import { ChangeDetectorRef, Component, inject, AfterViewChecked, OnDestroy, OnInit, ViewChild, ElementRef, NgZone } from '@angular/core';
import { CommonModule } from '@angular/common';
import { FormsModule } from '@angular/forms';
import { Chart, registerables } from 'chart.js';
import { BaseChartDirective } from 'ng2-charts';
import L from 'leaflet';
import { firstValueFrom } from 'rxjs';

import { StatsService } from '../services/stats.service';
import {
  StatsSummary,
  TimeSeriesPoint,
  GeoStat,
  TimePreset,
} from '../interfaces/visitor-stat';

import { getAppConfig } from '../services/app-config.service';

// Register Chart.js components once
Chart.register(...registerables);

@Component({
  selector: 'app-admin-stats-dashboard',
  standalone: true,
  imports: [CommonModule, FormsModule, BaseChartDirective],
  templateUrl: './admin-stats-dashboard.component.html',
  styleUrl: './admin-stats-dashboard.component.scss',
})
export class AdminStatsDashboardComponent implements OnInit, AfterViewChecked, OnDestroy {
  private readonly statsService: StatsService = inject(StatsService);
  private readonly cd = inject(ChangeDetectorRef);
  private readonly ngZone = inject(NgZone);

  @ViewChild('mapContainer', { static: false }) mapContainerRef!: ElementRef;

  // ── Time range ──────────────────────────────────────────
  readonly presets = [
    { label: 'Yesterday', value: 'yesterday' as TimePreset },
    { label: '7 Days', value: '7d' as TimePreset },
    { label: '30 Days', value: '30d' as TimePreset },
    { label: '90 Days', value: '90d' as TimePreset },
    { label: 'Year', value: 'year' as TimePreset },
    { label: 'Custom', value: 'custom' as TimePreset },
  ];
  selectedPreset: TimePreset = '30d';
  customStart = '';
  customEnd = '';

  // ── Data ────────────────────────────────────────────────
  summary: StatsSummary | null = null;
  timeSeries: TimeSeriesPoint[] = [];
  geoStats: GeoStat[] = [];
  loading = true;
  error: string | null = null;
  parsing = false;
  parseProgress = '';

  // ── Chart ───────────────────────────────────────────────
  chartData: { labels: string[]; datasets: any[] } = { labels: [], datasets: [] };
  chartOptions: any = {
    responsive: true,
    maintainAspectRatio: false,
    plugins: {
      legend: { display: true, position: 'top' as const },
    },
    scales: {
      x: { title: { display: true, text: 'Date' } },
      y: { title: { display: true, text: 'Visitors' }, beginAtZero: true },
    },
  };

  // ── Leaflet ─────────────────────────────────────────────
  private map: L.Map | null = null;
  private markersLayer: L.LayerGroup | null = null;
  private mapInitialized = false;

  ngOnInit(): void {
    this.loadAll();
  }

  ngAfterViewChecked(): void {
    // The map container is inside an @else block gated by loading=true.
    // ngAfterViewInit fires before loading completes, so the element
    // doesn't exist yet. ngAfterViewChecked detects when it appears.
    if (this.mapInitialized) return;
    if (!this.mapContainerRef) return;
    // Verify the native element actually exists in the DOM (not just that
    // the query ref was created — the @if block must have rendered too)
    if (!this.mapContainerRef.nativeElement?.isConnected) return;

    this.mapInitialized = true;
    this.ngZone.runOutsideAngular(() => {
      // Defer two frames so the browser has laid out the container
      requestAnimationFrame(() => {
        requestAnimationFrame(() => this._initMap());
      });
    });
  }

  private _initMap(): void {
    this.map = L.map(this.mapContainerRef.nativeElement, {
      center: [20, 0],
      zoom: 2,
      zoomControl: true,
      worldCopyJump: true,
    });

    L.tileLayer('https://{s}.basemaps.cartocdn.com/light_all/{z}/{x}/{y}{r}.png', {
      attribution: '&copy; <a href="https://www.openstreetmap.org/copyright">OpenStreetMap</a> contributors &copy; <a href="https://carto.com/">CARTO</a>',
      maxZoom: 19,
    }).addTo(this.map);

    // Ensure Leaflet uses the correct container size
    this.map.invalidateSize();

    // Data may have loaded in ngOnInit before the view was ready
    this._updateMapMarkers();
  }

  ngOnDestroy(): void {
    if (this.map) {
      this.map.remove();
      this.map = null;
    }
  }

  // ── Date helpers ────────────────────────────────────────

  private _localDateStr(d: Date): string {
    // Format as YYYY-MM-DD using local time (no UTC shift)
    const y = d.getFullYear();
    const m = String(d.getMonth() + 1).padStart(2, '0');
    const day = String(d.getDate()).padStart(2, '0');
    return `${y}-${m}-${day}`;
  }

  getDates(): { start: string; end: string } {
    const today = new Date();
    today.setHours(0, 0, 0, 0);
    const yesterday = new Date(today);
    yesterday.setDate(today.getDate() - 1);

    switch (this.selectedPreset) {
      case 'yesterday':
        return { start: this._localDateStr(yesterday), end: this._localDateStr(yesterday) };
      case '7d': {
        const start = new Date(yesterday);
        start.setDate(yesterday.getDate() - 6);
        return { start: this._localDateStr(start), end: this._localDateStr(yesterday) };
      }
      case '30d': {
        const start = new Date(yesterday);
        start.setDate(yesterday.getDate() - 29);
        return { start: this._localDateStr(start), end: this._localDateStr(yesterday) };
      }
      case '90d': {
        const start = new Date(yesterday);
        start.setDate(yesterday.getDate() - 89);
        return { start: this._localDateStr(start), end: this._localDateStr(yesterday) };
      }
      case 'year': {
        const start = new Date(yesterday);
        start.setDate(yesterday.getDate() - 364);
        return { start: this._localDateStr(start), end: this._localDateStr(yesterday) };
      }
      case 'custom':
        return {
          start: this.customStart || this._localDateStr(this._daysAgo(30)),
          end: this.customEnd || this._localDateStr(yesterday),
        };
      default:
        return { start: this._localDateStr(yesterday), end: this._localDateStr(yesterday) };
    }
  }

  private _daysAgo(n: number): Date {
    const d = new Date();
    d.setHours(0, 0, 0, 0);
    d.setDate(d.getDate() - n);
    return d;
  }

  onPresetChange(): void {
    this.loadAll();
  }

  // ── Data loading ────────────────────────────────────────

  async loadAll(): Promise<void> {
    this.loading = true;
    this.error = null;
    const { start, end } = this.getDates();
    try {
      const [summary, timeSeries, geoStats] = await Promise.all([
        firstValueFrom(this.statsService.getSummary(start, end)),
        firstValueFrom(this.statsService.getTimeSeries(start, end)),
        firstValueFrom(this.statsService.getGeoStats(start, end)),
      ]);

      // Angular 17+ uses fetch-based HTTP whose promise resolutions run
      // outside the zone. Re-enter the zone and markForCheck() to force
      // change detection through the OnPush parent chain.
      this.ngZone.run(() => {
        this.summary = summary;
        this.timeSeries = timeSeries;
        this.geoStats = geoStats;

        this._updateChart();
        this._updateMapMarkers();
        this.cd.markForCheck();
      });
    } catch (err) {
      console.error('Failed to load stats:', err);
      this.ngZone.run(() => {
        this.error = 'Failed to load stats data. Please check your connection and try again.';
        this.cd.markForCheck();
      });
    } finally {
      this.ngZone.run(() => {
        this.loading = false;
        this.cd.markForCheck();
      });
    }
  }

  async triggerParse(): Promise<void> {
    this.parsing = true;
    this.parseProgress = '';

    const apiUrl = `${getAppConfig().apiBaseUrl}/api/stats/parse`;
    // Append auth token as query param for SSE (EventSource can't send headers)
    let token: string | null = null;
    try {
      token = localStorage.getItem('kmtn_access_token');
    } catch {
      // localStorage may be blocked
    }
    const url = token ? `${apiUrl}?token=${encodeURIComponent(token)}` : apiUrl;

    return new Promise<void>((resolve) => {
      const es = new EventSource(url);

      es.addEventListener('progress', (e: MessageEvent) => {
        const data = JSON.parse(e.data);
        this.ngZone.run(() => {
          this.parseProgress = `Parsing ${data.file}... ${data.current}/${data.total}`;
        });
      });

      es.addEventListener('done', (e: MessageEvent) => {
        const data = JSON.parse(e.data);
        es.close();
        this.ngZone.run(() => {
          this.parseProgress = `Done — ${data.files_processed} files, ${data.rows_inserted} geo rows`;
          this.parsing = false;
          this.loadAll().then(() => resolve());
        });
      });

      es.onerror = (e: Event) => {
        console.error('Parse SSE error:', e);
        es.close();
        this.ngZone.run(() => {
          this.parseProgress = 'Parse failed';
          this.parsing = false;
          resolve();
        });
      };
    });
  }


  // ── Chart ───────────────────────────────────────────────

  private _updateChart(): void {
    this.chartData = {
      labels: this.timeSeries.map((p) => this._formatDate(p.date)),
      datasets: [
        {
          label: 'Unique Visitors',
          data: this.timeSeries.map((p) => p.unique_visitors),
          borderColor: '#1a3a5c',
          backgroundColor: 'rgba(26, 58, 92, 0.1)',
          fill: true,
          tension: 0.3,
          pointRadius: 2,
        },
      ],
    };
  }

  private _formatDate(dateStr: string): string {
    const d = new Date(dateStr);
    return `${d.getMonth() + 1}/${d.getDate()}`;
  }

  // ── Map ─────────────────────────────────────────────────

  private _updateMapMarkers(): void {
    if (!this.map) return;

    // Remove old markers
    if (this.markersLayer) {
      this.map.removeLayer(this.markersLayer);
    }

    this.markersLayer = L.layerGroup();

    const geoWithCoords = this.geoStats.filter((g) => g.latitude && g.longitude);

    if (geoWithCoords.length === 0) {
      this.markersLayer.addTo(this.map);
      return;
    }

    const maxVisitors = Math.max(...geoWithCoords.map((g) => g.visitors), 1);

    geoWithCoords.forEach((geo) => {
        const radius = Math.max(5, Math.min(30, 5 + (geo.visitors / maxVisitors) * 25));
        const marker = L.circleMarker([geo.latitude!, geo.longitude!], {
          radius,
          fillColor: '#e87a2e',
          color: '#c85a1e',
          weight: 1,
          opacity: 0.8,
          fillOpacity: 0.6,
        });
        marker.bindTooltip(`${geo.country}: ${geo.visitors} visitors`, {
          sticky: true,
          direction: 'top',
        });
        this.markersLayer?.addLayer(marker);
      });

    this.markersLayer.addTo(this.map);
  }
}