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Fix #57: emit fee provenance in withdraw events #187

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Fix #57: emit fee provenance in withdraw events #187

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102 changes: 94 additions & 8 deletions prediction_market/src/lib.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -15,8 +15,8 @@ use soroban_sdk::{
// market_cancelled (admin, id) net_pool
// cancel_refund (user, id) gross
// claim_processed (user, id) (is_winner, payout)
// fees_withdrawn (caller) (recipient, amount)
// withdraw_requested (caller) (recipient, amount)
// fees_withdrawn (caller, recipient) (amount, Vec<FeeProvenance>)
// withdraw_requested (caller, recipient) amount
// withdraw_cancelled (admin) caller
// config_changed (admin) Config
// paused / unpaused (admin) ()
Expand Down Expand Up @@ -232,6 +232,15 @@ pub struct ForfeitedPool {
pub frozen: bool,
}

/// Provenance of a fee withdrawal: how much was drawn from each market.
/// Legacy fees (pre-upgrade) are reported with market_id == 0.
#[contracttype]
#[derive(Clone, Debug, Eq, PartialEq)]
pub struct FeeProvenance {
pub market_id: u64,
pub amount: i128,
}

// ── Domain Structs ────────────────────────────────────────────────────────────

#[contracttype]
Expand Down Expand Up @@ -1393,7 +1402,7 @@ impl PredictionMarketContract {
return Err(MarketError::NoFeesToWithdraw);
}
let cap = fees * MAX_WITHDRAWAL_BPS / BPS_DENOM;
Self::debit_proven_fees(&env, cap)?;
let provenance = Self::debit_proven_fees(&env, cap)?;

let cfg: Config = env.storage().instance().get(&DataKey::Cfg).unwrap();
token::Client::new(&env, &cfg.xlm_sac).transfer(
Expand All @@ -1404,7 +1413,7 @@ impl PredictionMarketContract {

env.events().publish(
(Symbol::new(&env, "fees_withdrawn"), caller, recipient.clone()),
cap,
(cap, provenance),
);
Ok(cap)
}
Expand Down Expand Up @@ -1485,7 +1494,7 @@ impl PredictionMarketContract {
// Debit the per-market / legacy ledger so the cached sum stays in
// lockstep. Effects before interaction so a reentrant recipient
// cannot re-read stale accumulator state.
Self::debit_proven_fees(&env, req.amount)?;
let provenance = Self::debit_proven_fees(&env, req.amount)?;
env.storage().persistent().remove(&key);

let cfg: Config = env.storage().instance().get(&DataKey::Cfg).unwrap();
Expand All @@ -1497,7 +1506,7 @@ impl PredictionMarketContract {

env.events().publish(
(Symbol::new(&env, "fees_withdrawn"), caller, req.recipient.clone()),
req.amount,
(req.amount, provenance),
);
Ok(req.amount)
}
Expand Down Expand Up @@ -1612,6 +1621,17 @@ impl PredictionMarketContract {
.unwrap_or(0)
}

/// Preview which markets a withdrawal of `amount` would draw from, without
/// debiting. Returns a vec of (market_id, amount) pairs in drain order
/// (legacy first, then newest-to-oldest). Useful for indexers and UIs
/// that want to show fee provenance before a withdrawal executes.
pub fn get_withdrawal_provenance(
env: Env,
amount: i128,
) -> Result<Vec<FeeProvenance>, MarketError> {
Self::preview_fee_provenance(&env, amount)
}

/// Permissionless one-shot: snapshot the pre-upgrade global scalar into
/// LegacyFees. Fresh deploys already set FeeLedgerMigrated at initialize.
pub fn migrate_fee_ledger(env: Env) {
Expand Down Expand Up @@ -1780,7 +1800,11 @@ impl PredictionMarketContract {

/// Drain LegacyFees first, then per-market balances from newest to oldest,
/// keeping AccumulatedFees in lockstep. Used by withdraw paths.
fn debit_proven_fees(env: &Env, amount: i128) -> Result<(), MarketError> {
/// Returns the provenance: which markets were debited and how much.
fn debit_proven_fees(
env: &Env,
amount: i128,
) -> Result<Vec<FeeProvenance>, MarketError> {
Self::ensure_fee_ledger_migrated(env);
if amount <= 0 {
return Err(MarketError::InvalidAmount);
Expand All @@ -1794,11 +1818,16 @@ impl PredictionMarketContract {
return Err(MarketError::WithdrawalTooLarge);
}

let mut provenance: Vec<FeeProvenance> = Vec::new(env);
let mut remaining = amount;
let legacy = Self::market_fee_balance(env, LEGACY_MARKET_ID);
let take_legacy = if remaining < legacy { remaining } else { legacy };
if take_legacy > 0 {
Self::debit_market_fees(env, LEGACY_MARKET_ID, take_legacy);
provenance.push_back(FeeProvenance {
market_id: LEGACY_MARKET_ID,
amount: take_legacy,
});
remaining -= take_legacy;
}
if remaining > 0 {
Expand All @@ -1813,6 +1842,10 @@ impl PredictionMarketContract {
if mf > 0 {
let take = if remaining < mf { remaining } else { mf };
Self::debit_market_fees(env, id, take);
provenance.push_back(FeeProvenance {
market_id: id,
amount: take,
});
remaining -= take;
}
id -= 1;
Expand All @@ -1821,7 +1854,60 @@ impl PredictionMarketContract {
if remaining > 0 {
return Err(MarketError::WithdrawalTooLarge);
}
Ok(())
Ok(provenance)
}

/// Preview the provenance of a withdrawal without debiting.
/// Returns which markets would be debited and how much.
fn preview_fee_provenance(env: &Env, amount: i128) -> Result<Vec<FeeProvenance>, MarketError> {
Self::ensure_fee_ledger_migrated(env);
if amount <= 0 {
return Err(MarketError::InvalidAmount);
}
let acc: i128 = env
.storage()
.instance()
.get(&DataKey::AccumulatedFees)
.unwrap_or(0);
if amount > acc {
return Err(MarketError::WithdrawalTooLarge);
}

let mut provenance: Vec<FeeProvenance> = Vec::new(env);
let mut remaining = amount;
let legacy = Self::market_fee_balance(env, LEGACY_MARKET_ID);
let take_legacy = if remaining < legacy { remaining } else { legacy };
if take_legacy > 0 {
provenance.push_back(FeeProvenance {
market_id: LEGACY_MARKET_ID,
amount: take_legacy,
});
remaining -= take_legacy;
}
if remaining > 0 {
let count: u64 = env
.storage()
.instance()
.get(&DataKey::MarketCount)
.unwrap_or(0);
let mut id = count;
while remaining > 0 && id > 0 {
let mf = Self::market_fee_balance(env, id);
if mf > 0 {
let take = if remaining < mf { remaining } else { mf };
provenance.push_back(FeeProvenance {
market_id: id,
amount: take,
});
remaining -= take;
}
id -= 1;
}
}
if remaining > 0 {
return Err(MarketError::WithdrawalTooLarge);
}
Ok(provenance)
}

fn sac_sentinel(env: &Env) -> BytesN<32> {
Expand Down