import {
  ChangeDetectionStrategy,
  Component,
  OnDestroy,
  OnInit,
  computed,
  inject,
  signal,
} from '@angular/core';
import { CommonModule } from '@angular/common';
import { MatIconModule } from '@angular/material/icon';
import { MatChipsModule } from '@angular/material/chips';
import { MatTooltipModule } from '@angular/material/tooltip';
import { MatProgressBarModule } from '@angular/material/progress-bar';
import { FilamentService } from '../../services/filament.service';
import {
  classifyStockLevel,
} from '../../models/filament.model';
import { Subscription } from 'rxjs';

/**
 * Inventory Dashboard Summary — shows filament inventory at a glance.
 *
 * Displays:
 * - Total filament spool count
 * - Low stock count (spools ≤25% remaining, i.e. "low" or "critical")
 * - Estimated total filament value (sum of purchase prices for active spools)
 *
 * Data is sourced from the shared FilamentService signal,
 * which is loaded on init and can be refreshed via refresh().
 */
@Component({
  selector: 'app-inventory-summary',
  standalone: true,
  imports: [
    CommonModule,
    MatIconModule,
    MatChipsModule,
    MatTooltipModule,
    MatProgressBarModule,
  ],
  templateUrl: './inventory-summary.component.html',
  styleUrls: ['./inventory-summary.component.scss'],
  changeDetection: ChangeDetectionStrategy.OnPush,
})
export class InventorySummaryComponent implements OnInit, OnDestroy {
  private readonly filamentService = inject(FilamentService);
  private subscription: Subscription | null = null;

  /** All filament data — reactive signal from shared service */
  readonly filaments = this.filamentService.filaments;

  /** Loading state */
  readonly loading = signal<boolean>(true);

  /** Error state */
  readonly error = signal<string | null>(null);

  /** Computed: total number of filament spools */
  readonly totalCount = computed(() => this.filaments().length);

  /** Computed: count of active spools */
  readonly activeCount = computed(
    () => this.filaments().filter((f) => f.isActive).length
  );

  /** Computed: count of low/critical stock spools (≤25% remaining) */
  readonly lowStockCount = computed(
    () =>
      this.filaments().filter(
        (f) =>
          classifyStockLevel(f) === 'low' ||
          classifyStockLevel(f) === 'critical'
      ).length
  );

  /** Computed: count of critically low spools (≤10% remaining) */
  readonly criticalCount = computed(
    () =>
      this.filaments().filter((f) => classifyStockLevel(f) === 'critical')
        .length
  );

  /** Computed: estimated total value of active spools */
  readonly totalValue = computed(() =>
    this.filaments()
      .filter((f) => f.isActive && f.purchasePrice !== null)
      .reduce((sum, f) => sum + (f.purchasePrice ?? 0), 0)
  );

  /** Computed: total remaining weight across all spools in grams */
  readonly totalRemainingGrams = computed(() =>
    this.filaments().reduce((sum, f) => sum + f.weightRemainingGrams, 0)
  );

  /** Computed: total capacity weight across all spools in grams */
  readonly totalCapacityGrams = computed(() =>
    this.filaments().reduce((sum, f) => sum + f.weightTotalGrams, 0)
  );

  /** Computed: overall remaining percentage */
  readonly overallRemainingPercent = computed(() => {
    const capacity = this.totalCapacityGrams();
    if (capacity <= 0) return 0;
    return Math.round(
      (this.totalRemainingGrams() / capacity) * 100
    );
  });

  /** Computed: whether to show a low-stock alert */
  readonly hasLowStock = computed(() => this.lowStockCount() > 0);

  /** Computed: whether to show a critical-stock alert */
  readonly hasCritical = computed(() => this.criticalCount() > 0);

  /** Computed: status label for the inventory health */
  readonly healthLabel = computed(() => {
    if (this.hasCritical()) return 'Critical Stock';
    if (this.hasLowStock()) return 'Low Stock Alert';
    return 'Stock Healthy';
  });

  /** Computed: health status color class */
  readonly healthClass = computed(() => {
    if (this.hasCritical()) return 'critical';
    if (this.hasLowStock()) return 'low';
    return 'healthy';
  });

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

  ngOnDestroy(): void {
    this.subscription?.unsubscribe();
  }

  /** Load filament data from the API via FilamentService */
  loadFilaments(): void {
    this.loading.set(true);
    this.error.set(null);
    this.subscription = this.filamentService.getFilaments().subscribe({
      next: () => {
        this.loading.set(false);
      },
      error: (err) => {
        console.error('Failed to load filaments:', err);
        this.error.set('Failed to load inventory data');
        this.loading.set(false);
      },
    });
  }

  /** Refresh data — called externally when data changes (e.g., SignalR notification) */
  refresh(): void {
    this.loadFilaments();
  }

  /** Format weight for display */
  formatWeight(grams: number): string {
    if (grams >= 1000) {
      return `${(grams / 1000).toFixed(1)}kg`;
    }
    return `${Math.round(grams)}g`;
  }

  /** Format currency for display */
  formatCurrency(value: number): string {
    return new Intl.NumberFormat('en-US', {
      style: 'currency',
      currency: 'USD',
      minimumFractionDigits: 0,
      maximumFractionDigits: 0,
    }).format(value);
  }
}