init

.editiorconfig

@@ -0,0 +1,13 @@
+# editorconfig.org
+root = true
+
+[*]
+indent_style = space
+indent_size = 2
+end_of_line = lf
+charset = utf-8
+trim_trailing_whitespace = true
+insert_final_newline = true
+
+[*.md]
+trim_trailing_whitespace = false

.gitignore

@@ -0,0 +1,2 @@
+node_modules
+lib

.vscode/launch.json

@@ -0,0 +1,24 @@
+{
+    // Use IntelliSense to learn about possible attributes.
+    // Hover to view descriptions of existing attributes.
+    // For more information, visit: https://go.microsoft.com/fwlink/?linkid=830387
+    "version": "0.2.0",
+    "configurations": [
+        {
+            "type": "node",
+            "request": "launch",
+            "name": "Mocha Current File",
+            "program": "${workspaceFolder}/node_modules/mocha/bin/_mocha",
+            "args": [
+              "--no-timeouts",
+              "--colors",
+              "${file}",
+              "--require",
+              "ts-node/register"
+            ],
+            "console": "integratedTerminal",
+            "sourceMaps": true,
+            "internalConsoleOptions": "neverOpen"
+      }
+    ]
+}

README.md

@@ -0,0 +1,14 @@
+# Gas Price Oracle library for Ethereum dApps
+
+## Instalation
+`npm i gas-price-oracle`
+
+## Usage
+```js
+const { GasPriceOracle } = require('gas-price-oracle');
+const oracle = new GasPriceOracle();
+
+oracle.fetchGasPrices().then((gas) => {
+    console.log(gas)
+});
+```

package.json

@@ -0,0 +1,34 @@
+{
+  "name": "gas-price-oracle",
+  "version": "1.0.0",
+  "description": "Gas Price Oracle library for Ethereum dApps.",
+  "main": "lib/index.js",
+  "types": "lib/index.d.ts",
+  "prepare": "npm run build",
+  "prepublishOnly": "npm run lint",
+  "scripts": {
+    "test": "mocha -r ts-node/register tests/*.test.ts",
+    "build": "tsc",
+    "lint": "tslint -p tsconfig.json"
+  },
+  "author": "Alexey Pertsev <alexey@peppersec.com> (https://peppersec.com)",
+  "license": "MIT",
+  "devDependencies": {
+    "@types/chai": "^4.2.11",
+    "@types/mocha": "^7.0.2",
+    "chai": "^4.2.0",
+    "mocha": "^7.2.0",
+    "tslint": "^6.1.2",
+    "tslint-config-standard": "^9.0.0"
+  },
+  "dependencies": {
+    "@types/node": "^14.0.5",
+    "@types/node-fetch": "^2.5.7",
+    "node-fetch": "^2.6.0",
+    "ts-node": "^8.10.1",
+    "typescript": "^3.9.3"
+  },
+  "files": [
+    "lib/**/*"
+  ]
+}

src/config.ts

@@ -0,0 +1,28 @@
+
+import { Oracle } from './types';
+
+const ethgasstation: Oracle = {
+  name: 'ethgasstation',
+  url: 'https://ethgasstation.info/json/ethgasAPI.json',
+  instantPropertyName: 'fastest',
+  fastPropertyName: 'fast',
+  standardPropertyName: 'average',
+  lowPropertyName: 'safeLow',
+  denominator: 10
+};
+
+const zoltu: Oracle = {
+  name: 'zoltu',
+  url: 'https://gas-oracle.zoltu.io/',
+  instantPropertyName: 'percentile_99',
+  fastPropertyName: 'percentile_90',
+  standardPropertyName: 'percentile_60',
+  lowPropertyName: 'percentile_30',
+  denominator: 1
+};
+
+export default {
+  oracles: [
+    ethgasstation, zoltu
+  ]
+};

src/index.ts

@@ -0,0 +1,44 @@
+import fetch from 'node-fetch';
+import config from './config';
+import { GasPrice, Oracle } from './types';
+
+export class GasPriceOracle {
+  lastGasPrice: GasPrice = {
+    instant: 40,
+    fast: 21,
+    standard: 10,
+    low: 1
+  };
+
+  async fetchGasPrices(): Promise<GasPrice> {
+    for (let oracle of config.oracles) {
+      const { name, url, instantPropertyName, fastPropertyName, standardPropertyName, lowPropertyName, denominator } = oracle;
+      try {
+        const response = await fetch(url);
+        if (response.status === 200) {
+          const gas = await response.json();
+          if (Number(gas[fastPropertyName]) === 0) {
+            throw new Error(`${name} oracle provides corrupted values`);
+          }
+          const gasPrices: GasPrice = {
+            instant: parseFloat(gas[instantPropertyName]) / denominator,
+            fast: parseFloat(gas[fastPropertyName]) / denominator,
+            standard: parseFloat(gas[standardPropertyName]) / denominator,
+            low: parseFloat(gas[lowPropertyName]) / denominator
+          };
+          this.lastGasPrice = gasPrices;
+        } else {
+          throw new Error(`Fetch gasPrice from ${name} oracle failed. Trying another one...`);
+        }
+      } catch (e) {
+        console.error(e.message);
+      }
+    }
+    // TODO: additional arg `throwIfFailsToFetch` that throws if it fails to fetch from all oracles
+    return this.lastGasPrice;
+  }
+
+  addOracle(oracle: Oracle) {
+    config.oracles.push(oracle);
+  }
+}

src/types.ts

@@ -0,0 +1,16 @@
+export type Oracle = {
+  name: string
+  url: string
+  instantPropertyName: string,
+  fastPropertyName: string,
+  standardPropertyName: string,
+  lowPropertyName: string,
+  denominator: number
+};
+
+export type GasPrice = {
+  instant: number;
+  fast: number;
+  standard: number;
+  low: number;
+};

tests/index.test.ts

@@ -0,0 +1,10 @@
+import { GasPriceOracle } from '../src/index';
+import { GasPrice } from '../src/types';
+
+describe('Get gas price', function () {
+  it('should work', async function () {
+    const oracle = new GasPriceOracle();
+    const gas: GasPrice = await oracle.fetchGasPrices();
+    console.log(gas);
+  });
+});

tsconfig.json

@@ -0,0 +1,71 @@
+{
+  "compilerOptions": {
+    /* Basic Options */
+    "target": "es2017" /* Specify ECMAScript target version: 'ES3' (default), 'ES5', 'ES2015', 'ES2016', 'ES2017','ES2018' or 'ESNEXT'. */,
+    "module": "commonjs" /* Specify module code generation: 'none', 'commonjs', 'amd', 'system', 'umd', 'es2015', or 'ESNext'. */,
+    "lib": [
+      "es2017",
+      "esnext.asynciterable",
+      "es2019"
+      ] /* Specify library files to be included in the compilation. */,
+    "outDir": "./lib",                        /* Redirect output structure to the directory. */
+    "strict": true /* Enable all strict type-checking options. */,
+    "strictPropertyInitialization": false /* Enable strict checking of property initialization in classes. */,
+    "esModuleInterop": true /* Enables emit interoperability between CommonJS and ES Modules via creation of namespace objects for all imports. Implies 'allowSyntheticDefaultImports'. */,
+    "declaration": true,                   /* Generates corresponding '.d.ts' file. */
+    // "allowJs": true,                       /* Allow javascript files to be compiled. */
+    // "checkJs": true,                       /* Report errors in .js files. */
+    // "jsx": "preserve",                     /* Specify JSX code generation: 'preserve', 'react-native', or 'react'. */
+    // "declarationMap": true,                /* Generates a sourcemap for each corresponding '.d.ts' file. */
+    // "sourceMap": true,                     /* Generates corresponding '.map' file. */
+    // "outFile": "./",                       /* Concatenate and emit output to single file. */
+    // "rootDir": "./",                       /* Specify the root directory of input files. Use to control the output directory structure with --outDir. */
+    // "composite": true,                     /* Enable project compilation */
+    // "removeComments": true,                /* Do not emit comments to output. */
+    // "noEmit": true,                        /* Do not emit outputs. */
+    // "importHelpers": true,                 /* Import emit helpers from 'tslib'. */
+    // "downlevelIteration": true,            /* Provide full support for iterables in 'for-of', spread, and destructuring when targeting 'ES5' or 'ES3'. */
+    // "isolatedModules": true,               /* Transpile each file as a separate module (similar to 'ts.transpileModule'). */
+
+    /* Strict Type-Checking Options */
+    // "noImplicitAny": true,                 /* Raise error on expressions and declarations with an implied 'any' type. */
+    // "strictNullChecks": true,              /* Enable strict null checks. */
+    // "strictFunctionTypes": true,           /* Enable strict checking of function types. */
+    // "strictBindCallApply": true,           /* Enable strict 'bind', 'call', and 'apply' methods on functions. */
+    // "noImplicitThis": true,                /* Raise error on 'this' expressions with an implied 'any' type. */
+    // "alwaysStrict": true,                  /* Parse in strict mode and emit "use strict" for each source file. */
+
+    /* Additional Checks */
+    // "noUnusedLocals": true,                /* Report errors on unused locals. */
+    // "noUnusedParameters": true,            /* Report errors on unused parameters. */
+    // "noImplicitReturns": true,             /* Report error when not all code paths in function return a value. */
+    // "noFallthroughCasesInSwitch": true,    /* Report errors for fallthrough cases in switch statement. */
+
+    /* Module Resolution Options */
+    // "moduleResolution": "node",            /* Specify module resolution strategy: 'node' (Node.js) or 'classic' (TypeScript pre-1.6). */
+    // "baseUrl": "./",                       /* Base directory to resolve non-absolute module names. */
+    // "paths": {},                           /* A series of entries which re-map imports to lookup locations relative to the 'baseUrl'. */
+    // "rootDirs": [],                        /* List of root folders whose combined content represents the structure of the project at runtime. */
+    // "typeRoots": [],                       /* List of folders to include type definitions from. */
+    // "types": [],                           /* Type declaration files to be included in compilation. */
+    // "allowSyntheticDefaultImports": true,  /* Allow default imports from modules with no default export. This does not affect code emit, just typechecking. */
+    // "preserveSymlinks": true,              /* Do not resolve the real path of symlinks. */
+
+    /* Source Map Options */
+    // "sourceRoot": "",                      /* Specify the location where debugger should locate TypeScript files instead of source locations. */
+    // "mapRoot": "",                         /* Specify the location where debugger should locate map files instead of generated locations. */
+    // "inlineSourceMap": true,               /* Emit a single file with source maps instead of having a separate file. */
+    // "inlineSources": true,                 /* Emit the source alongside the sourcemaps within a single file; requires '--inlineSourceMap' or '--sourceMap' to be set. */
+
+    /* Experimental Options */
+    "experimentalDecorators": true /* Enables experimental support for ES7 decorators. */,
+    "emitDecoratorMetadata": true /* Enables experimental support for emitting type metadata for decorators. */,
+    "plugins": [
+      {
+        "name": "typescript-tslint-plugin"
+      }
+    ]
+  },
+  "include": ["src"],
+  "exclude": ["node_modules", "tests"]
+}

tslint.json

@@ -0,0 +1,9 @@
+{
+  "extends": "tslint-config-standard",
+  "defaultSeverity": "error",
+  "rules": {
+    "semicolon": [true, "always"],
+    "space-before-function-paren": [true, {"anonymous": "always", "named": "never", "asyncArrow": "always"}]
+  }
+}
+