const sqlite = require("sqlite3");

const logger = require("./logger");

const config = require("../config");
const { TimeTracker } = require("./time");
const dataFolder = "data/";

class Database {
  constructor(app) {
    this._app = app;
    this._sql = new sqlite.Database(dataFolder + "database.sql");
  }

  getDailyDatabase() {
    if (!config.createDailyDatabaseCopy) {
      return;
    }

    const date = new Date();
    const fileName = `database_copy_${date.getDate()}-${
      date.getMonth() + 1
    }-${date.getFullYear()}.sql`;

    if (fileName !== this._currentDatabaseCopyFileName) {
      if (this._currentDatabaseCopyInstance) {
        this._currentDatabaseCopyInstance.close();
      }

      this._currentDatabaseCopyInstance = new sqlite.Database(
        dataFolder + fileName
      );
      this._currentDatabaseCopyFileName = fileName;

      // Ensure the initial tables are created
      // This does not created indexes since it is only inserted to
      this._currentDatabaseCopyInstance.serialize(() => {
        this._currentDatabaseCopyInstance.run(
          "CREATE TABLE IF NOT EXISTS pings (timestamp BIGINT NOT NULL, ip TINYTEXT, playerCount MEDIUMINT)",
          (err) => {
            if (err) {
              logger.log(
                "error",
                "Cannot create initial table for daily database"
              );
              throw err;
            }
          }
        );
      });
    }

    return this._currentDatabaseCopyInstance;
  }

  ensureIndexes(callback) {
    const handleError = (err) => {
      if (err) {
        logger.log("error", "Cannot create table or table index");
        throw err;
      }
    };

    this._sql.serialize(() => {
      this._sql.run(
        "CREATE TABLE IF NOT EXISTS pings (timestamp BIGINT NOT NULL, ip TINYTEXT, playerCount MEDIUMINT)",
        handleError
      );
      this._sql.run(
        "CREATE TABLE IF NOT EXISTS players_record (timestamp BIGINT, ip TINYTEXT NOT NULL PRIMARY KEY, playerCount MEDIUMINT)",
        handleError
      );
      this._sql.run(
        "CREATE INDEX IF NOT EXISTS ip_index ON pings (ip, playerCount)",
        handleError
      );
      this._sql.run(
        "CREATE INDEX IF NOT EXISTS timestamp_index on PINGS (timestamp)",
        [],
        (err) => {
          handleError(err);
          // Queries are executed one at a time; this is the last one.
          // Note that queries not scheduled directly in the callback function of
          // #serialize are not necessarily serialized.
          callback();
        }
      );
    });
  }

  loadGraphPoints(graphDuration, callback) {
    // Query recent pings
    const endTime = TimeTracker.getEpochMillis();
    const startTime = endTime - graphDuration;

    this.getRecentPings(startTime, endTime, (pingData) => {
      const relativeGraphData = [];

      for (const row of pingData) {
        // Load into temporary array
        // This will be culled prior to being pushed to the serverRegistration
        let graphData = relativeGraphData[row.ip];
        if (!graphData) {
          relativeGraphData[row.ip] = graphData = [[], []];
        }

        // DANGER!
        // This will pull the timestamp from each row into memory
        // This is built under the assumption that each round of pings shares the same timestamp
        // This enables all timestamp arrays to have consistent point selection and graph correctly
        graphData[0].push(row.timestamp);
        graphData[1].push(row.playerCount);
      }

      Object.keys(relativeGraphData).forEach((ip) => {
        // Match IPs to serverRegistration object
        for (const serverRegistration of this._app.serverRegistrations) {
          if (serverRegistration.data.ip === ip) {
            const graphData = relativeGraphData[ip];

            // Push the data into the instance and cull if needed
            serverRegistration.loadGraphPoints(
              startTime,
              graphData[0],
              graphData[1]
            );

            break;
          }
        }
      });

      // Since all timestamps are shared, use the array from the first ServerRegistration
      // This is very dangerous and can break if data is out of sync
      if (Object.keys(relativeGraphData).length > 0) {
        const serverIp = Object.keys(relativeGraphData)[0];
        const timestamps = relativeGraphData[serverIp][0];

        this._app.timeTracker.loadGraphPoints(startTime, timestamps);
      }

      callback();
    });
  }

  loadRecords(callback) {
    let completedTasks = 0;

    this._app.serverRegistrations.forEach((serverRegistration) => {
      // Find graphPeaks
      // This pre-computes the values prior to clients connecting
      serverRegistration.findNewGraphPeak();

      // Query recordData
      // When complete increment completeTasks to know when complete
      this.getRecord(
        serverRegistration.data.ip,
        (hasRecord, playerCount, timestamp) => {
          if (hasRecord) {
            serverRegistration.recordData = {
              playerCount,
              timestamp: TimeTracker.toSeconds(timestamp),
            };
          } else {
            this.getRecordLegacy(
              serverRegistration.data.ip,
              (hasRecordLegacy, playerCountLegacy, timestampLegacy) => {
                // New values that will be inserted to table
                let newTimestamp = null;
                let newPlayerCount = null;

                // If legacy record found, use it for insertion
                if (hasRecordLegacy) {
                  newTimestamp = timestampLegacy;
                  newPlayerCount = playerCountLegacy;
                }

                // Set record to recordData
                serverRegistration.recordData = {
                  playerCount: newPlayerCount,
                  timestamp: TimeTracker.toSeconds(newTimestamp),
                };

                // Insert server entry to records table
                const statement = this._sql.prepare(
                  "INSERT INTO players_record (timestamp, ip, playerCount) VALUES (?, ?, ?)"
                );
                statement.run(
                  newTimestamp,
                  serverRegistration.data.ip,
                  newPlayerCount,
                  (err) => {
                    if (err) {
                      logger.error(
                        `Cannot insert initial player count record of ${serverRegistration.data.ip}`
                      );
                      throw err;
                    }
                  }
                );
                statement.finalize();
              }
            );
          }

          // Check if completedTasks hit the finish value
          // Fire callback since #readyDatabase is complete
          if (++completedTasks === this._app.serverRegistrations.length) {
            callback();
          }
        }
      );
    });
  }

  getRecentPings(startTime, endTime, callback) {
    this._sql.all(
      "SELECT * FROM pings WHERE timestamp >= ? AND timestamp <= ?",
      [startTime, endTime],
      (err, data) => {
        if (err) {
          logger.log("error", "Cannot get recent pings");
          throw err;
        }
        callback(data);
      }
    );
  }

  getRecord(ip, callback) {
    this._sql.all(
      "SELECT playerCount, timestamp FROM players_record WHERE ip = ?",
      [ip],
      (err, data) => {
        if (err) {
          logger.log("error", `Cannot get ping record for ${ip}`);
          throw err;
        }

        // Record not found
        if (data[0] === undefined) {
          callback(false);
          return;
        }

        const playerCount = data[0].playerCount;
        const timestamp = data[0].timestamp;

        // Allow null player counts and timestamps, the frontend will safely handle them
        callback(true, playerCount, timestamp);
      }
    );
  }

  // Retrieves record from pings table, used for converting to separate table
  getRecordLegacy(ip, callback) {
    this._sql.all(
      "SELECT MAX(playerCount), timestamp FROM pings WHERE ip = ?",
      [ip],
      (err, data) => {
        if (err) {
          logger.log("error", `Cannot get legacy ping record for ${ip}`);
          throw err;
        }

        // For empty results, data will be length 1 with [null, null]
        const playerCount = data[0]["MAX(playerCount)"];
        const timestamp = data[0].timestamp;

        // Allow null timestamps, the frontend will safely handle them
        // This allows insertion of free standing records without a known timestamp
        if (playerCount !== null) {
          callback(true, playerCount, timestamp);
        } else {
          callback(false);
        }
      }
    );
  }

  insertPing(ip, timestamp, unsafePlayerCount) {
    this._insertPingTo(ip, timestamp, unsafePlayerCount, this._sql);

    // Push a copy of the data into the database copy, if any
    // This creates an "insert only" copy of the database for archiving
    const dailyDatabase = this.getDailyDatabase();
    if (dailyDatabase) {
      this._insertPingTo(ip, timestamp, unsafePlayerCount, dailyDatabase);
    }
  }

  _insertPingTo(ip, timestamp, unsafePlayerCount, db) {
    const statement = db.prepare(
      "INSERT INTO pings (timestamp, ip, playerCount) VALUES (?, ?, ?)"
    );
    statement.run(timestamp, ip, unsafePlayerCount, (err) => {
      if (err) {
        logger.error(`Cannot insert ping record of ${ip} at ${timestamp}`);
        throw err;
      }
    });
    statement.finalize();
  }

  updatePlayerCountRecord(ip, playerCount, timestamp) {
    const statement = this._sql.prepare(
      "UPDATE players_record SET timestamp = ?, playerCount = ? WHERE ip = ?"
    );
    statement.run(timestamp, playerCount, ip, (err) => {
      if (err) {
        logger.error(
          `Cannot update player count record of ${ip} at ${timestamp}`
        );
        throw err;
      }
    });
    statement.finalize();
  }

  initOldPingsDelete(callback) {
    // Delete old pings on startup
    logger.info("Deleting old pings..");
    this.deleteOldPings(() => {
      const oldPingsCleanupInterval =
        config.oldPingsCleanup.interval || 3600000;
      if (oldPingsCleanupInterval > 0) {
        // Delete old pings periodically
        setInterval(() => this.deleteOldPings(), oldPingsCleanupInterval);
      }

      callback();
    });
  }

  deleteOldPings(callback) {
    // The oldest timestamp that will be kept
    const oldestTimestamp = TimeTracker.getEpochMillis() - config.graphDuration;

    const deleteStart = TimeTracker.getEpochMillis();
    const statement = this._sql.prepare(
      "DELETE FROM pings WHERE timestamp < ?;"
    );
    statement.run(oldestTimestamp, (err) => {
      if (err) {
        logger.error("Cannot delete old pings");
        throw err;
      } else {
        const deleteTook = TimeTracker.getEpochMillis() - deleteStart;
        logger.info(`Old pings deleted in ${deleteTook}ms`);

        if (callback) {
          callback();
        }
      }
    });
    statement.finalize();
  }
}

module.exports = Database;