package plugins import ( "context" "fmt" "net/http" "path" "reflect" "strings" "github.com/mitchellh/mapstructure" ) // Build builds a middleware plugin. func (b Builder) Build(pName string, config map[string]interface{}, middlewareName string) (Constructor, error) { if b.middlewareDescriptors == nil { return nil, fmt.Errorf("no plugin definition in the static configuration: %s", pName) } descriptor, ok := b.middlewareDescriptors[pName] if !ok { return nil, fmt.Errorf("unknown plugin type: %s", pName) } m, err := newMiddleware(descriptor, config, middlewareName) if err != nil { return nil, err } return m.NewHandler, err } // Middleware is a HTTP handler plugin wrapper. type Middleware struct { middlewareName string fnNew reflect.Value config reflect.Value } func newMiddleware(descriptor pluginContext, config map[string]interface{}, middlewareName string) (*Middleware, error) { basePkg := descriptor.BasePkg if basePkg == "" { basePkg = strings.ReplaceAll(path.Base(descriptor.Import), "-", "_") } vConfig, err := descriptor.interpreter.Eval(basePkg + `.CreateConfig()`) if err != nil { return nil, fmt.Errorf("failed to eval CreateConfig: %w", err) } cfg := &mapstructure.DecoderConfig{ DecodeHook: mapstructure.StringToSliceHookFunc(","), WeaklyTypedInput: true, Result: vConfig.Interface(), } decoder, err := mapstructure.NewDecoder(cfg) if err != nil { return nil, fmt.Errorf("failed to create configuration decoder: %w", err) } err = decoder.Decode(config) if err != nil { return nil, fmt.Errorf("failed to decode configuration: %w", err) } fnNew, err := descriptor.interpreter.Eval(basePkg + `.New`) if err != nil { return nil, fmt.Errorf("failed to eval New: %w", err) } return &Middleware{ middlewareName: middlewareName, fnNew: fnNew, config: vConfig, }, nil } // NewHandler creates a new HTTP handler. func (m *Middleware) NewHandler(ctx context.Context, next http.Handler) (http.Handler, error) { args := []reflect.Value{reflect.ValueOf(ctx), reflect.ValueOf(next), m.config, reflect.ValueOf(m.middlewareName)} results := m.fnNew.Call(args) if len(results) > 1 && results[1].Interface() != nil { return nil, results[1].Interface().(error) } handler, ok := results[0].Interface().(http.Handler) if !ok { return nil, fmt.Errorf("invalid handler type: %T", results[0].Interface()) } return handler, nil }