Add drink sizes to orders

docs/api.md

@@ -33,38 +33,46 @@ Request:
 
 ```json
 {
-  "items": [{ "id": "latte", "qty": 2 }],
+  "items": [{ "id": "latte", "qty": 2, "size": "large" }],
   "code": "WELCOME10"
 }
 ```
 
 - `items` is required and must not be empty. `qty` is 1–20.
+- `size` is optional: `small`, `medium`, or `large`. It defaults to `medium`.
+  It is case-sensitive.
 - `code` is optional and case-insensitive.
 
 Response `200`:
 
 ```json
 {
   "items": [
-    { "id": "latte", "name": "Latte", "qty": 2, "unit_cents": 450, "line_cents": 900 }
+    { "id": "latte", "name": "Latte", "qty": 2, "size": "large", "unit_cents": 525, "line_cents": 1050 }
   ],
-  "subtotal_cents": 900,
-  "discount_cents": 90,
-  "tax_cents": 71,
-  "total_cents": 881
+  "subtotal_cents": 1050,
+  "discount_cents": 105,
+  "tax_cents": 83,
+  "total_cents": 1028
 }
 ```
 
+Each quoted line includes `size`, which is always set: the size that was
+asked for, or `medium` if none was.
+
 Pricing rules:
 
-1. `subtotal_cents` is the sum of `line_cents`.
-2. `discount_cents` is the code's percentage of the subtotal, rounded down.
-3. Tax is 8.75% of `subtotal_cents - discount_cents`, rounded half up.
-4. `total_cents = subtotal_cents - discount_cents + tax_cents`.
+1. `unit_cents` is the menu price adjusted for size: `small` is 50 cents
+   less, `medium` is the menu price, and `large` is 75 cents more.
+   `line_cents = unit_cents * qty`.
+2. `subtotal_cents` is the sum of `line_cents`.
+3. `discount_cents` is the code's percentage of the subtotal, rounded down.
+4. Tax is 8.75% of `subtotal_cents - discount_cents`, rounded half up.
+5. `total_cents = subtotal_cents - discount_cents + tax_cents`.
 
 Errors return a JSON body `{"error": "..."}`:
 
 | Status | When |
 |--------|------|
 | `400` | Body is not valid JSON, or `items` is empty |
-| `422` | Unknown item, `qty` out of range, or unknown discount code |
+| `422` | Unknown item, `qty` out of range, unknown `size`, or unknown discount code |

orders.go

@@ -33,9 +33,19 @@ const taxBasisPoints = 875
 
 const maxQty = 20
 
+// sizeAdjustCents maps a drink size to its change from the menu price.
+var sizeAdjustCents = map[string]int{
+	"small":  -50,
+	"medium": 0,
+	"large":  75,
+}
+
+const defaultSize = "medium"
+
 type OrderLine struct {
-	ID  string `json:"id"`
-	Qty int    `json:"qty"`
+	ID   string `json:"id"`
+	Qty  int    `json:"qty"`
+	Size string `json:"size,omitempty"`
 }
 
 type OrderRequest struct {
@@ -47,6 +57,7 @@ type QuotedLine struct {
 	ID        string `json:"id"`
 	Name      string `json:"name"`
 	Qty       int    `json:"qty"`
+	Size      string `json:"size"`
 	UnitCents int    `json:"unit_cents"`
 	LineCents int    `json:"line_cents"`
 }
@@ -86,12 +97,22 @@ func quoteOrder(req OrderRequest) (Quote, error) {
 		if line.Qty < 1 || line.Qty > maxQty {
 			return Quote{}, fmt.Errorf("qty for %q must be between 1 and %d", line.ID, maxQty)
 		}
-		lineCents := item.PriceCents * line.Qty
+		size := line.Size
+		if size == "" {
+			size = defaultSize
+		}
+		adjust, ok := sizeAdjustCents[size]
+		if !ok {
+			return Quote{}, fmt.Errorf("size for %q must be small, medium, or large", line.ID)
+		}
+		unitCents := item.PriceCents + adjust
+		lineCents := unitCents * line.Qty
 		q.Items = append(q.Items, QuotedLine{
 			ID:        item.ID,
 			Name:      item.Name,
 			Qty:       line.Qty,
-			UnitCents: item.PriceCents,
+			Size:      size,
+			UnitCents: unitCents,
 			LineCents: lineCents,
 		})
 		q.SubtotalCents += lineCents

orders_test.go

@@ -1,6 +1,7 @@
 package main
 
 import (
+	"encoding/json"
 	"net/http"
 	"net/http/httptest"
 	"strings"
@@ -32,6 +33,33 @@ func TestQuoteOrder(t *testing.T) {
 		{name: "empty", req: OrderRequest{}, wantErr: true},
 		{name: "unknown item", req: OrderRequest{Items: []OrderLine{{ID: "tea", Qty: 1}}}, wantErr: true},
 		{name: "zero qty", req: OrderRequest{Items: []OrderLine{{ID: "latte", Qty: 0}}}, wantErr: true},
+		{
+			name: "large adds 75 cents",
+			req:  OrderRequest{Items: []OrderLine{{ID: "latte", Qty: 1, Size: "large"}}},
+			// 525 subtotal, tax 45.9375 -> 46
+			want: Quote{SubtotalCents: 525, TaxCents: 46, TotalCents: 571},
+		},
+		{
+			name: "small takes off 50 cents",
+			req:  OrderRequest{Items: []OrderLine{{ID: "espresso", Qty: 2, Size: "small"}}},
+			// 2 x 250 = 500 subtotal, tax 43.75 -> 44
+			want: Quote{SubtotalCents: 500, TaxCents: 44, TotalCents: 544},
+		},
+		{
+			name: "mixed sizes with discount",
+			req: OrderRequest{
+				Items: []OrderLine{
+					{ID: "cappuccino", Qty: 1, Size: "small"},
+					{ID: "cold-brew", Qty: 2, Size: "medium"},
+					{ID: "latte", Qty: 1, Size: "large"},
+				},
+				Code: "STAFF25",
+			},
+			// 375 + 800 + 525 = 1700 subtotal, 425 off, 1275 taxable,
+			// tax 111.5625 -> 112
+			want: Quote{SubtotalCents: 1700, DiscountCents: 425, TaxCents: 112, TotalCents: 1387},
+		},
+		{name: "unknown size", req: OrderRequest{Items: []OrderLine{{ID: "latte", Qty: 1, Size: "venti"}}}, wantErr: true},
 		{name: "bad code", req: OrderRequest{Items: []OrderLine{{ID: "latte", Qty: 1}}, Code: "FREE"}, wantErr: true},
 	}
 
@@ -70,4 +98,53 @@ func TestOrdersEndpoint(t *testing.T) {
 	if resp.StatusCode != http.StatusOK {
 		t.Fatalf("status = %d, want 200", resp.StatusCode)
 	}
+
+	var body struct {
+		Items []map[string]any `json:"items"`
+	}
+	if err := json.NewDecoder(resp.Body).Decode(&body); err != nil {
+		t.Fatal(err)
+	}
+	if len(body.Items) != 1 || body.Items[0]["size"] != "medium" {
+		t.Errorf("items = %v, want one line with size medium", body.Items)
+	}
+}
+
+func TestOrdersEndpointUnknownSize(t *testing.T) {
+	srv := httptest.NewServer(newMux())
+	defer srv.Close()
+
+	resp, err := http.Post(srv.URL+"/api/orders", "application/json",
+		strings.NewReader(`{"items":[{"id":"latte","qty":1,"size":"venti"}]}`))
+	if err != nil {
+		t.Fatal(err)
+	}
+	defer resp.Body.Close()
+	if resp.StatusCode != http.StatusUnprocessableEntity {
+		t.Fatalf("status = %d, want 422", resp.StatusCode)
+	}
+}
+
+func TestQuotedLineSize(t *testing.T) {
+	got, err := quoteOrder(OrderRequest{Items: []OrderLine{
+		{ID: "latte", Qty: 1},
+		{ID: "latte", Qty: 3, Size: "small"},
+		{ID: "espresso", Qty: 2, Size: "large"},
+	}})
+	if err != nil {
+		t.Fatalf("unexpected error: %v", err)
+	}
+	want := []QuotedLine{
+		{ID: "latte", Name: "Latte", Qty: 1, Size: "medium", UnitCents: 450, LineCents: 450},
+		{ID: "latte", Name: "Latte", Qty: 3, Size: "small", UnitCents: 400, LineCents: 1200},
+		{ID: "espresso", Name: "Espresso", Qty: 2, Size: "large", UnitCents: 375, LineCents: 750},
+	}
+	if len(got.Items) != len(want) {
+		t.Fatalf("got %d lines, want %d", len(got.Items), len(want))
+	}
+	for i := range want {
+		if got.Items[i] != want[i] {
+			t.Errorf("line %d: got %+v, want %+v", i, got.Items[i], want[i])
+		}
+	}
 }

static/index.html

@@ -17,6 +17,8 @@
     .card { background: var(--card); border: 1px solid var(--line); border-radius: 10px; padding: 16px; margin-bottom: 16px; }
     .row { display: flex; align-items: center; justify-content: space-between; gap: 12px; padding: 6px 0; }
     input[type=number] { width: 64px; padding: 4px 6px; }
+    select { padding: 4px 6px; }
+    .controls { display: flex; gap: 8px; }
     input[type=text] { width: 100%; padding: 6px 8px; }
     button { background: var(--accent); color: #fff; border: 0; border-radius: 6px; padding: 10px 16px; font-size: 16px; cursor: pointer; }
     #quote .row.total { font-weight: 700; border-top: 1px solid var(--line); margin-top: 6px; padding-top: 10px; }
@@ -40,21 +42,33 @@ <h1>Brewbar</h1>
 
 <script>
   const dollars = (cents) => "$" + (cents / 100).toFixed(2);
+  const capitalize = (s) => s.charAt(0).toUpperCase() + s.slice(1);
 
   async function loadMenu() {
     const res = await fetch("/api/menu");
     const { items } = await res.json();
     document.getElementById("menu").innerHTML = items.map((m) => `
-      <label class="row">
+      <div class="row" data-id="${m.id}">
         <span>${m.name} <small>${dollars(m.price_cents)}</small></span>
-        <input type="number" min="0" max="20" value="0" data-id="${m.id}">
-      </label>`).join("");
+        <span class="controls">
+          <select aria-label="${m.name} size">
+            <option value="small">Small (−$0.50)</option>
+            <option value="medium" selected>Medium</option>
+            <option value="large">Large (+$0.75)</option>
+          </select>
+          <input type="number" min="0" max="20" value="0" aria-label="${m.name} quantity">
+        </span>
+      </div>`).join("");
   }
 
   document.getElementById("order").addEventListener("submit", async (e) => {
     e.preventDefault();
-    const items = [...document.querySelectorAll("#menu input")]
-      .map((el) => ({ id: el.dataset.id, qty: Number(el.value) }))
+    const items = [...document.querySelectorAll("#menu .row")]
+      .map((row) => ({
+        id: row.dataset.id,
+        qty: Number(row.querySelector("input").value),
+        size: row.querySelector("select").value,
+      }))
       .filter((l) => l.qty > 0);
     const code = document.getElementById("code").value.trim();
 
@@ -75,7 +89,7 @@ <h1>Brewbar</h1>
     errEl.textContent = "";
     quoteEl.hidden = false;
     quoteEl.innerHTML =
-      data.items.map((l) => `<div class="row"><span>${l.qty} × ${l.name}</span><span>${dollars(l.line_cents)}</span></div>`).join("") +
+      data.items.map((l) => `<div class="row"><span>${l.qty} × ${capitalize(l.size)} ${l.name}</span><span>${dollars(l.line_cents)}</span></div>`).join("") +
       `<div class="row"><span>Subtotal</span><span>${dollars(data.subtotal_cents)}</span></div>` +
       (data.discount_cents ? `<div class="row"><span>Discount</span><span>−${dollars(data.discount_cents)}</span></div>` : "") +
       `<div class="row"><span>Tax</span><span>${dollars(data.tax_cents)}</span></div>` +