promotions

cmd/cart/promotions_evaluate.go

@@ -0,0 +1,29 @@
+package main
+
+import (
+	"encoding/json"
+	"errors"
+	"io"
+	"net/http"
+
+	"git.k6n.net/mats/go-cart-actor/pkg/promotions"
+)
+
+// newPromotionEvaluateHandler serves POST /promotions/evaluate: it takes a
+// (possibly partial) evaluation context and returns the totals plus the
+// applied/pending promotion effects, without creating or mutating a real cart.
+// An empty body is treated as an empty context (evaluates against no items).
+func newPromotionEvaluateHandler(store *promotions.Store, svc *promotions.PromotionService) http.HandlerFunc {
+	return func(w http.ResponseWriter, r *http.Request) {
+		var req promotions.EvaluateRequest
+		if err := json.NewDecoder(r.Body).Decode(&req); err != nil && !errors.Is(err, io.EOF) {
+			http.Error(w, "invalid JSON body: "+err.Error(), http.StatusBadRequest)
+			return
+		}
+		resp := svc.Evaluate(store.Snapshot(), req)
+		w.Header().Set("Content-Type", "application/json")
+		if err := json.NewEncoder(w).Encode(resp); err != nil {
+			http.Error(w, err.Error(), http.StatusInternalServerError)
+		}
+	}
+}