feat(flashloan): FlashLoanProvider trait + Aave V3 adapter + fee-priority router#39
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Shared abstraction for every flash-loan source. Router in
`charon-flashloan` will walk a list of these in fee-priority order
(Balancer 0% → Aave 0.05% → Uniswap pool fee), pick the cheapest
source with sufficient liquidity, and hand the resulting quote to the
tx builder.
- `FlashLoanQuote` — source, chain, token, amount, absolute fee,
fee_bps, pool address
- `FlashLoanProvider` async trait:
- `source` / `chain_id` / `fee_rate_bps` — static metadata
- `available_liquidity(token)` — on-chain reserve lookup
- `quote(token, amount)` — one-shot fitness check + pricing
- `build_flashloan_calldata(quote, inner_calldata)` — outer call
wrapping the protocol adapter's liquidation bytes
First adapter implementing `charon_core::FlashLoanProvider`. Lives in
the new `charon-flashloan` crate alongside future Balancer / Uniswap
sources; router lands next.
- `AaveFlashLoan::connect(provider, pool, receiver)`:
- caches `FLASHLOAN_PREMIUM_TOTAL` → `fee_bps`
- caches `eth_chainId`
- holds the receiver (`CharonLiquidator.sol`) for calldata emission
- `available_liquidity(token)`: resolves asset → aToken via
`PoolDataProvider.getReserveTokensAddresses`, then reads the
aToken's underlying balance. Missing reserves return `U256::ZERO`.
- `quote(token, amount)`: checks liquidity, computes absolute fee
(amount × fee_bps / 10_000), returns `None` if undersized.
- `build_flashloan_calldata` encodes
`Pool.flashLoanSimple(receiver, asset, amount, params, 0)` with the
inner liquidation bytes as params.
- BSC `PoolDataProvider` address is hardcoded (v0.1 single-chain
scope); moves into config when multi-chain arrives.
- Unit test pins the selector; live integration test hits BSC mainnet
and verifies USDT liquidity + quote shape.
Picks the cheapest flash-loan source that can cover a requested borrow. Providers are supplied as `Arc<dyn FlashLoanProvider>`; the router sorts by `fee_rate_bps` at construction so the walk starts with the least expensive option. - `FlashLoanRouter::new(providers)` — sorts once, cheapest first - `route(token, amount)` — walks in order, returns the first quote that fits; per-provider errors or insufficient-liquidity outcomes are logged + skipped rather than aborting - Returns `None` when no source can cover the amount — caller drops the liquidation rather than faking capital from elsewhere - Four unit tests via an in-memory `StubProvider`: cheapest-picked, fallthrough on insufficient liquidity, all-empty → None, empty provider list → None
This was referenced Apr 23, 2026
Closed
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Closed
[flashloan] AaveFlashLoan PoolDataProvider address hardcoded — should be in config/default.toml
#143
Closed
Closed
Closed
[executor] charon-executor still missing from workspace members — fourth consecutive PR flagged
#199
Closed
Closed
Closed
Closes #136: Rename FlashLoanProvider::fee_rate_bps -> fee_rate_millionths (u32, Uniswap 1e6 convention). Aave's 4-decimal-% premium is converted by x100 at connect time (Aave 5 -> 500). FlashLoanQuote.fee_rate_bps is renamed to match. Closes #138: build_flashloan_calldata argument renamed to liquidation_params and guarded against an empty buffer — every real executeOperation ABI-decodes this payload and reverts on 0x. Closes #141: Introduce FlashLoanError (thiserror, non_exhaustive) with InsufficientLiquidity, ReservePaused, ChainIdMismatch, Rpc, Other. Trait methods now return Result<T, FlashLoanError>; anyhow is kept only on connect() for config-time wiring. Closes #144: #[non_exhaustive] added to FlashLoanSource and FlashLoanError. Closes #137: AaveFlashLoan.available_liquidity calls getReserveConfigurationData and getReserveData on the PoolDataProvider and rejects the borrow with FlashLoanError::ReservePaused when isActive is false, isFrozen is true, or bits 57 (frozen) / 60 (paused) are set in the packed configuration bitmap. Closes #142: AaveFlashLoan::connect calls provider.get_chain_id() and anyhow::ensure!s it equals 56, failing fast on misconfigured RPC. Closes #143: FlashLoanConfig gains an optional data_provider: Address. config/default.toml pins the canonical Aave V3 BSC PoolDataProvider (0x41393e5e337606dc3821075Af65AeE84D7688CBD). connect() takes it as an argument instead of a hardcoded constant; the constant was removed. Closes #145: FlashLoanRouter grows with_liquidity_tiebreaker, an async constructor that probes available_liquidity(token) for each provider and sorts fee_rate_millionths asc, then available_liquidity desc. The plain new() keeps the fee-only ordering for call sites that don't want the probe cost. Closes #139: aave_live integration test is now #[ignore]-gated so cargo test --workspace does not require BNB_WS_URL. Run explicitly with cargo test -p charon-flashloan -- --ignored. Refs #140: charon-flashloan was already in workspace.members; no change required. thiserror is added to the workspace dependency table and pulled into charon-core / charon-flashloan. Gates green: cargo fmt, cargo clippy --all-targets --all-features -D warnings, cargo test --workspace --all-targets, cargo test --workspace --doc.
# Conflicts: # Cargo.lock # Cargo.toml # crates/charon-core/src/lib.rs
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Closes #14
Three archive commits consolidated on squash. Gives the executor a uniform way to source flash capital; for v0.1 Aave V3 on BSC is the only implementation, but the abstraction admits Balancer / Uniswap flash-swap adapters without refactoring.
FlashLoanProvidertrait +FlashLoanQuoteincharon-core—source,chain_id,fee_rate_bps,available_liquidity,quote,build_flashloan_calldataAaveFlashLoanadapter in newcharon-flashloancrate:connect(provider, pool, receiver)cachesFLASHLOAN_PREMIUM_TOTAL+ chain idavailable_liquidityresolves asset → aToken via PoolDataProvider; reads aToken underlying balancequotechecks liquidity, computesamount × fee_bps / 10_000feebuild_flashloan_calldataencodesflashLoanSimple(receiver, asset, amount, params, 0)FlashLoanRouter— sorts providers byfee_rate_bpsascending; walks cheapest-first, returns first quote that fits;Nonewhen no source can coverfee_bps = 5(0.05%); live test + 4 router unit tests covering cheapest-picked / fallthrough / all-emptyDepends on #23 (
feat/13-foundry-fork-tests).