// Copyright (c) 2017, the Dart project authors.  Please see the AUTHORS file
// for details. All rights reserved. Use of this source code is governed by a
// BSD-style license that can be found in the LICENSE file.

/// Standalone utility that manages loading source maps for all Dart scripts
/// on the page compiled with DDC.
///
/// Example JavaScript usage:
///
/// ```js
/// $dartStackTraceUtility.setSourceMapProvider(function(modulePath) {
///   return dartDevEmbedder.debugger.getSourceMap(modulePath);
/// });
/// ```
///
/// If `$dartStackTraceUtility` is set, the dart:core StackTrace class calls
/// `$dartStackTraceUtility.mapper(someJSStackTrace)`
/// to apply source maps.
///
/// This utility can be compiled to JavaScript using Dart2JS while the rest
/// of the application is compiled with DDC or could be compiled with DDC.
library;

import 'dart:js_interop';

import 'package:path/path.dart' as p;
import 'package:source_maps/source_maps.dart';
import 'package:source_span/source_span.dart';
import 'package:stack_trace/stack_trace.dart';

import 'source_map_stack_trace.dart';

/// Global object DDC uses to see if a stack trace utility has been registered.
@JS(r'$dartStackTraceUtility')
external set dartStackTraceUtility(DartStackTraceUtility value);

@JS(r'$dartLoader.rootDirectories')
external JSArray<JSString> get _rootDirectories;

typedef SourceMapProvider = JSAny? Function(String modulePath);

extension type DartStackTraceUtility._(JSObject _) implements JSObject {
  external factory DartStackTraceUtility({
    required JSFunction<String Function(String rawStackTrace)> mapper,
    required JSFunction<void Function(JSFunction<SourceMapProvider>)>
    setSourceMapProvider,
  });
}

@JS('JSON.stringify')
external String _stringify(JSAny? json);

/// Source mapping that waits to parse source maps until they match the uri
/// of a requested source map.
///
/// This improves startup performance compared to using MappingBundle directly.
/// The unparsed data for the source maps must still be loaded before
/// LazyMapping is used.
class LazyMapping extends Mapping {
  final MappingBundle _bundle = MappingBundle();
  final SourceMapProvider _provider;

  LazyMapping(this._provider);

  List toJson() => _bundle.toJson();

  @override
  SourceMapSpan? spanFor(
    int line,
    int column, {
    Map<String, SourceFile>? files,
    String? uri,
  }) {
    if (uri == null) {
      throw ArgumentError.notNull('uri');
    }

    if (!_bundle.containsMapping(uri)) {
      var rawMap = _provider(uri);
      if (rawMap != null) {
        var strMap = rawMap.isA<JSString>()
            ? (rawMap as JSString).toDart
            : _stringify(rawMap);
        var mapping = parse(strMap) as SingleMapping;
        mapping
          ..targetUrl = uri
          ..sourceRoot = '${p.dirname(uri)}/';
        _bundle.addMapping(mapping);
      }
    }
    var span = _bundle.spanFor(line, column, files: files, uri: uri);
    // TODO(jacobr): we shouldn't have to filter out invalid sourceUrl entries
    // here.
    if (span == null || span.start.sourceUrl == null) return null;
    var pathSegments = span.start.sourceUrl!.pathSegments;
    if (pathSegments.isNotEmpty && pathSegments.last == 'null') return null;
    return span;
  }
}

LazyMapping? _mapping;

final List<String> roots = _rootDirectories.toDart
    .map((s) => s.toDart)
    .toList();

String mapper(String rawStackTrace) {
  var mapping = _mapping;
  if (mapping == null) {
    // This shouldn't happen if `setSourceMapProvider` was called
    // before the application was started.
    throw StateError('Source maps are not done loading.');
  }
  var trace = Trace.parse(rawStackTrace);
  return mapStackTrace(mapping, trace, roots: roots).toString();
}

void setSourceMapProvider(JSFunction<SourceMapProvider> provider) {
  _mapping = LazyMapping(
    (modulePath) => provider.callAsFunction(null, modulePath.toJS),
  );
}

void main() {
  // Register with DDC.
  dartStackTraceUtility = DartStackTraceUtility(
    mapper: mapper.toJS,
    setSourceMapProvider: setSourceMapProvider.toJS,
  );
}