Implement multisig transfer approval workflow with core functionalities and error handling

contracts/multisig_transfer/src/approval.rs

@@ -0,0 +1,29 @@
+use soroban_sdk::{Address, Env};
+
+use crate::{errors::MultiSigError, storage};
+
+pub fn was_approved(e: &Env, request_id: u64, approver: &Address) -> bool {
+    let key = (request_id, approver.clone());
+    e.storage().persistent().get::<_, bool>(&key).unwrap_or(false)
+}
+
+pub fn mark_approved(e: &Env, request_id: u64, approver: &Address) {
+    let key = (request_id, approver.clone());
+    e.storage().persistent().set(&key, &true);
+}
+
+pub fn is_authorized_approver(approvers: &soroban_sdk::Vec<Address>, who: &Address) -> bool {
+    for a in approvers.iter() {
+        if &a == who {
+            return true;
+        }
+    }
+    false
+}
+
+pub fn ensure_not_double_approved(e: &Env, request_id: u64, approver: &Address) -> Result<(), MultiSigError> {
+    if was_approved(e, request_id, approver) {
+        return Err(MultiSigError::AlreadyApproved);
+    }
+    Ok(())
+}

contracts/multisig_transfer/src/errors.rs

@@ -0,0 +1,31 @@
+use soroban_sdk::contracterror;
+
+#[contracterror]
+#[derive(Copy, Clone, Debug, Eq, PartialEq)]
+pub enum MultiSigError {
+    NotInitialized = 1,
+    Unauthorized = 2,
+
+    InvalidOwner = 3,
+    InvalidNewOwner = 4,
+
+    AssetNotFound = 5,
+    AssetRetired = 6,
+    PendingRequestExists = 7,
+
+    RuleNotFound = 8,
+    ApproverNotAuthorized = 9,
+    CannotApproveOwnRequest = 10,
+    AlreadyApproved = 11,
+
+    RequestNotFound = 12,
+    RequestNotPending = 13,
+
+    RequestExpired = 14,
+    ApprovalDeadlinePassed = 15,
+
+    NotEnoughApprovals = 16,
+    ExecuteTooEarly = 17,
+
+    RegistryCallFailed = 18,
+}

contracts/multisig_transfer/src/events.rs

@@ -0,0 +1,55 @@
+use soroban_sdk::{Address, BytesN, Env};
+
+pub fn transfer_requested(
+    e: &Env,
+    request_id: u64,
+    asset_id: &BytesN<32>,
+    from_owner: &Address,
+    to_owner: &Address,
+    timestamp: u64,
+) {
+    e.events().publish(
+        ("TransferRequested",),
+        (request_id, asset_id.clone(), from_owner.clone(), to_owner.clone(), timestamp),
+    );
+}
+
+pub fn transfer_approved(e: &Env, request_id: u64, approver: &Address, count: u32, timestamp: u64) {
+    e.events().publish(("TransferApproved",), (request_id, approver.clone(), count, timestamp));
+}
+
+pub fn transfer_rejected(
+    e: &Env,
+    request_id: u64,
+    rejector: &Address,
+    reason_hash: &BytesN<32>,
+    timestamp: u64,
+) {
+    e.events().publish(
+        ("TransferRejected",),
+        (request_id, rejector.clone(), reason_hash.clone(), timestamp),
+    );
+}
+
+pub fn transfer_executed(e: &Env, request_id: u64, asset_id: &BytesN<32>, new_owner: &Address, timestamp: u64) {
+    e.events().publish(
+        ("TransferExecuted",),
+        (request_id, asset_id.clone(), new_owner.clone(), timestamp),
+    );
+}
+
+pub fn transfer_cancelled(e: &Env, request_id: u64, cancelled_by: &Address, timestamp: u64) {
+    e.events().publish(("TransferCancelled",), (request_id, cancelled_by.clone(), timestamp));
+}
+
+pub fn approval_rule_updated(e: &Env, category: &BytesN<32>, required: u32, timestamp: u64) {
+    e.events().publish(("ApprovalRuleUpdated",), (category.clone(), required, timestamp));
+}
+
+pub fn approver_added(e: &Env, approver: &Address, added_by: &Address, timestamp: u64) {
+    e.events().publish(("ApproverAdded",), (approver.clone(), added_by.clone(), timestamp));
+}
+
+pub fn approver_removed(e: &Env, approver: &Address, removed_by: &Address, timestamp: u64) {
+    e.events().publish(("ApproverRemoved",), (approver.clone(), removed_by.clone(), timestamp));
+}