SETTLEMENT_ID_IMPLEMENTATION.md

Settlement ID Implementation

Overview

Each settlement has a unique, sequential identifier for traceability and auditing. Settlement IDs are the same as remittance IDs since settlements are the completion of remittances.

Implementation

ID Generation

Settlement IDs are generated incrementally using a counter:

// Counter starts at 0, first remittance gets ID 1
let counter = get_remittance_counter(&env)?;
let remittance_id = counter.checked_add(1)?;
set_remittance_counter(&env, remittance_id);

ID Storage

IDs are stored in the Remittance struct:

pub struct Remittance {
    pub id: u64,              // Unique settlement ID
    pub sender: Address,
    pub agent: Address,
    pub amount: i128,
    pub fee: i128,
    pub status: RemittanceStatus,
    pub expiry: Option<u64>,
}

ID Return

The confirm_payout function now returns the settlement ID:

pub fn confirm_payout(env: Env, remittance_id: u64) -> Result<u64, ContractError>

Before:

contract.confirm_payout(&remittance_id)?; // Returns ()

After:

let settlement_id = contract.confirm_payout(&remittance_id)?; // Returns ID

Querying Settlements

Use the settlement ID to query settlement data:

// Query by settlement ID
let settlement = contract.get_settlement(&settlement_id)?;

println!("Settlement ID: {}", settlement.id);
println!("Status: {:?}", settlement.status);
println!("Amount: {}", settlement.amount);
println!("Fee: {}", settlement.fee);

Properties

✅ Unique

Each settlement ID is unique across the entire contract:

let id1 = contract.create_remittance(&sender1, &agent, &1000, &None); // ID: 1
let id2 = contract.create_remittance(&sender2, &agent, &2000, &None); // ID: 2
let id3 = contract.create_remittance(&sender1, &agent, &3000, &None); // ID: 3

// All IDs are different
assert_ne!(id1, id2);
assert_ne!(id1, id3);
assert_ne!(id2, id3);

✅ Sequential

IDs are generated in sequential order:

let id1 = contract.create_remittance(...); // 1
let id2 = contract.create_remittance(...); // 2
let id3 = contract.create_remittance(...); // 3

assert_eq!(id1, 1);
assert_eq!(id2, 2);
assert_eq!(id3, 3);

✅ Persistent

Settlement IDs remain the same throughout the lifecycle:

let remittance_id = contract.create_remittance(...);  // ID: 5
let settlement_id = contract.confirm_payout(&remittance_id)?; // Returns: 5

assert_eq!(remittance_id, settlement_id);

let settlement = contract.get_settlement(&settlement_id)?;
assert_eq!(settlement.id, 5); // Still 5

Usage Examples

Basic Settlement Flow

// 1. Create remittance (generates ID)
let remittance_id = contract.create_remittance(
    &sender,
    &agent,
    &10000,
    &None
)?;
println!("Created remittance with ID: {}", remittance_id);

// 2. Confirm payout (returns settlement ID)
let settlement_id = contract.confirm_payout(&remittance_id)?;
println!("Settlement completed with ID: {}", settlement_id);

// 3. Query settlement data
let settlement = contract.get_settlement(&settlement_id)?;
println!("Settlement status: {:?}", settlement.status);

Audit Trail

// Track all settlements for auditing
let mut settlement_ids = vec![];

for remittance_id in pending_remittances {
    let settlement_id = contract.confirm_payout(&remittance_id)?;
    settlement_ids.push(settlement_id);
}

// Later, audit all settlements
for id in settlement_ids {
    let settlement = contract.get_settlement(&id)?;
    audit_log.record(settlement);
}

Batch Processing

// Process multiple settlements and track IDs
let results: Vec<(u64, Result<u64, ContractError>)> = remittance_ids
    .iter()
    .map(|id| (*id, contract.confirm_payout(id)))
    .collect();

// Report results
for (remittance_id, result) in results {
    match result {
        Ok(settlement_id) => {
            println!("✅ Remittance {} settled as {}", remittance_id, settlement_id);
        }
        Err(e) => {
            println!("❌ Remittance {} failed: {:?}", remittance_id, e);
        }
    }
}

API Changes

confirm_payout Return Type

Old:

pub fn confirm_payout(env: Env, remittance_id: u64) -> Result<(), ContractError>

New:

pub fn confirm_payout(env: Env, remittance_id: u64) -> Result<u64, ContractError>

Migration Guide

If you have existing code:

// Before
contract.confirm_payout(&remittance_id)?;
do_something();

// After - just capture the ID
let settlement_id = contract.confirm_payout(&remittance_id)?;
do_something();

Test Coverage

3 Comprehensive Tests

1. test_settlement_id_returned

   • Verifies ID is returned from confirm_payout
   • Confirms ID can be used to query settlement

2. test_settlement_ids_sequential

   • Verifies IDs are generated sequentially (1, 2, 3...)
   • Confirms settlement IDs match remittance IDs

3. test_settlement_id_uniqueness

   • Verifies all IDs are unique
   • Tests across multiple senders and agents

Benefits

For Auditing

• Track every settlement with unique ID
• Query historical settlements
• Build audit trails

For Monitoring

• Monitor settlement completion by ID
• Track settlement metrics
• Identify specific settlements in logs

For Integration

• Return settlement ID to users
• Store IDs in external databases
• Link settlements to external systems

Acceptance Criteria

✅ IDs are unique and sequential

• Counter-based generation ensures uniqueness
• Sequential increment (1, 2, 3...)
• No ID collisions

✅ Can query settlement using the ID

• get_settlement(id) returns settlement data
• ID persists throughout lifecycle
• Works for all settlement states

✅ Generate incremental settlement IDs

• Counter starts at 0
• Each remittance gets next ID
• Overflow protected

✅ Store ID alongside settlement data

• ID stored in Remittance struct
• Persisted in contract storage
• Accessible via queries

✅ Return ID after execution

• confirm_payout returns settlement ID
• ID matches original remittance ID
• Can be used immediately for queries

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Status: ✅ IMPLEMENTED

Note: Settlement IDs are identical to remittance IDs since settlements are completed remittances. This provides a unified identifier throughout the remittance lifecycle.