eslint.config.js

const tsParser = require('@typescript-eslint/parser');
const tsPlugin = require('@typescript-eslint/eslint-plugin');
const prettierPlugin = require('eslint-plugin-prettier');
const prettierConfig = require('eslint-config-prettier');

/**
 * ESLint v9 flat config.
 * Lints TypeScript sources in branches-api and functions.
 */
module.exports = [
  {
    ignores: ['**/node_modules/**', '**/dist/**', '**/coverage/**'],
  },
  {
    files: ['**/*.ts'],
    languageOptions: {
      parser: tsParser,
      ecmaVersion: 2022,
      sourceType: 'commonjs',
    },
    plugins: {
      '@typescript-eslint': tsPlugin,
      prettier: prettierPlugin,
    },
    rules: {
      ...tsPlugin.configs.recommended.rules,
      ...prettierConfig.rules,

      // Prefer TS-aware unused-vars and allow underscore-prefixed unused params.
      'no-unused-vars': 'off',
      '@typescript-eslint/no-unused-vars': [
        'error',
        { argsIgnorePattern: '^_', varsIgnorePattern: '^_' },
      ],

      // Formatting is enforced via Prettier.
      'prettier/prettier': 'error',

      // Pragmatic for an interview task.
      '@typescript-eslint/no-explicit-any': 'off',
    },
  },
];