// 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 'dart:developer' as developer;
import 'dart:io';

import 'package:analysis_server/protocol/protocol_constants.dart'
    show PROTOCOL_VERSION;
import 'package:analysis_server/protocol/protocol_generated.dart';
import 'package:analysis_server/src/analysis_server.dart';
import 'package:analysis_server/src/analysis_server_abstract.dart';
import 'package:analysis_server/src/analytics/noop_analytics.dart';
import 'package:analysis_server/src/lsp/lsp_analysis_server.dart'
    show LspAnalysisServer;
import 'package:analysis_server/src/plugin/plugin_manager.dart';
import 'package:analysis_server/src/server/http_server.dart';
import 'package:analysis_server/src/server/performance.dart';
import 'package:analysis_server/src/services/completion/completion_performance.dart';
import 'package:analysis_server/src/socket_server.dart';
import 'package:analysis_server/src/status/ast_writer.dart';
import 'package:analysis_server/src/status/element_writer.dart';
import 'package:analysis_server/src/status/pages.dart';
import 'package:analysis_server/src/utilities/profiling.dart';
import 'package:analyzer/dart/analysis/context_root.dart';
import 'package:analyzer/dart/analysis/results.dart';
import 'package:analyzer/dart/element/element.dart';
import 'package:analyzer/src/context/source.dart';
import 'package:analyzer/src/dart/sdk/sdk.dart';
import 'package:analyzer/src/dartdoc/dartdoc_directive_info.dart';
import 'package:analyzer/src/generated/engine.dart';
import 'package:analyzer/src/generated/source.dart';
import 'package:analyzer/src/source/package_map_resolver.dart';
import 'package:analyzer/src/util/file_paths.dart' as file_paths;
import 'package:collection/collection.dart';
import 'package:path/path.dart' as path;

final String kCustomCss = '''
.lead, .page-title+.markdown-body>p:first-child {
  margin-bottom: 30px;
  font-size: 20px;
  font-weight: 300;
  color: #555;
}

.container {
  width: 1160px;
}

.masthead {
  padding-top: 1rem;
  padding-bottom: 1rem;
  margin-bottom: 1.5rem;
  text-align: center;
  background-color: #4078c0;
}

.masthead .masthead-logo {
  display: inline-block;
  font-size: 1.5rem;
  color: #fff;
  float: left;
}

.masthead .mega-octicon {
  font-size: 1.5rem;
}

.masthead-nav {
  float: right;
  margin-top: .5rem;
}

.masthead-nav a:not(:last-child) {
  margin-right: 1.25rem;
}

.masthead a {
  color: rgba(255,255,255,0.5);
  font-size: 1rem;
}

.masthead a:hover {
  color: #fff;
  text-decoration: none;
}

.masthead-nav .active {
  color: #fff;
  font-weight: 500;
}

.counter {
  display: inline-block;
  padding: 2px 5px;
  font-size: 11px;
  font-weight: bold;
  line-height: 1;
  color: #666;
  background-color: #eee;
  border-radius: 20px;
}

.menu-item .counter {
  float: right;
  margin-left: 5px;
}

td.right {
  text-align: right;
}

table td {
  max-width: 600px;
  vertical-align: text-top;
}

td.pre {
  white-space: pre;
}

.nowrap {
  white-space: nowrap;
}

.scroll-table {
  max-height: 190px;
  overflow-x: auto;
}

.footer {
  padding-top: 3rem;
  padding-bottom: 3rem;
  margin-top: 3rem;
  line-height: 1.75;
  color: #7a7a7a;
  border-top: 1px solid #eee;
}

.footer strong {
  color: #333;
}

.subtle {
  color: #333;
}
''';

String get _sdkVersion {
  var version = Platform.version;
  if (version.contains(' ')) {
    version = version.substring(0, version.indexOf(' '));
  }
  return version;
}

String writeOption(String name, dynamic value) {
  return '$name: <code>$value</code><br> ';
}

class AnalyticsPage extends DiagnosticPageWithNav {
  AnalyticsPage(DiagnosticsSite site)
      : super(site, 'analytics', 'Analytics',
            description: 'Analytics gathered by the analysis server.');

  @override
  String? get navDetail => null;

  @override
  Future generateContent(Map<String, String> params) async {
    var manager = server.analyticsManager;
    //
    // Display the standard header.
    //
    if (manager.analytics is NoopAnalytics) {
      p('Analytics reporting disabled. In order to enable it, run:');
      p('&nbsp;&nbsp;<code>dart --enable-analytics</code>');
      p('If analytics had been enabled, the information below would be '
          'reported on shutdown.');
    } else {
      p('The Dart tool uses Google Analytics to report feature usage '
          'statistics and to send basic crash reports. This data is used to '
          'help improve the Dart platform and tools over time.');
      p('To disable reporting of analytics, run:');
      p('&nbsp;&nbsp;<code>dart --disable-analytics</code>');
      p('The information below will be reported on shutdown.');
    }
    //
    // Display the analytics data that has been gathered.
    //
    manager.toHtml(buf);
  }
}

class AstPage extends DiagnosticPageWithNav {
  String? _description;

  AstPage(DiagnosticsSite site)
      : super(site, 'ast', 'AST', description: 'The AST for a file.');

  @override
  String? get description => _description ?? super.description;

  @override
  bool get showInNav => false;

  @override
  Future<void> generateContent(Map<String, String> params) async {
    var filePath = params['file'];
    if (filePath == null) {
      p('No file path provided.');
      return;
    }
    var driver = server.getAnalysisDriver(filePath);
    if (driver == null) {
      p('The file <code>${escape(filePath)}</code> is not being analyzed.',
          raw: true);
      return;
    }
    var result = await driver.getResult(filePath);
    if (result is ResolvedUnitResult) {
      var writer = AstWriter(buf);
      result.unit.accept(writer);
    } else {
      p(
          'An AST could not be produced for the file '
          '<code>${escape(filePath)}</code>.',
          raw: true);
    }
  }

  @override
  Future<void> generatePage(Map<String, String> params) async {
    try {
      _description = params['file'];
      await super.generatePage(params);
    } finally {
      _description = null;
    }
  }
}

class CommunicationsPage extends DiagnosticPageWithNav {
  CommunicationsPage(DiagnosticsSite site)
      : super(site, 'communications', 'Communications',
            description:
                'Latency statistics for analysis server communications.');

  @override
  Future generateContent(Map<String, String> params) async {
    void writeRow(List<String> data, {List<String?>? classes}) {
      buf.write('<tr>');
      for (var i = 0; i < data.length; i++) {
        var c = classes == null ? null : classes[i];
        if (c != null) {
          buf.write('<td class="$c">${escape(data[i])}</td>');
        } else {
          buf.write('<td>${escape(data[i])}</td>');
        }
      }
      buf.writeln('</tr>');
    }

    buf.writeln('<div class="columns">');

    var performanceAfterStartup = server.performanceAfterStartup;
    if (performanceAfterStartup != null) {
      buf.writeln('<div class="column one-half">');

      h3('Current');
      _writePerformanceTable(performanceAfterStartup, writeRow);

      var time = server.uptime.toString();
      if (time.contains('.')) {
        time = time.substring(0, time.indexOf('.'));
      }
      buf.writeln(writeOption('Uptime', time));

      buf.write('</div>');
    }

    buf.writeln('<div class="column one-half">');

    h3('Startup');
    _writePerformanceTable(server.performanceDuringStartup, writeRow);

    if (performanceAfterStartup != null) {
      var startupTime = performanceAfterStartup.startTime -
          server.performanceDuringStartup.startTime;
      buf.writeln(
          writeOption('Initial analysis time', printMilliseconds(startupTime)));
    }

    buf.write('</div>');

    buf.write('</div>');
  }

  void _writePerformanceTable(ServerPerformance perf,
      void Function(List<String> data, {List<String?> classes}) writeRow) {
    var requestCount = perf.requestCount;
    var latencyCount = perf.latencyCount;
    var averageLatency =
        latencyCount > 0 ? (perf.requestLatency ~/ latencyCount) : 0;
    var maximumLatency = perf.maxLatency;
    var slowRequestPercent =
        latencyCount > 0 ? (perf.slowRequestCount / latencyCount) : 0.0;

    buf.write('<table>');
    writeRow(['$requestCount', 'requests'], classes: ['right', null]);
    writeRow(['$latencyCount', 'requests with latency information'],
        classes: ['right', null]);
    if (latencyCount > 0) {
      writeRow([printMilliseconds(averageLatency), 'average latency'],
          classes: ['right', null]);
      writeRow([printMilliseconds(maximumLatency), 'maximum latency'],
          classes: ['right', null]);
      writeRow([printPercentage(slowRequestPercent), '> 150 ms latency'],
          classes: ['right', null]);
    }
    buf.write('</table>');
  }
}

class CompletionPage extends DiagnosticPageWithNav with PerformanceChartMixin {
  CompletionPage(DiagnosticsSite site)
      : super(site, 'completion', 'Code Completion',
            description: 'Latency statistics for code completion.');

  path.Context get pathContext => server.resourceProvider.pathContext;

  List<CompletionPerformance> get performanceItems =>
      server.recentPerformance.completion.items.toList();

  @override
  Future generateContent(Map<String, String> params) async {
    var completions = performanceItems;

    if (completions.isEmpty) {
      blankslate('No completions recorded.');
      return;
    }

    var fastCount =
        completions.where((c) => c.elapsedInMilliseconds <= 100).length;
    p('${completions.length} results; ${printPercentage(fastCount / completions.length)} within 100ms.');

    drawChart(completions);

    // emit the data as a table
    buf.writeln('<table>');
    buf.writeln(
        '<tr><th>Time</th><th>Computed Results</th><th>Transmitted Results</th><th>Source</th><th>Snippet</th></tr>');
    for (var completion in completions) {
      var shortName = pathContext.basename(completion.path);
      buf.writeln(
        '<tr>'
        '<td class="pre right"><a href="/timing?id=${completion.id}&kind=completion">'
        '${_formatTiming(completion)}'
        '</a></td>'
        '<td class="right">${completion.computedSuggestionCountStr}</td>'
        '<td class="right">${completion.transmittedSuggestionCountStr}</td>'
        '<td>${escape(shortName)}</td>'
        '<td><code>${escape(completion.snippet)}</code></td>'
        '</tr>',
      );
    }
    buf.writeln('</table>');
  }

  String _formatTiming(CompletionPerformance completion) {
    var buffer = StringBuffer();
    buffer.write(printMilliseconds(completion.elapsedInMilliseconds));

    var latency = completion.requestLatency;
    if (latency != null) {
      buffer
        ..write(' <small class="subtle" title="client-to-server latency">(+ ')
        ..write(printMilliseconds(latency))
        ..write(')</small>');
    }

    return buffer.toString();
  }
}

class ContentsPage extends DiagnosticPageWithNav {
  String? _description;

  ContentsPage(DiagnosticsSite site)
      : super(site, 'contents', 'Contents',
            description: 'The Contents/Overlay of a file.');

  @override
  String? get description => _description ?? super.description;

  @override
  bool get showInNav => false;

  @override
  Future<void> generateContent(Map<String, String> params) async {
    var filePath = params['file'];
    if (filePath == null) {
      p('No file path provided.');
      return;
    }
    var driver = server.getAnalysisDriver(filePath);
    if (driver == null) {
      p('The file <code>${escape(filePath)}</code> is not being analyzed.',
          raw: true);
      return;
    }
    var file = server.resourceProvider.getFile(filePath);
    if (!file.exists) {
      p('The file <code>${escape(filePath)}</code> does not exist.', raw: true);
      return;
    }

    if (server.resourceProvider.hasOverlay(filePath)) {
      p('Showing overlay for file.');
    } else {
      p('Showing file system contents for file.');
    }

    pre(() {
      buf.write('<code>');
      buf.write(escape(file.readAsStringSync()));
      buf.writeln('</code>');
    });
  }

  @override
  Future<void> generatePage(Map<String, String> params) async {
    try {
      _description = params['file'];
      await super.generatePage(params);
    } finally {
      _description = null;
    }
  }
}

class ContextsPage extends DiagnosticPageWithNav {
  ContextsPage(DiagnosticsSite site)
      : super(site, 'contexts', 'Contexts',
            description:
                'An analysis context defines the options and the set of sources being analyzed.');

  @override
  String get navDetail => '${server.driverMap.length}';

  String describe(AnalysisOptionsImpl options) {
    var b = StringBuffer();

    b.write(writeOption('Implicit dynamic', options.implicitDynamic));
    b.write(writeOption('Implicit casts', options.implicitCasts));
    b.write(writeOption('Feature set', options.contextFeatures.toString()));
    b.write('<br>');

    b.write(writeOption('Generate hints', options.hint));

    return b.toString();
  }

  @override
  Future generateContent(Map<String, String> params) async {
    var driverMap = server.driverMap;
    if (driverMap.isEmpty) {
      blankslate('No contexts.');
      return;
    }

    var contextPath = params['context'];
    var entries = driverMap.entries.toList();
    entries.sort(
        (first, second) => first.key.shortName.compareTo(second.key.shortName));
    var entry = entries.firstWhereOrNull((f) => f.key.path == contextPath);

    if (entry == null) {
      entry = entries.first;
      contextPath = entry.key.path;
    }

    var folder = entry.key;
    var driver = entry.value;

    buf.writeln('<div class="tabnav">');
    buf.writeln('<nav class="tabnav-tabs">');
    for (var entry in entries) {
      var f = entry.key;
      if (f == folder) {
        buf.writeln(
            '<a class="tabnav-tab selected">${escape(f.shortName)}</a>');
      } else {
        var p = '${this.path}?context=${Uri.encodeQueryComponent(f.path)}';
        buf.writeln(
            '<a href="$p" class="tabnav-tab">${escape(f.shortName)}</a>');
      }
    }
    buf.writeln('</nav>');
    buf.writeln('</div>');

    buf.writeln(writeOption('Context location', escape(contextPath)));
    buf.writeln(writeOption(
        'Analysis options path',
        escape(
            driver.analysisContext?.contextRoot.optionsFile?.path ?? 'none')));
    buf.writeln(
        writeOption('SDK root', escape(driver.analysisContext?.sdkRoot?.path)));

    buf.writeln('<div class="columns">');

    buf.writeln('<div class="column one-half">');
    h3('Analysis options');
    p(describe(driver.analysisOptions as AnalysisOptionsImpl), raw: true);

    h3('Pub files');
    buf.writeln('<p>');
    buf.writeln(
        writeOption('Has .packages file', folder.getChild('.packages').exists));
    buf.writeln(writeOption('Has pubspec.yaml file',
        folder.getChild(file_paths.pubspecYaml).exists));
    buf.writeln('</p>');

    buf.writeln('</div>');

    buf.writeln('</div>');

    h3('Lints');
    var lints = driver.analysisOptions.lintRules.map((l) => l.name).toList()
      ..sort();
    ul(lints, (String lint) => buf.write(lint), classes: 'scroll-table');

    h3('Error processors');
    p(driver.analysisOptions.errorProcessors
        .map((e) => e.description)
        .join(', '));

    h3('Plugins');
    p(driver.analysisOptions.enabledPluginNames.join(', '));

    var priorityFiles = driver.priorityFiles;
    var addedFiles = driver.addedFiles.toList();
    var implicitFiles =
        driver.knownFiles.difference(driver.addedFiles).toList();
    addedFiles.sort();
    implicitFiles.sort();

    String lenCounter(List list) {
      return '<span class="counter" style="float: right;">${list.length}</span>';
    }

    h3('Context files');

    void writeFile(String file) {
      var astPath = '/ast?file=${Uri.encodeQueryComponent(file)}';
      var elementPath = '/element?file=${Uri.encodeQueryComponent(file)}';
      var contentsPath = '/contents?file=${Uri.encodeQueryComponent(file)}';
      var hasOverlay = server.resourceProvider.hasOverlay(file);

      buf.write(file);
      buf.writeln(' <a href="$astPath">ast</a>');
      buf.writeln(' <a href="$elementPath">element</a>');
      buf.writeln(
          ' <a href="$contentsPath">contents${hasOverlay ? '*' : ''}</a>');
    }

    h4('Priority files ${lenCounter(priorityFiles)}', raw: true);
    ul(priorityFiles, writeFile, classes: 'scroll-table');

    h4('Added files ${lenCounter(addedFiles)}', raw: true);
    ul(addedFiles, writeFile, classes: 'scroll-table');

    h4('Implicit files ${lenCounter(implicitFiles)}', raw: true);
    ul(implicitFiles, writeFile, classes: 'scroll-table');

    var sourceFactory = driver.sourceFactory;
    if (sourceFactory is SourceFactoryImpl) {
      h3('Resolvers');
      for (var resolver in sourceFactory.resolvers) {
        h4(resolver.runtimeType.toString());
        buf.write('<p class="scroll-table">');
        if (resolver is DartUriResolver) {
          var sdk = resolver.dartSdk;
          buf.write(' (sdk = ');
          buf.write(sdk.runtimeType);
          if (sdk is FolderBasedDartSdk) {
            buf.write(' (path = ');
            buf.write(sdk.directory.path);
            buf.write(')');
          } else if (sdk is EmbedderSdk) {
            buf.write(' (map = ');
            writeMap(sdk.urlMappings);
            buf.write(')');
          }
          buf.write(')');
        } else if (resolver is PackageMapUriResolver) {
          writeMap(resolver.packageMap);
        }
        buf.write('</p>');
      }
    }

    h3('Dartdoc template info');
    var info = server.declarationsTracker
            ?.getContext(driver.analysisContext!)
            ?.dartdocDirectiveInfo ??
        DartdocDirectiveInfo();
    buf.write('<p class="scroll-table">');
    writeMap(info.templateMap);
    buf.write('</p>');
  }

  void writeList<E>(List<E> list) {
    buf.writeln('[${list.join(', ')}]');
  }

  void writeMap<V>(Map<String, V> map) {
    var keys = map.keys.toList();
    keys.sort();
    var length = keys.length;
    buf.write('{');
    for (var i = 0; i < length; i++) {
      buf.write('<br>');
      var key = keys[i];
      var value = map[key];
      buf.write(key);
      buf.write(' = ');
      if (value is List) {
        writeList(value);
      } else {
        buf.write(value);
      }
      buf.write(',');
    }
    buf.write('<br>}');
  }
}

/// A page with a proscriptive notion of layout.
abstract class DiagnosticPage extends Page {
  final DiagnosticsSite site;

  DiagnosticPage(this.site, String id, String title, {String? description})
      : super(id, title, description: description);

  bool get isNavPage => false;

  AbstractAnalysisServer get server => site.socketServer.analysisServer!;

  Future<void> generateContainer(Map<String, String> params) async {
    buf.writeln('<div class="columns docs-layout">');
    buf.writeln('<div class="three-fourths column markdown-body">');
    h1(title, classes: 'page-title');
    await asyncDiv(() async {
      p(description ?? 'Unknown Page');
      await generateContent(params);
    }, classes: 'markdown-body');
    buf.writeln('</div>');
    buf.writeln('</div>');
  }

  Future<void> generateContent(Map<String, String> params);

  void generateFooter() {
    buf.writeln('''
    <footer class="footer">
      Dart ${site.title} <span style="float:right">SDK $_sdkVersion</span>
    </footer>
''');
  }

  void generateHeader() {
    buf.writeln('''
    <header class="masthead">
    <div class="container">
      <span class="masthead-logo">
      <span class="mega-octicon octicon-dashboard"></span>
        ${site.title} Diagnostics
      </span>

      <nav class="masthead-nav">
        <a href="/status" ${isNavPage ? ' class="active"' : ''}>Diagnostics</a>
        <a href="/feedback" ${isCurrentPage('/feedback') ? ' class="active"' : ''}>Feedback</a>
        <a href="https://dart.dev/tools/dart-analyze" target="_blank">Docs</a>
        <a href="https://htmlpreview.github.io/?https://github.com/dart-lang/sdk/blob/main/pkg/analysis_server/doc/api.html" target="_blank">Spec</a>
      </nav>
    </div>
    </header>
''');
  }

  @override
  Future<void> generatePage(Map<String, String> params) async {
    buf.writeln('<!DOCTYPE html><html lang="en">');
    buf.write('<head>');
    buf.write('<meta charset="utf-8">');
    buf.write('<meta name="viewport" content="width=device-width, '
        'initial-scale=1.0">');
    buf.writeln('<title>${site.title}</title>');
    buf.writeln('<link rel="stylesheet" '
        'href="https://cdnjs.cloudflare.com/ajax/libs/Primer/6.0.0/build.css">');
    buf.writeln('<link rel="stylesheet" '
        'href="https://cdnjs.cloudflare.com/ajax/libs/octicons/4.4.0/font/octicons.css">');
    buf.writeln('<script type="text/javascript" '
        'src="https://www.gstatic.com/charts/loader.js"></script>');
    buf.writeln('<style>${site.customCss}</style>');
    buf.writeln('</head>');

    buf.writeln('<body>');
    generateHeader();
    buf.writeln('<div class="container">');
    await generateContainer(params);
    generateFooter();
    buf.writeln('</div>'); // div.container
    buf.writeln('</body>');
    buf.writeln('</html>');
  }
}

abstract class DiagnosticPageWithNav extends DiagnosticPage {
  DiagnosticPageWithNav(super.site, super.id, super.title, {super.description});

  @override
  bool get isNavPage => true;

  String? get navDetail => null;

  bool get showInNav => true;

  @override
  Future<void> generateContainer(Map<String, String> params) async {
    buf.writeln('<div class="columns docs-layout">');

    bool shouldShowInNav(Page page) {
      return page is DiagnosticPageWithNav && page.showInNav;
    }

    buf.writeln('<div class="one-fifth column">');
    buf.writeln('<nav class="menu docs-menu">');
    for (var page in site.pages.where(shouldShowInNav)) {
      buf.write('<a class="menu-item ${page == this ? ' selected' : ''}" '
          'href="${page.path}">${escape(page.title)}');
      var detail = (page as DiagnosticPageWithNav).navDetail;
      if (detail != null) {
        buf.write('<span class="counter">$detail</span>');
      }
      buf.writeln('</a>');
    }
    buf.writeln('</nav>');
    buf.writeln('</div>');

    buf.writeln('<div class="four-fifths column markdown-body">');
    h1(title, classes: 'page-title');
    await asyncDiv(() async {
      p(description ?? 'Unknown Page');
      await generateContent(params);
    }, classes: 'markdown-body');
    buf.writeln('</div>');

    buf.writeln('</div>');
  }
}

class DiagnosticsSite extends Site implements AbstractGetHandler {
  /// An object that can handle either a WebSocket connection or a connection
  /// to the client over stdio.
  AbstractSocketServer socketServer;

  /// The last few lines printed.
  final List<String> lastPrintedLines;

  DiagnosticsSite(this.socketServer, this.lastPrintedLines)
      : super('Analysis Server') {
    pages.add(CommunicationsPage(this));
    pages.add(ContextsPage(this));
    pages.add(EnvironmentVariablesPage(this));
    pages.add(ExceptionsPage(this));
    // pages.add(new InstrumentationPage(this));
    // pages.add(AnalyticsPage(this));

    // Add server-specific pages. Ordering doesn't matter as the items are
    // sorted later.
    var server = socketServer.analysisServer;
    if (server != null) {
      pages.add(PluginsPage(this, server));
    }
    pages.add(CompletionPage(this));
    if (server is AnalysisServer) {
      pages.add(SubscriptionsPage(this, server));
    } else if (server is LspAnalysisServer) {
      pages.add(LspCapabilitiesPage(this, server));
    }
    pages.add(TimingPage(this));

    var profiler = ProcessProfiler.getProfilerForPlatform();
    if (profiler != null) {
      pages.add(MemoryAndCpuPage(this, profiler));
    }

    pages.sort((Page a, Page b) =>
        a.title.toLowerCase().compareTo(b.title.toLowerCase()));

    // Add the status page at the beginning.
    pages.insert(0, StatusPage(this));

    // Add non-nav pages.
    pages.add(FeedbackPage(this));
    pages.add(AstPage(this));
    pages.add(ElementModelPage(this));
    pages.add(ContentsPage(this));
  }

  @override
  String get customCss => kCustomCss;

  @override
  Page createExceptionPage(String message, StackTrace trace) =>
      ExceptionPage(this, message, trace);

  @override
  Page createUnknownPage(String unknownPath) => NotFoundPage(this, unknownPath);
}

class ElementModelPage extends DiagnosticPageWithNav {
  String? _description;

  ElementModelPage(DiagnosticsSite site)
      : super(site, 'element', 'Element model',
            description: 'The element model for a file.');

  @override
  String? get description => _description ?? super.description;

  @override
  bool get showInNav => false;

  @override
  Future<void> generateContent(Map<String, String> params) async {
    var filePath = params['file'];
    if (filePath == null) {
      p('No file path provided.');
      return;
    }
    var driver = server.getAnalysisDriver(filePath);
    if (driver == null) {
      p('The file <code>${escape(filePath)}</code> is not being analyzed.',
          raw: true);
      return;
    }
    var result = await driver.getResult(filePath);
    CompilationUnitElement? compilationUnitElement;
    if (result is ResolvedUnitResult) {
      compilationUnitElement = result.unit.declaredElement;
    }
    if (compilationUnitElement != null) {
      var writer = ElementWriter(buf);
      compilationUnitElement.accept(writer);
    } else {
      p(
          'An element model could not be produced for the file '
          '<code>${escape(filePath)}</code>.',
          raw: true);
    }
  }

  @override
  Future<void> generatePage(Map<String, String> params) async {
    try {
      _description = params['file'];
      await super.generatePage(params);
    } finally {
      _description = null;
    }
  }
}

class EnvironmentVariablesPage extends DiagnosticPageWithNav {
  EnvironmentVariablesPage(DiagnosticsSite site)
      : super(site, 'environment', 'Environment Variables',
            description:
                'System environment variables as seen from the analysis server.');

  @override
  Future generateContent(Map<String, String> params) async {
    buf.writeln('<table>');
    buf.writeln('<tr><th>Variable</th><th>Value</th></tr>');
    for (var key in Platform.environment.keys.toList()..sort()) {
      var value = Platform.environment[key];
      buf.writeln('<tr><td>${escape(key)}</td><td>${escape(value)}</td></tr>');
    }
    buf.writeln('</table>');
  }
}

class ExceptionPage extends DiagnosticPage {
  final StackTrace trace;

  ExceptionPage(DiagnosticsSite site, String message, this.trace)
      : super(site, '', '500 Oops', description: message);

  @override
  Future generateContent(Map<String, String> params) async {
    p(trace.toString(), style: 'white-space: pre');
  }
}

class ExceptionsPage extends DiagnosticPageWithNav {
  ExceptionsPage(DiagnosticsSite site)
      : super(site, 'exceptions', 'Exceptions',
            description: 'Exceptions from the analysis server.');

  Iterable<ServerException> get exceptions => server.exceptions.items;

  @override
  String get navDetail => '${exceptions.length}';

  @override
  Future generateContent(Map<String, String> params) async {
    if (exceptions.isEmpty) {
      blankslate('No exceptions encountered!');
    } else {
      for (var ex in exceptions) {
        h3('Exception ${ex.exception}');
        p('${escape(ex.message)}<br>${writeOption('fatal', ex.fatal)}',
            raw: true);
        pre(() {
          buf.writeln('<code>${escape(ex.stackTrace.toString())}</code>');
        }, classes: 'scroll-table');
      }
    }
  }
}

class FeedbackPage extends DiagnosticPage {
  FeedbackPage(DiagnosticsSite site)
      : super(site, 'feedback', 'Feedback',
            description: 'Providing feedback and filing issues.');

  @override
  Future generateContent(Map<String, String> params) async {
    var issuesUrl = 'https://github.com/dart-lang/sdk/issues';
    p(
      'To file issues or feature requests, see our '
      '<a href="$issuesUrl">bug tracker</a>. When filing an issue, please describe:',
      raw: true,
    );
    ul([
      'what you were doing',
      'what occurred',
      'what you think the expected behavior should have been',
    ], (line) => buf.writeln(line));

    var ideInfo = <String>[];
    var clientId = server.options.clientId;
    if (clientId != null) {
      ideInfo.add(clientId);
    }
    var clientVersion = server.options.clientVersion;
    if (clientVersion != null) {
      ideInfo.add(clientVersion);
    }
    var ideText = ideInfo.map((str) => '<code>$str</code>').join(', ');

    p('Other data to include:');
    ul([
      "the IDE you are using and its version${ideText.isEmpty ? '' : ' ($ideText)'}",
      'the Dart SDK version (<code>${escape(_sdkVersion)}</code>)',
      'your operating system (<code>${escape(Platform.operatingSystem)}</code>)',
    ], (line) => buf.writeln(line));

    p('Thanks!');
  }
}

class LspCapabilitiesPage extends DiagnosticPageWithNav {
  @override
  LspAnalysisServer server;

  LspCapabilitiesPage(DiagnosticsSite site, this.server)
      : super(site, 'lsp_capabilities', 'LSP Capabilities',
            description: 'Client and Server LSP Capabilities.');

  @override
  Future generateContent(Map<String, String> params) async {
    buf.writeln('<div class="columns">');

    buf.writeln('<div class="column one-half">');
    h3('Client Capabilities');
    var clientCapabilities = server.clientCapabilities;
    if (clientCapabilities == null) {
      p('Client capabilities have not yet been received.');
    } else {
      prettyJson(clientCapabilities.raw.toJson());
    }
    buf.writeln('</div>');

    buf.writeln('<div class="column one-half">');
    h3('Server Capabilities');
    var capabilities = server.capabilities;
    if (capabilities == null) {
      p('Server capabilities have not yet been computed.');
    } else {
      prettyJson(capabilities.toJson());
    }
    buf.writeln('</div>'); // half for server capabilities
    buf.writeln('</div>'); // columns

    h3('Current registrations');
    p('Showing the LSP method name and the registration params sent to the '
        'client.');
    prettyJson(server.capabilitiesComputer.currentRegistrations.toList());
  }
}

// class InstrumentationPage extends DiagnosticPageWithNav {
//   InstrumentationPage(DiagnosticsSite site)
//       : super(site, 'instrumentation', 'Instrumentation',
//             description:
//                 'Verbose instrumentation data from the analysis server.');
//
//   @override
//   Future generateContent(Map<String, String> params) async {
//     p(
//         'Instrumentation can be enabled by starting the analysis server with the '
//         '<code>--instrumentation-log-file=path/to/file</code> flag.',
//         raw: true);
//
//     if (!AnalysisEngine.instance.instrumentationService.isActive) {
//       blankslate('Instrumentation not active.');
//       return;
//     }
//
//     h3('Instrumentation');
//
//     p('Instrumentation active.');
//
//     InstrumentationServer instrumentation =
//         AnalysisEngine.instance.instrumentationService.instrumentationServer;
//     String description = instrumentation.describe;
//     HtmlEscape htmlEscape = new HtmlEscape(HtmlEscapeMode.element);
//     description = htmlEscape.convert(description);
//     // Convert http(s): references to hyperlinks.
//     final RegExp urlRegExp = new RegExp(r'[http|https]+:\/*(\S+)');
//     description = description.replaceAllMapped(urlRegExp, (Match match) {
//       return '<a href="${match.group(0)}">${match.group(1)}</a>';
//     });
//     p(description.replaceAll('\n', '<br>'), raw: true);
//   }
// }

class MemoryAndCpuPage extends DiagnosticPageWithNav {
  final ProcessProfiler profiler;

  MemoryAndCpuPage(DiagnosticsSite site, this.profiler)
      : super(site, 'memory', 'Memory and CPU Usage',
            description: 'Memory and CPU usage for the analysis server.');

  @override
  Future generateContent(Map<String, String> params) async {
    var usage = await profiler.getProcessUsage(pid);

    var serviceProtocolInfo = await developer.Service.getInfo();

    if (usage != null) {
      buf.writeln(
          writeOption('CPU', printPercentage(usage.cpuPercentage / 100.0)));
      buf.writeln(writeOption('Memory', '${usage.memoryMB.round()} MB'));

      h3('VM');

      if (serviceProtocolInfo.serverUri == null) {
        p('Service protocol not enabled.');
      } else {
        buf.writeln(writeOption('Service protocol connection available at',
            '${serviceProtocolInfo.serverUri}'));
        buf.writeln('<br>');
        p(
          'To get detailed performance data on the analysis server, we '
          'recommend using Dart DevTools. For instructions on installing and '
          'using DevTools, see '
          '<a href="https://dart.dev/tools/dart-devtools">dart.dev/tools/dart-devtools</a>.',
          raw: true,
        );
      }
    } else {
      p('Error retrieving the memory and cpu usage information.');
    }
  }
}

class NotFoundPage extends DiagnosticPage {
  @override
  final String path;

  NotFoundPage(DiagnosticsSite site, this.path)
      : super(site, '', '404 Not found', description: "'$path' not found.");

  @override
  Future generateContent(Map<String, String> params) async {}
}

class PluginsPage extends DiagnosticPageWithNav {
  @override
  AbstractAnalysisServer server;

  PluginsPage(DiagnosticsSite site, this.server)
      : super(site, 'plugins', 'Plugins', description: 'Plugins in use.');

  @override
  Future generateContent(Map<String, String> params) async {
    h3('Analysis plugins');
    var analysisPlugins = server.pluginManager.plugins;

    if (analysisPlugins.isEmpty) {
      blankslate('No known analysis plugins.');
    } else {
      analysisPlugins
          .sort((first, second) => first.pluginId.compareTo(second.pluginId));
      for (var plugin in analysisPlugins) {
        var id = plugin.pluginId;
        var data = plugin.data;
        var responseTimes = PluginManager.pluginResponseTimes[plugin] ?? {};

        var components = path.split(id);
        var length = components.length;
        String name;
        if (length == 0) {
          name = 'unknown plugin';
        } else if (length > 2) {
          name = components[length - 3];
        } else {
          name = components[length - 1];
        }
        h4(name);
        p('bootstrap package path: $id');
        if (plugin is DiscoveredPluginInfo) {
          p('execution path: ${plugin.executionPath}');
          p('packages file path: ${plugin.packagesPath}');
        }
        if (data.name == null) {
          if (plugin.exception != null) {
            p('not running');
            pre(() {
              buf.write(plugin.exception);
            });
          } else {
            p('not running for unknown reason');
          }
        } else {
          p('name: ${data.name}');
          p('version: ${data.version}');
          p('Associated contexts:');
          var contexts = plugin.contextRoots;
          if (contexts.isEmpty) {
            blankslate('none');
          } else {
            ul(contexts.toList(), (ContextRoot root) {
              buf.writeln(root.root);
            });
          }
          p('Performance:');
          var entries = responseTimes.entries.toList();
          entries.sort((first, second) => first.key.compareTo(second.key));
          for (var entry in entries) {
            var requestName = entry.key;
            var data = entry.value;
            // TODO(brianwilkerson) Consider displaying these times as a graph,
            //  similar to the one in CompletionPage.generateContent.
            var buffer = StringBuffer();
            buffer.write(requestName);
            buffer.write(' ');
            buffer.write(data.toAnalyticsString());
            p(buffer.toString());
          }
        }
      }
    }
  }
}

class StatusPage extends DiagnosticPageWithNav {
  StatusPage(DiagnosticsSite site)
      : super(site, 'status', 'Status',
            description:
                'General status and diagnostics for the analysis server.');

  @override
  Future generateContent(Map<String, String> params) async {
    buf.writeln('<div class="columns">');

    buf.writeln('<div class="column one-half">');
    h3('Status');
    buf.writeln(writeOption('Server type', server.runtimeType));
    // buf.writeln(writeOption('Instrumentation enabled',
    //     AnalysisEngine.instance.instrumentationService.isActive));
    buf.writeln(writeOption('Server process ID', pid));
    buf.writeln('</div>');

    buf.writeln('<div class="column one-half">');
    h3('Versions');
    buf.writeln(writeOption('Analysis server version', PROTOCOL_VERSION));
    buf.writeln(writeOption('Dart SDK', Platform.version));
    buf.writeln('</div>');

    buf.writeln('</div>');

    // SDK configuration overrides.
    var sdkConfig = server.options.configurationOverrides;
    if (sdkConfig?.hasAnyOverrides == true) {
      buf.writeln('<div class="columns">');

      buf.writeln('<div class="column one-half">');
      h3('Configuration Overrides');
      buf.writeln(
          '<pre><code>${sdkConfig?.displayString ?? '<unknown overrides>'}</code></pre><br>');
      buf.writeln('</div>');

      buf.writeln('</div>');
    }

    var lines = site.lastPrintedLines;
    if (lines.isNotEmpty) {
      h3('Debug output');
      p(lines.join('\n'), style: 'white-space: pre');
    }
  }
}

class SubscriptionsPage extends DiagnosticPageWithNav {
  @override
  AnalysisServer server;

  SubscriptionsPage(DiagnosticsSite site, this.server)
      : super(site, 'subscriptions', 'Subscriptions',
            description: 'Registered subscriptions to analysis server events.');

  @override
  Future generateContent(Map<String, String> params) async {
    // server domain
    h3('Server domain subscriptions');
    ul(ServerService.VALUES, (item) {
      if (server.serverServices.contains(item)) {
        buf.write('$item (has subscriptions)');
      } else {
        buf.write('$item (no subscriptions)');
      }
    });

    // analysis domain
    h3('Analysis domain subscriptions');
    for (var service in AnalysisService.VALUES) {
      buf.writeln('${service.name}<br>');
      ul(server.analysisServices[service] ?? {}, (item) {
        buf.write('$item');
      });
    }

    // completion domain
    h3('Completion domain subscriptions');
    ul(CompletionService.VALUES, (service) {
      if (server.completionState.subscriptions.contains(service)) {
        buf.write('$service (has subscriptions)');
      } else {
        buf.write('$service (no subscriptions)');
      }
    });
  }
}

class TimingPage extends DiagnosticPageWithNav with PerformanceChartMixin {
  TimingPage(DiagnosticsSite site)
      : super(site, 'timing', 'Timing', description: 'Timing statistics.');

  @override
  Future generateContent(Map<String, String> params) async {
    var kind = params['kind'];

    List<RequestPerformance> items;
    if (kind == 'completion') {
      items = server.recentPerformance.completion.items.toList();
    } else {
      items = server.recentPerformance.requests.items.toList();
    }

    var id = int.tryParse(params['id'] ?? '');
    if (id == null) {
      return _generateList(items);
    } else {
      return _generateDetails(id, items);
    }
  }

  String _formatTiming(RequestPerformance item) {
    var buffer = StringBuffer();
    buffer.write(printMilliseconds(item.performance.elapsed.inMilliseconds));

    var latency = item.requestLatency;
    if (latency != null) {
      buffer
        ..write(' <small class="subtle" title="client-to-server latency">(+ ')
        ..write(printMilliseconds(latency))
        ..write(')</small>');
    }

    return buffer.toString();
  }

  void _generateDetails(int id, List<RequestPerformance> items) {
    var item = items.firstWhereOrNull((info) => info.id == id);

    if (item == null) {
      blankslate('Unable to find data for $id. '
          'Perhaps newer requests have pushed it out of the buffer?');
      return;
    }

    var buffer = StringBuffer();
    item.performance.write(buffer: buffer);
    pre(() {
      buf.write('<code>');
      buf.write(escape('$buffer'));
      buf.writeln('</code>');
    });
  }

  void _generateList(List<RequestPerformance> items) {
    if (items.isEmpty) {
      blankslate('No requests recorded.');
      return;
    }

    drawChart(items);

    // emit the data as a table
    buf.writeln('<table>');
    buf.writeln('<tr><th>Time</th><th>Request</th></tr>');
    for (var item in items) {
      buf.writeln(
        '<tr>'
        '<td class="pre right"><a href="/timing?id=${item.id}">'
        '${_formatTiming(item)}'
        '</a></td>'
        '<td>${escape(item.operation)}</td>'
        '</tr>',
      );
    }
    buf.writeln('</table>');
  }
}