updates

contracts/smart_wallet/README.md

@@ -1,25 +1,93 @@
 # Smart Wallet Contract
 
-This contract account example supports mixed signer sets:
+A Soroban custom-account contract that supports mixed signer sets and an M-of-N signing threshold.
 
-- Stellar Ed25519 account keys
-- secp256k1 public keys for Ethereum-style wallets and bridge tooling
+Supported key types:
+
+- **Ed25519** — standard Stellar account keys
+- **secp256k1** — Ethereum-style keys for bridge tooling and hardware wallets
+
+---
+
+## Contract functions
+
+### Lifecycle
+
+| Function | Description |
+|---|---|
+| `init(signers, threshold)` | One-time setup. Stores the initial signer list and threshold. Returns `AlreadyInitialized` if called again. |
+| `name() → String` | SEP-0034 contract name. |
+| `version() → String` | SEP-0034 contract version. |
+| `author() → String` | SEP-0034 contract author. |
+
+### Signer management
+
+All mutating operations require the contract account itself to authorise the call (i.e. the current threshold of signers must sign).
+
+| Function | Description |
+|---|---|
+| `add_signer(signer)` | Adds a new key. Returns `DuplicateSigner` if the key is already registered. |
+| `remove_signer(signer)` | Removes a key. Returns `UnknownSigner` if the key is not registered; returns `InvalidThreshold` if removal would leave fewer signers than the threshold. |
+| `set_threshold(threshold)` | Updates the M-of-N requirement. Returns `InvalidThreshold` if the new value is zero or exceeds the signer count. |
+| `signer_count() → u32` | Returns the number of registered signers. |
+| `threshold() → u32` | Returns the current threshold. |
+
+### Authentication (`__check_auth`)
+
+Soroban calls this automatically when the wallet account must authorise an operation. Callers supply a `Vec<SignatureProof>`. The contract:
+
+1. Verifies each proof against a registered signer slot (type-aware — an Ed25519 proof cannot satisfy a secp256k1 slot).
+2. Prevents the same signer slot from being counted twice.
+3. Returns `NotEnoughSignatures` if the number of valid, distinct signatures is below the threshold.
+
+---
+
+## Error codes (`WalletError`)
+
+| Variant | Value | Meaning |
+|---|---|---|
+| `AlreadyInitialized` | 1 | `init` called more than once. |
+| `NotInitialized` | 2 | A function was called before `init`. |
+| `InvalidThreshold` | 3 | Threshold is zero, exceeds signer count, or removal would drop below it. |
+| `DuplicateSigner` | 4 | Attempted to add a key that is already registered. |
+| `UnknownSigner` | 5 | Proof or removal target does not match any registered signer. |
+| `InvalidSignature` | 6 | Cryptographic verification failed (wrong key or bad signature bytes). |
+| `NotEnoughSignatures` | 7 | Fewer valid signatures were supplied than the threshold requires. |
+
+---
+
+## Events
+
+| Event | Fields | Emitted by |
+|---|---|---|
+| `WalletInitializedEvent` | `signer_count`, `threshold` | `init` |
+| `SignerAddedEvent` | `added: SignerKey`, `total_signers` | `add_signer` |
+| `SignerRemovedEvent` | `removed: SignerKey`, `total_signers` | `remove_signer` |
+| `ThresholdChangedEvent` | `old_threshold`, `new_threshold` | `set_threshold` |
+
+---
 
 ## Signing payloads
 
-Soroban passes a 32-byte `Hash<32>` into `__check_auth`. Sign that exact payload, and do not add any extra prefix or chain-specific message formatting unless the contract explicitly hashes it first.
+Soroban passes a raw 32-byte `Hash<32>` into `__check_auth`. Sign that exact digest — do not add any prefix or chain-specific framing.
 
 ### Ed25519
 
-- Sign the raw 32-byte payload bytes.
-- Provide the 32-byte Ed25519 public key and 64-byte signature.
+- Sign the raw 32-byte payload.
+- Provide `Ed25519Proof { public_key: BytesN<32>, signature: BytesN<64> }`.
 
 ### secp256k1
 
-- Sign the same 32-byte payload digest with ECDSA secp256k1.
-- Provide the 65-byte SEC-1 public key and 64-byte compact signature.
-- The wallet should sign the exact payload the contract receives. Do not use `personal_sign`-style prefixes unless the contract is designed to expect them.
+- Sign the same 32-byte payload with ECDSA secp256k1.
+- Provide `Secp256k1Proof { public_key: BytesN<65>, signature: BytesN<64>, recovery_id: u32 }`.
+- The wallet recovers the public key from the signature and compares it to the registered key; do not use `personal_sign`-style prefixes.
+
+---
+
+## Testing
 
-## Benchmarking
+```
+cargo test --features testutils --target aarch64-apple-darwin
+```
 
-The test suite includes budget-printing checks for both Ed25519 and secp256k1 verification so you can compare CPU instruction usage in the Soroban test environment.
+The test suite covers signer management, threshold enforcement, auth verification for both key types, mixed M-of-N scenarios, duplicate-proof rejection, and all error paths. Budget-printing tests are included so you can compare CPU instruction usage between Ed25519 and secp256k1 verification in the Soroban environment.