vendix-calculated-pricing

Core Rule

Do not persist calculated display prices for products. Persist base/sale inputs and tax assignments; calculate final display price on read.

Current product API uses final_price for calculated tax-inclusive responses. Do not standardize new code on price_with_tax unless the existing endpoint/interface already uses that name.

Product Pattern

• Persist: base_price, cost_price, profit_margin, is_on_sale, sale_price.
• Persist variant override: product_variants.price_override.
• Persist tax links: product_tax_assignments.
• Calculate: final_price = effectiveBase * (1 + sum(taxRates)).
• Effective base uses sale_price when is_on_sale is true and sale price is valid.

Snapshot Exception

Orders, invoices, payments, refunds, and accounting documents can store totals because they are historical transaction snapshots. Those amounts must not change if product prices or tax rates change later.

Frontend Display

• Calculated prices are read-only UI values.
• Label them as calculated/final values when user input could be confused with persisted price.
• Use the custom Vendix currency pipe/service for display.

DTO/API Rules

• Create/update DTOs should not accept final_price or equivalent calculated fields.
• Read responses may include final_price for convenience.
• If an API returns both stored and calculated values, name them clearly.

Related Skills

• vendix-product-pricing
• vendix-currency-formatting
• vendix-date-timezone for historical timestamp semantics