discounts

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,