// 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.

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

/// This is a fork of package:source_map_stack_trace, a tool for
/// dart2js-compiled code, reworked for DDC.

/// Convert [stackTrace], a stack trace generated by DDC-compiled
/// JavaScript, to a native-looking stack trace using [sourceMap].
///
/// [roots] are the paths (usually `http:` URI strings) that DDC applications
/// are served from.  This is used to identify sdk and package URIs.
StackTrace mapStackTrace(
  Mapping sourceMap,
  StackTrace stackTrace, {
  required List<String?> roots,
}) {
  if (stackTrace is Chain) {
    return Chain(
      stackTrace.traces.map((trace) {
        return Trace.from(mapStackTrace(sourceMap, trace, roots: roots));
      }),
    );
  }

  var trace = Trace.from(stackTrace);
  return Trace(
    trace.frames.map((frame) {
      // If there's no line information, there's no way to translate this frame.
      // We could return it as-is, but these lines are usually not useful anyways.
      if (frame.line == null) return null;

      // If there's no column, try using the first column of the line.
      var column = frame.column ?? 0;

      // Subtract 1 because stack traces use 1-indexed lines and columns and
      // source maps uses 0-indexed.
      var span = sourceMap.spanFor(
        frame.line! - 1,
        column - 1,
        uri: frame.uri.toString(),
      );

      // If we can't find a source span, ignore the frame. It's probably something
      // internal that the user doesn't care about.
      if (span == null) return null;

      var sourceUrl = span.sourceUrl.toString();
      for (var root in roots) {
        if (root != null && p.url.isWithin(root, sourceUrl)) {
          var relative = p.url.relative(sourceUrl, from: root);
          if (relative.contains('dart:')) {
            sourceUrl = relative.substring(relative.indexOf('dart:'));
            break;
          }
          var packageRoot = '$root/packages';
          if (p.url.isWithin(packageRoot, sourceUrl)) {
            sourceUrl =
                'package:${p.url.relative(sourceUrl, from: packageRoot)}';
            break;
          }
        }
      }

      if (!sourceUrl.startsWith('dart:') &&
          !sourceUrl.startsWith('package:') &&
          sourceUrl.contains('dart_sdk')) {
        // This compresses the long dart_sdk URLs if SDK source maps are missing.
        // It's no longer linkable, but neither are the properly mapped ones
        // above.
        sourceUrl = 'dart:sdk_internal';
      }

      return Frame(
        Uri.parse(sourceUrl),
        span.start.line + 1,
        span.start.column + 1,
        _prettifyMember(frame.member!),
      );
    }).nonNulls,
  );
}

final escapedPipe = '\$124';
final escapedPound = '\$35';

/// Reformats a JS member name to make it look more Dart-like.
///
/// Logic copied from build/build_web_compilers/web/stack_trace_mapper.dart.
/// TODO(https://github.com/dart-lang/sdk/issues/38869): Remove this logic when
/// DDC stack trace deobfuscation is overhauled.
String _prettifyMember(String member) {
  var last = member.lastIndexOf('.');
  if (last < 0) return member;
  var suffix = member.substring(last + 1);
  member = suffix == 'fn' ? member : suffix;
  // We avoid unescaping the entire member here due to DDC's deduping mechanism
  // introducing trailing $N.
  member = member.replaceAll(escapedPipe, '|');
  return member.contains('|') ? _prettifyExtension(member) : member;
}

/// Reformats a JS member name as an extension method invocation.
String _prettifyExtension(String member) {
  var isSetter = false;
  var pipeIndex = member.indexOf('|');
  var spaceIndex = member.indexOf(' ');
  var poundIndex = member.indexOf('escapedPound');
  if (spaceIndex >= 0) {
    // Here member is a static field or static getter/setter.
    isSetter = member.substring(0, spaceIndex) == 'set';
    member = member.substring(spaceIndex + 1, member.length);
  } else if (poundIndex >= 0) {
    // Here member is a tearoff or local property getter/setter.
    isSetter = member.substring(pipeIndex + 1, poundIndex) == 'set';
    member = member.replaceRange(pipeIndex + 1, poundIndex + 3, '');
  } else {
    var body = member.substring(pipeIndex + 1, member.length);
    if (body.startsWith('unary') || body.startsWith('\$')) {
      // Here member's an operator, so it's safe to unescape everything lazily.
      member = _unescape(member);
    }
  }
  member = member.replaceAll('|', '.');
  return isSetter ? '$member=' : member;
}

/// Unescapes a DDC-escaped JS identifier name.
///
/// Identifier names that contain illegal JS characters are escaped by DDC to a
/// decimal representation of the symbol's UTF-16 value.
/// Warning: this greedily escapes characters, so it can be unsafe in the event
/// that an escaped sequence precedes a number literal in the JS name.
String _unescape(String name) {
  return name.replaceAllMapped(
    RegExp(r'\$[0-9]+'),
    (m) => String.fromCharCode(int.parse(name.substring(m.start + 1, m.end))),
  );
}