qMsXHuosmB',
+ *   nonce: {
+ *     type: 'blockhash',
+ *     value: 'GWaQEymC3Z9SHM2gkh8u12xL1zJPMHPCSVR3pSDpEXE4'
+ *   },
+ *   instructions: [
+ *     { type: 'transfer', from: '...', to: '...', lamports: '1000000' }
+ *   ]
+ * };
+ * ```
+ */
+export interface TransactionIntent {
+  /** The fee payer's public key (base58) */
+  feePayer: string;
+  /** The nonce source (blockhash or durable nonce) */
+  nonce: NonceSource;
+  /** List of instructions to include */
+  instructions: Instruction[];
+}
+
+// =============================================================================
+// buildTransaction function
+// =============================================================================
+
+/**
+ * Build a Solana transaction from a high-level intent.
+ *
+ * This function takes a declarative TransactionIntent and produces serialized
+ * transaction bytes that can be signed and submitted to the network.
+ *
+ * The returned transaction is unsigned - signatures should be added before
+ * broadcasting.
+ *
+ * @param intent - The transaction intent describing what to build
+ * @returns Serialized unsigned transaction bytes (Uint8Array)
+ * @throws Error if the intent cannot be built (e.g., invalid addresses)
+ *
+ * @example
+ * ```typescript
+ * import { buildTransaction } from '@bitgo/wasm-solana';
+ *
+ * // Build a simple SOL transfer
+ * const txBytes = buildTransaction({
+ *   feePayer: sender,
+ *   nonce: { type: 'blockhash', value: blockhash },
+ *   instructions: [
+ *     { type: 'transfer', from: sender, to: recipient, lamports: '1000000' }
+ *   ]
+ * });
+ *
+ * // The returned bytes can be signed and broadcast
+ * ```
+ *
+ * @example
+ * ```typescript
+ * // Build with durable nonce and priority fee
+ * const txBytes = buildTransaction({
+ *   feePayer: sender,
+ *   nonce: { type: 'durable', address: nonceAccount, authority: sender, value: nonceValue },
+ *   instructions: [
+ *     { type: 'computeBudget', unitLimit: 200000, unitPrice: 5000 },
+ *     { type: 'transfer', from: sender, to: recipient, lamports: '1000000' },
+ *     { type: 'memo', message: 'BitGo transfer' }
+ *   ]
+ * });
+ * ```
+ */
+export function buildTransaction(intent: TransactionIntent): Uint8Array {
+  return BuilderNamespace.build_transaction(intent);
+}

packages/wasm-solana/js/builder.ts

@@ -8,6 +8,7 @@ export * as keypair from "./keypair.js";
 export * as pubkey from "./pubkey.js";
 export * as transaction from "./transaction.js";
 export * as parser from "./parser.js";
+export * as builder from "./builder.js";
 
 // Top-level class exports for convenience
 export { Keypair } from "./keypair.js";
@@ -16,6 +17,7 @@ export { Transaction } from "./transaction.js";
 
 // Top-level function exports
 export { parseTransaction } from "./parser.js";
+export { buildTransaction } from "./builder.js";
 
 // Type exports
 export type { AccountMeta, Instruction } from "./transaction.js";
@@ -40,3 +42,20 @@ export type {
   MemoParams,
   UnknownInstructionParams,
 } from "./parser.js";
+
+// Builder type exports (prefixed to avoid conflict with parser/transaction types)
+export type {
+  TransactionIntent,
+  NonceSource,
+  BlockhashNonceSource,
+  DurableNonceSource,
+  Instruction as BuilderInstruction,
+  TransferInstruction,
+  CreateAccountInstruction,
+  NonceAdvanceInstruction,
+  NonceInitializeInstruction,
+  AllocateInstruction,
+  AssignInstruction,
+  MemoInstruction,
+  ComputeBudgetInstruction,
+} from "./builder.js";