Initial commit with contracts and boilerplate files

.eslintignore

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+node_modules
+.env
+dist
+
+# Hardhat files
+/cache
+/artifacts
+
+# TypeChain files
+/typechain
+/typechain-types
+
+# solidity-coverage files
+/coverage
+/coverage.json
+
+gas_report
+
+contracts/vendor

.eslintrc.js

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+module.exports = {
+  extends: ['plugin:@api3/eslint-plugin-commons/universal', 'plugin:@api3/eslint-plugin-commons/jest'],
+  parserOptions: {
+    project: ['./tsconfig.json'],
+  },
+  rules: {
+    camelcase: 'off',
+    'no-nested-ternary': 'off',
+
+    'functional/no-try-statements': 'off',
+
+    'jest/no-conditional-in-test': 'off',
+
+    'lodash/prefer-constant': 'off',
+    'lodash/prefer-lodash-typecheck': 'off',
+    'lodash/prefer-noop': 'off',
+
+    'unicorn/filename-case': 'off',
+    'unicorn/no-anonymous-default-export': 'off',
+    'unicorn/prefer-export-from': 'off',
+    'unicorn/prefer-object-from-entries': 'off',
+    'unicorn/prefer-ternary': 'off',
+
+    '@typescript-eslint/max-params': 'off',
+    '@typescript-eslint/no-unnecessary-type-assertion': 'off',
+    '@typescript-eslint/no-unsafe-call': 'off',
+    '@typescript-eslint/require-await': 'off',
+  },
+};

.github/config/linkspector.yml

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+aliveStatusCodes:
+  - 200
+  - 406
+dirs:
+  - .
+  - .github
+useGitIgnore: true

.github/workflows/check-md-links.yml

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+name: Check Markdown links
+
+on: push
+
+jobs:
+  check-md-links:
+    runs-on: ubuntu-latest
+    steps:
+      - name: Clone @api3/data-feed-proxy-combinators
+        uses: actions/checkout@v4
+      - name: Check Markdown links
+        uses: umbrelladocs/action-linkspector@v1
+        with:
+          reporter: github-pr-review
+          config_file: .github/config/linkspector.yml
+          fail_on_error: true

.github/workflows/continuous-build.yml

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+name: Continuous build
+
+on:
+  push:
+    branches:
+      - main
+  pull_request:
+    branches:
+      - main
+
+jobs:
+  lint-build-test:
+    runs-on: ubuntu-latest
+    steps:
+      - name: Clone @api3/data-feed-proxy-combinators
+        uses: actions/checkout@v4
+
+      - name: Set up pnpm
+        uses: pnpm/action-setup@v3
+
+      - name: Set up Node
+        uses: actions/setup-node@v4
+        with:
+          node-version: '20.17.0'
+          cache: 'pnpm'
+
+      - name: Install dependencies
+        run: pnpm install
+
+      - name: Lint
+        run: pnpm lint
+
+      - name: Build
+        run: pnpm build
+
+      - name: Verify vendor contracts
+        run: pnpm verify-vendor-contracts
+
+      - name: Test
+        run: pnpm test

.gitignore

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+node_modules
+.env
+dist
+
+# Hardhat files
+/cache
+/artifacts
+
+# TypeChain files
+/typechain
+/typechain-types
+
+# solidity-coverage files
+/coverage
+/coverage.json
+
+gas_report

.prettierignore

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+node_modules
+.env
+dist
+
+# Hardhat files
+/cache
+/artifacts
+
+# TypeChain files
+/typechain
+/typechain-types
+
+# solidity-coverage files
+/coverage
+/coverage.json
+
+gas_report
+
+contracts/vendor

.prettierrc

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+{
+  "bracketSpacing": true,
+  "printWidth": 120,
+  "singleQuote": true,
+  "trailingComma": "es5",
+  "useTabs": false,
+  "plugins": ["prettier-plugin-solidity"],
+  "overrides": [
+    {
+      "files": "*.md",
+      "options": {
+        "parser": "markdown"
+      }
+    },
+    {
+      "files": "*.sol",
+      "options": {
+        "parser": "antlr",
+        "printWidth": 80,
+        "tabWidth": 4,
+        "useTabs": false,
+        "singleQuote": false,
+        "bracketSpacing": false
+      }
+    }
+  ]
+}

.solcover.js

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+module.exports = {
+  skipFiles: ['mock', 'test', 'vendor'],
+};

.solhint.json

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+{
+  "extends": "solhint:recommended",
+  "rules": {
+    "compiler-version": "off",
+    "func-visibility": ["warn", { "ignoreConstructors": true }],
+    "not-rely-on-time": "off",
+    "no-empty-blocks": "off",
+    "no-global-import": "off",
+    "func-name-mixedcase": "off",
+    "immutable-vars-naming": "off",
+    "gas-custom-errors": "off"
+  }
+}

.solhintignore

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+node_modules
+.env
+dist
+
+# Hardhat files
+/cache
+/artifacts
+
+# TypeChain files
+/typechain
+/typechain-types
+
+# solidity-coverage files
+/coverage
+/coverage.json
+
+gas_report
+
+contracts/vendor

LICENSE

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+MIT License
+
+Copyright (c) 2024 API3 Foundation
+
+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.

README.md

@@ -1 +1 @@
-# data-feed-proxy-combinators
+# data-feed-proxy-combinators

contracts/InverseApi3ReaderProxyV1.sol

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+// SPDX-License-Identifier: MIT
+pragma solidity ^0.8.27;
+
+import "@api3/contracts/interfaces/IApi3ReaderProxy.sol";
+import "./interfaces/IInverseApi3ReaderProxyV1.sol";
+
+/// @title An immutable proxy contract that inverts the value returned by an
+/// IApi3ReaderProxy data feed
+/// @dev This contract implements the AggregatorV2V3Interface to be compatible
+/// with Chainlink aggregators. This allows the contract to be used as a drop-in
+/// replacement for Chainlink aggregators in existing dApps.
+/// Refer to https://github.com/api3dao/migrate-from-chainlink-to-api3 for more
+/// information about the Chainlink interface implementation.
+contract InverseApi3ReaderProxyV1 is IInverseApi3ReaderProxyV1 {
+    /// @notice IApi3ReaderProxy contract address
+    address public immutable override proxy;
+
+    /// @param proxy_ IApi3ReaderProxy contract address
+    constructor(address proxy_) {
+        if (proxy_ == address(0)) {
+            revert ZeroProxyAddress();
+        }
+        proxy = proxy_;
+    }
+
+    /// @notice Returns the inverted value of the underlying IApi3ReaderProxy
+    /// @dev This inverts the 18-decimal fixed-point value using 1e36 / value.
+    /// The operation will revert if `baseValue` is zero (division by zero) or if
+    /// `baseValue` is so small (yet non-zero) that the resulting inverted value
+    /// would overflow the `int224` type.
+    /// @return value Inverted value of the underlying proxy
+    /// @return timestamp Timestamp from the underlying proxy
+    function read()
+        public
+        view
+        override
+        returns (int224 value, uint32 timestamp)
+    {
+        (int224 baseValue, uint32 baseTimestamp) = IApi3ReaderProxy(proxy)
+            .read();
+
+        value = int224((1e36) / int256(baseValue));
+        timestamp = baseTimestamp;
+    }
+
+    /// @dev AggregatorV2V3Interface users are already responsible with
+    /// validating the values that they receive (e.g., revert if the spot price
+    /// of an asset is negative). Therefore, this contract omits validation.
+    function latestAnswer() external view override returns (int256 value) {
+        (value, ) = read();
+    }
+
+    /// @dev A Chainlink feed contract returns the block timestamp at which the
+    /// feed was last updated. On the other hand, an Api3 feed timestamp
+    /// denotes the point in time at which the first-party oracles signed the
+    /// data used to do the last update. We find this to be a reasonable
+    /// approximation, considering that usually the timestamp is only used to
+    /// check if the last update is stale.
+    function latestTimestamp()
+        external
+        view
+        override
+        returns (uint256 timestamp)
+    {
+        (, timestamp) = read();
+    }
+
+    /// @dev Api3 feeds are updated asynchronously and not in rounds
+    function latestRound() external pure override returns (uint256) {
+        revert FunctionIsNotSupported();
+    }
+
+    /// @dev Functions that use the round ID as an argument are not supported
+    function getAnswer(uint256) external pure override returns (int256) {
+        revert FunctionIsNotSupported();
+    }
+
+    /// @dev Functions that use the round ID as an argument are not supported
+    function getTimestamp(uint256) external pure override returns (uint256) {
+        revert FunctionIsNotSupported();
+    }
+
+    /// @dev Api3 feeds always use 18 decimals
+    function decimals() external pure override returns (uint8) {
+        return 18;
+    }
+
+    /// @dev Underlying proxy dApp ID and dAPI name act as the description, and
+    /// this is left empty to save gas on contract deployment
+    function description() external pure override returns (string memory) {
+        return "";
+    }
+
+    /// @dev A unique version is chosen to easily check if an unverified
+    /// contract that acts as a Chainlink feed is a InverseApi3ReaderProxyV1
+    function version() external pure override returns (uint256) {
+        return 4915;
+    }
+
+    /// @dev Functions that use the round ID as an argument are not supported
+    function getRoundData(
+        uint80
+    )
+        external
+        pure
+        override
+        returns (uint80, int256, uint256, uint256, uint80)
+    {
+        revert FunctionIsNotSupported();
+    }
+
+    /// @dev Rounds IDs are returned as `0` as invalid values.
+    /// Similar to `latestAnswer()`, we leave the validation of the returned
+    /// value to the caller.
+    function latestRoundData()
+        external
+        view
+        override
+        returns (
+            uint80 roundId,
+            int256 answer,
+            uint256 startedAt,
+            uint256 updatedAt,
+            uint80 answeredInRound
+        )
+    {
+        roundId = answeredInRound = 0;
+        (answer, startedAt) = read();
+        updatedAt = startedAt;
+    }
+}