// Copyright Amazon.com, Inc. or its affiliates. All Rights Reserved.
// SPDX-License-Identifier: Apache-2.0

import 'package:code_builder/code_builder.dart';
import 'package:smithy_codegen/smithy_codegen.dart';
import 'package:smithy_codegen/src/generator/types.dart';

/// Operates similar to [Allocator.simplePrefixing], prefixing symbols using
/// a simple incrementor.
///
/// Unlike [Allocator.simplePrefixing], though, it accepts a [library] parameter
/// so that references to values in the same file are not prefixed.
class SmithyAllocator implements Allocator {
  SmithyAllocator(
    this.library,
    this.smithyLibrary, {
    this.withPrefixing = true,
  });

  final bool withPrefixing;

  /// Prefixing core makes things messy, although it does require escaping all
  /// core names.
  ///
  /// Some libraries like `built_value` do not like to be prefixed (their code
  /// generator will simply not work).
  static const _doNotPrefix = [
    'dart:core',
    BuiltValueType.mainUrl,
    BuiltValueType.serializerUrl,
    ShelfRouter.url,
  ];

  /// Tracks dependencies by looking at the packages we import.
  final dependencies = <String>{};

  final _imports = <String, int>{};
  var _keys = 1;

  final Library library;
  final SmithyLibrary smithyLibrary;

  /// The URL for the [library] being generated.
  String? get libraryUrl {
    if (smithyLibrary.libraryType == SmithyLibrary_LibraryType.TEST) {
      return null;
    }
    return 'package:${smithyLibrary.packageName}/${smithyLibrary.libRelativePath}';
  }

  /// Gets the package name from a [url].
  String packageName(String url) =>
      url.substring('package:'.length).split('/').first;

  @override
  String allocate(Reference reference) {
    final symbol = reference.symbol;
    final url = reference.url;
    final thisLibrary = libraryUrl;
    if (url == null || url == thisLibrary) {
      return symbol!;
    }

    // Track dependencies via the URLs we import
    if (thisLibrary != null) {
      final thisPackage = packageName(thisLibrary);
      if (!url.startsWith('dart:')) {
        final package = packageName(url);
        if (package != thisPackage) {
          dependencies.add(package);
        }
      }
    }

    if (!withPrefixing || _doNotPrefix.contains(url)) {
      _imports[url] = -1;
      return symbol!;
    }
    // if (url == 'dart:core') {
    //   return '_i${_imports[url] = 0}.$symbol';
    // }
    return '_i${_imports.putIfAbsent(url, _nextKey)}.$symbol';
  }

  int _nextKey() => _keys++;

  @override
  Iterable<Directive> get imports =>
      _imports.keys.where((key) => key != 'dart:core').map(
            (u) => Directive.import(
              u,
              as: !withPrefixing || _doNotPrefix.contains(u)
                  ? null
                  : '_i${_imports[u]}',
            ),
          );
}