func resolveHeaderModels()

in codegen/gateway.go [608:673]
64 lines of code
15 McCabe index (conditional complexity)

func resolveHeaderModels(ms *ModuleSpec, modelPath string) (map[string]*TypedHeader, error) {
	const (
		headerPreix   = "headers"
		httpRefSuffix = "http.ref"
	)
	loadModuleFromInclude := func(moduleName string) *compile.Module {
		for pkgKey, pkg := range ms.CompiledModule.Includes {
			if pkgKey == moduleName {
				return pkg.Module
			}
		}
		return nil
	}
	loadHeaderKeyFromField := func(field *compile.FieldSpec) *string {
		for ak, av := range field.Annotations {
			if avs := strings.Split(av, "."); len(avs) == 2 &&
				avs[0] == headerPreix &&
				strings.HasSuffix(ak, httpRefSuffix) {
				headerKey := avs[1]
				return &headerKey
			}
		}
		return nil
	}
	loadHeadersFromCompiledModule := func(module *compile.Module, structName string) (map[string]*TypedHeader, error) {
		var typeStruct *compile.StructSpec
		var typedHeaders = make(map[string]*TypedHeader)
		for tk, tv := range module.Types {
			if ts, ok := tv.(*compile.StructSpec); tk == structName && ok {
				typeStruct = ts
				break
			}
		}
		if typeStruct == nil {
			return nil, errors.Errorf("unable to find typedHeaders %q", structName)
		}
		for _, field := range typeStruct.Fields {
			hk := loadHeaderKeyFromField(field)
			if hk == nil {
				return nil, errors.Errorf("unable to find header key %q", field.Name)
			}
			headerKey := textproto.CanonicalMIMEHeaderKey(*hk)
			typedHeaders[headerKey] = &TypedHeader{
				Name:        headerKey,
				TransformTo: headerKey,
				Field:       field,
			}
		}
		return typedHeaders, nil
	}
	switch paths := strings.Split(modelPath, "."); len(paths) {
	case 2:
		moduleName := paths[0]
		structName := paths[1]
		module := loadModuleFromInclude(moduleName)
		if module == nil {
			return nil, errors.Errorf("missing module spec %q", moduleName)
		}
		return loadHeadersFromCompiledModule(module, structName)
	default:
		// TODO case 1:
		// default header schema path to .
		return nil, errors.Errorf(
			"malformed header model %q, expecting <module>.<struct>", modelPath)
	}
}