modify proxy handler

internal/proxy/module_contract.go

@@ -0,0 +1,56 @@
+package proxy
+
+import (
+	"errors"
+	"fmt"
+	"strings"
+
+	"github.com/any-hub/any-hub/internal/server"
+)
+
+// ModuleHandler is the runtime contract each hubmodule must provide to serve requests.
+// It aligns with server.ProxyHandler so existing handlers remain compatible.
+type ModuleHandler = server.ProxyHandler
+
+// ModuleRegistration captures a module_key and its handler for safe registration.
+// Future registration flows can validate this struct before wiring into the dispatcher.
+type ModuleRegistration struct {
+	Key     string
+	Handler ModuleHandler
+}
+
+// ErrModuleHandlerExists indicates a handler has already been registered for the key.
+var ErrModuleHandlerExists = errors.New("module handler already registered")
+
+// Validate ensures both key and handler are present before registration.
+func (r ModuleRegistration) Validate() error {
+	if strings.TrimSpace(r.Key) == "" {
+		return errors.New("module key required")
+	}
+	if r.Handler == nil {
+		return errors.New("module handler required")
+	}
+	return nil
+}
+
+// RegisterModule registers validated metadata/runtime handler pair.
+func RegisterModule(reg ModuleRegistration) error {
+	if err := reg.Validate(); err != nil {
+		return err
+	}
+	normalized := normalizeModuleKey(reg.Key)
+	if normalized == "" {
+		return errors.New("module key required")
+	}
+	if _, loaded := moduleHandlers.LoadOrStore(normalized, reg.Handler); loaded {
+		return fmt.Errorf("%w: %s", ErrModuleHandlerExists, normalized)
+	}
+	return nil
+}
+
+// MustRegisterModule panics when registration fails; suitable for module init().
+func MustRegisterModule(reg ModuleRegistration) {
+	if err := RegisterModule(reg); err != nil {
+		panic(err)
+	}
+}