const crypto = require("crypto");

const DNSResolver = require("./dns");
const Server = require("./server");

const { GRAPH_UPDATE_TIME_GAP, TimeTracker } = require("./time");
const { getPlayerCountOrNull } = require("./util");

const config = require("../config");
const minecraftVersions = require("../minecraft_versions");

class ServerRegistration {
  serverId;
  lastFavicon;
  versions = [];
  recordData;
  graphData = [];

  constructor(app, serverId, data) {
    this._app = app;
    this.serverId = serverId;
    this.data = data;
    this._pingHistory = [];
    this.dnsResolver = new DNSResolver(this.data.ip, this.data.port);
  }

  handlePing(timestamp, resp, err, version, updateHistoryGraph) {
    // Use null to represent a failed ping
    const unsafePlayerCount = getPlayerCountOrNull(resp);

    // Store into in-memory ping data
    TimeTracker.pushAndShift(
      this._pingHistory,
      unsafePlayerCount,
      TimeTracker.getMaxServerGraphDataLength()
    );

    // Only notify the frontend to append to the historical graph
    // if both the graphing behavior is enabled and the backend agrees
    // that the ping is eligible for addition
    if (updateHistoryGraph) {
      TimeTracker.pushAndShift(
        this.graphData,
        unsafePlayerCount,
        TimeTracker.getMaxGraphDataLength()
      );
    }

    // Delegate out update payload generation
    return this.getUpdate(timestamp, resp, err, version);
  }

  getUpdate(timestamp, resp, err, version) {
    const update = {};

    // Always append a playerCount value
    // When resp is undefined (due to an error), playerCount will be null
    update.playerCount = getPlayerCountOrNull(resp);

    if (resp) {
      if (
        resp.version &&
        this.updateProtocolVersionCompat(
          resp.version,
          version.protocolId,
          version.protocolIndex
        )
      ) {
        // Append an updated version listing
        update.versions = this.versions;
      }

      if (
        config.logToDatabase &&
        (!this.recordData || resp.players.online > this.recordData.playerCount)
      ) {
        this.recordData = {
          playerCount: resp.players.online,
          timestamp: TimeTracker.toSeconds(timestamp),
        };

        // Append an updated recordData
        update.recordData = this.recordData;

        // Update record in database
        this._app.database.updatePlayerCountRecord(
          this.data.ip,
          resp.players.online,
          timestamp
        );
      }

      if (this.updateFavicon(resp.favicon)) {
        update.favicon = this.getFaviconUrl();
      }

      if (config.logToDatabase) {
        // Update calculated graph peak regardless if the graph is being updated
        // This can cause a (harmless) desync between live and stored data, but it allows it to be more accurate for long surviving processes
        if (this.findNewGraphPeak()) {
          update.graphPeakData = this.getGraphPeak();
        }
      }
    } else if (err) {
      // Append a filtered copy of err
      // This ensures any unintended data is not leaked
      update.error = this.filterError(err);
    }

    return update;
  }

  getPingHistory() {
    if (this._pingHistory.length > 0) {
      const payload = {
        versions: this.versions,
        recordData: this.recordData,
        favicon: this.getFaviconUrl(),
      };

      // Only append graphPeakData if defined
      // The value is lazy computed and conditional that config->logToDatabase == true
      const graphPeakData = this.getGraphPeak();

      if (graphPeakData) {
        payload.graphPeakData = graphPeakData;
      }

      // Assume the ping was a success and define result
      // pingHistory does not keep error references, so its impossible to detect if this is an error
      // It is also pointless to store that data since it will be short lived
      payload.playerCount = this._pingHistory[this._pingHistory.length - 1];

      // Send a copy of pingHistory
      // Include the last value even though it is contained within payload
      // The frontend will only push to its graphData from playerCountHistory
      payload.playerCountHistory = this._pingHistory;

      return payload;
    }

    return {
      error: {
        message: "Pinging...",
      },
      recordData: this.recordData,
      graphPeakData: this.getGraphPeak(),
      favicon: this.data.favicon,
    };
  }

  loadGraphPoints(startTime, timestamps, points) {
    this.graphData = TimeTracker.everyN(
      timestamps,
      startTime,
      GRAPH_UPDATE_TIME_GAP,
      (i) => points[i]
    );
  }

  findNewGraphPeak() {
    let index = -1;
    for (let i = 0; i < this.graphData.length; i++) {
      const point = this.graphData[i];
      if (point !== null && (index === -1 || point > this.graphData[index])) {
        index = i;
      }
    }
    if (index >= 0) {
      const lastGraphPeakIndex = this._graphPeakIndex;
      this._graphPeakIndex = index;
      return index !== lastGraphPeakIndex;
    } else {
      this._graphPeakIndex = undefined;
      return false;
    }
  }

  getGraphPeak() {
    if (this._graphPeakIndex === undefined) {
      return;
    }
    return {
      playerCount: this.graphData[this._graphPeakIndex],
      timestamp: this._app.timeTracker.getGraphPointAt(this._graphPeakIndex),
    };
  }

  updateFavicon(favicon) {
    // If data.favicon is defined, then a favicon override is present
    // Disregard the incoming favicon, regardless if it is different
    if (this.data.favicon) {
      return false;
    }

    if (favicon && favicon !== this.lastFavicon) {
      this.lastFavicon = favicon;

      // Generate an updated hash
      // This is used by #getFaviconUrl
      this.faviconHash = crypto
        .createHash("md5")
        .update(favicon)
        .digest("hex")
        .toString();

      return true;
    }

    return false;
  }

  getFaviconUrl() {
    if (this.faviconHash) {
      return Server.getHashedFaviconUrl(this.faviconHash);
    } else if (this.data.favicon) {
      return this.data.favicon;
    }
  }

  updateProtocolVersionCompat(incomingId, outgoingId, protocolIndex) {
    // If the result version matches the attempted version, the version is supported
    const isSuccess = incomingId === outgoingId;
    const indexOf = this.versions.indexOf(protocolIndex);

    // Test indexOf to avoid inserting previously recorded protocolIndex values
    if (isSuccess && indexOf < 0) {
      this.versions.push(protocolIndex);

      // Sort versions in ascending order
      // This matches protocol ids to Minecraft versions release order
      this.versions.sort((a, b) => a - b);

      return true;
    } else if (!isSuccess && indexOf >= 0) {
      this.versions.splice(indexOf, 1);
      return true;
    }
    return false;
  }

  getNextProtocolVersion() {
    // Minecraft Bedrock Edition does not have protocol versions
    if (this.data.type === "PE") {
      return {
        protocolId: 0,
        protocolIndex: 0,
      };
    }
    const protocolVersions = minecraftVersions[this.data.type];
    if (
      typeof this._nextProtocolIndex === "undefined" ||
      this._nextProtocolIndex + 1 >= protocolVersions.length
    ) {
      this._nextProtocolIndex = 0;
    } else {
      this._nextProtocolIndex++;
    }
    return {
      protocolId: protocolVersions[this._nextProtocolIndex].protocolId,
      protocolIndex: this._nextProtocolIndex,
    };
  }

  filterError(err) {
    let message = "Unknown error";

    // Attempt to match to the first possible value
    for (const key of ["message", "description", "errno"]) {
      if (err[key]) {
        message = err[key];
        break;
      }
    }

    // Trim the message if too long
    if (message.length > 28) {
      message = message.substring(0, 28) + "...";
    }

    return {
      message: message,
    };
  }

  getPublicData() {
    // Return a custom object instead of data directly to avoid data leakage
    return {
      name: this.data.name,
      ip: this.data.ip,
      type: this.data.type,
      color: this.data.color,
    };
  }
}

module.exports = ServerRegistration;