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# Swap Routing
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Core swap routing functionality for encoding transactions across Uniswap V2, V3, and V4 protocols. The SwapRouter class handles single and multi-protocol routes with automatic optimization and gas-efficient execution.
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## Capabilities
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### SwapRouter Class
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Abstract class representing the Uniswap V2 + V3 SwapRouter02 contract, providing static methods for encoding swap transactions.
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```typescript { .api }
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/**
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 * Represents the Uniswap V2 + V3 SwapRouter02, and has static methods for helping execute trades
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 */
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abstract class SwapRouter {
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  /** Contract interface for ISwapRouter02 */
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  static INTERFACE: Interface;
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  /**
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   * Produces the on-chain method name to call and the hex encoded parameters to pass as arguments for a given trade
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   * @param trades - Single trade or array of trades to execute
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   * @param options - Options for the call parameters
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   * @returns Method parameters with calldata and value
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   */
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  static swapCallParameters(
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    trades: Trade<Currency, Currency, TradeType> 
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      | V2Trade<Currency, Currency, TradeType>
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      | V3Trade<Currency, Currency, TradeType> 
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      | MixedRouteTrade<Currency, Currency, TradeType>
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      | (V2Trade<Currency, Currency, TradeType> | V3Trade<Currency, Currency, TradeType> | MixedRouteTrade<Currency, Currency, TradeType>)[],
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    options: SwapOptions
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  ): MethodParameters;
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  /**
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   * Produces call parameters for swap and add liquidity operations
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   * @param trades - Trades to execute before adding liquidity
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   * @param options - Swap and add options
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   * @param position - Target liquidity position
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   * @param addLiquidityOptions - Options for adding liquidity
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   * @param tokenInApprovalType - Approval type for input token
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   * @param tokenOutApprovalType - Approval type for output token
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   * @returns Method parameters with calldata and value
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   */
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  static swapAndAddCallParameters(
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    trades: AnyTradeType,
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    options: SwapAndAddOptions,
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    position: Position,
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    addLiquidityOptions: CondensedAddLiquidityOptions,
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    tokenInApprovalType: ApprovalTypes,
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    tokenOutApprovalType: ApprovalTypes
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  ): MethodParameters;
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}
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```
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### Swap Options
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Configuration options for swap operations including slippage tolerance, recipient, and validation.
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```typescript { .api }
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/**
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 * Options for producing the arguments to send calls to the router
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 */
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interface SwapOptions {
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  /** How much the execution price is allowed to move unfavorably from the trade execution price */
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  slippageTolerance: Percent;
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  /** The account that should receive the output. If omitted, output is sent to msg.sender */
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  recipient?: string;
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  /** Either deadline (when the transaction expires, in epoch seconds), or previousBlockhash */
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  deadlineOrPreviousBlockhash?: Validation;
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  /** The optional permit parameters for spending the input */
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  inputTokenPermit?: PermitOptions;
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  /** Optional information for taking a fee on output */
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  fee?: FeeOptions;
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}
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/**
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 * Extended options for swap and add operations
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 */
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interface SwapAndAddOptions extends SwapOptions {
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  /** The optional permit parameters for pulling in remaining output token */
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  outputTokenPermit?: PermitOptions;
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}
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```
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### Method Parameters
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Return type for swap encoding methods containing transaction calldata and value.
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```typescript { .api }
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/**
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 * Parameters for calling router methods
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 */
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interface MethodParameters {
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  /** Hex-encoded calldata for the transaction */
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  calldata: string;
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  /** Hex-encoded value to send with the transaction */
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  value: string;
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}
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```
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**Usage Examples:**
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```typescript
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import { SwapRouter, Trade, SwapOptions } from "@uniswap/router-sdk";
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import { CurrencyAmount, TradeType, Percent, Token } from "@uniswap/sdk-core";
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// Create a simple V3 trade
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const trade = new V3Trade(route, amount, TradeType.EXACT_INPUT);
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// Configure swap options
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const options: SwapOptions = {
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  slippageTolerance: new Percent(50, 10000), // 0.5%
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  recipient: "0x742d35Cc6435C6329Eb54F0d86C05B1E11a02E6B",
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  deadlineOrPreviousBlockhash: Math.floor(Date.now() / 1000) + 1800, // 30 minutes
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};
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// Generate swap call parameters
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const { calldata, value } = SwapRouter.swapCallParameters(trade, options);
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// Use with ethers.js
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const tx = await wallet.sendTransaction({
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  to: SWAP_ROUTER_ADDRESS,
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  data: calldata,
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  value: value,
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});
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```
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```typescript
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// Multi-protocol trade example
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const aggregatedTrade = new Trade({
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  v2Routes: [{ routev2: v2Route, inputAmount, outputAmount }],
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  v3Routes: [{ routev3: v3Route, inputAmount, outputAmount }],
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  tradeType: TradeType.EXACT_INPUT
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});
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const params = SwapRouter.swapCallParameters(aggregatedTrade, options);
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```
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```typescript
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// Swap and add liquidity example
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import { Position } from "@uniswap/v3-sdk";
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const position = new Position({
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  pool: v3Pool,
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  liquidity: targetLiquidity,
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  tickLower: -887220,
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  tickUpper: 887220
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});
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const swapAndAddOptions: SwapAndAddOptions = {
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  ...options,
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  outputTokenPermit: {
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    v: 27,
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    r: "0x...",
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    s: "0x...",
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    deadline: deadline,
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    amount: permitAmount
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  }
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};
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const params = SwapRouter.swapAndAddCallParameters(
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  trade,
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  swapAndAddOptions,
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  position,
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  addLiquidityOptions,
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  ApprovalTypes.MAX,
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  ApprovalTypes.NOT_REQUIRED
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);
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```
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### Constants
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Routing-related constants used throughout the SDK.
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```typescript { .api }
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/** Zero address constant */
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const ADDRESS_ZERO = "0x0000000000000000000000000000000000000000";
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/** Message sender placeholder address */
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const MSG_SENDER = "0x0000000000000000000000000000000000000001";  
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/** Contract address placeholder */
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const ADDRESS_THIS = "0x0000000000000000000000000000000000000002";
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/** Mixed quoter fee path placeholders for different protocol combinations */
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const MIXED_QUOTER_V1_V2_FEE_PATH_PLACEHOLDER = 8388608;
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const MIXED_QUOTER_V2_V2_FEE_PATH_PLACEHOLDER = 32;
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const MIXED_QUOTER_V2_V3_FEE_PATH_PLACEHOLDER = 3145728;
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const MIXED_QUOTER_V2_V4_FEE_PATH_PLACEHOLDER = 4194304;
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/** Percentage constants */
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const ZERO_PERCENT: Percent;
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const ONE_HUNDRED_PERCENT: Percent;
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```