/* This Source Code Form is subject to the terms of the Mozilla Public
 * License, v. 2.0. If a copy of the MPL was not distributed with this
 * file, You can obtain one at http://mozilla.org/MPL/2.0/. */

// This file implements test NNTP servers

import { MimeParser } from "resource:///modules/mimeParser.sys.mjs";

export class NntpDaemon {
  constructor(flags) {
    this._groups = {};
    this._messages = {};
    this._flags = flags;
  }
  addGroup(group, postable) {
    var flags = 0;
    if (postable) {
      flags |= NNTP_POSTABLE;
    }
    this._groups[group] = { keys: [], flags, nextKey: 1 };
  }
  addArticle(article) {
    this._messages[article.messageID] = article;
    for (const group of article.groups) {
      if (group in this._groups) {
        var key = this._groups[group].nextKey++;
        this._groups[group][key] = article;
        this._groups[group].keys.push(key);
      }
    }
  }
  addArticleToGroup(article, group, key) {
    this._groups[group][key] = article;
    this._messages[article.messageID] = article;
    this._groups[group].keys.push(key);
    if (this._groups[group].nextKey <= key) {
      this._groups[group].nextKey = key + 1;
    }
  }
  removeArticleFromGroup(groupName, key) {
    const group = this._groups[groupName];
    delete group[key];
    group.keys = group.keys.filter(x => x != key);
  }
  getGroup(group) {
    if (this._groups.hasOwnProperty(group)) {
      return this._groups[group];
    }
    return null;
  }
  getGroupStats(group) {
    if (group.keys.length == 0) {
      return [0, 0, 0];
    }
    var min = 1 << 30;
    var max = 0;
    group.keys.forEach(function (key) {
      if (key < min) {
        min = key;
      }
      if (key > max) {
        max = key;
      }
    });

    var length;
    if (hasFlag(this._flags, NNTP_REAL_LENGTH)) {
      length = group.keys.length;
    } else {
      length = max - min + 1;
    }

    return [length, min, max];
  }
  getArticle(msgid) {
    if (msgid in this._messages) {
      return this._messages[msgid];
    }
    return null;
  }
}

export function NewsArticle(text) {
  this.headers = new Map();
  this.body = "";
  this.messageID = "";
  this.fullText = text;

  var headerMap;
  [headerMap, this.body] = MimeParser.extractHeadersAndBody(text);
  for (var [header, values] of headerMap._rawHeaders) {
    var value = values[0];
    this.headers.set(header, value);
    if (header == "message-id") {
      var start = value.indexOf("<");
      var end = value.indexOf(">", start);
      this.messageID = value.substring(start, end + 1);
    } else if (header == "newsgroups") {
      this.groups = value.split(/[ \t]*,[ \t]*/);
    }
  }

  // Add in non-existent fields
  if (!this.headers.has("lines")) {
    const lines = this.body.split("\n").length;
    this.headers.set("lines", lines);
  }
}

/**
 * This function converts an NNTP wildmat into a regular expression.
 *
 * I don't know how accurate it is wrt i18n characters, but its primary usage
 * right now is just XPAT, where i18n effects are utterly unspecified, so I am
 * not too concerned.
 *
 * This also neglects cases where special characters are in [] blocks.
 */
function wildmat2regex(wildmat) {
  // Special characters in regex that aren't special in wildmat
  wildmat = wildmat.replace(/[$+.()|{}^]/, function (str) {
    return "\\" + str;
  });
  wildmat = wildmat.replace(/(\\*)([*?])/, function (str, p1, p2) {
    // TODO: This function appears to be wrong on closer inspection.
    if (p1.length % 2 == 0) {
      return p2 == "*" ? ".*" : ".";
    }
    return str;
  });
  return new RegExp(wildmat);
}

// NNTP FLAGS
export var NNTP_POSTABLE = 0x0001;

export var NNTP_REAL_LENGTH = 0x0100;

function hasFlag(flags, flag) {
  return (flags & flag) == flag;
}

// NNTP TEST SERVERS
// -----------------
// To be comprehensive about testing and fallback, we define these varying
// levels of RFC-compliance:
// * RFC 977 solely (there's not a lot there!)
// * RFC 977 + 2980 (note that there are varying levels of this impl)
// * RFC 3977 bare bones
// * RFC 3977 full
// * RFC 3977 + post-3977 extensions
// * Giganews (Common newsserver for ISP stuff; highest importance)
// * INN 2.4 (Gold standard common implementation; second highest importance)
// Note too that we want various levels of brokenness:
// * Perm errors that require login
// * "I can't handle that" (e.g., news.mozilla.org only supports XOVER for
//   searching with XHDR)
// * Naive group counts, missing articles
// * Limitations on what can be posted

// This handler implements the bare minimum required by RFC 977. Actually, not
// even that much: IHAVE and SLAVE are not implemented, as those two are
// explicitly server implementations.
export class NNTP_RFC977_handler {
  constructor(daemon) {
    this._daemon = daemon;
    this.closing = false;
    this.resetTest();
  }
  resetTest() {
    this.extraCommands = "";
    this.articleKey = null;
    this.group = null;
  }
  ARTICLE(args) {
    var info = this._selectArticle(args, 220);
    if (info[0] == null) {
      return info[1];
    }

    var response = info[1] + "\n";
    response += info[0].fullText.replace(/^\./gm, "..");
    response += ".";
    return response;
  }
  BODY(args) {
    var info = this._selectArticle(args, 222);
    if (info[0] == null) {
      return info[1];
    }

    var response = info[1] + "\n";
    response += info[0].body.replace(/^\./gm, "..");
    response += ".";
    return response;
  }
  GROUP(args) {
    var group = this._daemon.getGroup(args);
    if (group == null) {
      return "411 no such news group";
    }

    this.group = group;
    this.articleKey = 0 in this.group.keys ? this.group.keys[0] : null;

    var stats = this._daemon.getGroupStats(group);
    return (
      "211 " +
      stats[0] +
      " " +
      stats[1] +
      " " +
      stats[2] +
      " " +
      args +
      " group selected"
    );
  }
  HEAD(args) {
    var info = this._selectArticle(args, 221);
    if (info[0] == null) {
      return info[1];
    }

    var response = info[1] + "\n";
    for (const [header, value] of info[0].headers) {
      response += header + ": " + value + "\n";
    }
    response += ".";
    return response;
  }
  HELP() {
    var response = "100 Why certainly, here is my help:\n";
    response += "Mozilla fake NNTP RFC 977 testing server";
    response += "Commands supported:\n";
    response += "\tARTICLE <message-id> | [nnn]\n";
    response += "\tBODY\n";
    response += "\tGROUP group\n";
    response += "\tHEAD\n";
    response += "\tHELP\n";
    response += "\tLAST\n";
    response += "\tLIST\n";
    response += "\tNEWGROUPS\n";
    response += "\tNEWNEWS\n";
    response += "\tNEXT\n";
    response += "\tPOST\n";
    response += "\tQUIT\n";
    response += "\tSTAT\n";
    response += this.extraCommands;
    response += ".";
    return response;
  }
  LAST() {
    if (this.group == null) {
      return "412 no newsgroup selected";
    }
    if (this.articleKey == null) {
      return "420 no current article has been selected";
    }
    return "502 Command not implemented";
  }
  LIST() {
    var response = "215 list of newsgroup follows\n";
    for (const groupname in this._daemon._groups) {
      const group = this._daemon._groups[groupname];
      const stats = this._daemon.getGroupStats(group);
      response +=
        groupname +
        " " +
        stats[1] +
        " " +
        stats[0] +
        " " +
        (hasFlag(group.flags, NNTP_POSTABLE) ? "y" : "n") +
        "\n";
    }
    response += ".";
    return response;
  }
  NEWGROUPS() {
    return "502 Command not implemented";
  }
  NEWNEWS() {
    return "502 Command not implemented";
  }
  NEXT() {
    if (this.group == null) {
      return "412 no newsgroup selected";
    }
    if (this.articleKey == null) {
      return "420 no current article has been selected";
    }
    return "502 Command not implemented";
  }
  POST() {
    this.posting = true;
    this.post = "";
    return "340 Please continue";
  }
  QUIT() {
    this.closing = true;
    return "205 closing connection - goodbye!";
  }
  STAT(args) {
    var info = this._selectArticle(args, 223);
    return info[1];
  }
  LISTGROUP(args) {
    // Yes, I know this isn't RFC 977, but I doubt that mailnews will ever drop
    // its requirement for this, so I'll stuff it in here anyways...
    var group = args == "" ? this.group : this._daemon.getGroup(args);
    if (group == null) {
      return "411 This newsgroup does not exist";
    }

    var response = "211 Articles follow:\n";
    for (const key of group.keys) {
      response += key + "\n";
    }
    response += ".\n";
    return response;
  }

  onError() {
    return "500 command not recognized";
  }
  onServerFault(e) {
    return "500 internal server error: " + e;
  }
  onStartup() {
    this.closing = false;
    this.group = null;
    this.article = null;
    this.posting = false;
    return "200 posting allowed";
  }
  onMultiline(line) {
    if (line == ".") {
      if (this.posting) {
        var article = new NewsArticle(this.post);
        this._daemon.addArticle(article);
        this.posting = false;
        return "240 Wonderful article, your style is gorgeous!";
      }
    }

    if (this.posting) {
      if (line.startsWith(".")) {
        line = line.substring(1);
      }

      this.post += line + "\n";
    }

    return undefined;
  }
  postCommand(reader) {
    if (this.closing) {
      reader.closeSocket();
    }
    reader.setMultiline(this.posting);
  }

  /**
   * Selects an article based on args.
   *
   * Returns an array of objects consisting of:
   * # The selected article (or null if non was selected
   * # The first line response
   */
  _selectArticle(args, responseCode) {
    var art, key;
    if (args == "") {
      if (this.group == null) {
        return [null, "412 no newsgroup has been selected"];
      }
      if (this.articleKey == null) {
        return [null, "420 no current article has been selected"];
      }

      art = this.group[this.articleKey];
      key = this.articleKey;
    } else if (args.startsWith("<")) {
      art = this._daemon.getArticle(args);
      key = 0;

      if (art == null) {
        return [null, "430 no such article found"];
      }
    } else {
      if (this.group == null) {
        return [null, "412 no newsgroup has been selected"];
      }

      key = parseInt(args);
      if (key in this.group) {
        this.articleKey = key;
        art = this.group[key];
      } else {
        return [null, "423 no such article number in this group"];
      }
    }

    var respCode =
      responseCode + " " + key + " " + art.messageID + " article selected";
    return [art, respCode];
  }
}

export class NNTP_RFC2980_handler extends NNTP_RFC977_handler {
  DATE() {
    return "502 Command not implemented";
  }
  LIST(args) {
    var index = args.indexOf(" ");
    var command = index == -1 ? args : args.substring(0, index);
    args = index == -1 ? "" : args.substring(index + 1);
    command = command.toUpperCase();
    if ("LIST_" + command in this) {
      return this["LIST_" + command](args);
    }
    return super.LIST(command + " " + args);
  }
  LIST_ACTIVE(args) {
    return super.LIST(args);
  }
  MODE(args) {
    if (args == "READER") {
      return this.onStartup();
    }
    return "500 What do you think you're trying to pull here?";
  }
  XHDR(args) {
    if (!this.group) {
      return "412 No group selected";
    }

    args = args.split(" ");
    var header = args[0].toLowerCase();
    var found = false;
    var response = "221 Headers abound\n";
    for (const key of this._filterRange(args[1], this.group.keys)) {
      if (!this.group[key].headers.has(header)) {
        continue;
      }
      found = true;
      response += key + " " + this.group[key].headers.get(header) + "\n";
    }
    if (!found) {
      return "420 No such article";
    }
    response += ".";
    return response;
  }
  XOVER(args) {
    if (!this.group) {
      return "412 No group selected";
    }

    args = args.split(/ +/, 3);
    var response = "224 List of articles\n";
    for (const key of this._filterRange(args[0], this.group.keys)) {
      response += key + "\t";
      var article = this.group[key];
      response +=
        article.headers.get("subject") +
        "\t" +
        article.headers.get("from") +
        "\t" +
        article.headers.get("date") +
        "\t" +
        article.headers.get("message-id") +
        "\t" +
        (article.headers.get("references") || "") +
        "\t" +
        article.fullText.replace(/\r?\n/, "\r\n").length +
        "\t" +
        article.body.split(/\r?\n/).length +
        "\t" +
        (article.headers.get("xref") || "") +
        "\n";
    }
    response += ".\n";
    return response;
  }
  XPAT(args) {
    if (!this.group) {
      return "412 No group selected";
    }

    /* XPAT header range ... */
    args = args.split(/ +/, 3);
    const header = args[0].toLowerCase();
    const regex = wildmat2regex(args[2]);

    let response = "221 Results follow\n";
    for (const key of this._filterRange(args[1], this.group.keys)) {
      const article = this.group[key];
      if (
        article.headers.has(header) &&
        regex.test(article.headers.get(header))
      ) {
        response += key + " " + article.headers.get(header) + "\n";
      }
    }
    return response + ".";
  }

  _filterRange(range, keys) {
    const dash = range.indexOf("-");
    let low, high;
    if (dash < 0) {
      low = high = parseInt(range);
    } else {
      low = parseInt(range.substring(0, dash));
      if (dash < range.length - 1) {
        high = range.substring(dash + 1);
      } else {
        // Everything is less than this.
        high = 1.0 / 0.0;
      }
    }
    return keys.filter(function (e) {
      return low <= e && e <= high;
    });
  }
}

export class NNTP_Giganews_handler extends NNTP_RFC2980_handler {
  XHDR(args) {
    var header = args.split(" ")[0].toLowerCase();
    if (
      header in ["subject", "from", "xref", "date", "message-id", "references"]
    ) {
      return super.XHDR(args);
    }
    return "503 unsupported header field";
  }
}

export class NNTP_RFC4643_extension extends NNTP_RFC2980_handler {
  constructor(daemon, { username = "testnews", password = "newstest" } = {}) {
    super(daemon);

    this.extraCommands += "\tAUTHINFO USER\n";
    this.extraCommands += "\tAUTHINFO PASS\n";
    this.expectedUsername = username;
    this.expectedPassword = password;
    this.requireBoth = true;
    this.authenticated = false;
    this.usernameReceived = false;
  }

  AUTHINFO(args) {
    if (this.authenticated) {
      return "502 Command unavailable";
    }

    var argSplit = args.split(" ");
    var action = argSplit[0];
    var param = argSplit[1];

    if (action == "user") {
      if (this.usernameReceived) {
        return "502 Command unavailable";
      }

      var expectUsername = this.lastGroupTried
        ? this._daemon.groupCredentials[this.lastGroupTried][0]
        : this.expectedUsername;
      if (param != expectUsername) {
        return "481 Authentication failed";
      }

      this.usernameReceived = true;
      if (this.requireBoth) {
        return "381 Password required";
      }

      this.authenticated = this.lastGroupTried ? this.lastGroupTried : true;
      return "281 Authentication Accepted";
    } else if (action == "pass") {
      if (!this.requireBoth || !this.usernameReceived) {
        return "482 Authentication commands issued out of sequence";
      }

      this.usernameReceived = false;

      var expectPassword = this.lastGroupTried
        ? this._daemon.groupCredentials[this.lastGroupTried][1]
        : this.expectedPassword;
      if (param != expectPassword) {
        return "481 Authentication failed";
      }

      this.authenticated = this.lastGroupTried ? this.lastGroupTried : true;
      return "281 Authentication Accepted";
    }
    return "502 Invalid Command";
  }
  LIST(args) {
    if (this.authenticated) {
      return args ? super.LIST(args) : "502 Invalid command: LIST";
    }
    return "480 Authentication required";
  }
  GROUP(args) {
    if (
      (this._daemon.groupCredentials != null && this.authenticated == args) ||
      (this._daemon.groupCredentials == null && this.authenticated)
    ) {
      return super.GROUP(args);
    }
    if (this._daemon.groupCredentials != null) {
      this.lastGroupTried = args;
    }
    return "480 Authentication required";
  }
}
