import js from '@eslint/js'
import globals from 'globals'
import tseslint from 'typescript-eslint'

/**
 * ESLint configuration for the runtime SDK.
 *
 * The SDK is written in JavaScript with JSDoc types rather than TypeScript,
 * because it is served as source to be read as well as to be executed. That
 * choice drives the rule set:
 *
 *   - The rules designed for a `.ts` boundary (`explicit-module-boundary-types`)
 *     are redundant here: a JSDoc `@returns` annotation is the same information,
 *     and the linter cannot see it as an annotation.
 *   - The rules that catch real defects — floating promises, misused promises,
 *     unreachable switch cases, unused variables — stay, and are errors.
 *   - `no-console` is an error rather than a warning, because this module runs in
 *     someone else's page and must not write to their console on a path they did
 *     not ask for. The two exceptions below are deliberate diagnostics that only
 *     fire when the theme itself has already failed.
 *
 * The SDK is loaded by third-party pages, so anything it gets wrong is somebody
 * else's incident. The strictness here is proportionate to that.
 */
export default tseslint.config(
  { ignores: ['dist', 'node_modules', '*.config.js'] },
  js.configs.recommended,
  ...tseslint.configs.recommendedTypeChecked,
  ...tseslint.configs.stylisticTypeChecked,
  {
    languageOptions: {
      parserOptions: { projectService: true, tsconfigRootDir: import.meta.dirname },
      globals: { ...globals.browser, ...globals.es2022 },
    },
    plugins: { '@typescript-eslint': tseslint.plugin },
    rules: {
      // JSDoc already declares every boundary type in a JavaScript project.
      '@typescript-eslint/explicit-module-boundary-types': 'off',
      // A fetch stub that returns a Response directly has nothing to await.
      '@typescript-eslint/require-await': 'off',
      // `||` is deliberate where an empty string should fall through, which is
      // not what `??` does.
      '@typescript-eslint/prefer-nullish-coalescing': 'off',

      // --- correctness -----------------------------------------------------
      '@typescript-eslint/no-floating-promises': 'error',
      '@typescript-eslint/no-misused-promises': 'error',
      '@typescript-eslint/await-thenable': 'error',
      '@typescript-eslint/switch-exhaustiveness-check': 'error',
      // Disabled in this package. The DOM type definitions describe a fully
      // featured modern browser, but the runtime guards below exist for Safari
      // below 14 (no `MediaQueryList.addEventListener`) and for embedded
      // webviews with no `matchMedia` at all. Those guards are load-bearing for
      // the consumers this package exists to serve, and the rule reports them as
      // dead code.
      '@typescript-eslint/no-unnecessary-condition': 'off',
      '@typescript-eslint/no-unnecessary-type-assertion': 'error',
      '@typescript-eslint/consistent-type-imports': [
        'error',
        { prefer: 'type-imports', fixStyle: 'inline-type-imports' },
      ],
      '@typescript-eslint/no-unused-vars': [
        'error',
        { argsIgnorePattern: '^_', varsIgnorePattern: '^_', caughtErrors: 'none' },
      ],

      // --- host safety -----------------------------------------------------
      'no-console': ['error', { allow: ['warn', 'error'] }],
      eqeqeq: ['error', 'always', { null: 'ignore' }],
      'prefer-const': 'error',
      'no-var': 'error',
      'object-shorthand': 'error',
      // An unsubscribe function that does nothing is the correct return value
      // when there is nothing to unsubscribe from.
      '@typescript-eslint/no-empty-function': [
        'error',
        { allow: ['arrowFunctions'] },
      ],
    },
  },
  {
    // Tests build doubles that are deliberately loosely typed, and a test's
    // console output is how a failure is diagnosed.
    files: ['**/*.test.js'],
    rules: {
      '@typescript-eslint/no-explicit-any': 'off',
      '@typescript-eslint/no-unsafe-assignment': 'off',
      '@typescript-eslint/no-unsafe-member-access': 'off',
      '@typescript-eslint/no-unsafe-call': 'off',
      '@typescript-eslint/no-unsafe-return': 'off',
      '@typescript-eslint/unbound-method': 'off',
      'no-console': 'off',
    },
  },
)