feat(lp-sdk): add LP gas-estimation helpers

.changeset/lp-sdk-gas-estimation.md

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+---
+'@uniswap/lp-sdk': minor
+---
+
+Introduce @uniswap/lp-sdk with LP gas-estimation helpers: pickPreEstimateIndependentAmount for choosing a representative simulation amount from wallet balances, and getV2/getV3/getV4AddLiquidityGasEstimateTransactions for building the ordered approval + create/increase transaction lists to run eth_estimateGas over.

sdks/lp-sdk/.eslintrc.js

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+module.exports = {
+  root: true,
+  parser: '@typescript-eslint/parser',
+  parserOptions: {
+    ecmaVersion: 2020,
+    sourceType: 'module'
+  },
+  extends: [
+    'react-app',
+    'prettier',
+    'plugin:prettier/recommended'
+  ],
+  settings: {
+    react: {
+      version: '999.999.999'
+    }
+  }
+};
+

sdks/lp-sdk/.gitignore

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+# build 
+dist
+
+# dependencies
+node_modules

sdks/lp-sdk/LICENSE

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+MIT License
+
+Copyright (c) 2021 Uniswap Labs
+
+Permission is hereby granted, free of charge, to any person obtaining a copy
+of this software and associated documentation files (the "Software"), to deal
+in the Software without restriction, including without limitation the rights
+to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+copies of the Software, and to permit persons to whom the Software is
+furnished to do so, subject to the following conditions:
+
+The above copyright notice and this permission notice shall be included in all
+copies or substantial portions of the Software.
+
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+SOFTWARE.

sdks/lp-sdk/README.md

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+# @uniswap/lp-sdk
+
+An SDK for building liquidity-provision flows on top of Uniswap v2, v3, and v4. It composes the
+position calldata builders from `@uniswap/v2-sdk`, `@uniswap/v3-sdk`, and `@uniswap/v4-sdk` into
+cross-version helpers, following the same pattern `@uniswap/router-sdk` uses for swaps.
+
+Like all SDKs in this repository, it is chain-agnostic and makes no network calls: helpers take
+onchain state (balances, allowances, pool state) as inputs and return transaction tuples
+(`{ to, calldata, value }`).
+
+## Gas estimation helpers
+
+Estimating the real cost of an LP flow (instead of reserving a hardcoded native-token buffer)
+requires estimating every transaction the user will send — token approvals included — before the
+user has entered an amount. These helpers produce that transaction list:
+
+- `pickPreEstimateIndependentAmount(balance0, balance1)` — picks which pool token (and how much of
+  it) to drive a representative simulation with, from the wallet's two token balances. Balances are
+  capped at 10^(decimals + 3) raw units; returns `null` when both are zero.
+- `getV2AddLiquidityGasEstimateTransactions(params)` — approvals to the v2 router plus the
+  `addLiquidity`/`addLiquidityETH` transaction.
+- `getV3AddLiquidityGasEstimateTransactions(params)` — approvals to the `NonfungiblePositionManager`
+  plus the mint/increase transaction (`NonfungiblePositionManager.addCallParameters`).
+- `getV4AddLiquidityGasEstimateTransactions(params)` — ERC-20 approvals to Permit2, Permit2
+  approvals to the v4 position manager, plus the mint/increase transaction
+  (`V4PositionManager.addCallParameters`).
+
+Callers run `eth_estimateGas` over the returned transactions in order (from the wallet's address)
+and sum the results. Approvals are included pessimistically when no allowance state is provided.

sdks/lp-sdk/package.json

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+{
+  "name": "@uniswap/lp-sdk",
+  "version": "0.0.0",
+  "description": "An SDK for building liquidity-provision flows on top of Uniswap v2, v3, and v4",
+  "repository": "https://github.com/Uniswap/sdks.git",
+  "keywords": [
+    "uniswap",
+    "ethereum"
+  ],
+  "license": "MIT",
+  "main": "./dist/cjs/src/index.js",
+  "typings": "./dist/types/src/index.d.ts",
+  "module": "./dist/esm/src/index.js",
+  "exports": {
+    ".": {
+      "types": "./dist/types/src/index.d.ts",
+      "import": "./dist/esm/src/index.js",
+      "require": "./dist/cjs/src/index.js"
+    }
+  },
+  "sideEffects": false,
+  "files": [
+    "dist"
+  ],
+  "engines": {
+    "node": ">=18"
+  },
+  "scripts": {
+    "build": "bun run clean && tsc -p tsconfig.cjs.json && tsc -p tsconfig.esm.json && tsc -p tsconfig.types.json",
+    "clean": "rm -rf dist",
+    "lint": "eslint 'src/**/*.{js,ts,tsx}' --max-warnings 0",
+    "release": "changeset publish",
+    "test": "bun test"
+  },
+  "dependencies": {
+    "@ethersproject/abi": "^5.5.0",
+    "@uniswap/permit2-sdk": "workspace:*",
+    "@uniswap/sdk-core": "workspace:*",
+    "@uniswap/v2-sdk": "workspace:*",
+    "@uniswap/v3-sdk": "workspace:*",
+    "@uniswap/v4-sdk": "workspace:*",
+    "jsbi": "^3.1.4",
+    "tiny-invariant": "^1.1.0",
+    "tslib": "^2.3.0"
+  },
+  "devDependencies": {
+    "@typescript-eslint/parser": "^5.0.0",
+    "eslint": "^8.57.0",
+    "eslint-config-prettier": "^9.1.0",
+    "eslint-config-react-app": "7.0.1",
+    "eslint-plugin-prettier": "^3.4.1",
+    "prettier": "^2.4.1",
+    "typescript": "^4.3.3"
+  },
+  "prettier": {
+    "printWidth": 120,
+    "semi": false,
+    "singleQuote": true
+  },
+  "publishConfig": {
+    "access": "public",
+    "provenance": true
+  }
+}

sdks/lp-sdk/src/constants.ts

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+import { Percent } from '@uniswap/sdk-core'
+
+/**
+ * Default slippage tolerance applied when none is provided. Matches the default used
+ * by the Uniswap Labs liquidity service so estimates line up with the transactions
+ * users actually sign.
+ */
+export const DEFAULT_LP_SLIPPAGE_TOLERANCE = new Percent(250, 10_000) // 2.5%
+
+/**
+ * Default slippage tolerance for v4 pools with a native currency side. Matches the
+ * Uniswap Labs liquidity service default for native v4 pools.
+ */
+export const DEFAULT_NATIVE_V4_SLIPPAGE_TOLERANCE = new Percent(5, 10_000) // 0.05%

sdks/lp-sdk/src/index.ts

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+export { DEFAULT_LP_SLIPPAGE_TOLERANCE, DEFAULT_NATIVE_V4_SLIPPAGE_TOLERANCE } from './constants'
+export type { LpGasEstimateTransaction, Permit2AllowanceInput, TokenAllowanceInput } from './types'
+export { pickPreEstimateIndependentAmount } from './utils/pickPreEstimateIndependentAmount'
+export { getV2AddLiquidityGasEstimateTransactions } from './v2'
+export type { V2AddLiquidityGasEstimateParams } from './v2'
+export { getV3AddLiquidityGasEstimateTransactions } from './v3'
+export type { V3AddLiquidityGasEstimateParams } from './v3'
+export { getV4AddLiquidityGasEstimateTransactions } from './v4'
+export type { V4AddLiquidityGasEstimateParams } from './v4'

sdks/lp-sdk/src/types.ts

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+import { BigintIsh } from '@uniswap/sdk-core'
+
+/**
+ * A transaction to include in a gas-estimation batch.
+ *
+ * The SDK never talks to the chain: callers run `eth_estimateGas` over the returned
+ * list (in order, from the position owner's address) with their own client and sum
+ * the results to get the full cost of the flow.
+ */
+export interface LpGasEstimateTransaction {
+  to: string
+  calldata: string
+  value: string
+}
+
+/**
+ * The caller-provided allowance state for one pool token. All fields are optional:
+ * when omitted the token is assumed to have zero allowance, which yields the
+ * worst-case (most transactions) estimate.
+ */
+export interface TokenAllowanceInput {
+  /**
+   * Current ERC-20 allowance granted by the wallet to the relevant spender
+   * (v2 router / v3 position manager / Permit2 for v4). Assumed 0 when omitted.
+   */
+  allowance?: BigintIsh
+  /**
+   * USDT-style tokens revert on approve when the current allowance is non-zero, so
+   * they need an approve(0) reset transaction first. Only relevant when `allowance`
+   * is non-zero but insufficient.
+   */
+  requiresReset?: boolean
+}
+
+/**
+ * Allowance state for one pool token in a v4 flow, which pulls funds through Permit2.
+ */
+export interface Permit2AllowanceInput extends TokenAllowanceInput {
+  /**
+   * Current Permit2 allowance (token -> position manager) for the wallet. Assumed
+   * absent when omitted. The allowance counts as active when `amount` covers the
+   * required amount and `expiration` is at or after the flow's `deadline`.
+   */
+  permit2Allowance?: {
+    amount: BigintIsh
+    expiration: BigintIsh
+  }
+}