import {
  ChangeDetectionStrategy,
  Component,
  computed,
  inject,
} from '@angular/core';
import { CommonModule } from '@angular/common';
import { MatIconModule } from '@angular/material/icon';
import { MatTooltipModule } from '@angular/material/tooltip';
import { FilamentService } from '../../services/filament.service';
import { classifyStockLevel } from '../../models/filament.model';

/**
 * InventorySummaryComponent — dashboard summary for filament inventory metrics.
 *
 * Displays three key metrics driven by FilamentService:
 * - Total filament count (active spools)
 * - Low stock count (spools classified as 'low' or 'critical')
 * - Estimated total filament value (sum of purchase prices for active spools)
 *
 * All values update dynamically whenever FilamentService data changes.
 */
@Component({
  selector: 'app-inventory-summary',
  standalone: true,
  imports: [
    CommonModule,
    MatIconModule,
    MatTooltipModule,
  ],
  templateUrl: './inventory-summary.component.html',
  styleUrl: './inventory-summary.component.scss',
  changeDetection: ChangeDetectionStrategy.OnPush,
})
export class InventorySummaryComponent {
  private readonly filamentService = inject(FilamentService);

  /** Computed: total number of active filament spools */
  readonly totalFilamentCount = computed(() =>
    this.filamentService.filaments().filter((f) => f.isActive).length
  );

  /** Computed: count of spools at low or critical stock levels */
  readonly lowStockCount = computed(() =>
    this.filamentService.filaments().filter((f) => {
      const level = classifyStockLevel(f);
      return level === 'low' || level === 'critical';
    }).length
  );

  /** Computed: count of spools at critical stock level only */
  readonly criticalStockCount = computed(() =>
    this.filamentService.filaments().filter(
      (f) => classifyStockLevel(f) === 'critical'
    ).length
  );

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

  /** Computed: whether there are low-stock spools to highlight */
  readonly hasLowStock = computed(() => this.lowStockCount() > 0);

  /** Computed: whether there are critical-stock spools */
  readonly hasCriticalStock = computed(() => this.criticalStockCount() > 0);

  /** Format a currency value for display */
  formatCurrency(value: number): string {
    return new Intl.NumberFormat('en-US', {
      style: 'currency',
      currency: 'USD',
      minimumFractionDigits: 0,
      maximumFractionDigits: 2,
    }).format(value);
  }
}