import { IEventBus, ICalendarEvent } from '../types/CalendarTypes';
import { CoreEvents } from '../constants/CoreEvents';
import { Configuration } from '../configurations/CalendarConfig';
import { DateService } from '../utils/DateService';
import { IEventRepository } from '../repositories/IEventRepository';

/**
 * EventManager - Event lifecycle and CRUD operations
 * Handles event management and CRUD operations
 */
export class EventManager {

    private events: ICalendarEvent[] = [];
    private dateService: DateService;
    private config: Configuration;
    private repository: IEventRepository;

    constructor(
        private eventBus: IEventBus,
        dateService: DateService,
        config: Configuration,
        repository: IEventRepository
    ) {
        this.dateService = dateService;
        this.config = config;
        this.repository = repository;
    }

    /**
     * Load event data from repository
     */
    public async loadData(): Promise<void> {
        try {
            this.events = await this.repository.loadEvents();
        } catch (error) {
            console.error('Failed to load event data:', error);
            this.events = [];
            throw error;
        }
    }

    /**
     * Get events with optional copying for performance
     */
    public getEvents(copy: boolean = false): ICalendarEvent[] {
        return copy ? [...this.events] : this.events;
    }

    /**
     * Optimized event lookup with early return
     */
    public getEventById(id: string): ICalendarEvent | undefined {
        // Use find for better performance than filter + first
        return this.events.find(event => event.id === id);
    }

    /**
     * Get event by ID and return event info for navigation
     * @param id Event ID to find
     * @returns Event with navigation info or null if not found
     */
    public getEventForNavigation(id: string): { event: ICalendarEvent; eventDate: Date } | null {
        const event = this.getEventById(id);
        if (!event) {
            return null;
        }

        // Validate event dates
        const validation = this.dateService.validateDate(event.start);
        if (!validation.valid) {
            console.warn(`EventManager: Invalid event start date for event ${id}:`, validation.error);
            return null;
        }

        // Validate date range
        if (!this.dateService.isValidRange(event.start, event.end)) {
            console.warn(`EventManager: Invalid date range for event ${id}: start must be before end`);
            return null;
        }

        return {
            event,
            eventDate: event.start
        };
    }

    /**
     * Navigate to specific event by ID
     * Emits navigation events for other managers to handle
     * @param eventId Event ID to navigate to
     * @returns true if event found and navigation initiated, false otherwise
     */
    public navigateToEvent(eventId: string): boolean {
        const eventInfo = this.getEventForNavigation(eventId);
        if (!eventInfo) {
            console.warn(`EventManager: Event with ID ${eventId} not found`);
            return false;
        }

        const { event, eventDate } = eventInfo;

        // Emit navigation request event
        this.eventBus.emit(CoreEvents.NAVIGATE_TO_EVENT, {
            eventId,
            event,
            eventDate,
            eventStartTime: event.start
        });

        return true;
    }

    /**
     * Get events that overlap with a given time period
     */
    public getEventsForPeriod(startDate: Date, endDate: Date): ICalendarEvent[] {
        // Event overlaps period if it starts before period ends AND ends after period starts
        return this.events.filter(event => {
            return event.start <= endDate && event.end >= startDate;
        });
    }

    /**
     * Create a new event and add it to the calendar
     */
    public addEvent(event: Omit<ICalendarEvent, 'id'>): ICalendarEvent {
        const newEvent: ICalendarEvent = {
            ...event,
            id: `event_${Date.now()}_${Math.random().toString(36).substr(2, 9)}`
        };

        this.events.push(newEvent);

        this.eventBus.emit(CoreEvents.EVENT_CREATED, {
            event: newEvent
        });

        return newEvent;
    }

    /**
     * Update an existing event
     */
    public updateEvent(id: string, updates: Partial<ICalendarEvent>): ICalendarEvent | null {
        const eventIndex = this.events.findIndex(event => event.id === id);
        if (eventIndex === -1) return null;

        const updatedEvent = { ...this.events[eventIndex], ...updates };
        this.events[eventIndex] = updatedEvent;

        this.eventBus.emit(CoreEvents.EVENT_UPDATED, {
            event: updatedEvent
        });

        return updatedEvent;
    }
}