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The Route Optimizer is a Stylus contract that evaluates swap routes across multiple registered DEXes to find the best output amount. It supports Uniswap V3 concentrated liquidity pools and AMM V2-style constant product pools, with single-hop and two-hop routing through configurable intermediate tokens.

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DEX Registry

DEXes are stored in a dynamic registry using the indexed mapping + soft-delete pattern. Each entry has an address, a type discriminant, and an active flag. Removal sets active = false without shifting indices. 
sol_storage! {
    #[entrypoint]
    pub struct RouteOptimizer {
        address owner;
        uint256 dex_count;
        mapping(uint256 => address) dex_addresses;
        mapping(uint256 => uint256) dex_types;
        mapping(uint256 => bool) dex_active;
        address[] routing_tokens;
    }
}

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DEX Types

ConstantValueProtocol StyleInterface
DEX_TYPE_UNIV30Concentrated liquidityIUniswapV3Quoter
DEX_TYPE_AMM_V21Constant productIAmmRouter
The registry is capped at 20 DEXes (MAX_DEXES).

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Routing Tokens

Routing tokens are intermediate assets used for two-hop paths (e.g. USDC -> WETH -> ARB). On initialization, the contract seeds two defaults:
  • WETH — 0x82aF49447D8a07e3bd95BD0d56f35241523fBab1
  • USDC — 0xaf88d065e77c8cc2239327c5edb3a432268e5831
Additional tokens can be added up to a cap of 50.

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Quote Dispatch

When find_best_route is called, the contract iterates over all active DEXes and dispatches to the appropriate quoter based on DEX type:
Single-hop: Calls quoteExactInputSingle for each of the four standard fee tiers (100, 500, 3000, 10000 bps).Two-hop: For each intermediate routing token, encodes a packed path and calls quoteExactInput across all fee tier combinations (4 x 4 = 16 combinations per intermediate token).The best output across all tiers and hops wins.
Single-hop: Calls getAmountsOut with a direct [tokenIn, tokenOut] path.Two-hop: For each intermediate routing token, calls getAmountsOut with a [tokenIn, intermediate, tokenOut] path.AMM V2 pools have flat fee structures, so there are no fee tier iterations.

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Public Methods

Set the caller as owner and seed the default routing tokens (WETH, USDC). Can only be called once.
Register a new DEX quoter/router. Owner only.
  • Rejects zero addresses and reverts if the registry is full (20 DEXes).
  • Returns the new DEX index.
  • Emits DexAdded(index, dexAddress, dexType).
Soft-delete a DEX by setting dex_active[index] = false. Owner only.
  • Reverts if index is out of bounds or already removed.
  • Emits DexRemoved(index, dexAddress).
Add an intermediate token for two-hop routing. Owner only.
  • Rejects zero addresses, duplicates, and reverts at the 50-token cap.
Remove a routing token using swap-and-pop. Owner only.
Find the route with the highest output amount across all active DEXes.Returns (amountOut, tokenPath, feePath):
  • tokenPath — ordered list of token addresses in the route.
  • feePath — Uniswap V3 fee tiers for each hop (empty for AMM V2).
  • Reverts with "no route found" if no DEX returns a quote.
Simplified comparison that returns (best_dex_index, best_amount_out) using direct quotes only (no multi-hop). Useful for quick price checks.
Total number of DEXes ever registered (including soft-deleted).
Read a DEX entry: (address, type, active).
Number of currently active routing tokens.

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Route Selection Example

Given two registered DEXes (Uniswap V3 and Camelot V2) and routing tokens WETH + USDC, a call to find_best_route(ARB, GMX, 1000e18) would evaluate: 
Uniswap V3:
  Direct: ARB->GMX @ 100bps, 500bps, 3000bps, 10000bps
  Via WETH: ARB->WETH->GMX @ 16 fee combos
  Via USDC: ARB->USDC->GMX @ 16 fee combos

Camelot V2:
  Direct: ARB->GMX
  Via WETH: ARB->WETH->GMX
  Via USDC: ARB->USDC->GMX
The route returning the highest amountOut is selected.
Private helper methods (quote_univ3, quote_amm_v2) live in a separate impl block because they accept &mut references that are not ABI-compatible. This is a Stylus SDK requirement — only the #[public] block generates ABI exports.

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Test Coverage

The contract has 38 tests covering:
  • DEX registry CRUD (add, remove, soft-delete verification)
  • Routing token management (add, remove, duplicate rejection, cap enforcement)
  • UniV3 single-hop and multi-hop quote dispatch
  • AMM V2 direct and two-hop quote dispatch
  • Best route selection across multiple DEXes
  • Access control on all owner-only methods
  • Edge cases: empty registry, all DEXes removed, no route found