discounts

assets/i18n/en/main.ftl

@@ -208,6 +208,17 @@ edit-category = Edit category
 product = Product
 name = Name
 price = Price
+sale-price = Sale price
+admin-discounts = Discounts
+admin-discounts-desc = Set discounted product prices. A discount shows up as a sale in the shop.
+on-sale = On sale
+no-discount = No discount
+set-discount = Set discount
+remove-discount = Remove discount
+discount-hint = Enter the discounted price (below the regular price). Leave empty to remove the discount.
+discount-invalid = Invalid price.
+discount-must-be-positive = The sale price must be greater than zero.
+discount-below-regular = The sale price must be below the regular price.
 stock = Stock
 sku = SKU
 currency = Currency

assets/i18n/sk/main.ftl

@@ -208,6 +208,17 @@ edit-category = Upraviť kategóriu
 product = Produkt
 name = Názov
 price = Cena
+sale-price = Zľavnená cena
+admin-discounts = Zľavy
+admin-discounts-desc = Nastavte zľavnené ceny produktov. Zľava sa v obchode zobrazí ako akcia.
+on-sale = V akcii
+no-discount = Bez zľavy
+set-discount = Nastaviť zľavu
+remove-discount = Zrušiť zľavu
+discount-hint = Zadajte zľavnenú cenu (nižšiu ako bežná cena). Nechajte prázdne pre zrušenie zľavy.
+discount-invalid = Neplatná cena.
+discount-must-be-positive = Zľavnená cena musí byť väčšia ako nula.
+discount-below-regular = Zľavnená cena musí byť nižšia ako bežná cena.
 stock = Sklad
 sku = Kód (SKU)
 currency = Mena

assets/views/admin/base.html

@@ -78,6 +78,10 @@
           class="flex items-center gap-2 rounded-radius px-2 py-1.5 text-sm font-medium text-on-surface underline-offset-2 transition hover:bg-primary/5 hover:text-on-surface-strong focus:outline-hidden focus-visible:underline aria-[current=page]:bg-primary/10 aria-[current=page]:text-on-surface-strong dark:text-on-surface-dark dark:hover:bg-primary-dark/5 dark:hover:text-on-surface-dark-strong dark:aria-[current=page]:bg-primary-dark/10 dark:aria-[current=page]:text-on-surface-dark-strong">
           {{ t(key="admin-products", lang=lang | default(value='sk')) }}
         </a>
+        <a href="/admin/catalog/discounts" data-nav="/admin/catalog/discounts"
+          class="flex items-center gap-2 rounded-radius px-2 py-1.5 text-sm font-medium text-on-surface underline-offset-2 transition hover:bg-primary/5 hover:text-on-surface-strong focus:outline-hidden focus-visible:underline aria-[current=page]:bg-primary/10 aria-[current=page]:text-on-surface-strong dark:text-on-surface-dark dark:hover:bg-primary-dark/5 dark:hover:text-on-surface-dark-strong dark:aria-[current=page]:bg-primary-dark/10 dark:aria-[current=page]:text-on-surface-dark-strong">
+          {{ t(key="admin-discounts", lang=lang | default(value='sk')) }}
+        </a>
         <a href="/admin/catalog/categories" data-nav="/admin/catalog/categories"
           class="flex items-center gap-2 rounded-radius px-2 py-1.5 text-sm font-medium text-on-surface underline-offset-2 transition hover:bg-primary/5 hover:text-on-surface-strong focus:outline-hidden focus-visible:underline aria-[current=page]:bg-primary/10 aria-[current=page]:text-on-surface-strong dark:text-on-surface-dark dark:hover:bg-primary-dark/5 dark:hover:text-on-surface-dark-strong dark:aria-[current=page]:bg-primary-dark/10 dark:aria-[current=page]:text-on-surface-dark-strong">
           {{ t(key="admin-categories", lang=lang | default(value='sk')) }}

assets/views/admin/catalog/discount_form.html

@@ -0,0 +1,39 @@
+{% extends "admin/base.html" %}
+{% import "macros/ui.html" as ui %}
+
+{% block title %}{{ t(key="set-discount", lang=lang | default(value='sk')) }}{% endblock title %}
+{% block crumb %}{{ t(key="admin-discounts", lang=lang | default(value='sk')) }}{% endblock crumb %}
+
+{% block content %}
+<div class="flex items-center justify-between gap-3">
+  <h1 class="text-2xl font-bold text-on-surface-strong dark:text-on-surface-dark-strong">{{ product.name }}</h1>
+  {{ ui::button(variant="outline-secondary", label=t(key="cancel", lang=lang | default(value='sk')), href="/admin/catalog/discounts", size="px-3 py-2 text-sm") }}
+</div>
+
+<form method="post" action="/admin/catalog/discounts/{{ product.id }}"
+  class="mt-6 max-w-md space-y-5 rounded-radius border border-outline bg-surface p-6 dark:border-outline-dark dark:bg-surface-dark-alt">
+  {{ ui::csrf_field() }}
+
+  {% if error %}
+  {{ ui::alert_danger(message=t(key=error, lang=lang | default(value='sk'))) }}
+  {% endif %}
+
+  <div class="flex items-center justify-between gap-3 rounded-radius bg-surface-alt px-4 py-3 dark:bg-surface-dark/40">
+    <span class="text-sm text-on-surface/70 dark:text-on-surface-dark/70">{{ t(key="price", lang=lang | default(value='sk')) }}</span>
+    <span class="font-semibold tabular-nums text-on-surface-strong dark:text-on-surface-dark-strong">{{ product.regular_price }} {{ product.currency }}</span>
+  </div>
+
+  <div class="space-y-1.5">
+    <label for="sale_price" class="text-sm font-medium text-on-surface-strong dark:text-on-surface-dark-strong">{{ t(key="sale-price", lang=lang | default(value='sk')) }}</label>
+    {{ ui::input(name="sale_price", id="sale_price", value=value, placeholder="0.00", attrs='inputmode="decimal"') }}
+    <p class="text-xs text-on-surface/60 dark:text-on-surface-dark/60">{{ t(key="discount-hint", lang=lang | default(value='sk')) }}</p>
+  </div>
+
+  <div class="flex flex-wrap gap-3 pt-2">
+    {{ ui::button(label=t(key="save", lang=lang | default(value='sk')), type="submit") }}
+    {% if product.on_sale %}
+    {{ ui::button(variant="outline-danger", label=t(key="remove-discount", lang=lang | default(value='sk')), type="submit", attrs='formaction="/admin/catalog/discounts/' ~ product.id ~ '/remove"') }}
+    {% endif %}
+  </div>
+</form>
+{% endblock content %}

assets/views/admin/catalog/discounts.html

@@ -0,0 +1,70 @@
+{% extends "admin/base.html" %}
+{% import "macros/ui.html" as ui %}
+
+{% block title %}{{ t(key="admin-discounts", lang=lang | default(value='sk')) }}{% endblock title %}
+{% block crumb %}{{ t(key="admin-discounts", lang=lang | default(value='sk')) }}{% endblock crumb %}
+
+{% block content %}
+<div class="flex flex-wrap items-end justify-between gap-3">
+  <div>
+    <h1 class="text-2xl font-bold text-on-surface-strong dark:text-on-surface-dark-strong">{{ t(key="admin-discounts", lang=lang | default(value='sk')) }}</h1>
+    <p class="text-sm text-on-surface/70 dark:text-on-surface-dark/70">{{ t(key="admin-discounts-desc", lang=lang | default(value='sk')) }}</p>
+  </div>
+</div>
+
+<div class="mt-6 {{ ui::table_wrap_cls() }}">
+  {% if products | length > 0 %}
+  <table class="{{ ui::table_cls() }}">
+    <thead class="{{ ui::thead_cls() }}">
+      <tr>
+        {{ ui::th(label=t(key="product", lang=lang | default(value='sk'))) }}
+        {{ ui::th(label=t(key="price", lang=lang | default(value='sk'))) }}
+        {{ ui::th(label=t(key="sale-price", lang=lang | default(value='sk'))) }}
+        {{ ui::th(label=t(key="status", lang=lang | default(value='sk'))) }}
+        {{ ui::th(label=t(key="actions", lang=lang | default(value='sk')), align="text-right") }}
+      </tr>
+    </thead>
+    <tbody class="{{ ui::tbody_cls() }}">
+      {% for product in products %}
+      <tr class="{{ ui::row_cls() }}">
+        <td class="px-4 py-3">
+          <div class="font-medium text-on-surface-strong dark:text-on-surface-dark-strong">{{ product.name }}</div>
+        </td>
+        <td class="px-4 py-3 tabular-nums">{{ product.regular_price }} {{ product.currency }}</td>
+        <td class="px-4 py-3 tabular-nums">
+          {% if product.on_sale %}
+          <span class="font-medium text-danger">{{ product.sale_price }} {{ product.currency }}</span>
+          <span class="ml-1 text-xs text-on-surface/60 dark:text-on-surface-dark/60">(−{{ product.percent_off }}%)</span>
+          {% else %}
+          <span class="text-on-surface/40 dark:text-on-surface-dark/40">—</span>
+          {% endif %}
+        </td>
+        <td class="px-4 py-3">
+          {% if product.on_sale %}
+          {{ ui::badge(label=t(key="on-sale", lang=lang | default(value='sk')), variant="danger") }}
+          {% else %}
+          {{ ui::badge(label=t(key="no-discount", lang=lang | default(value='sk')), variant="neutral") }}
+          {% endif %}
+        </td>
+        <td class="px-4 py-3">
+          <div class="flex flex-wrap justify-end gap-2">
+            {{ ui::button(variant="outline-secondary", label=t(key="set-discount", lang=lang | default(value='sk')), href="/admin/catalog/discounts/" ~ product.id ~ "/edit", size="px-3 py-1.5 text-xs") }}
+            {% if product.on_sale %}
+            <form method="post" action="/admin/catalog/discounts/{{ product.id }}/remove">
+              {{ ui::csrf_field() }}
+              {{ ui::button(variant="outline-danger", label=t(key="remove-discount", lang=lang | default(value='sk')), type="submit", size="px-3 py-1.5 text-xs") }}
+            </form>
+            {% endif %}
+          </div>
+        </td>
+      </tr>
+      {% endfor %}
+    </tbody>
+  </table>
+  {% else %}
+  <div class="flex flex-col items-center gap-3 px-4 py-16 text-center">
+    <p class="text-on-surface/70 dark:text-on-surface-dark/70">{{ t(key="admin-no-products", lang=lang | default(value='sk')) }}</p>
+  </div>
+  {% endif %}
+</div>
+{% endblock content %}

assets/views/admin/catalog/products.html

@@ -41,7 +41,14 @@
             </div>
           </div>
         </td>
-        <td class="px-4 py-3 tabular-nums">{{ product.price }} {{ product.currency }}</td>
+        <td class="px-4 py-3 tabular-nums">
+          {% if product.on_sale %}
+          <span class="font-medium text-danger">{{ product.price }} {{ product.currency }}</span>
+          <span class="text-xs text-on-surface/50 line-through dark:text-on-surface-dark/50">{{ product.regular_price }}</span>
+          {% else %}
+          {{ product.price }} {{ product.currency }}
+          {% endif %}
+        </td>
         <td class="px-4 py-3 tabular-nums">{{ product.stock }}</td>
         <td class="px-4 py-3">
           {% if product.published %}
@@ -53,6 +60,7 @@
         <td class="px-4 py-3">
           <div class="flex flex-wrap justify-end gap-2">
             {{ ui::button(variant="outline-secondary", label=t(key="edit", lang=lang | default(value='sk')), href="/admin/catalog/products/" ~ product.id ~ "/edit", size="px-3 py-1.5 text-xs") }}
+            {{ ui::button(variant="outline-secondary", label=t(key="set-discount", lang=lang | default(value='sk')), href="/admin/catalog/discounts/" ~ product.id ~ "/edit", size="px-3 py-1.5 text-xs") }}
             {{ ui::button(variant="outline-secondary", label=t(key="view", lang=lang | default(value='sk')), href="/shop/" ~ product.slug, size="px-3 py-1.5 text-xs") }}
             <form method="post" action="/admin/catalog/products/{{ product.id }}/delete"
               onsubmit="return confirm('{{ t(key="confirm-delete", lang=lang | default(value='sk')) }}')">

assets/views/macros/ui.html

@@ -127,7 +127,7 @@
 
 {# Text/email/number/password input. #}
 {% macro input(name, type="text", id="", value="", placeholder="", required=false, autocomplete="", attrs="", extra="", width="w-full") -%}
-<input {% if id %}id="{{ id }}" {% endif %}name="{{ name }}" type="{{ type }}"{% if value != "" %} value="{{ value }}"{% endif %}{% if placeholder %} placeholder="{{ placeholder }}"{% endif %}{% if required %} required{% endif %}{% if autocomplete %} autocomplete="{{ autocomplete }}"{% endif %} class="{{ width }} rounded-radius border border-outline bg-surface-alt px-2 py-2 text-sm text-on-surface focus-visible:outline-2 focus-visible:outline-offset-2 focus-visible:outline-primary disabled:cursor-not-allowed disabled:opacity-75 dark:border-outline-dark dark:bg-surface-dark-alt/50 dark:text-on-surface-dark dark:focus-visible:outline-primary-dark {{ extra }}" {{ attrs | safe }}/>
+<input {% if id %}id="{{ id }}" {% endif %}name="{{ name }}" type="{{ type }}"{% if value is number or value != "" %} value="{{ value }}"{% endif %}{% if placeholder %} placeholder="{{ placeholder }}"{% endif %}{% if required %} required{% endif %}{% if autocomplete %} autocomplete="{{ autocomplete }}"{% endif %} class="{{ width }} rounded-radius border border-outline bg-surface-alt px-2 py-2 text-sm text-on-surface focus-visible:outline-2 focus-visible:outline-offset-2 focus-visible:outline-primary disabled:cursor-not-allowed disabled:opacity-75 dark:border-outline-dark dark:bg-surface-dark-alt/50 dark:text-on-surface-dark dark:focus-visible:outline-primary-dark {{ extra }}" {{ attrs | safe }}/>
 {%- endmacro input %}
 
 {% macro textarea(name, id="", value="", rows="3", placeholder="", required=false, attrs="", extra="") -%}

assets/views/shop/_card.html

@@ -17,7 +17,14 @@
       <!-- Header: Title & Price -->
       <div class="flex justify-between gap-4">
         <h3 class="text-lg font-bold text-on-surface-strong dark:text-on-surface-dark-strong">{{ product.name }}</h3>
+        {% if product.on_sale %}
+        <span class="flex flex-col items-end whitespace-nowrap leading-tight">
+          <span class="text-sm text-on-surface/50 line-through dark:text-on-surface-dark/50">{{ product.regular_price }} {{ product.currency }}</span>
+          <span class="text-xl font-semibold text-danger"><span class="sr-only">Price</span>{{ product.price }} {{ product.currency }}</span>
+        </span>
+        {% else %}
         <span class="whitespace-nowrap text-xl"><span class="sr-only">Price</span>{{ product.price }} {{ product.currency }}</span>
+        {% endif %}
       </div>
     </div>
   </a>

assets/views/shop/show.html

@@ -54,7 +54,14 @@
     <a href="/category/{{ category.slug }}" class="text-sm font-medium text-primary dark:text-primary-dark">{{ category.name }}</a>
     {% endif %}
     <h1 class="text-3xl font-bold text-on-surface-strong dark:text-on-surface-dark-strong">{{ product.name }}</h1>
+    {% if product.on_sale %}
+    <div class="flex items-baseline gap-3">
+      <p class="text-2xl font-semibold text-danger">{{ product.price }} {{ product.currency }}</p>
+      <p class="text-lg text-on-surface/50 line-through dark:text-on-surface-dark/50">{{ product.regular_price }} {{ product.currency }}</p>
+    </div>
+    {% else %}
     <p class="text-2xl font-semibold text-primary dark:text-primary-dark">{{ product.price }} {{ product.currency }}</p>
+    {% endif %}
 
     {% if product.description %}
     <div class="whitespace-pre-line leading-relaxed text-on-surface/80 dark:text-on-surface-dark/80">{{ product.description }}</div>

migration/src/lib.rs

@@ -35,6 +35,7 @@ mod m20260618_000002_customer_profiles;
 mod m20260618_000003_account_type;
 mod m20260618_000004_account_ownership;
 mod m20260620_000001_add_totp_to_users;
+mod m20260621_000001_add_sale_price_to_products;
 pub struct Migrator;
 
 #[async_trait::async_trait]
@@ -74,6 +75,7 @@ impl MigratorTrait for Migrator {
             Box::new(m20260618_000003_account_type::Migration),
             Box::new(m20260618_000004_account_ownership::Migration),
             Box::new(m20260620_000001_add_totp_to_users::Migration),
+            Box::new(m20260621_000001_add_sale_price_to_products::Migration),
             // inject-above (do not remove this comment)
         ]
     }

migration/src/m20260621_000001_add_sale_price_to_products.rs

@@ -0,0 +1,19 @@
+use loco_rs::schema::*;
+use sea_orm_migration::prelude::*;
+
+#[derive(DeriveMigrationName)]
+pub struct Migration;
+
+#[async_trait::async_trait]
+impl MigrationTrait for Migration {
+    async fn up(&self, m: &SchemaManager) -> Result<(), DbErr> {
+        // Optional discounted price in minor units. When set (and below
+        // `price_cents`) the product is on sale; the regular price is shown
+        // struck through and this is the effective price everywhere.
+        add_column(m, "products", "sale_price_cents", ColType::BigIntegerNull).await
+    }
+
+    async fn down(&self, m: &SchemaManager) -> Result<(), DbErr> {
+        remove_column(m, "products", "sale_price_cents").await
+    }
+}

src/app.rs

@@ -17,7 +17,7 @@ use std::{path::Path, sync::Arc};
 #[allow(unused_imports)]
 use crate::{
     controllers::{
-        account, admin_categories, admin_dashboard, admin_form, admin_orders,
+        account, admin_categories, admin_dashboard, admin_discounts, admin_form, admin_orders,
         admin_products, admin_shipping, auth, auth_pages, cart, checkout, home, i18n, media, oauth2,
         shop,
     },
@@ -104,6 +104,7 @@ impl Hooks for App {
             // admin
             .add_route(admin_dashboard::routes())
             .add_route(admin_products::routes())
+            .add_route(admin_discounts::routes())
             .add_route(admin_categories::routes())
             .add_route(admin_orders::routes())
             .add_route(admin_shipping::routes())

src/controllers/admin_discounts.rs

@@ -0,0 +1,185 @@
+//! Admin management of per-product discounts.
+//!
+//! Discounts live on the product (`sale_price_cents`) but are set here, in a
+//! place of their own, rather than on the product editor: an admin picks a
+//! product, enters a discounted price, and the storefront then shows it on sale.
+//! Editing a product never touches its discount, and vice versa.
+
+use axum_extra::extract::cookie::CookieJar;
+use loco_rs::prelude::*;
+use sea_orm::{ActiveModelTrait, EntityTrait, QueryOrder, Set};
+use serde::Deserialize;
+use serde_json::json;
+
+use crate::{
+    controllers::i18n::current_lang,
+    models::products,
+    shared::{
+        guard,
+        money::{format_price, parse_price_to_cents},
+    },
+};
+
+#[derive(Debug, Deserialize)]
+struct DiscountForm {
+    sale_price: String,
+}
+
+async fn product_by_id(ctx: &AppContext, id: i32) -> Result<products::Model> {
+    products::Entity::find_by_id(id)
+        .one(&ctx.db)
+        .await?
+        .ok_or_else(|| Error::NotFound)
+}
+
+/// Percent off the regular price, rounded to a whole number. `0` when there is
+/// no positive regular price to discount from.
+fn percent_off(regular_cents: i64, sale_cents: i64) -> i64 {
+    if regular_cents <= 0 {
+        return 0;
+    }
+    let off = (regular_cents - sale_cents) as f64 / regular_cents as f64 * 100.0;
+    off.round() as i64
+}
+
+/// Row shape for the discounts list.
+fn list_row(product: &products::Model) -> serde_json::Value {
+    json!({
+        "id": product.id,
+        "name": product.name,
+        "slug": product.slug,
+        "currency": product.currency,
+        "regular_price": format_price(product.price_cents),
+        "on_sale": product.on_sale(),
+        "sale_price": product.sale_price_cents.map(format_price),
+        "percent_off": product.sale_price_cents.map(|sale| percent_off(product.price_cents, sale)),
+    })
+}
+
+#[debug_handler]
+async fn index(
+    auth: auth::JWT,
+    jar: CookieJar,
+    ViewEngine(v): ViewEngine<TeraView>,
+    State(ctx): State<AppContext>,
+) -> Result<Response> {
+    guard::current_admin(auth, &ctx).await?;
+    let list = products::Entity::find()
+        .order_by_asc(products::Column::Name)
+        .all(&ctx.db)
+        .await?;
+    let rows: Vec<serde_json::Value> = list.iter().map(list_row).collect();
+    format::view(
+        &v,
+        "admin/catalog/discounts.html",
+        json!({ "products": rows, "lang": current_lang(&jar) }),
+    )
+}
+
+/// Render the single-product discount form, optionally with a validation error
+/// and the value the admin just typed (so a rejected submit isn't lost).
+fn render_form(
+    v: &TeraView,
+    jar: &CookieJar,
+    product: &products::Model,
+    entered: Option<String>,
+    error: Option<&str>,
+) -> Result<Response> {
+    let current = product.sale_price_cents.map(format_price);
+    let value = entered.or_else(|| current.clone()).unwrap_or_default();
+    format::view(
+        v,
+        "admin/catalog/discount_form.html",
+        json!({
+            "product": {
+                "id": product.id,
+                "name": product.name,
+                "currency": product.currency,
+                "regular_price": format_price(product.price_cents),
+                "on_sale": product.on_sale(),
+                "sale_price": current,
+            },
+            "value": value,
+            "error": error,
+            "lang": current_lang(jar),
+        }),
+    )
+}
+
+#[debug_handler]
+async fn edit(
+    auth: auth::JWT,
+    jar: CookieJar,
+    ViewEngine(v): ViewEngine<TeraView>,
+    Path(id): Path<i32>,
+    State(ctx): State<AppContext>,
+) -> Result<Response> {
+    guard::current_admin(auth, &ctx).await?;
+    let product = product_by_id(&ctx, id).await?;
+    render_form(&v, &jar, &product, None, None)
+}
+
+#[debug_handler]
+async fn update(
+    auth: auth::JWT,
+    jar: CookieJar,
+    ViewEngine(v): ViewEngine<TeraView>,
+    Path(id): Path<i32>,
+    State(ctx): State<AppContext>,
+    Form(form): Form<DiscountForm>,
+) -> Result<Response> {
+    guard::current_admin(auth, &ctx).await?;
+    let product = product_by_id(&ctx, id).await?;
+
+    let entered = form.sale_price.trim().to_string();
+
+    // An empty value clears the discount (same as the Remove action).
+    if entered.is_empty() {
+        return clear_discount(&ctx, product).await;
+    }
+
+    // A discount must be a valid, positive price strictly below the regular
+    // price — otherwise it isn't a discount. Reject inline, keeping the input.
+    let render_err = |key: &str| render_form(&v, &jar, &product, Some(entered.clone()), Some(key));
+    let sale_cents = match parse_price_to_cents(&entered) {
+        Ok(cents) => cents,
+        Err(_) => return render_err("discount-invalid"),
+    };
+    if sale_cents <= 0 {
+        return render_err("discount-must-be-positive");
+    }
+    if sale_cents >= product.price_cents {
+        return render_err("discount-below-regular");
+    }
+
+    let mut active = product.into_active_model();
+    active.sale_price_cents = Set(Some(sale_cents));
+    active.update(&ctx.db).await?;
+    format::redirect("/admin/catalog/discounts")
+}
+
+async fn clear_discount(ctx: &AppContext, product: products::Model) -> Result<Response> {
+    let mut active = product.into_active_model();
+    active.sale_price_cents = Set(None);
+    active.update(&ctx.db).await?;
+    format::redirect("/admin/catalog/discounts")
+}
+
+#[debug_handler]
+async fn remove(
+    auth: auth::JWT,
+    Path(id): Path<i32>,
+    State(ctx): State<AppContext>,
+) -> Result<Response> {
+    guard::current_admin(auth, &ctx).await?;
+    let product = product_by_id(&ctx, id).await?;
+    clear_discount(&ctx, product).await
+}
+
+pub fn routes() -> Routes {
+    Routes::new()
+        .add("/admin/catalog/discounts", get(index))
+        .add("/admin/catalog/discounts/{id}/edit", get(edit))
+        .add("/admin/catalog/discounts/{id}", post(update))
+        .add("/admin/catalog/discounts/{id}/remove", post(remove))
+}

src/controllers/cart.rs

@@ -201,14 +201,15 @@ pub(crate) async fn resolve_cart(
         if qty == 0 {
             continue;
         }
-        let line_total = product.price_cents * i64::from(qty);
+        let unit_price = product.effective_price_cents();
+        let line_total = unit_price * i64::from(qty);
         total += line_total;
         valid.push((product.id, qty));
         lines.push(json!({
             "id": product.id,
             "name": product.name,
             "slug": product.slug,
-            "price": format_price(product.price_cents),
+            "price": format_price(unit_price),
             "currency": product.currency,
             "quantity": qty,
             "stock": product.stock,

src/controllers/mod.rs

@@ -4,6 +4,7 @@ pub mod auth_pages;
 pub mod oauth2;
 pub mod admin_categories;
 pub mod admin_dashboard;
+pub mod admin_discounts;
 pub mod admin_form;
 pub mod admin_orders;
 pub mod admin_products;

src/models/_entities/products.rs

@@ -16,6 +16,7 @@ pub struct Model {
     #[sea_orm(column_type = "Text", nullable)]
     pub description: Option<String>,
     pub price_cents: i64,
+    pub sale_price_cents: Option<i64>,
     pub currency: String,
     pub sku: Option<String>,
     pub stock: i32,

src/models/orders.rs

@@ -61,13 +61,15 @@ pub async fn place(ctx: &AppContext, items: &[(i32, i32)], details: Checkout) ->
             )));
         }
         currency = product.currency.clone();
-        subtotal += product.price_cents * i64::from(*qty);
+        // Snapshot the effective price (honouring any active discount).
+        let unit_price_cents = product.effective_price_cents();
+        subtotal += unit_price_cents * i64::from(*qty);
 
         let mut active = product.clone().into_active_model();
         active.stock = Set(product.stock - *qty);
         active.update(&txn).await?;
 
-        snapshots.push((product.id, product.name, product.price_cents, *qty));
+        snapshots.push((product.id, product.name, unit_price_cents, *qty));
     }
 
     let order = ActiveModel {

src/models/products.rs

@@ -19,7 +19,25 @@ impl ActiveModelBehavior for ActiveModel {
 }
 
 // implement your read-oriented logic here
-impl Model {}
+impl Model {
+    /// Whether a discount is currently active: a sale price is set and is
+    /// strictly below the regular price.
+    #[must_use]
+    pub fn on_sale(&self) -> bool {
+        matches!(self.sale_price_cents, Some(sale) if sale < self.price_cents)
+    }
+
+    /// The price actually charged: the sale price when [`Model::on_sale`],
+    /// otherwise the regular price.
+    #[must_use]
+    pub fn effective_price_cents(&self) -> i64 {
+        if self.on_sale() {
+            self.sale_price_cents.unwrap_or(self.price_cents)
+        } else {
+            self.price_cents
+        }
+    }
+}
 
 // implement your write-oriented logic here
 impl ActiveModel {}

src/views/shop.rs

@@ -17,7 +17,9 @@ pub fn product_card(
         "name": product.name,
         "slug": product.slug,
         "description": product.description,
-        "price": format_price(product.price_cents),
+        "price": format_price(product.effective_price_cents()),
+        "on_sale": product.on_sale(),
+        "regular_price": format_price(product.price_cents),
         "currency": product.currency,
         "sku": product.sku,
         "stock": product.stock,