percentage discounts

assets/i18n/en/main.ftl

@@ -213,12 +213,19 @@ 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
+discount = 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-mode-fixed = Fixed price
+discount-mode-percent = Percentage
+discount-percent = Discount (%)
+discount-preview-before = Original price
+discount-preview-after = New price
+discount-preview-save = You save
 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.
+discount-percent-range = The percentage must be between 0 and 100.
 stock = Stock
 sku = SKU
 currency = Currency

assets/i18n/sk/main.ftl

@@ -213,12 +213,19 @@ 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
+discount = Zľava
 set-discount = Nastaviť zľavu
 remove-discount = Zrušiť zľavu
-discount-hint = Zadajte zľavnenú cenu (nižšiu ako bežná cena). Nechajte prázdne pre zrušenie zľavy.
+discount-mode-fixed = Pevná cena
+discount-mode-percent = Percentá
+discount-percent = Zľava (%)
+discount-preview-before = Pôvodná cena
+discount-preview-after = Nová cena
+discount-preview-save = Ušetríte
 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.
+discount-percent-range = Percento musí byť medzi 0 a 100.
 stock = Sklad
 sku = Kód (SKU)
 currency = Mena

assets/views/admin/catalog/discount_form.html

@@ -11,6 +11,24 @@
 </div>
 
 <form method="post" action="/admin/catalog/discounts/{{ product.id }}"
+  x-data="{
+    mode: '{{ mode }}',
+    fixed: '{{ fixed }}',
+    percent: '{{ percent }}',
+    regular: {{ product.regular_cents }},
+    num(v) { let n = parseFloat(String(v).replace(',', '.')); return isFinite(n) ? n : null; },
+    get afterCents() {
+      if (this.mode === 'percent') {
+        let p = this.num(this.percent); if (p === null) return null;
+        return this.regular - Math.round(this.regular * p / 100);
+      }
+      let f = this.num(this.fixed); if (f === null) return null;
+      return Math.round(f * 100);
+    },
+    money(c) { return (c / 100).toFixed(2); },
+    get valid() { let a = this.afterCents; return a !== null && a > 0 && a < this.regular; },
+    get percentOff() { let a = this.afterCents; return (a === null || this.regular <= 0) ? null : Math.round((this.regular - a) / this.regular * 100); }
+  }"
   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() }}
 
@@ -23,10 +41,50 @@
     <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">
+  <!-- mode toggle -->
+  <div class="grid grid-cols-2 gap-2">
+    <label class="flex cursor-pointer items-center justify-center gap-2 rounded-radius border px-3 py-2 text-sm transition"
+      :class="mode === 'fixed' ? 'border-primary bg-primary/10 text-on-surface-strong dark:border-primary-dark dark:bg-primary-dark/10 dark:text-on-surface-dark-strong' : 'border-outline text-on-surface dark:border-outline-dark dark:text-on-surface-dark'">
+      <input type="radio" name="mode" value="fixed" x-model="mode" class="sr-only">
+      {{ t(key="discount-mode-fixed", lang=lang | default(value='sk')) }}
+    </label>
+    <label class="flex cursor-pointer items-center justify-center gap-2 rounded-radius border px-3 py-2 text-sm transition"
+      :class="mode === 'percent' ? 'border-primary bg-primary/10 text-on-surface-strong dark:border-primary-dark dark:bg-primary-dark/10 dark:text-on-surface-dark-strong' : 'border-outline text-on-surface dark:border-outline-dark dark:text-on-surface-dark'">
+      <input type="radio" name="mode" value="percent" x-model="mode" class="sr-only">
+      {{ t(key="discount-mode-percent", lang=lang | default(value='sk')) }}
+    </label>
+  </div>
+
+  <!-- fixed price input -->
+  <div class="space-y-1.5" x-show="mode === 'fixed'">
     <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>
+    {{ ui::input(name="sale_price", id="sale_price", value=fixed, placeholder="0.00", attrs='inputmode="decimal" x-model="fixed"') }}
+  </div>
+
+  <!-- percentage input -->
+  <div class="space-y-1.5" x-show="mode === 'percent'">
+    <label for="percent" class="text-sm font-medium text-on-surface-strong dark:text-on-surface-dark-strong">{{ t(key="discount-percent", lang=lang | default(value='sk')) }}</label>
+    {{ ui::input(name="percent", id="percent", value=percent, placeholder="0", attrs='inputmode="decimal" min="0" max="100" x-model="percent"') }}
+  </div>
+
+  <!-- live preview -->
+  <div x-show="afterCents !== null" x-cloak
+    class="space-y-2 rounded-radius border border-outline bg-surface-alt px-4 py-3 dark:border-outline-dark dark:bg-surface-dark/40">
+    <div class="flex items-center justify-between gap-3 text-sm">
+      <span class="text-on-surface/70 dark:text-on-surface-dark/70">{{ t(key="discount-preview-before", lang=lang | default(value='sk')) }}</span>
+      <span class="tabular-nums text-on-surface/60 line-through dark:text-on-surface-dark/60"><span x-text="money(regular)"></span> {{ product.currency }}</span>
+    </div>
+    <div class="flex items-center justify-between gap-3">
+      <span class="text-sm text-on-surface/70 dark:text-on-surface-dark/70">{{ t(key="discount-preview-after", lang=lang | default(value='sk')) }}</span>
+      <span class="text-lg font-semibold tabular-nums" :class="valid ? 'text-danger' : 'text-on-surface/40 dark:text-on-surface-dark/40'">
+        <span x-text="money(afterCents)"></span> {{ product.currency }}
+      </span>
+    </div>
+    <div x-show="valid" class="flex items-center justify-between gap-3 text-xs text-on-surface/60 dark:text-on-surface-dark/60">
+      <span>{{ t(key="discount-preview-save", lang=lang | default(value='sk')) }}</span>
+      <span class="tabular-nums"><span x-text="money(regular - afterCents)"></span> {{ product.currency }} (−<span x-text="percentOff"></span>%)</span>
+    </div>
+    <p x-show="!valid" class="text-xs text-danger">{{ t(key="discount-below-regular", lang=lang | default(value='sk')) }}</p>
   </div>
 
   <div class="flex flex-wrap gap-3 pt-2">

assets/views/admin/catalog/products.html

@@ -60,7 +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="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')) }}')">

src/controllers/admin_discounts.rs

@@ -22,7 +22,24 @@ use crate::{
 
 #[derive(Debug, Deserialize)]
 struct DiscountForm {
-    sale_price: String,
+    /// "fixed" (enter the new price) or "percent" (enter % off). Defaults to
+    /// fixed for older/JSON callers.
+    mode: Option<String>,
+    sale_price: Option<String>,
+    percent: Option<String>,
+}
+
+/// Parse a percentage typed as "20", "20.5" or "20,5" into an `f64`.
+fn parse_percent(value: &str) -> Option<f64> {
+    let parsed: f64 = value.trim().replace(',', ".").parse().ok()?;
+    parsed.is_finite().then_some(parsed)
+}
+
+/// Resolve a percentage off the regular price into a fixed sale price in cents.
+/// Rounds the discount amount to the nearest cent.
+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
 }
 
 async fn product_by_id(ctx: &AppContext, id: i32) -> Result<products::Model> {
@@ -76,17 +93,24 @@ async fn index(
     )
 }
 
-/// 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).
+/// What to pre-fill the form with: the chosen input mode and the raw values for
+/// each field, so a rejected submit (or a re-edit) shows what the admin had.
+#[derive(Default)]
+struct FormPrefill {
+    mode: String,
+    fixed: String,
+    percent: String,
+}
+
+/// Render the single-product discount form, optionally with a validation error.
 fn render_form(
     v: &TeraView,
     jar: &CookieJar,
     product: &products::Model,
-    entered: Option<String>,
+    prefill: &FormPrefill,
     error: Option<&str>,
 ) -> Result<Response> {
-    let current = product.sale_price_cents.map(format_price);
-    let value = entered.or_else(|| current.clone()).unwrap_or_default();
+    let mode = if prefill.mode == "percent" { "percent" } else { "fixed" };
     format::view(
         v,
         "admin/catalog/discount_form.html",
@@ -96,10 +120,13 @@ fn render_form(
                 "name": product.name,
                 "currency": product.currency,
                 "regular_price": format_price(product.price_cents),
+                "regular_cents": product.price_cents,
                 "on_sale": product.on_sale(),
-                "sale_price": current,
+                "sale_price": product.sale_price_cents.map(format_price),
             },
-            "value": value,
+            "mode": mode,
+            "fixed": prefill.fixed,
+            "percent": prefill.percent,
             "error": error,
             "lang": current_lang(jar),
         }),
@@ -116,7 +143,13 @@ async fn edit(
 ) -> Result<Response> {
     guard::current_admin(auth, &ctx).await?;
     let product = product_by_id(&ctx, id).await?;
-    render_form(&v, &jar, &product, None, None)
+    // Re-editing always opens in fixed mode showing the current sale price.
+    let prefill = FormPrefill {
+        mode: "fixed".to_string(),
+        fixed: product.sale_price_cents.map(format_price).unwrap_or_default(),
+        percent: String::new(),
+    };
+    render_form(&v, &jar, &product, &prefill, None)
 }
 
 #[debug_handler]
@@ -131,20 +164,48 @@ async fn update(
     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"),
+    let mode = match form.mode.as_deref() {
+        Some("percent") => "percent",
+        _ => "fixed",
     };
+    let fixed = form.sale_price.unwrap_or_default().trim().to_string();
+    let percent = form.percent.unwrap_or_default().trim().to_string();
+
+    // Whatever the mode, both raw inputs are echoed back on error so neither tab
+    // loses what was typed.
+    let prefill = FormPrefill {
+        mode: mode.to_string(),
+        fixed: fixed.clone(),
+        percent: percent.clone(),
+    };
+    let render_err = |key: &str| render_form(&v, &jar, &product, &prefill, Some(key));
+
+    // Resolve the entered discount into a fixed sale price in cents. An empty
+    // input in the active mode clears the discount (same as the Remove action).
+    let sale_cents = if mode == "percent" {
+        if percent.is_empty() {
+            return clear_discount(&ctx, product).await;
+        }
+        let pct = match parse_percent(&percent) {
+            Some(pct) => pct,
+            None => return render_err("discount-invalid"),
+        };
+        if pct <= 0.0 || pct >= 100.0 {
+            return render_err("discount-percent-range");
+        }
+        percent_to_sale_cents(product.price_cents, pct)
+    } else {
+        if fixed.is_empty() {
+            return clear_discount(&ctx, product).await;
+        }
+        match parse_price_to_cents(&fixed) {
+            Ok(cents) => cents,
+            Err(_) => return render_err("discount-invalid"),
+        }
+    };
+
+    // A discount must be a positive price strictly below the regular price —
+    // otherwise it isn't a discount.
     if sale_cents <= 0 {
         return render_err("discount-must-be-positive");
     }