payit/internal/web/handlers.go

package web

import (
	"encoding/json"
	"errors"
	"io"
	"net/http"

	"github.com/rjNemo/payit/internal/payments"
)

func (h *Handler) createCheckoutSession() http.HandlerFunc {
	return func(w http.ResponseWriter, r *http.Request) {
		var req payments.CheckoutSessionRequest

		if r.Body != nil {
			defer func(body io.ReadCloser) {
				_ = body.Close()
			}(r.Body)
			dec := json.NewDecoder(r.Body)
			dec.DisallowUnknownFields()

			if err := dec.Decode(&req); err != nil {
				if errors.Is(err, io.EOF) {
					// Empty body is acceptable; default quantity applies.
				} else {
					http.Error(w, "invalid request payload", http.StatusBadRequest)
					return
				}
			} else if dec.More() {
				http.Error(w, "unexpected data in request body", http.StatusBadRequest)
				return
			}
		}

		session, err := h.checkout.CreateSession(r.Context(), req)
		if err != nil {
			http.Error(w, "checkout session failed", http.StatusInternalServerError)
			return
		}

		w.Header().Set("Content-Type", "application/json")
		if err := json.NewEncoder(w).Encode(session); err != nil {
			http.Error(w, "failed to encode response", http.StatusInternalServerError)
			return
		}
	}
}