// Copyright (c) 2016, 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 'dart:convert';
import 'dart:typed_data';

import 'package:analyzer/dart/ast/ast.dart';
import 'package:analyzer/dart/ast/token.dart';
import 'package:analyzer/error/listener.dart';
import 'package:analyzer/file_system/file_system.dart';
import 'package:analyzer/src/dart/analysis/byte_store.dart';
import 'package:analyzer/src/dart/analysis/driver.dart';
import 'package:analyzer/src/dart/scanner/reader.dart';
import 'package:analyzer/src/dart/scanner/scanner.dart';
import 'package:analyzer/src/generated/engine.dart';
import 'package:analyzer/src/generated/parser.dart';
import 'package:analyzer/src/generated/source.dart';
import 'package:analyzer/src/generated/utilities_dart.dart';
import 'package:analyzer/src/source/source_resource.dart';
import 'package:analyzer/src/summary/api_signature.dart';
import 'package:analyzer/src/summary/format.dart';
import 'package:analyzer/src/summary/idl.dart';
import 'package:analyzer/src/summary/summarize_ast.dart';
import 'package:analyzer/src/util/fast_uri.dart';
import 'package:convert/convert.dart';
import 'package:crypto/crypto.dart';

/**
 * [FileContentOverlay] is used to temporary override content of files.
 */
class FileContentOverlay {
  final _map = <String, String>{};

  /**
   * Return the content of the file with the given [path], or `null` the
   * overlay does not override the content of the file.
   *
   * The [path] must be absolute and normalized.
   */
  String operator [](String path) => _map[path];

  /**
   * Return the new [content] of the file with the given [path].
   *
   * The [path] must be absolute and normalized.
   */
  void operator []=(String path, String content) {
    if (content == null) {
      _map.remove(path);
    } else {
      _map[path] = content;
    }
  }
}

/**
 * Information about a file being analyzed, explicitly or implicitly.
 *
 * It provides a consistent view on its properties.
 *
 * The properties are not guaranteed to represent the most recent state
 * of the file system. To update the file to the most recent state, [refresh]
 * should be called.
 */
class FileState {
  final FileSystemState _fsState;

  /**
   * The absolute path of the file.
   */
  final String path;

  /**
   * The absolute URI of the file.
   */
  final Uri uri;

  /**
   * The [Source] of the file with the [uri].
   */
  Source source;

  String _content;
  String _contentHash;
  LineInfo _lineInfo;
  UnlinkedUnit _unlinked;
  List<int> _apiSignature;

  List<FileState> _importedFiles;
  List<FileState> _exportedFiles;
  List<FileState> _partedFiles;
  List<FileState> _dependencies;

  FileState._(this._fsState, this.path, this.uri, this.source);

  /**
   * The unlinked API signature of the file.
   */
  List<int> get apiSignature => _apiSignature;

  /**
   * The content of the file.
   */
  String get content => _content;

  /**
   * The MD5 hash of the [content].
   */
  String get contentHash => _contentHash;

  /**
   * Return the list of all direct dependencies.
   */
  List<FileState> get dependencies => _dependencies;

  /**
   * The list of files this file exports.
   */
  List<FileState> get exportedFiles => _exportedFiles;

  @override
  int get hashCode => uri.hashCode;

  /**
   * The list of files this file imports.
   */
  List<FileState> get importedFiles => _importedFiles;

  /**
   * Return information about line in the file.
   */
  LineInfo get lineInfo => _lineInfo;

  /**
   * The list of files this library file references as parts.
   */
  List<FileState> get partedFiles => _partedFiles;

  /**
   * The [UnlinkedUnit] of the file.
   */
  UnlinkedUnit get unlinked => _unlinked;

  @override
  bool operator ==(Object other) {
    return other is FileState && other.uri == uri;
  }

  /**
   * Return a new parsed unresolved [CompilationUnit].
   */
  CompilationUnit parse(AnalysisErrorListener errorListener) {
    AnalysisOptions analysisOptions = _fsState._analysisOptions;

    CharSequenceReader reader = new CharSequenceReader(content);
    Scanner scanner = new Scanner(source, reader, errorListener);
    scanner.scanGenericMethodComments = analysisOptions.strongMode;
    Token token = scanner.tokenize();
    LineInfo lineInfo = new LineInfo(scanner.lineStarts);

    Parser parser = new Parser(source, errorListener);
    parser.parseGenericMethodComments = analysisOptions.strongMode;
    CompilationUnit unit = parser.parseCompilationUnit(token);
    unit.lineInfo = lineInfo;
    return unit;
  }

  /**
   * Read the file content and ensure that all of the file properties are
   * consistent with the read content, including API signature.
   *
   * Return `true` if the API signature changed since the last refresh.
   */
  bool refresh() {
    // Read the content.
    try {
      _content = _fsState._contentOverlay[path];
      _content ??= _fsState._resourceProvider.getFile(path).readAsStringSync();
    } catch (_) {
      _content = '';
      // TODO(scheglov) We fail to report URI_DOES_NOT_EXIST.
      // On one hand we need to provide an unlinked bundle to prevent
      // analysis context from reading the file (we want it to work
      // hermetically and handle one one file at a time). OTOH,
      // ResynthesizerResultProvider happily reports that any source in the
      // SummaryDataStore has MODIFICATION_TIME `0`. We need to return `-1`
      // for missing files. Maybe add this feature to SummaryDataStore?
    }

    // Compute the content hash.
    List<int> contentBytes = UTF8.encode(_content);
    {
      List<int> hashBytes = md5.convert(contentBytes).bytes;
      _contentHash = hex.encode(hashBytes);
    }

    // Prepare the unlinked bundle key.
    String unlinkedKey;
    {
      ApiSignature signature = new ApiSignature();
      signature.addUint32List(_fsState._salt);
      signature.addBytes(contentBytes);
      unlinkedKey = '${signature.toHex()}.unlinked';
    }

    // Prepare bytes of the unlinked bundle - existing or new.
    List<int> bytes;
    {
      bytes = _fsState._byteStore.get(unlinkedKey);
      if (bytes == null) {
        CompilationUnit unit = parse(AnalysisErrorListener.NULL_LISTENER);
        _fsState._logger.run('Create unlinked for $path', () {
          UnlinkedUnitBuilder unlinkedUnit = serializeAstUnlinked(unit);
          bytes = unlinkedUnit.toBuffer();
          _fsState._byteStore.put(unlinkedKey, bytes);
        });
      }
    }

    // Read the unlinked bundle.
    _unlinked = new UnlinkedUnit.fromBuffer(bytes);
    _lineInfo = new LineInfo(_unlinked.lineStarts);
    List<int> newApiSignature = _unlinked.apiSignature;
    bool apiSignatureChanged = _apiSignature != null &&
        !_equalByteLists(_apiSignature, newApiSignature);
    _apiSignature = newApiSignature;

    // Build the graph.
    _importedFiles = <FileState>[];
    _exportedFiles = <FileState>[];
    _partedFiles = <FileState>[];
    for (UnlinkedImport import in _unlinked.imports) {
      if (!import.isImplicit) {
        String uri = import.uri;
        if (!_isDartUri(uri)) {
          FileState file = _fileForRelativeUri(uri);
          if (file != null) {
            _importedFiles.add(file);
          }
        }
      }
    }
    for (UnlinkedExportPublic export in _unlinked.publicNamespace.exports) {
      String uri = export.uri;
      if (!_isDartUri(uri)) {
        FileState file = _fileForRelativeUri(uri);
        if (file != null) {
          _exportedFiles.add(file);
        }
      }
    }
    for (String uri in _unlinked.publicNamespace.parts) {
      if (!_isDartUri(uri)) {
        FileState file = _fileForRelativeUri(uri);
        if (file != null) {
          _partedFiles.add(file);
        }
      }
    }

    // Compute direct dependencies.
    _dependencies = (new Set<FileState>()
          ..addAll(_importedFiles)
          ..addAll(_exportedFiles)
          ..addAll(_partedFiles))
        .toList();

    // Return whether the API signature changed.
    return apiSignatureChanged;
  }

  @override
  String toString() => path;

  /**
   * Return the [FileState] for the given [relativeUri].
   */
  FileState _fileForRelativeUri(String relativeUri) {
    Uri absoluteUri = resolveRelativeUri(uri, FastUri.parse(relativeUri));
    return _fsState.getFileForUri(absoluteUri);
  }

  /**
   * Return `true` if the given byte lists are equal.
   */
  static bool _equalByteLists(List<int> a, List<int> b) {
    if (a == null) {
      return b == null;
    } else if (b == null) {
      return false;
    }
    if (a.length != b.length) {
      return false;
    }
    for (int i = 0; i < a.length; i++) {
      if (a[i] != b[i]) {
        return false;
      }
    }
    return true;
  }

  static bool _isDartUri(String uri) {
    return uri.startsWith('dart:');
  }
}

/**
 * Information about known file system state.
 */
class FileSystemState {
  final PerformanceLog _logger;
  final ResourceProvider _resourceProvider;
  final ByteStore _byteStore;
  final FileContentOverlay _contentOverlay;
  final SourceFactory _sourceFactory;
  final AnalysisOptions _analysisOptions;
  final Uint32List _salt;

  /**
   * Mapping from a URI to the corresponding [FileState].
   */
  final Map<Uri, FileState> _uriToFile = {};

  /**
   * Mapping from a path to the corresponding [FileState]s, canonical or not.
   */
  final Map<String, List<FileState>> _pathToFiles = {};

  /**
   * Mapping from a path to the corresponding canonical [FileState].
   */
  final Map<String, FileState> _pathToCanonicalFile = {};

  FileSystemState(
      this._logger,
      this._byteStore,
      this._contentOverlay,
      this._resourceProvider,
      this._sourceFactory,
      this._analysisOptions,
      this._salt);

  /**
   * Return the canonical [FileState] for the given absolute [path]. The
   * returned file has the last known state since if was last refreshed.
   *
   * Here "canonical" means that if the [path] is in a package `lib` then the
   * returned file will have the `package:` style URI.
   */
  FileState getFileForPath(String path) {
    FileState file = _pathToCanonicalFile[path];
    if (file == null) {
      File resource = _resourceProvider.getFile(path);
      Source fileSource = resource.createSource();
      Uri uri = _sourceFactory.restoreUri(fileSource);
      // Try to get the existing instance.
      file = _uriToFile[uri];
      // If we have a file, call it the canonical one and return it.
      if (file != null) {
        _pathToCanonicalFile[path] = file;
        return file;
      }
      // Create a new file.
      FileSource uriSource = new FileSource(resource, uri);
      file = new FileState._(this, path, uri, uriSource);
      _uriToFile[uri] = file;
      _pathToFiles.putIfAbsent(path, () => <FileState>[]).add(file);
      _pathToCanonicalFile[path] = file;
      file.refresh();
    }
    return file;
  }

  /**
   * Return the [FileState] for the given absolute [uri]. May return `null` if
   * the [uri] is invalid, e.g. a `package:` URI without a package name. The
   * returned file has the last known state since if was last refreshed.
   */
  FileState getFileForUri(Uri uri) {
    FileState file = _uriToFile[uri];
    if (file == null) {
      Source uriSource = _sourceFactory.resolveUri(null, uri.toString());
      // If the URI is invalid, for example package:/test/d.dart (note the
      // leading '/'), then `null` is returned. We should ignore this URI.
      if (uriSource == null) {
        return null;
      }
      String path = uriSource.fullName;
      File resource = _resourceProvider.getFile(path);
      FileSource source = new FileSource(resource, uri);
      file = new FileState._(this, path, uri, source);
      _uriToFile[uri] = file;
      _pathToFiles.putIfAbsent(path, () => <FileState>[]).add(file);
      file.refresh();
    }
    return file;
  }

  /**
   * Return the list of all [FileState]s corresponding to the given [path]. The
   * list has at least one item, and the first item is the canonical file.
   */
  List<FileState> getFilesForPath(String path) {
    FileState canonicalFile = getFileForPath(path);
    List<FileState> allFiles = _pathToFiles[path].toList();
    if (allFiles.length == 1) {
      return allFiles;
    }
    return allFiles
      ..remove(canonicalFile)
      ..insert(0, canonicalFile);
  }
}