vendix-product-pricing

name	vendix-product-pricing
description	Patterns for advanced product pricing logic, rentability calculations, and reactive price management in Vendix. Trigger: When editing product schemas, pricing logic, or advanced product forms.
license	Apache-2.0
metadata	{"author":"gentleman-programming","version":"1.0"}

When to Use

• Implementing new pricing fields in Product or ProductVariant models.
• Building UI components that require bidirectional price/margin calculations.
• Handling tax-inclusive pricing displays in frontend.
• Managing "On Sale" (Offer) price logic.

Critical Patterns

1. Database Fields

Always include the four pillars of pricing in both products and product_variants tables:

• cost_price: The acquisition cost.
• profit_margin: The target profitability percentage.
• base_price: The listing price (PVP) before taxes.
• sale_price: The promotional price (Offer).
• is_on_sale: Boolean flag to activate the offer.

2. Bidirectional Calculation Logic (Angular)

When one price field changes, others should update reactively:

• Margin -> Base Price: base_price = cost_price * (1 + margin / 100)
• Base Price -> Margin: margin = ((base_price - cost_price) / cost_price) * 100 (Only if cost > 0)

3. Tax Integration

The final price should always be calculated dynamically based on selected tax_categories:

• final_price = base_price * (1 + sum(tax_rates))

Code Examples

Reactive Form Setup (Angular)

private setupPriceCalculations(form: FormGroup): void {
  const costCtrl = form.get('cost_price');
  const marginCtrl = form.get('profit_margin');
  const basePriceCtrl = form.get('base_price');

  // Cost or Margin changed -> Update Base Price
  merge(costCtrl.valueChanges, marginCtrl.valueChanges).subscribe(() => {
    const cost = Number(costCtrl.value || 0);
    const margin = Number(marginCtrl.value || 0);
    const basePrice = cost * (1 + margin / 100);
    basePriceCtrl.setValue(basePrice, { emitEvent: false });
  });

  // Base Price changed -> Update Margin
  basePriceCtrl.valueChanges.subscribe((val) => {
    const cost = Number(costCtrl.value || 0);
    if (cost > 0) {
      const margin = ((val - cost) / cost) * 100;
      marginCtrl.setValue(margin, { :  });
    }
  });
}

Prisma Schema Fields

model products {
  base_price               Decimal                    @db.Decimal(12, 2)
  cost_price               Decimal?                   @db.Decimal(12, 2)
  profit_margin            Decimal?                   @db.Decimal(5, 2)
  is_on_sale               Boolean                    @default(false)
  sale_price               Decimal?                   @db.Decimal(12, 2)
}

Commands

# Regenerate Prisma client after adding pricing fields
npx prisma generate

# Apply pricing schema changes
npx prisma migrate dev --name add_pricing_fields