import "dart:convert";
import "dart:io";
import "dart:typed_data";

import "package:html/dom.dart" as dom;
import "package:html/parser.dart" as html_parser;
import "package:path/path.dart" as path;

import "../api/openrouter_client.dart";
import "base_tool.dart";

const int _maxUrlLength = 2000;
const int _maxFetchBytes = 10 * 1024 * 1024;
const int _maxPromptContentChars = 100000;
const int _maxRedirects = 10;
const Duration _cacheTtl = Duration(minutes: 15);
const int _maxCacheEntries = 64;

final List<_CacheKey> _cacheOrder = <_CacheKey>[];
final Map<_CacheKey, _CacheEntry> _cache = <_CacheKey, _CacheEntry>{};

const Set<String> _preapprovedHosts = {
  "platform.claude.com",
  "code.claude.com",
  "modelcontextprotocol.io",
  "docs.python.org",
  "en.cppreference.com",
  "docs.oracle.com",
  "learn.microsoft.com",
  "developer.mozilla.org",
  "go.dev",
  "pkg.go.dev",
  "www.php.net",
  "docs.swift.org",
  "kotlinlang.org",
  "ruby-doc.org",
  "doc.rust-lang.org",
  "www.typescriptlang.org",
  "react.dev",
  "angular.io",
  "vuejs.org",
  "nextjs.org",
  "expressjs.com",
  "nodejs.org",
  "bun.sh",
  "getbootstrap.com",
  "tailwindcss.com",
  "redux.js.org",
  "webpack.js.org",
  "jestjs.io",
  "reactrouter.com",
  "docs.djangoproject.com",
  "flask.palletsprojects.com",
  "fastapi.tiangolo.com",
  "pandas.pydata.org",
  "numpy.org",
  "www.tensorflow.org",
  "pytorch.org",
  "scikit-learn.org",
  "matplotlib.org",
  "requests.readthedocs.io",
  "jupyter.org",
  "laravel.com",
  "symfony.com",
  "wordpress.org",
  "docs.spring.io",
  "hibernate.org",
  "tomcat.apache.org",
  "gradle.org",
  "maven.apache.org",
  "asp.net",
  "dotnet.microsoft.com",
  "nuget.org",
  "reactnative.dev",
  "docs.flutter.dev",
  "developer.apple.com",
  "developer.android.com",
  "keras.io",
  "spark.apache.org",
  "huggingface.co",
  "www.kaggle.com",
  "www.mongodb.com",
  "redis.io",
  "www.postgresql.org",
  "dev.mysql.com",
  "www.sqlite.org",
  "graphql.org",
  "prisma.io",
  "docs.aws.amazon.com",
  "cloud.google.com",
  "kubernetes.io",
  "www.docker.com",
  "www.terraform.io",
  "www.ansible.com",
  "docs.netlify.com",
  "devcenter.heroku.com",
  "cypress.io",
  "selenium.dev",
  "docs.unity.com",
  "docs.unrealengine.com",
  "git-scm.com",
  "nginx.org",
  "httpd.apache.org",
};

const Map<String, List<String>> _preapprovedPathPrefixes = {
  "github.com": <String>["/anthropics"],
  "vercel.com": <String>["/docs"],
};

class WebFetchTool extends BaseTool {
  @override
  final String name = "WebFetch";

  @override
  final String description =
      "Fetch content from a URL, convert it to readable markdown-like text, and answer a prompt about that page.";

  @override
  Future<String> execute(Map<String, dynamic> input) async {
    final rawUrl = requireString(input, "url").trim();
    final prompt = requireString(input, "prompt").trim();
    final apiKey = optionalString(input, "_api_key") ?? "";
    final model = optionalString(input, "_model") ?? "openrouter/auto";
    final permissionMode = optionalString(input, "_permission_mode") ?? "default";
    final allowRules = _readStringList(input["_allow_rules"]);
    final askRules = _readStringList(input["_ask_rules"]);
    final denyRules = _readStringList(input["_deny_rules"]);

    if (prompt.isEmpty) {
      throw ArgumentError("prompt must not be empty");
    }
    if (apiKey.isEmpty) {
      throw StateError("WebFetch requires an OpenRouter API key");
    }

    final url = _normalizeUrl(rawUrl);
    final uri = Uri.parse(url);
    _enforcePermissions(
      uri: uri,
      permissionMode: permissionMode,
      allowRules: allowRules,
      askRules: askRules,
      denyRules: denyRules,
    );

    final isPreapproved = _isPreapprovedUrl(url);
    final startTime = DateTime.now();
    final fetched = await _fetchUrl(url);
    final durationMs = DateTime.now().difference(startTime).inMilliseconds;

    if (fetched.isRedirectNotice) {
      return _formatOutput(
        fetched: fetched,
        durationMs: durationMs,
        result: fetched.content,
      );
    }

    final result = await _summarizeFetchedContent(
      apiKey: apiKey,
      model: model,
      fetched: fetched,
      prompt: prompt,
      isPreapproved: isPreapproved,
    );

    return _formatOutput(
      fetched: fetched,
      durationMs: durationMs,
      result: result,
    );
  }

  String _normalizeUrl(String rawUrl) {
    if (rawUrl.isEmpty || rawUrl.length > _maxUrlLength) {
      throw ArgumentError("Invalid URL");
    }

    Uri uri;
    try {
      uri = Uri.parse(rawUrl);
    } catch (_) {
      throw ArgumentError("Invalid URL: $rawUrl");
    }

    if (!uri.hasScheme) {
      throw ArgumentError("URL must include a scheme");
    }
    if (uri.userInfo.isNotEmpty || uri.host.isEmpty) {
      throw ArgumentError("Invalid URL");
    }
    if (uri.scheme == "http") {
      uri = uri.replace(scheme: "https");
    }
    if (uri.scheme != "https") {
      throw ArgumentError("Only https URLs are supported");
    }

    final host = uri.host.toLowerCase();
    if (_isLocalOrPrivateHost(host)) {
      throw ArgumentError("Fetching local or private network URLs is not allowed");
    }

    return uri.toString();
  }

  void _enforcePermissions({
    required Uri uri,
    required String permissionMode,
    required List<String> allowRules,
    required List<String> askRules,
    required List<String> denyRules,
  }) {
    final bypassModes = <String>{"bypassPermissions", "dontAsk"};
    if (bypassModes.contains(permissionMode)) {
      return;
    }

    final domainRule = "domain:${uri.host.toLowerCase()}";
    final matchingDeny = denyRules.where((rule) => _matchesRule(rule, uri)).toList();
    if (matchingDeny.isNotEmpty) {
      throw StateError("WebFetch denied access to $domainRule.");
    }

    final matchingAllow = allowRules.where((rule) => _matchesRule(rule, uri)).toList();
    if (matchingAllow.isNotEmpty) {
      return;
    }

    final matchingAsk = askRules.where((rule) => _matchesRule(rule, uri)).toList();
    if (matchingAsk.isNotEmpty) {
      throw StateError(
        "WebFetch requires permission for $domainRule. Add an allow rule to proceed.",
      );
    }
  }

  bool _matchesRule(String rawRule, Uri uri) {
    var rule = rawRule.trim();
    if (rule.startsWith("WebFetch(") && rule.endsWith(")")) {
      rule = rule.substring("WebFetch(".length, rule.length - 1);
    }
    if (!rule.startsWith("domain:")) {
      return false;
    }

    final pattern = rule.substring("domain:".length).toLowerCase();
    final host = uri.host.toLowerCase();
    if (pattern.isEmpty) {
      return false;
    }
    if (pattern == host) {
      return true;
    }
    if (pattern.startsWith("*.")) {
      final suffix = pattern.substring(1);
      return host.endsWith(suffix);
    }
    if (pattern.endsWith(".*")) {
      final prefix = pattern.substring(0, pattern.length - 1);
      return host.startsWith(prefix);
    }
    return false;
  }

  Future<_FetchedContent> _fetchUrl(String originalUrl) async {
    _pruneCache();
    final cacheKey = _CacheKey(originalUrl);
    final cached = _cache[cacheKey];
    if (cached != null && DateTime.now().difference(cached.fetchedAt) < _cacheTtl) {
      _touchCacheEntry(cacheKey);
      return cached.content;
    }

    final httpClient = HttpClient()..connectionTimeout = const Duration(seconds: 60);
    try {
      var currentUrl = Uri.parse(originalUrl);
      final originalComparableHost = _stripWww(currentUrl.host);

      for (var redirectCount = 0; redirectCount <= _maxRedirects; redirectCount++) {
        final request = await httpClient.getUrl(currentUrl);
        request.headers.set("Accept", "text/markdown, text/html, text/plain, */*");
        request.headers.set("User-Agent", "clawd_code/0.1.0 (WebFetch)");

        final response = await request.close().timeout(const Duration(seconds: 60));
        final statusCode = response.statusCode;
        final statusText = response.reasonPhrase;
        final location = response.headers.value(HttpHeaders.locationHeader);

        if (_isRedirect(statusCode) && location != null) {
          final redirectUrl = currentUrl.resolve(location);
          if (_stripWww(redirectUrl.host) != originalComparableHost) {
            final redirectNotice = _FetchedContent(
              finalUrl: currentUrl.toString(),
              statusCode: statusCode,
              reasonPhrase: statusText,
              bytes: 0,
              contentType: "text/plain",
              content:
                  "REDIRECT DETECTED: The URL redirects to a different host.\n\n"
                  "Original URL: $currentUrl\n"
                  "Redirect URL: $redirectUrl\n"
                  "Status: $statusCode $statusText\n\n"
                  "To complete your request, use WebFetch again with these parameters:\n"
                  "- url: \"$redirectUrl\"",
              isRedirectNotice: true,
            );
            _storeCacheEntry(cacheKey, redirectNotice);
            return redirectNotice;
          }

          currentUrl = redirectUrl;
          continue;
        }

        final bytes = await _readResponseBytes(response);
        final contentType =
            response.headers.contentType?.mimeType ?? "application/octet-stream";
        final isBinary = _looksBinary(contentType, bytes);
        final persistedBinary = isBinary
            ? await _persistBinaryContent(bytes, contentType)
            : null;
        final decodedText = _decodeBody(bytes, isBinary: isBinary);
        final readableContent = _extractReadableContent(
          decodedText,
          contentType: contentType,
          url: currentUrl.toString(),
        );

        final fetched = _FetchedContent(
          finalUrl: currentUrl.toString(),
          statusCode: statusCode,
          reasonPhrase: statusText,
          bytes: bytes.length,
          contentType: contentType,
          content: readableContent,
          persistedBinaryPath: persistedBinary?.path,
          persistedBinarySize: persistedBinary?.size,
        );
        _storeCacheEntry(cacheKey, fetched);
        return fetched;
      }

      throw StateError("Too many redirects");
    } finally {
      httpClient.close();
    }
  }

  Future<List<int>> _readResponseBytes(HttpClientResponse response) async {
    final builder = BytesBuilder(copy: false);
    await for (final chunk in response) {
      builder.add(chunk);
      if (builder.length > _maxFetchBytes) {
        throw StateError("Response exceeded ${_maxFetchBytes} bytes");
      }
    }
    return builder.takeBytes();
  }

  String _decodeBody(List<int> bytes, {required bool isBinary}) {
    if (isBinary) {
      return latin1.decode(bytes, allowInvalid: true);
    }

    try {
      return utf8.decode(bytes);
    } catch (_) {
      return latin1.decode(bytes, allowInvalid: true);
    }
  }

  Future<_PersistedBinary?> _persistBinaryContent(
    List<int> bytes,
    String contentType,
  ) async {
    try {
      final extension = _extensionForMimeType(contentType);
      final fileName =
          "webfetch-${DateTime.now().millisecondsSinceEpoch}-${_randomSuffix()}$extension";
      final file = File(path.join(Directory.systemTemp.path, fileName));
      await file.writeAsBytes(bytes, flush: true);
      return _PersistedBinary(path: file.path, size: bytes.length);
    } catch (_) {
      return null;
    }
  }

  String _extractReadableContent(
    String rawContent, {
    required String contentType,
    required String url,
  }) {
    if (contentType.contains("markdown") || contentType.contains("plain")) {
      return _truncateContent(rawContent.trim());
    }

    final document = html_parser.parse(rawContent);
    document.querySelectorAll("script,style,noscript,svg,iframe").forEach((node) {
      node.remove();
    });

    final title = document.querySelector("title")?.text.trim();
    final description = document
        .querySelector('meta[name="description"], meta[property="og:description"]')
        ?.attributes["content"]
        ?.trim();

    final root =
        document.querySelector("article") ??
        document.querySelector("main") ??
        document.body ??
        document.documentElement;

    if (root == null) {
      throw StateError("No readable content found at $url");
    }

    final buffer = StringBuffer();
    if (title != null && title.isNotEmpty) {
      buffer.writeln("# $title");
      buffer.writeln();
    }
    if (description != null && description.isNotEmpty) {
      buffer.writeln(description);
      buffer.writeln();
    }

    for (final node in root.nodes) {
      _writeNode(node, buffer, listDepth: 0, inPre: false);
    }

    var result = buffer.toString();
    result = result.replaceAll(RegExp(r"\n{3,}"), "\n\n").trim();
    result = _decodeHtmlEntities(result);
    if (result.isEmpty) {
      throw StateError("No readable content found at $url");
    }

    return _truncateContent(result);
  }

  void _writeNode(
    dom.Node node,
    StringBuffer buffer, {
    required int listDepth,
    required bool inPre,
  }) {
    if (node is dom.Text) {
      final text = inPre
          ? node.text
          : node.text.replaceAll(RegExp(r"\s+"), " ");
      if (text.trim().isNotEmpty) {
        buffer.write(text);
      }
      return;
    }

    if (node is! dom.Element) {
      return;
    }

    final tag = node.localName?.toLowerCase() ?? "";
    switch (tag) {
      case "h1":
      case "h2":
      case "h3":
      case "h4":
      case "h5":
      case "h6":
        final level = int.tryParse(tag.substring(1)) ?? 1;
        buffer
          ..writeln()
          ..write("${"#" * level} ${node.text.trim()}")
          ..writeln()
          ..writeln();
        return;
      case "p":
        _writeChildren(node, buffer, listDepth: listDepth, inPre: false);
        buffer.writeln();
        buffer.writeln();
        return;
      case "br":
        buffer.writeln();
        return;
      case "pre":
        final code = node.text.trimRight();
        if (code.isNotEmpty) {
          buffer
            ..writeln()
            ..writeln("```")
            ..writeln(code)
            ..writeln("```")
            ..writeln();
        }
        return;
      case "code":
        final code = node.text.replaceAll(RegExp(r"\s+"), " ").trim();
        if (code.isNotEmpty) {
          buffer.write("`$code`");
        }
        return;
      case "ul":
      case "ol":
        buffer.writeln();
        var index = 1;
        for (final child in node.children.where((child) => child.localName == "li")) {
          final prefix = tag == "ol" ? "${index++}." : "-";
          buffer.write("${"  " * listDepth}$prefix ");
          _writeChildren(child, buffer, listDepth: listDepth + 1, inPre: false);
          buffer.writeln();
        }
        buffer.writeln();
        return;
      case "li":
        _writeChildren(node, buffer, listDepth: listDepth, inPre: false);
        return;
      case "a":
        final label = node.text.replaceAll(RegExp(r"\s+"), " ").trim();
        final href = node.attributes["href"]?.trim();
        if (label.isNotEmpty && href != null && href.isNotEmpty) {
          buffer.write("[$label]($href)");
        } else {
          _writeChildren(node, buffer, listDepth: listDepth, inPre: false);
        }
        return;
      case "blockquote":
        final quote = node.text.trim();
        if (quote.isNotEmpty) {
          buffer
            ..writeln()
            ..writeln("> ${quote.replaceAll("\n", "\n> ")}")
            ..writeln();
        }
        return;
      case "table":
        final tableText = node.text.replaceAll(RegExp(r"\s+"), " ").trim();
        if (tableText.isNotEmpty) {
          buffer
            ..writeln()
            ..writeln(tableText)
            ..writeln();
        }
        return;
      case "hr":
        buffer
          ..writeln()
          ..writeln("---")
          ..writeln();
        return;
      default:
        final blockTags = <String>{
          "article",
          "section",
          "main",
          "div",
          "header",
          "footer",
          "nav",
          "aside",
        };
        final wasBlock = blockTags.contains(tag);
        if (wasBlock) {
          buffer.writeln();
        }
        _writeChildren(node, buffer, listDepth: listDepth, inPre: inPre);
        if (wasBlock) {
          buffer.writeln();
        }
    }
  }

  void _writeChildren(
    dom.Element element,
    StringBuffer buffer, {
    required int listDepth,
    required bool inPre,
  }) {
    for (final child in element.nodes) {
      _writeNode(child, buffer, listDepth: listDepth, inPre: inPre);
    }
  }

  Future<String> _summarizeFetchedContent({
    required String apiKey,
    required String model,
    required _FetchedContent fetched,
    required String prompt,
    required bool isPreapproved,
  }) async {
    if (isPreapproved &&
        fetched.contentType.contains("markdown") &&
        fetched.content.length <= _maxPromptContentChars) {
      return fetched.content;
    }

    final client = await OpenRouterClientFactory.create(apiKey: apiKey);
    try {
      final response = await client.createMessage(
        model: model,
        maxTokens: 2048,
        messages: <Map<String, dynamic>>[
          <String, dynamic>{
            "role": "system",
            "content": isPreapproved
                ? "Provide a concise response based on the fetched content. Include relevant details and code examples when present."
                : "Provide a concise response based only on the fetched content. Use short quotes only when necessary.",
          },
          <String, dynamic>{
            "role": "user",
            "content":
                "URL: ${fetched.finalUrl}\n"
                "Content-Type: ${fetched.contentType}\n\n"
                "Web page content:\n---\n${fetched.content}\n---\n\n"
                "$prompt",
          },
        ],
      );

      final parts = <String>[];
      for (final block in response.content) {
        if (block is Map<String, dynamic> && block["type"] == "text") {
          final text = block["text"];
          if (text is String && text.isNotEmpty) {
            parts.add(text);
          }
        }
      }

      final result = parts.join("\n").trim();
      return result.isEmpty ? "No response from model." : result;
    } finally {
      client.close();
    }
  }

  String _formatOutput({
    required _FetchedContent fetched,
    required int durationMs,
    required String result,
  }) {
    final lines = <String>[
      "URL: ${fetched.finalUrl}",
      "Status: ${fetched.statusCode} ${fetched.reasonPhrase}",
      "Bytes: ${fetched.bytes}",
      "Duration: ${_formatDuration(durationMs)}",
    ];

    if (fetched.persistedBinaryPath != null && fetched.persistedBinarySize != null) {
      lines.add(
        "Binary content saved: ${fetched.persistedBinaryPath} (${fetched.persistedBinarySize} bytes)",
      );
    }

    lines
      ..add("")
      ..add(result.trim());

    return lines.join("\n");
  }

  void _pruneCache() {
    final now = DateTime.now();
    _cacheOrder.removeWhere((key) {
      final entry = _cache[key];
      final expired = entry == null || now.difference(entry.fetchedAt) >= _cacheTtl;
      if (expired) {
        _cache.remove(key);
      }
      return expired;
    });
  }

  void _storeCacheEntry(_CacheKey key, _FetchedContent content) {
    _cache[key] = _CacheEntry(content: content, fetchedAt: DateTime.now());
    _touchCacheEntry(key);
    while (_cacheOrder.length > _maxCacheEntries) {
      final removed = _cacheOrder.removeAt(0);
      _cache.remove(removed);
    }
  }

  void _touchCacheEntry(_CacheKey key) {
    _cacheOrder.remove(key);
    _cacheOrder.add(key);
  }

  bool _isPreapprovedUrl(String url) {
    final uri = Uri.parse(url);
    final host = uri.host.toLowerCase();
    if (_preapprovedHosts.contains(host)) {
      return true;
    }
    final prefixes = _preapprovedPathPrefixes[host];
    if (prefixes == null) {
      return false;
    }
    final pathName = uri.path;
    return prefixes.any(
      (prefix) => pathName == prefix || pathName.startsWith("$prefix/"),
    );
  }

  bool _isLocalOrPrivateHost(String host) {
    final lower = host.toLowerCase();
    if (lower == "localhost" || !lower.contains(".")) {
      return true;
    }
    if (lower.endsWith(".local")) {
      return true;
    }

    final ipv4 = RegExp(r"^(\d{1,3}\.){3}\d{1,3}$");
    if (ipv4.hasMatch(lower)) {
      final parts = lower.split(".").map(int.parse).toList();
      if (parts.any((part) => part < 0 || part > 255)) {
        return true;
      }
      return parts[0] == 10 ||
          parts[0] == 127 ||
          (parts[0] == 172 && parts[1] >= 16 && parts[1] <= 31) ||
          (parts[0] == 192 && parts[1] == 168) ||
          (parts[0] == 169 && parts[1] == 254);
    }

    if (lower == "::1" || lower.startsWith("fc") || lower.startsWith("fd")) {
      return true;
    }

    return false;
  }

  bool _isRedirect(int statusCode) {
    return statusCode == 301 ||
        statusCode == 302 ||
        statusCode == 307 ||
        statusCode == 308;
  }

  bool _looksBinary(String contentType, List<int> bytes) {
    if (contentType.startsWith("text/") ||
        contentType.contains("json") ||
        contentType.contains("xml") ||
        contentType.contains("javascript") ||
        contentType.contains("xhtml")) {
      return false;
    }

    for (final byte in bytes.take(256)) {
      if (byte == 0) {
        return true;
      }
    }
    return true;
  }

  String _truncateContent(String content) {
    if (content.length <= _maxPromptContentChars) {
      return content;
    }
    return "${content.substring(0, _maxPromptContentChars)}\n\n[Content truncated due to length...]";
  }

  String _decodeHtmlEntities(String text) {
    return text
        .replaceAll("&nbsp;", " ")
        .replaceAll("&amp;", "&")
        .replaceAll("&lt;", "<")
        .replaceAll("&gt;", ">")
        .replaceAll("&quot;", "\"")
        .replaceAll("&#39;", "'")
        .replaceAll("&#x27;", "'")
        .replaceAll("&apos;", "'");
  }

  String _extensionForMimeType(String contentType) {
    if (contentType.contains("pdf")) return ".pdf";
    if (contentType.contains("zip")) return ".zip";
    if (contentType.contains("png")) return ".png";
    if (contentType.contains("jpeg")) return ".jpg";
    if (contentType.contains("gif")) return ".gif";
    if (contentType.contains("webp")) return ".webp";
    if (contentType.contains("json")) return ".json";
    return ".bin";
  }

  List<String> _readStringList(Object? value) {
    if (value is! List) {
      return const <String>[];
    }
    return value
        .whereType<String>()
        .map((item) => item.trim())
        .where((item) => item.isNotEmpty)
        .toList(growable: false);
  }

  String _randomSuffix() {
    final radix = DateTime.now().microsecondsSinceEpoch.toRadixString(36);
    return radix.substring(radix.length - 6);
  }

  String _stripWww(String host) => host.replaceFirst(RegExp(r"^www\."), "");

  String _formatDuration(int durationMs) {
    if (durationMs < 1000) {
      return "${durationMs}ms";
    }
    return "${(durationMs / 1000).toStringAsFixed(1)}s";
  }
}

class _FetchedContent {
  const _FetchedContent({
    required this.finalUrl,
    required this.statusCode,
    required this.reasonPhrase,
    required this.bytes,
    required this.contentType,
    required this.content,
    this.persistedBinaryPath,
    this.persistedBinarySize,
    this.isRedirectNotice = false,
  });

  final String finalUrl;
  final int statusCode;
  final String reasonPhrase;
  final int bytes;
  final String contentType;
  final String content;
  final String? persistedBinaryPath;
  final int? persistedBinarySize;
  final bool isRedirectNotice;
}

class _PersistedBinary {
  const _PersistedBinary({required this.path, required this.size});

  final String path;
  final int size;
}

class _CacheEntry {
  const _CacheEntry({required this.content, required this.fetchedAt});

  final _FetchedContent content;
  final DateTime fetchedAt;
}

class _CacheKey {
  const _CacheKey(this.url);

  final String url;

  @override
  bool operator ==(Object other) =>
      identical(this, other) || other is _CacheKey && other.url == url;

  @override
  int get hashCode => url.hashCode;
}