first commit

internal/handlers/respond.go

@@ -0,0 +1,28 @@
+package handlers
+
+import (
+	"encoding/json"
+	"net/http"
+)
+
+// writeJSON is a tiny shared helper used by every handler in this package
+// to avoid repeating the "set Content-Type header, write status code,
+// encode body as JSON" sequence over and over.
+//
+// data is typed `any` (Go's built-in alias for interface{}, since Go 1.18)
+// so this one function can serialize maps, structs, slices - anything
+// encoding/json knows how to handle.
+func writeJSON(w http.ResponseWriter, status int, data any) {
+	w.Header().Set("Content-Type", "application/json")
+	w.WriteHeader(status)
+	// Encoder writes JSON directly to the ResponseWriter (which is just an
+	// io.Writer under the hood) - no need to build the JSON bytes in a
+	// separate variable first.
+	json.NewEncoder(w).Encode(data)
+}
+
+// writeError is a thin wrapper around writeJSON for the extremely common
+// case of returning a single {"error": "..."} body.
+func writeError(w http.ResponseWriter, status int, message string) {
+	writeJSON(w, status, map[string]string{"error": message})
+}