// Copyright (c) 2019, 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 'errors.dart';
import 'package_config_impl.dart';
import 'util.dart';

/// The language version prior to the release of language versioning.
///
/// This is the default language version used by all packages from a
/// `.packages` file.
final LanguageVersion _languageVersion = LanguageVersion(2, 7);

/// Parses a `.packages` file into a [PackageConfig].
///
/// The [source] is the byte content of a `.packages` file, assumed to be
/// UTF-8 encoded. In practice, all significant parts of the file must be ASCII,
/// so Latin-1 or Windows-1252 encoding will also work fine.
///
/// If the file content is available as a string, its [String.codeUnits] can
/// be used as the `source` argument of this function.
///
/// The [baseLocation] is used as a base URI to resolve all relative
/// URI references against.
/// If the content was read from a file, `baseLocation` should be the
/// location of that file.
///
/// Returns a simple package configuration where each package's
/// [Package.packageUriRoot] is the same as its [Package.root]
/// and it has no [Package.languageVersion].
PackageConfig parse(
    List<int> source, Uri baseLocation, void Function(Object error) onError) {
  if (baseLocation.isScheme('package')) {
    onError(PackageConfigArgumentError(
        baseLocation, 'baseLocation', 'Must not be a package: URI'));
    return PackageConfig.empty;
  }
  var index = 0;
  var packages = <Package>[];
  var packageNames = <String>{};
  while (index < source.length) {
    var ignoreLine = false;
    var start = index;
    var separatorIndex = -1;
    var end = source.length;
    var char = source[index++];
    if (char == $cr || char == $lf) {
      continue;
    }
    if (char == $colon) {
      onError(PackageConfigFormatException(
          'Missing package name', source, index - 1));
      ignoreLine = true; // Ignore if package name is invalid.
    } else {
      ignoreLine = char == $hash; // Ignore if comment.
    }
    var queryStart = -1;
    var fragmentStart = -1;
    while (index < source.length) {
      char = source[index++];
      if (char == $colon && separatorIndex < 0) {
        separatorIndex = index - 1;
      } else if (char == $cr || char == $lf) {
        end = index - 1;
        break;
      } else if (char == $question && queryStart < 0 && fragmentStart < 0) {
        queryStart = index - 1;
      } else if (char == $hash && fragmentStart < 0) {
        fragmentStart = index - 1;
      }
    }
    if (ignoreLine) continue;
    if (separatorIndex < 0) {
      onError(
          PackageConfigFormatException("No ':' on line", source, index - 1));
      continue;
    }
    var packageName = String.fromCharCodes(source, start, separatorIndex);
    var invalidIndex = checkPackageName(packageName);
    if (invalidIndex >= 0) {
      onError(PackageConfigFormatException(
          'Not a valid package name', source, start + invalidIndex));
      continue;
    }
    if (queryStart >= 0) {
      onError(PackageConfigFormatException(
          'Location URI must not have query', source, queryStart));
      end = queryStart;
    } else if (fragmentStart >= 0) {
      onError(PackageConfigFormatException(
          'Location URI must not have fragment', source, fragmentStart));
      end = fragmentStart;
    }
    var packageValue = String.fromCharCodes(source, separatorIndex + 1, end);
    Uri packageLocation;
    try {
      packageLocation = Uri.parse(packageValue);
    } on FormatException catch (e) {
      onError(PackageConfigFormatException.from(e));
      continue;
    }
    var relativeRoot = !hasAbsolutePath(packageLocation);
    packageLocation = baseLocation.resolveUri(packageLocation);
    if (packageLocation.isScheme('package')) {
      onError(PackageConfigFormatException(
          'Package URI as location for package', source, separatorIndex + 1));
      continue;
    }
    var path = packageLocation.path;
    if (!path.endsWith('/')) {
      path += '/';
      packageLocation = packageLocation.replace(path: path);
    }
    if (packageNames.contains(packageName)) {
      onError(PackageConfigFormatException(
          'Same package name occurred more than once', source, start));
      continue;
    }
    var rootUri = packageLocation;
    if (path.endsWith('/lib/')) {
      // Assume default Pub package layout. Include package itself in root.
      rootUri =
          packageLocation.replace(path: path.substring(0, path.length - 4));
    }
    var package = SimplePackage.validate(packageName, rootUri, packageLocation,
        _languageVersion, null, relativeRoot, (error) {
      if (error is ArgumentError) {
        onError(PackageConfigFormatException(error.message.toString(), source));
      } else {
        onError(error);
      }
    });
    if (package != null) {
      packages.add(package);
      packageNames.add(packageName);
    }
  }
  return SimplePackageConfig(1, packages, null, onError);
}

/// Writes the configuration to a [StringSink].
///
/// If [comment] is provided, the output will contain this comment
/// with `# ` in front of each line.
/// Lines are defined as ending in line feed (`'\n'`). If the final
/// line of the comment doesn't end in a line feed, one will be added.
///
/// If [baseUri] is provided, package locations will be made relative
/// to the base URI, if possible, before writing.
void write(StringSink output, PackageConfig config,
    {Uri? baseUri, String? comment}) {
  if (baseUri != null && !baseUri.isAbsolute) {
    throw PackageConfigArgumentError(baseUri, 'baseUri', 'Must be absolute');
  }

  if (comment != null) {
    var lines = comment.split('\n');
    if (lines.last.isEmpty) lines.removeLast();
    for (var commentLine in lines) {
      output.write('# ');
      output.writeln(commentLine);
    }
  } else {
    output.write('# generated by package:package_config at ');
    output.write(DateTime.now());
    output.writeln();
  }
  for (var package in config.packages) {
    var packageName = package.name;
    var uri = package.packageUriRoot;
    // Validate packageName.
    if (!isValidPackageName(packageName)) {
      throw PackageConfigArgumentError(
          config, 'config', '"$packageName" is not a valid package name');
    }
    if (uri.scheme == 'package') {
      throw PackageConfigArgumentError(
          config, 'config', 'Package location must not be a package URI: $uri');
    }
    output.write(packageName);
    output.write(':');
    // If baseUri is provided, make the URI relative to baseUri.
    if (baseUri != null) {
      uri = relativizeUri(uri, baseUri)!;
    }
    if (!uri.path.endsWith('/')) {
      uri = uri.replace(path: '${uri.path}/');
    }
    output.write(uri);
    output.writeln();
  }
}