/**
 * Copyright (c) Meta Platforms, Inc. and affiliates.
 *
 * This source code is licensed under the MIT license found in the
 * LICENSE file in the root directory of this source tree.
 *
 * @flow strict-local
 * @format
 * @oncall react_native
 */

'use strict';

import type {PluginObj} from '@babel/core';
import typeof * as Types from '@babel/types';
import type {MetroBabelFileMetadata} from 'metro-babel-transformer';

const invariant = require('invariant');

type ImportDeclarationLocs = Set<string>;

function importLocationsPlugin({types: t}: {types: Types, ...}): PluginObj<> {
  const importDeclarationLocs: ImportDeclarationLocs = new Set();
  return {
    visitor: {
      ImportDeclaration(path) {
        if (
          // Ignore type imports
          path.node.importKind !== 'type' &&
          // loc may not be set if this plugin runs alongside others which
          // inject imports - eg Babel runtime helpers. We don't regard these
          // as source import declarations.
          path.node.loc != null
        ) {
          importDeclarationLocs.add(locToKey(path.node.loc));
        }
      },
      ExportDeclaration(path) {
        if (
          // If `source` is set, this is a re-export, so it declares an ESM
          // dependency.
          path.node.source != null &&
          // Ignore type exports
          path.node.exportKind !== 'type' &&
          // As above, ignore injected imports.
          path.node.loc != null
        ) {
          importDeclarationLocs.add(locToKey(path.node.loc));
        }
      },
    },
    pre: ({path, metadata}) => {
      invariant(
        path && t.isProgram(path.node),
        'path missing or not a program node',
      );

      // $FlowFixMe[prop-missing] Babel `File` is not generically typed
      const metroMetadata: MetroBabelFileMetadata = metadata;

      // Set the result on a metadata property
      if (!metroMetadata.metro) {
        metroMetadata.metro = {
          unstable_importDeclarationLocs: importDeclarationLocs,
        };
      } else {
        metroMetadata.metro.unstable_importDeclarationLocs =
          importDeclarationLocs;
      }
    },
  };
}

// Very simple serialisation of a source location. This should remain opaque to
// the caller.
const MISSING_LOC = {line: -1, column: -1};
function locToKey(loc: BabelSourceLocation): string {
  const {start = MISSING_LOC, end = MISSING_LOC} = loc;
  return `${start.line},${start.column}:${end.line},${end.column}`;
}

module.exports = {importLocationsPlugin, locToKey};