Bills initially working just as proof of concept

ng linted
modifier categories list is better at displaying data sanely now

bookie/src/app/sales/bill.service.ts

@@ -0,0 +1,84 @@
+import { Injectable } from '@angular/core';
+import { Product } from '../core/product';
+import { ModifiersComponent } from './modifiers/modifiers.component';
+import { MatDialog } from '@angular/material';
+import { ModifierCategoryService } from '../modifier-categories/modifier-category.service';
+import {Subject} from "rxjs";
+import {Modifier} from "../core/modifier";
+import {ModifierCategory} from "../core/modifier-category";
+import {isNotNullOrUndefined} from "codelyzer/util/isNotNullOrUndefined";
+
+@Injectable()
+export class BillService {
+  public dataObs = new Subject<any[]>();
+  public data = [];
+  constructor(
+        private dialog: MatDialog,
+    private modifierCategoryService: ModifierCategoryService
+  ) { }
+
+  addProduct(product: Product) {
+    let item = {
+      isKot: false,
+      product: product,
+      productId: product.id,
+      info: `${product.name} (${product.units}) @ ${product.price}`,
+      quantity: 1,
+      modifiers: []
+    };
+    this.data.push(item);
+    this.modifierCategoryService.listIsActiveOfProduct(product.id).subscribe(result => {
+      if (result.reduce((a: any, c: ModifierCategory) => {return a + c.minimum}, 0)) {
+        this.showModifier(item);
+      }
+    });
+    this.dataObs.next(this.data);
+  }
+
+  showModifier(item: any): void {
+    // [routerLink]="['/sales', 'modifiers', item.id]"
+    const dialogRef = this.dialog.open(ModifiersComponent, {
+      position: {
+        top: '10vh'
+      },
+      data: {
+        list: this.modifierCategoryService.listIsActiveOfProduct(item.productId),
+        selected: item.modifiers
+      }
+    });
+
+    dialogRef.afterClosed().subscribe(result => {
+      if (isNotNullOrUndefined(result)) {
+        item.modifiers = result;
+      }
+    });
+  }
+
+  addOne(item: any): void {
+    item.quantity += 1;
+    this.dataObs.next(this.data);
+  }
+
+  quantity(item: any): void {
+
+  }
+
+  subtractOne(item: any): void {
+    if (item.quantity > 1) {
+      item.quantity -= 1;
+      this.dataObs.next(this.data);
+    } else if (item.quantity === 0) {
+      this.removeItem(item);
+    }
+  }
+
+  removeItem(item: any): void {
+    this.data.splice(this.data.indexOf(item), 1);
+    this.dataObs.next(this.data);
+  }
+
+  modifier(item: any): void {
+    this.showModifier(item);
+  }
+
+}