discounts now work well

src/controllers/admin_products.rs

@@ -26,7 +26,7 @@ use crate::{
     },
     shared::{
         guard,
-        money::{format_bp, format_price, parse_price_to_cents},
+        money::{format_bp, format_price, parse_percent, parse_price_to_cents},
         pricing,
         slug::{slugify, unique_slug},
     },
@@ -105,30 +105,9 @@ struct VariantInput {
     /// `None` = available but not inventory-tracked.
     stock: Option<i32>,
     price_cents: i64,
-    business_sale_cents: Option<i64>,
     position: i32,
 }
 
-/// The optional business-sale price field on a variant row: blank means "no
-/// business quick-sale", a value must parse and be below the regular price.
-fn parse_optional_sale(
-    form: &MultipartForm,
-    i: usize,
-    key: &str,
-    price_cents: i64,
-) -> Result<Option<i64>> {
-    let Some(raw) = form.text(&format!("variants[{i}][{key}]")) else {
-        return Ok(None);
-    };
-    let cents = parse_price_to_cents(&raw)?;
-    if cents <= 0 || cents >= price_cents {
-        return Err(Error::BadRequest(
-            "a sale price must be positive and below the regular price".to_string(),
-        ));
-    }
-    Ok(Some(cents))
-}
-
 /// Parse the repeated variant rows from the form, in submission order. Blank
 /// rows (no price and no label) are skipped; at least one valid row is required.
 fn parse_variants(form: &MultipartForm) -> Result<Vec<VariantInput>> {
@@ -168,7 +147,6 @@ fn parse_variants(form: &MultipartForm) -> Result<Vec<VariantInput>> {
                     .ok_or_else(|| Error::BadRequest("stock must be 0 or more".to_string()))?,
             ),
         };
-        let business_sale_cents = parse_optional_sale(form, i, "business_sale", price_cents)?;
         let id = form
             .text(&format!("variants[{i}][id]"))
             .and_then(|s| s.parse::<i32>().ok());
@@ -179,7 +157,6 @@ fn parse_variants(form: &MultipartForm) -> Result<Vec<VariantInput>> {
             sku,
             stock,
             price_cents,
-            business_sale_cents,
             position: out.len() as i32,
         });
     }
@@ -197,9 +174,9 @@ fn apply_variant(active: &mut product_variants::ActiveModel, input: &VariantInpu
     active.sku = Set(input.sku.clone());
     active.stock = Set(input.stock);
     active.price_cents = Set(input.price_cents);
-    // The per-variant public sale price was removed from the UI; keep it cleared.
-    active.sale_price_cents = Set(None);
-    active.business_sale_price_cents = Set(input.business_sale_cents);
+    // Discounts (public + business sale) are owned by the discount page and keyed
+    // per option/audience; the product form must leave those columns untouched so
+    // it never clobbers a discount. New variants default them to NULL.
     active.position = Set(input.position);
 }
 
@@ -257,7 +234,6 @@ fn variant_form_json(variant: &product_variants::Model) -> serde_json::Value {
         "sku": variant.sku,
         "stock": variant.stock,
         "price": format_price(variant.price_cents),
-        "business_sale": variant.business_sale_price_cents.map(format_price),
     })
 }
 
@@ -340,9 +316,13 @@ async fn index(
                 .sum::<i32>()
                 .to_string()
         };
+        // The product is "on sale" for this audience if any option carries a
+        // discount; the per-option amounts live on the discount page.
+        let on_sale = variants.iter().any(|v| current_value(v, audience).is_some());
         rows.push(product_row(
             product,
             priced,
+            on_sale,
             variants.len(),
             stock_display,
             image,
@@ -373,6 +353,7 @@ async fn index(
 fn product_row(
     product: &products::Model,
     effective: &pricing::PricedProduct,
+    on_sale: bool,
     variant_count: usize,
     stock_display: String,
     image: Option<String>,
@@ -390,6 +371,7 @@ fn product_row(
         "image": image,
         "category_name": category_name,
         "regular_price": format_price(effective.regular_cents),
+        "on_sale": on_sale,
         "effective_price": format_price(effective.price_cents),
         "effective_reduced": effective.is_reduced(),
         "effective_percent_off": percent_off(effective.regular_cents, effective.price_cents),
@@ -619,6 +601,30 @@ fn list_redirect(audience: &str) -> Result<Response> {
     format::redirect(&format!("/admin/catalog/products?audience={audience}"))
 }
 
+/// Resolve a percentage off the regular price into a fixed sale price in cents.
+fn percent_to_sale_cents(regular_cents: i64, percent: f64) -> i64 {
+    let off = (regular_cents as f64 * percent / 100.0).round() as i64;
+    regular_cents - off
+}
+
+/// Which discount value an audience tab sees on a variant.
+fn current_value(variant: &product_variants::Model, audience: &str) -> Option<i64> {
+    if audience == BUSINESS {
+        variant.business_sale_price_cents
+    } else {
+        variant.sale_price_cents
+    }
+}
+
+/// Set the discount column on a variant for a given audience.
+fn set_value(active: &mut product_variants::ActiveModel, audience: &str, value: Option<i64>) {
+    if audience == BUSINESS {
+        active.business_sale_price_cents = Set(value);
+    } else {
+        active.sale_price_cents = Set(value);
+    }
+}
+
 /// Percent off the regular price, rounded to a whole number.
 fn percent_off(regular_cents: i64, sale_cents: i64) -> i64 {
     if regular_cents <= 0 {
@@ -742,6 +748,231 @@ async fn sync_profiles(
     list_redirect(audience)
 }
 
+// --- Per-variant discounts ---------------------------------------------------
+//
+// Each product is sold as one or more options (variants). A discount can be set
+// on every option individually, for the active audience: personal writes the
+// public `sale_price_cents`, business writes `business_sale_price_cents`. Per
+// option the admin picks a fixed sale price or a percentage off the regular
+// price; an empty value clears that option's discount.
+
+/// One option row in the discount form. Carries enough to pre-fill the editor
+/// and to survive a validation-error round-trip.
+struct DiscountRow {
+    id: i32,
+    label: String,
+    regular_cents: i64,
+    mode: String,
+    fixed: String,
+    percent: String,
+    has_discount: bool,
+}
+
+impl DiscountRow {
+    /// Pre-fill from the discount stored for this audience.
+    fn from_db(v: &product_variants::Model, audience: &str) -> Self {
+        let sale = current_value(v, audience);
+        DiscountRow {
+            id: v.id,
+            label: v.label.clone(),
+            regular_cents: v.price_cents,
+            mode: "fixed".to_string(),
+            fixed: sale.map(format_price).unwrap_or_default(),
+            percent: String::new(),
+            has_discount: sale.is_some(),
+        }
+    }
+
+    /// Pre-fill from the submitted values, to repaint the form after an error.
+    fn from_submitted(
+        v: &product_variants::Model,
+        audience: &str,
+        pairs: &HashMap<String, String>,
+    ) -> Self {
+        let get = |key: &str| {
+            pairs
+                .get(&format!("v[{}][{key}]", v.id))
+                .map(|s| s.trim().to_string())
+                .unwrap_or_default()
+        };
+        let mode = get("mode");
+        DiscountRow {
+            id: v.id,
+            label: v.label.clone(),
+            regular_cents: v.price_cents,
+            mode: if mode == "percent" {
+                mode
+            } else {
+                "fixed".to_string()
+            },
+            fixed: get("fixed"),
+            percent: get("percent"),
+            has_discount: current_value(v, audience).is_some(),
+        }
+    }
+
+    fn to_json(&self, currency: &str) -> serde_json::Value {
+        json!({
+            "id": self.id,
+            "label": self.label,
+            "regular_cents": self.regular_cents,
+            "regular_price": format_price(self.regular_cents),
+            "currency": currency,
+            "mode": self.mode,
+            "fixed": self.fixed,
+            "percent": self.percent,
+            "has_discount": self.has_discount,
+        })
+    }
+}
+
+/// Resolve one submitted option into the sale price to store. `Ok(None)` clears
+/// the discount; `Err` is an i18n key for the validation message.
+fn resolve_row(
+    regular_cents: i64,
+    mode: &str,
+    fixed: &str,
+    percent: &str,
+) -> std::result::Result<Option<i64>, &'static str> {
+    let sale_cents = if mode == "percent" {
+        if percent.is_empty() {
+            return Ok(None);
+        }
+        let pct = parse_percent(percent).ok_or("discount-invalid")?;
+        if pct <= 0.0 || pct >= 100.0 {
+            return Err("discount-percent-range");
+        }
+        percent_to_sale_cents(regular_cents, pct)
+    } else {
+        if fixed.is_empty() {
+            return Ok(None);
+        }
+        parse_price_to_cents(fixed).map_err(|_| "discount-invalid")?
+    };
+    if sale_cents <= 0 {
+        return Err("discount-must-be-positive");
+    }
+    if sale_cents >= regular_cents {
+        return Err("discount-below-regular");
+    }
+    Ok(Some(sale_cents))
+}
+
+async fn discount_view(
+    v: &TeraView,
+    jar: &CookieJar,
+    product: &products::Model,
+    rows: &[DiscountRow],
+    audience: &str,
+    error: Option<&str>,
+) -> Result<Response> {
+    let rows_json: Vec<_> = rows.iter().map(|r| r.to_json(&product.currency)).collect();
+    let has_discount = rows.iter().any(|r| r.has_discount);
+    format::view(
+        v,
+        "admin/catalog/discount_form.html",
+        json!({
+            "product": {
+                "id": product.id,
+                "name": product.name,
+                "currency": product.currency,
+            },
+            "rows": rows_json,
+            "audience": audience,
+            "has_discount": has_discount,
+            "error": error.map(|e| e.to_string()),
+            "lang": current_lang(jar),
+        }),
+    )
+}
+
+#[debug_handler]
+async fn discount_show(
+    auth: auth::JWT,
+    jar: CookieJar,
+    ViewEngine(v): ViewEngine<TeraView>,
+    Path(id): Path<i32>,
+    Query(params): Query<HashMap<String, String>>,
+    State(ctx): State<AppContext>,
+) -> Result<Response> {
+    guard::current_admin(auth, &ctx).await?;
+    let audience = read_audience(&params);
+    let product = product_by_id(&ctx, id).await?;
+    let variants = product_variants::Entity::for_product(&ctx.db, id).await?;
+    let rows: Vec<DiscountRow> = variants
+        .iter()
+        .map(|variant| DiscountRow::from_db(variant, audience))
+        .collect();
+    discount_view(&v, &jar, &product, &rows, audience, None).await
+}
+
+#[debug_handler]
+async fn discount_update(
+    auth: auth::JWT,
+    jar: CookieJar,
+    ViewEngine(v): ViewEngine<TeraView>,
+    Path(id): Path<i32>,
+    Query(params): Query<HashMap<String, String>>,
+    State(ctx): State<AppContext>,
+    body: String,
+) -> Result<Response> {
+    guard::current_admin(auth, &ctx).await?;
+    let audience = read_audience(&params);
+    let product = product_by_id(&ctx, id).await?;
+    let variants = product_variants::Entity::for_product(&ctx.db, id).await?;
+
+    let pairs: HashMap<String, String> = form_urlencoded::parse(body.as_bytes())
+        .into_owned()
+        .collect();
+
+    // Resolve every option before persisting anything, so one bad row can't leave
+    // the product half-discounted. On the first error, repaint with the inputs.
+    let mut resolved: Vec<(product_variants::Model, Option<i64>)> = Vec::new();
+    for variant in &variants {
+        let row = DiscountRow::from_submitted(variant, audience, &pairs);
+        match resolve_row(variant.price_cents, &row.mode, &row.fixed, &row.percent) {
+            Ok(value) => resolved.push((variant.clone(), value)),
+            Err(key) => {
+                let rows: Vec<DiscountRow> = variants
+                    .iter()
+                    .map(|v| DiscountRow::from_submitted(v, audience, &pairs))
+                    .collect();
+                return discount_view(&v, &jar, &product, &rows, audience, Some(key)).await;
+            }
+        }
+    }
+
+    let txn = ctx.db.begin().await?;
+    for (variant, value) in &resolved {
+        let mut active = variant.clone().into_active_model();
+        set_value(&mut active, audience, *value);
+        active.update(&txn).await?;
+    }
+    txn.commit().await?;
+    list_redirect(audience)
+}
+
+#[debug_handler]
+async fn discount_remove(
+    auth: auth::JWT,
+    Path(id): Path<i32>,
+    Query(params): Query<HashMap<String, String>>,
+    State(ctx): State<AppContext>,
+) -> Result<Response> {
+    guard::current_admin(auth, &ctx).await?;
+    let audience = read_audience(&params);
+    let _product = product_by_id(&ctx, id).await?;
+    let variants = product_variants::Entity::for_product(&ctx.db, id).await?;
+    let txn = ctx.db.begin().await?;
+    for variant in &variants {
+        let mut active = variant.clone().into_active_model();
+        set_value(&mut active, audience, None);
+        active.update(&txn).await?;
+    }
+    txn.commit().await?;
+    list_redirect(audience)
+}
+
 pub fn routes() -> Routes {
     // Several images may be uploaded in one submission; allow a generous total
     // (per-file size is still capped at IMAGE_MAX_BYTES while reading).
@@ -764,4 +995,16 @@ pub fn routes() -> Routes {
             post(update).layer(image_limit),
         )
         .add("/admin/catalog/products/{id}/delete", post(delete))
+        .add(
+            "/admin/catalog/products/{id}/discount/edit",
+            get(discount_show),
+        )
+        .add(
+            "/admin/catalog/products/{id}/discount",
+            post(discount_update),
+        )
+        .add(
+            "/admin/catalog/products/{id}/discount/remove",
+            post(discount_remove),
+        )
 }