GopherShy/lib/gopherlib.dart

import 'dart:async';
import 'dart:convert';
import 'dart:io';
import 'dart:typed_data';

enum DocumentType {
  /*Canonical types RFC1436 line 548*/
  /// Item is a file (0)
  TextFile("0"),

  /// Item is a directory (1)
  Directory("1"),

  /// Item is a CSO phone-book server (2)
  CSO("2"),

  /// Error returned by server (3)
  ErrorCode("3"),

  /// Item is a BinHexed Macintosh file. (4)
  BinHex("4"),

  /// Item is DOS binary archive of some sort. (5)
  DosBinary("5"),

  /// Item is a UNIX uuencoded file. (6)
  Uuencoded("6"),

  /// Item is an Index-Search server. (7)
  Search("7"),

  /// Item points to a text-based telnet session. (8)
  Telnet("8"),

  /// Item is a binary file! (9)
  Binary("9"),

  /// It em is a redundant server (*)
  MirrorOrAlternate("*"),

  /// Item points to a text-based tn3270 session. (T)
  Telnet3270("T"),

  /// Item is a GIF format graphics file. (g)
  Gif("g"),

  /// Item is some kind of image file.  Client decides how to display. (I)
  Image("I"),
  /**** Gopher+ ****/
  /// Bitmap image (:)
  Bitmap(":"),

  /// Movie file (;)
  Movie(";"),

  /// Sound file (<)
  Soundfile("<"),
  /*non-canonical types*/
  /// Doc. Used for .doc and .pdf (d)
  Doc("d"),

  /// HTML file (h)
  Html("h"),

  /// Informational message, widely used (i)
  Informational("i"),

  /// Usually png image (p)
  PngImage("p"),

  /// Rich text document (r)
  RichTextDocument("r"),

  /// usually WAV (s)
  SoundFile("s"),

  /// Pdf (P)
  Pdf("P"),

  /// XML file (X)
  Xml("X"),

  /// Document type isn't any of the known types
  Unknown("?");

  const DocumentType(this.code);
  final String code;

  /// Returns the canonical name of the document type
  String get typeName => name;

  /// Returns character code used for this document type
  String get typeCode => code;
}

class ParsedGopherItem {
  static final docMap = {for (var item in DocumentType.values) item.code: item};

  Uri url;
  String? name;
  DocumentType documentType;

  ParsedGopherItem._(this.url, this.name, this.documentType);

  /// Parse gopher item from url, from url file type is not known
  /// so it is guessed by file extension
  // TODO: Do actuall filetype guessing
  static ParsedGopherItem parseUrl(String url) {
    if (!url.startsWith("gopher://")) url = "gopher://$url";
    var uri = Uri.parse(url);

    // We expect TextFile by default unless we think it's menu
    final doctype = (uri.path == "" || uri.path.endsWith("/")) ? DocumentType.Directory :  DocumentType.TextFile;

    if (uri.port == 0) uri = uri.replace(port: 70);

    return ParsedGopherItem._(uri, "", doctype);
  }

  /// Parses single gopher item from single menu line
  static ParsedGopherItem? parseMenuLine(String menuLine) {
    // If theres not even the item type and name we won't bother
    if (menuLine.length < 2) return null;

    var parts = menuLine.split("\t");

    if (parts.length != 4) return null;

    // If string is correct, we should have 4 parts
    // 0Pony Prices	Prices/Ponies	pserver.bookstore.umn.edu	70
    //type;name       ; selektor     ;  host                     ;  port
    //   0;Pony Prices;	Prices/Ponies;	pserver.bookstore.umn.edu;	70
    var uri = Uri(
      scheme: "gopher",
      path: parts[1],
      host: parts[2],
      port: int.tryParse(parts[3]) ?? 70,
    );

    String type = menuLine[0];
    String name = parts[0].substring(1);

    final docType = docMap.containsKey(type) ? docMap[type]! : docMap["?"]!;
    return ParsedGopherItem._(uri, name, docType);
  }

  /// Reads gopher directory/menu from host:port and optionally selector
  static Future<LoadedGopherItem> loadMenu(String host, int port,
      {String selector = ""}) async {

    final Socket sock = await Socket.connect(host, port);
    sock.write("$selector\r\n");
    await sock.flush();
    print("Entered load menu");
    final ret = <ParsedGopherItem>[];
    final List<Uint8List> rawRet = <Uint8List>[];
    final subscription = sock.listen(
      (Uint8List data) {
        rawRet.add(data);
        String rcvd = utf8.decode(data, allowMalformed: true);

        ParsedGopherItem? apend;
        // TODO: This is flawed, it usually works but it's just a matter of time before it breaks
        //       If \n is in the next buffer, the part before \n gets cutoff
        //       resulting in unparsable line
        //       the substrining must begin outside the loop listen call
        //       or it must be rewritten using LineSplitter()
        int start = 0;
        for (int i = 0; i < rcvd.length; i++) {
          if (rcvd[i] == "\n") {
            var menuLine = rcvd.substring(start, i);
            // TODO: Gophernicus sends .\r for some reason which doesnt seem acording to spec
            // Maybe ignore when sent from menu=forced?
            if (menuLine.startsWith(".")) {
              print("Received starting dot, this should be the end I guess");
              return;
            }
            apend = parseMenuLine(menuLine);
            if (apend != null) ret.add(apend);
            start = i + 1;
          }
        }
      });
    await subscription.asFuture<void>();
    sock.close();
    return LoadedGopherItem(
      ParsedGopherItem._(Uri.parse("gopher://$host:$port$selector"), selector,
        DocumentType.Directory),
      asMenu: ret,
      data: rawRet,
    );
  }

  Future<LoadedGopherItem> loadItem() async {
    final Socket sock = await Socket.connect(url.host, url.port);

    print("Sending request to ${url.host}[:${url.port}] => '${url.path}'");
    sock.write("${url.path}\r\n");
    var data = await sock.toList();
    print("Closing: ${sock.close()} as type ${this.documentType}");

    return LoadedGopherItem(this, data: data);
  }

  Future<LoadedGopherItem> load({bool? forceMenu}) async {
    if ((documentType == DocumentType.Directory) || (forceMenu ?? false)) {
      print("Forcing? ($forceMenu) reload as menu for: $url");
      return loadMenu(url.host, url.port, selector: url.path);
    }
    return loadItem();
  }
}

class LoadedGopherItem {
  final ParsedGopherItem parsed;
  final List<Uint8List>? data;
  final List<ParsedGopherItem>? asMenu;

  LoadedGopherItem(this.parsed, {this.data, this.asMenu});
}