import { ParkingGetterSetterRepository } from "./ParkingGetterSetterRepository";
import {
  IParkingStructure,
  IParkingStructureTimestampRecord
} from "../entities/ParkingRepositoryEntities";
import { HistoricalParkingAverageQueryResult, ParkingStructureCountOptions } from "./ParkingGetterRepository";
import { CircularQueue } from "../types/CircularQueue";

export type ParkingStructureID = string;

// Every 10 minutes
// 6x per hour * 24x per day * 7x per week = 1008 entries for one week
export const PARKING_LOGGING_INTERVAL_MS = 600000;

// This will last two weeks
export const MAX_NUM_ENTRIES = 2016;

export class InMemoryParkingRepository implements ParkingGetterSetterRepository {
  private dataLastAdded: Map<ParkingStructureID, Date> = new Map();

  constructor(
    private structures: Map<ParkingStructureID, IParkingStructure> = new Map(),
    private historicalData: Map<ParkingStructureID, CircularQueue<IParkingStructureTimestampRecord>> = new Map(),
  ) {
  }

  addOrUpdateParkingStructure = async (structure: IParkingStructure): Promise<void> => {
    this.structures.set(structure.id, { ...structure });
    await this.addHistoricalDataForStructure(structure);
  };

  private addHistoricalDataForStructure = async (structure: IParkingStructure): Promise<void> => {
    const now = Date.now();
    const lastAdded = this.dataLastAdded.get(structure.id);

    function parkingLoggingIntervalExceeded() {
      return !lastAdded || (now - lastAdded.getTime()) >= PARKING_LOGGING_INTERVAL_MS;
    }

    if (parkingLoggingIntervalExceeded()) {
      const timestampRecord: IParkingStructureTimestampRecord = {
        id: structure.id,
        spotsAvailable: structure.spotsAvailable,
        timestampMs: now,
      };

      if (!this.historicalData.has(structure.id)) {
        this.historicalData.set(structure.id, new CircularQueue<IParkingStructureTimestampRecord>(MAX_NUM_ENTRIES));
      }

      const sortingCallback = (a: IParkingStructureTimestampRecord, b: IParkingStructureTimestampRecord) => a.timestampMs - b.timestampMs;
      this.historicalData.get(structure.id)?.appendWithSorting(timestampRecord, sortingCallback);
      this.dataLastAdded.set(structure.id, new Date(now));
    }
  }

  clearParkingStructureData = async (): Promise<void> => {
    this.structures.clear();
  };

  getParkingStructureById = async (id: string): Promise<IParkingStructure | null> => {
    const structure = this.structures.get(id);
    return structure ? { ...structure } : null;
  };

  getParkingStructures = async (): Promise<IParkingStructure[]> => Array.from(this.structures.values()).map(structure => ({...structure}));

  removeParkingStructureIfExists = async (id: string): Promise<IParkingStructure | null> => {
    const structure = this.structures.get(id);
    if (structure) {
      this.structures.delete(id);
      return { ...structure };
    }
    return null;
  };

  getHistoricalAveragesOfParkingStructureCounts = async (id: string, options: ParkingStructureCountOptions): Promise<HistoricalParkingAverageQueryResult[]> => {
    const queue = this.historicalData.get(id);
    if (!queue || queue.size() === 0) {
      return [];
    }

    const results: HistoricalParkingAverageQueryResult[] = [];
    const { startUnixEpochMs, endUnixEpochMs, intervalMs } = options;
    
    let currentIntervalStart = startUnixEpochMs;
    
    while (currentIntervalStart < endUnixEpochMs) {
      const currentIntervalEnd = Math.min(currentIntervalStart + intervalMs, endUnixEpochMs);
      const recordsInInterval = this.getRecordsInTimeRange(queue, currentIntervalStart, currentIntervalEnd);
      
      if (recordsInInterval.length > 0) {
        const averageResult = this.calculateAverageForInterval(currentIntervalStart, currentIntervalEnd, recordsInInterval);
        results.push(averageResult);
      }
      
      currentIntervalStart = currentIntervalEnd;
    }
    
    return results;
  };

  private getRecordsInTimeRange = (
    queue: CircularQueue<IParkingStructureTimestampRecord>, 
    startMs: number, 
    endMs: number
  ): IParkingStructureTimestampRecord[] => {
    const recordsInInterval: IParkingStructureTimestampRecord[] = [];
    
    for (let i = 0; i < queue.size(); i++) {
      const record = queue.get(i);
      if (record && record.timestampMs >= startMs && record.timestampMs < endMs) {
        recordsInInterval.push(record);
      }
    }
    
    return recordsInInterval;
  };

  private calculateAverageForInterval = (
    fromMs: number,
    toMs: number,
    records: IParkingStructureTimestampRecord[]
  ): HistoricalParkingAverageQueryResult => {
    const totalSpotsAvailable = records.reduce((sum, record) => sum + record.spotsAvailable, 0);
    const averageSpotsAvailable = totalSpotsAvailable / records.length;
    
    return {
      fromUnixEpochMs: fromMs,
      toUnixEpochMs: toMs,
      averageSpotsAvailable
    };
  };
}