// Copyright (c) 2015, 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.

library source.analysis_options_provider;

import 'package:analyzer/file_system/file_system.dart';
import 'package:analyzer/src/generated/engine.dart';
import 'package:source_span/source_span.dart';
import 'package:yaml/yaml.dart';

/// Provide the options found in the `.analysis_options` file.
class AnalysisOptionsProvider {
  /// Provide the options found in [root]/[ANALYSIS_OPTIONS_FILE].
  /// Return an empty options map if the file does not exist.
  Map<String, YamlNode> getOptions(Folder root) {
    var optionsSource = _readAnalysisOptionsFile(
        root.getChild(AnalysisEngine.ANALYSIS_OPTIONS_FILE));
    return getOptionsFromString(optionsSource);
  }

  /// Provide the options found in [file].
  /// Return an empty options map if the file does not exist.
  Map<String, YamlNode> getOptionsFromFile(File file) {
    var optionsSource = _readAnalysisOptionsFile(file);
    return getOptionsFromString(optionsSource);
  }

  /// Provide the options found in [optionsSource].
  /// Return an empty options map if the source is null.
  Map<String, YamlNode> getOptionsFromString(String optionsSource) {
    var options = <String, YamlNode>{};
    if (optionsSource == null) {
      return options;
    }
    YamlNode doc = loadYamlNode(optionsSource);
    // Empty options.
    if (doc is YamlScalar && doc.value == null) {
      return options;
    }
    if ((doc != null) && (doc is! YamlMap)) {
      throw new OptionsFormatException(
          'Bad options file format (expected map, got ${doc.runtimeType})',
          doc.span);
    }
    if (doc is YamlMap) {
      doc.forEach((k, v) {
        if (k is! String) {
          throw new OptionsFormatException(
              'Bad options file format (expected String scope key, '
              'got ${k.runtimeType})',
              k != null ? k.span : doc.span);
        }
        options[k] = v;
      });
    }
    return options;
  }

  /// Read the contents of [file] as a string.
  /// Returns null if file does not exist.
  String _readAnalysisOptionsFile(File file) {
    try {
      return file.readAsStringSync();
    } on FileSystemException {
      // File can't be read.
      return null;
    }
  }
}

/// Thrown on options format exceptions.
class OptionsFormatException implements Exception {
  final String message;
  final SourceSpan span;
  OptionsFormatException(this.message, [this.span]);

  @override
  String toString() =>
      'OptionsFormatException: ${message?.toString()}, ${span?.toString()}';
}