build: move e2e dependencies into e2e/go.mod

Several packages are only used while running the e2e suite. These
packages are less important to update, as the they can not influence the
final executable that is part of the Ceph-CSI container-image.

By moving these dependencies out of the main Ceph-CSI go.mod, it is
easier to identify if a reported CVE affects Ceph-CSI, or only the
testing (like most of the Kubernetes CVEs).

Signed-off-by: Niels de Vos <ndevos@ibm.com>

e2e/vendor/k8s.io/kube-openapi/pkg/util/proto/OWNERS

@@ -0,0 +1,2 @@
+approvers:
+- apelisse

e2e/vendor/k8s.io/kube-openapi/pkg/util/proto/doc.go

@@ -0,0 +1,19 @@
+/*
+Copyright 2017 The Kubernetes Authors.
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+*/
+
+// Package proto is a collection of libraries for parsing and indexing the type definitions.
+// The openapi spec contains the object model definitions and extensions metadata.
+package proto

e2e/vendor/k8s.io/kube-openapi/pkg/util/proto/document.go

@@ -0,0 +1,362 @@
+/*
+Copyright 2017 The Kubernetes Authors.
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+*/
+
+package proto
+
+import (
+	"fmt"
+	"sort"
+	"strings"
+
+	openapi_v2 "github.com/google/gnostic-models/openapiv2"
+	yaml "sigs.k8s.io/yaml/goyaml.v2"
+)
+
+func newSchemaError(path *Path, format string, a ...interface{}) error {
+	err := fmt.Sprintf(format, a...)
+	if path.Len() == 0 {
+		return fmt.Errorf("SchemaError: %v", err)
+	}
+	return fmt.Errorf("SchemaError(%v): %v", path, err)
+}
+
+// VendorExtensionToMap converts openapi VendorExtension to a map.
+func VendorExtensionToMap(e []*openapi_v2.NamedAny) map[string]interface{} {
+	values := map[string]interface{}{}
+
+	for _, na := range e {
+		if na.GetName() == "" || na.GetValue() == nil {
+			continue
+		}
+		if na.GetValue().GetYaml() == "" {
+			continue
+		}
+		var value interface{}
+		err := yaml.Unmarshal([]byte(na.GetValue().GetYaml()), &value)
+		if err != nil {
+			continue
+		}
+
+		values[na.GetName()] = value
+	}
+
+	return values
+}
+
+// Definitions is an implementation of `Models`. It looks for
+// models in an openapi Schema.
+type Definitions struct {
+	models map[string]Schema
+}
+
+var _ Models = &Definitions{}
+
+// NewOpenAPIData creates a new `Models` out of the openapi document.
+func NewOpenAPIData(doc *openapi_v2.Document) (Models, error) {
+	definitions := Definitions{
+		models: map[string]Schema{},
+	}
+
+	// Save the list of all models first. This will allow us to
+	// validate that we don't have any dangling reference.
+	for _, namedSchema := range doc.GetDefinitions().GetAdditionalProperties() {
+		definitions.models[namedSchema.GetName()] = nil
+	}
+
+	// Now, parse each model. We can validate that references exists.
+	for _, namedSchema := range doc.GetDefinitions().GetAdditionalProperties() {
+		path := NewPath(namedSchema.GetName())
+		schema, err := definitions.ParseSchema(namedSchema.GetValue(), &path)
+		if err != nil {
+			return nil, err
+		}
+		definitions.models[namedSchema.GetName()] = schema
+	}
+
+	return &definitions, nil
+}
+
+// We believe the schema is a reference, verify that and returns a new
+// Schema
+func (d *Definitions) parseReference(s *openapi_v2.Schema, path *Path) (Schema, error) {
+	// TODO(wrong): a schema with a $ref can have properties. We can ignore them (would be incomplete), but we cannot return an error.
+	if len(s.GetProperties().GetAdditionalProperties()) > 0 {
+		return nil, newSchemaError(path, "unallowed embedded type definition")
+	}
+	// TODO(wrong): a schema with a $ref can have a type. We can ignore it (would be incomplete), but we cannot return an error.
+	if len(s.GetType().GetValue()) > 0 {
+		return nil, newSchemaError(path, "definition reference can't have a type")
+	}
+
+	// TODO(wrong): $refs outside of the definitions are completely valid. We can ignore them (would be incomplete), but we cannot return an error.
+	if !strings.HasPrefix(s.GetXRef(), "#/definitions/") {
+		return nil, newSchemaError(path, "unallowed reference to non-definition %q", s.GetXRef())
+	}
+	reference := strings.TrimPrefix(s.GetXRef(), "#/definitions/")
+	if _, ok := d.models[reference]; !ok {
+		return nil, newSchemaError(path, "unknown model in reference: %q", reference)
+	}
+	base, err := d.parseBaseSchema(s, path)
+	if err != nil {
+		return nil, err
+	}
+	return &Ref{
+		BaseSchema:  base,
+		reference:   reference,
+		definitions: d,
+	}, nil
+}
+
+func parseDefault(def *openapi_v2.Any) (interface{}, error) {
+	if def == nil {
+		return nil, nil
+	}
+	var i interface{}
+	if err := yaml.Unmarshal([]byte(def.Yaml), &i); err != nil {
+		return nil, err
+	}
+	return i, nil
+}
+
+func (d *Definitions) parseBaseSchema(s *openapi_v2.Schema, path *Path) (BaseSchema, error) {
+	def, err := parseDefault(s.GetDefault())
+	if err != nil {
+		return BaseSchema{}, err
+	}
+	return BaseSchema{
+		Description: s.GetDescription(),
+		Default:     def,
+		Extensions:  VendorExtensionToMap(s.GetVendorExtension()),
+		Path:        *path,
+	}, nil
+}
+
+// We believe the schema is a map, verify and return a new schema
+func (d *Definitions) parseMap(s *openapi_v2.Schema, path *Path) (Schema, error) {
+	if len(s.GetType().GetValue()) != 0 && s.GetType().GetValue()[0] != object {
+		return nil, newSchemaError(path, "invalid object type")
+	}
+	var sub Schema
+	// TODO(incomplete): this misses the boolean case as AdditionalProperties is a bool+schema sum type.
+	if s.GetAdditionalProperties().GetSchema() == nil {
+		base, err := d.parseBaseSchema(s, path)
+		if err != nil {
+			return nil, err
+		}
+		sub = &Arbitrary{
+			BaseSchema: base,
+		}
+	} else {
+		var err error
+		sub, err = d.ParseSchema(s.GetAdditionalProperties().GetSchema(), path)
+		if err != nil {
+			return nil, err
+		}
+	}
+	base, err := d.parseBaseSchema(s, path)
+	if err != nil {
+		return nil, err
+	}
+	return &Map{
+		BaseSchema: base,
+		SubType:    sub,
+	}, nil
+}
+
+func (d *Definitions) parsePrimitive(s *openapi_v2.Schema, path *Path) (Schema, error) {
+	var t string
+	if len(s.GetType().GetValue()) > 1 {
+		return nil, newSchemaError(path, "primitive can't have more than 1 type")
+	}
+	if len(s.GetType().GetValue()) == 1 {
+		t = s.GetType().GetValue()[0]
+	}
+	switch t {
+	case String: // do nothing
+	case Number: // do nothing
+	case Integer: // do nothing
+	case Boolean: // do nothing
+	// TODO(wrong): this misses "null". Would skip the null case (would be incomplete), but we cannot return an error.
+	default:
+		return nil, newSchemaError(path, "Unknown primitive type: %q", t)
+	}
+	base, err := d.parseBaseSchema(s, path)
+	if err != nil {
+		return nil, err
+	}
+	return &Primitive{
+		BaseSchema: base,
+		Type:       t,
+		Format:     s.GetFormat(),
+	}, nil
+}
+
+func (d *Definitions) parseArray(s *openapi_v2.Schema, path *Path) (Schema, error) {
+	if len(s.GetType().GetValue()) != 1 {
+		return nil, newSchemaError(path, "array should have exactly one type")
+	}
+	if s.GetType().GetValue()[0] != array {
+		return nil, newSchemaError(path, `array should have type "array"`)
+	}
+	if len(s.GetItems().GetSchema()) != 1 {
+		// TODO(wrong): Items can have multiple elements. We can ignore Items then (would be incomplete), but we cannot return an error.
+		// TODO(wrong): "type: array" witohut any items at all is completely valid.
+		return nil, newSchemaError(path, "array should have exactly one sub-item")
+	}
+	sub, err := d.ParseSchema(s.GetItems().GetSchema()[0], path)
+	if err != nil {
+		return nil, err
+	}
+	base, err := d.parseBaseSchema(s, path)
+	if err != nil {
+		return nil, err
+	}
+	return &Array{
+		BaseSchema: base,
+		SubType:    sub,
+	}, nil
+}
+
+func (d *Definitions) parseKind(s *openapi_v2.Schema, path *Path) (Schema, error) {
+	if len(s.GetType().GetValue()) != 0 && s.GetType().GetValue()[0] != object {
+		return nil, newSchemaError(path, "invalid object type")
+	}
+	if s.GetProperties() == nil {
+		return nil, newSchemaError(path, "object doesn't have properties")
+	}
+
+	fields := map[string]Schema{}
+	fieldOrder := []string{}
+
+	for _, namedSchema := range s.GetProperties().GetAdditionalProperties() {
+		var err error
+		name := namedSchema.GetName()
+		path := path.FieldPath(name)
+		fields[name], err = d.ParseSchema(namedSchema.GetValue(), &path)
+		if err != nil {
+			return nil, err
+		}
+		fieldOrder = append(fieldOrder, name)
+	}
+
+	base, err := d.parseBaseSchema(s, path)
+	if err != nil {
+		return nil, err
+	}
+	return &Kind{
+		BaseSchema:     base,
+		RequiredFields: s.GetRequired(),
+		Fields:         fields,
+		FieldOrder:     fieldOrder,
+	}, nil
+}
+
+func (d *Definitions) parseArbitrary(s *openapi_v2.Schema, path *Path) (Schema, error) {
+	base, err := d.parseBaseSchema(s, path)
+	if err != nil {
+		return nil, err
+	}
+	return &Arbitrary{
+		BaseSchema: base,
+	}, nil
+}
+
+// ParseSchema creates a walkable Schema from an openapi schema. While
+// this function is public, it doesn't leak through the interface.
+func (d *Definitions) ParseSchema(s *openapi_v2.Schema, path *Path) (Schema, error) {
+	if s.GetXRef() != "" {
+		// TODO(incomplete): ignoring the rest of s is wrong. As long as there are no conflict, everything from s must be considered
+		// Reference: https://github.com/OAI/OpenAPI-Specification/blob/master/versions/2.0.md#path-item-object
+		return d.parseReference(s, path)
+	}
+	objectTypes := s.GetType().GetValue()
+	switch len(objectTypes) {
+	case 0:
+		// in the OpenAPI schema served by older k8s versions, object definitions created from structs did not include
+		// the type:object property (they only included the "properties" property), so we need to handle this case
+		// TODO: validate that we ever published empty, non-nil properties. JSON roundtripping nils them.
+		if s.GetProperties() != nil {
+			// TODO(wrong): when verifying a non-object later against this, it will be rejected as invalid type.
+			// TODO(CRD validation schema publishing): we have to filter properties (empty or not) if type=object is not given
+			return d.parseKind(s, path)
+		} else {
+			// Definition has no type and no properties. Treat it as an arbitrary value
+			// TODO(incomplete): what if it has additionalProperties=false or patternProperties?
+			// ANSWER: parseArbitrary is less strict than it has to be with patternProperties (which is ignored). So this is correct (of course not complete).
+			return d.parseArbitrary(s, path)
+		}
+	case 1:
+		t := objectTypes[0]
+		switch t {
+		case object:
+			if s.GetProperties() != nil {
+				return d.parseKind(s, path)
+			} else {
+				return d.parseMap(s, path)
+			}
+		case array:
+			return d.parseArray(s, path)
+		}
+		return d.parsePrimitive(s, path)
+	default:
+		// the OpenAPI generator never generates (nor it ever did in the past) OpenAPI type definitions with multiple types
+		// TODO(wrong): this is rejecting a completely valid OpenAPI spec
+		// TODO(CRD validation schema publishing): filter these out
+		return nil, newSchemaError(path, "definitions with multiple types aren't supported")
+	}
+}
+
+// LookupModel is public through the interface of Models. It
+// returns a visitable schema from the given model name.
+func (d *Definitions) LookupModel(model string) Schema {
+	return d.models[model]
+}
+
+func (d *Definitions) ListModels() []string {
+	models := []string{}
+
+	for model := range d.models {
+		models = append(models, model)
+	}
+
+	sort.Strings(models)
+	return models
+}
+
+type Ref struct {
+	BaseSchema
+
+	reference   string
+	definitions *Definitions
+}
+
+var _ Reference = &Ref{}
+
+func (r *Ref) Reference() string {
+	return r.reference
+}
+
+func (r *Ref) SubSchema() Schema {
+	return r.definitions.models[r.reference]
+}
+
+func (r *Ref) Accept(v SchemaVisitor) {
+	v.VisitReference(r)
+}
+
+func (r *Ref) GetName() string {
+	return fmt.Sprintf("Reference to %q", r.reference)
+}

e2e/vendor/k8s.io/kube-openapi/pkg/util/proto/document_v3.go

@@ -0,0 +1,324 @@
+/*
+Copyright 2022 The Kubernetes Authors.
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+*/
+
+package proto
+
+import (
+	"fmt"
+	"reflect"
+	"strings"
+
+	openapi_v3 "github.com/google/gnostic-models/openapiv3"
+	"gopkg.in/yaml.v3"
+)
+
+// Temporary parse implementation to be used until gnostic->kube-openapi conversion
+// is possible.
+func NewOpenAPIV3Data(doc *openapi_v3.Document) (Models, error) {
+	definitions := Definitions{
+		models: map[string]Schema{},
+	}
+
+	schemas := doc.GetComponents().GetSchemas()
+	if schemas == nil {
+		return &definitions, nil
+	}
+
+	// Save the list of all models first. This will allow us to
+	// validate that we don't have any dangling reference.
+	for _, namedSchema := range schemas.GetAdditionalProperties() {
+		definitions.models[namedSchema.GetName()] = nil
+	}
+
+	// Now, parse each model. We can validate that references exists.
+	for _, namedSchema := range schemas.GetAdditionalProperties() {
+		path := NewPath(namedSchema.GetName())
+		val := namedSchema.GetValue()
+
+		if val == nil {
+			continue
+		}
+
+		if schema, err := definitions.ParseV3SchemaOrReference(namedSchema.GetValue(), &path); err != nil {
+			return nil, err
+		} else if schema != nil {
+			// Schema may be nil if we hit incompleteness in the conversion,
+			// but not a fatal error
+			definitions.models[namedSchema.GetName()] = schema
+		}
+	}
+
+	return &definitions, nil
+}
+
+func (d *Definitions) ParseV3SchemaReference(s *openapi_v3.Reference, path *Path) (Schema, error) {
+	base := &BaseSchema{
+		Description: s.Description,
+	}
+
+	if !strings.HasPrefix(s.GetXRef(), "#/components/schemas") {
+		// Only resolve references to components/schemas. We may add support
+		// later for other in-spec paths, but otherwise treat unrecognized
+		// refs as arbitrary/unknown values.
+		return &Arbitrary{
+			BaseSchema: *base,
+		}, nil
+	}
+
+	reference := strings.TrimPrefix(s.GetXRef(), "#/components/schemas/")
+	if _, ok := d.models[reference]; !ok {
+		return nil, newSchemaError(path, "unknown model in reference: %q", reference)
+	}
+
+	return &Ref{
+		BaseSchema: BaseSchema{
+			Description: s.Description,
+		},
+		reference:   reference,
+		definitions: d,
+	}, nil
+}
+
+func (d *Definitions) ParseV3SchemaOrReference(s *openapi_v3.SchemaOrReference, path *Path) (Schema, error) {
+	var schema Schema
+	var err error
+
+	switch v := s.GetOneof().(type) {
+	case *openapi_v3.SchemaOrReference_Reference:
+		// Any references stored in #!/components/... are bound to refer
+		// to external documents. This API does not support such a
+		// feature.
+		//
+		// In the weird case that this is a reference to a schema that is
+		// not external, we attempt to parse anyway
+		schema, err = d.ParseV3SchemaReference(v.Reference, path)
+	case *openapi_v3.SchemaOrReference_Schema:
+		schema, err = d.ParseSchemaV3(v.Schema, path)
+	default:
+		panic("unexpected type")
+	}
+
+	return schema, err
+}
+
+// ParseSchema creates a walkable Schema from an openapi v3 schema. While
+// this function is public, it doesn't leak through the interface.
+func (d *Definitions) ParseSchemaV3(s *openapi_v3.Schema, path *Path) (Schema, error) {
+	switch s.GetType() {
+	case object:
+		for _, extension := range s.GetSpecificationExtension() {
+			if extension.Name == "x-kubernetes-group-version-kind" {
+				// Objects with x-kubernetes-group-version-kind are always top
+				// level types.
+				return d.parseV3Kind(s, path)
+			}
+		}
+
+		if len(s.GetProperties().GetAdditionalProperties()) > 0 {
+			return d.parseV3Kind(s, path)
+		}
+		return d.parseV3Map(s, path)
+	case array:
+		return d.parseV3Array(s, path)
+	case String, Number, Integer, Boolean:
+		return d.parseV3Primitive(s, path)
+	default:
+		return d.parseV3Arbitrary(s, path)
+	}
+}
+
+func (d *Definitions) parseV3Kind(s *openapi_v3.Schema, path *Path) (Schema, error) {
+	if s.GetType() != object {
+		return nil, newSchemaError(path, "invalid object type")
+	} else if s.GetProperties() == nil {
+		return nil, newSchemaError(path, "object doesn't have properties")
+	}
+
+	fields := map[string]Schema{}
+	fieldOrder := []string{}
+
+	for _, namedSchema := range s.GetProperties().GetAdditionalProperties() {
+		var err error
+		name := namedSchema.GetName()
+		path := path.FieldPath(name)
+		fields[name], err = d.ParseV3SchemaOrReference(namedSchema.GetValue(), &path)
+		if err != nil {
+			return nil, err
+		}
+		fieldOrder = append(fieldOrder, name)
+	}
+
+	base, err := d.parseV3BaseSchema(s, path)
+	if err != nil {
+		return nil, err
+	}
+
+	return &Kind{
+		BaseSchema:     *base,
+		RequiredFields: s.GetRequired(),
+		Fields:         fields,
+		FieldOrder:     fieldOrder,
+	}, nil
+}
+
+func (d *Definitions) parseV3Arbitrary(s *openapi_v3.Schema, path *Path) (Schema, error) {
+	base, err := d.parseV3BaseSchema(s, path)
+	if err != nil {
+		return nil, err
+	}
+	return &Arbitrary{
+		BaseSchema: *base,
+	}, nil
+}
+
+func (d *Definitions) parseV3Primitive(s *openapi_v3.Schema, path *Path) (Schema, error) {
+	switch s.GetType() {
+	case String: // do nothing
+	case Number: // do nothing
+	case Integer: // do nothing
+	case Boolean: // do nothing
+	default:
+		// Unsupported primitive type. Treat as arbitrary type
+		return d.parseV3Arbitrary(s, path)
+	}
+
+	base, err := d.parseV3BaseSchema(s, path)
+	if err != nil {
+		return nil, err
+	}
+
+	return &Primitive{
+		BaseSchema: *base,
+		Type:       s.GetType(),
+		Format:     s.GetFormat(),
+	}, nil
+}
+
+func (d *Definitions) parseV3Array(s *openapi_v3.Schema, path *Path) (Schema, error) {
+	if s.GetType() != array {
+		return nil, newSchemaError(path, `array should have type "array"`)
+	} else if len(s.GetItems().GetSchemaOrReference()) != 1 {
+		// This array can have multiple types in it (or no types at all)
+		// This is not supported by this conversion.
+		// Just return an arbitrary type
+		return d.parseV3Arbitrary(s, path)
+	}
+
+	sub, err := d.ParseV3SchemaOrReference(s.GetItems().GetSchemaOrReference()[0], path)
+	if err != nil {
+		return nil, err
+	}
+
+	base, err := d.parseV3BaseSchema(s, path)
+	if err != nil {
+		return nil, err
+	}
+	return &Array{
+		BaseSchema: *base,
+		SubType:    sub,
+	}, nil
+}
+
+// We believe the schema is a map, verify and return a new schema
+func (d *Definitions) parseV3Map(s *openapi_v3.Schema, path *Path) (Schema, error) {
+	if s.GetType() != object {
+		return nil, newSchemaError(path, "invalid object type")
+	}
+	var sub Schema
+
+	switch p := s.GetAdditionalProperties().GetOneof().(type) {
+	case *openapi_v3.AdditionalPropertiesItem_Boolean:
+		// What does this boolean even mean?
+		base, err := d.parseV3BaseSchema(s, path)
+		if err != nil {
+			return nil, err
+		}
+		sub = &Arbitrary{
+			BaseSchema: *base,
+		}
+	case *openapi_v3.AdditionalPropertiesItem_SchemaOrReference:
+		if schema, err := d.ParseV3SchemaOrReference(p.SchemaOrReference, path); err != nil {
+			return nil, err
+		} else {
+			sub = schema
+		}
+	case nil:
+		// no subtype?
+		sub = &Arbitrary{}
+	default:
+		panic("unrecognized type " + reflect.TypeOf(p).Name())
+	}
+
+	base, err := d.parseV3BaseSchema(s, path)
+	if err != nil {
+		return nil, err
+	}
+	return &Map{
+		BaseSchema: *base,
+		SubType:    sub,
+	}, nil
+}
+
+func parseV3Interface(def *yaml.Node) (interface{}, error) {
+	if def == nil {
+		return nil, nil
+	}
+	var i interface{}
+	if err := def.Decode(&i); err != nil {
+		return nil, err
+	}
+	return i, nil
+}
+
+func (d *Definitions) parseV3BaseSchema(s *openapi_v3.Schema, path *Path) (*BaseSchema, error) {
+	if s == nil {
+		return nil, fmt.Errorf("cannot initialize BaseSchema from nil")
+	}
+
+	def, err := parseV3Interface(s.GetDefault().ToRawInfo())
+	if err != nil {
+		return nil, err
+	}
+
+	return &BaseSchema{
+		Description: s.GetDescription(),
+		Default:     def,
+		Extensions:  SpecificationExtensionToMap(s.GetSpecificationExtension()),
+		Path:        *path,
+	}, nil
+}
+
+func SpecificationExtensionToMap(e []*openapi_v3.NamedAny) map[string]interface{} {
+	values := map[string]interface{}{}
+
+	for _, na := range e {
+		if na.GetName() == "" || na.GetValue() == nil {
+			continue
+		}
+		if na.GetValue().GetYaml() == "" {
+			continue
+		}
+		var value interface{}
+		err := yaml.Unmarshal([]byte(na.GetValue().GetYaml()), &value)
+		if err != nil {
+			continue
+		}
+
+		values[na.GetName()] = value
+	}
+
+	return values
+}

e2e/vendor/k8s.io/kube-openapi/pkg/util/proto/openapi.go

@@ -0,0 +1,285 @@
+/*
+Copyright 2017 The Kubernetes Authors.
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+*/
+
+package proto
+
+import (
+	"fmt"
+	"sort"
+	"strings"
+)
+
+// Defines openapi types.
+const (
+	Integer = "integer"
+	Number  = "number"
+	String  = "string"
+	Boolean = "boolean"
+
+	// These types are private as they should never leak, and are
+	// represented by actual structs.
+	array  = "array"
+	object = "object"
+)
+
+// Models interface describe a model provider. They can give you the
+// schema for a specific model.
+type Models interface {
+	LookupModel(string) Schema
+	ListModels() []string
+}
+
+// SchemaVisitor is an interface that you need to implement if you want
+// to "visit" an openapi schema. A dispatch on the Schema type will call
+// the appropriate function based on its actual type:
+// - Array is a list of one and only one given subtype
+// - Map is a map of string to one and only one given subtype
+// - Primitive can be string, integer, number and boolean.
+// - Kind is an object with specific fields mapping to specific types.
+// - Reference is a link to another definition.
+type SchemaVisitor interface {
+	VisitArray(*Array)
+	VisitMap(*Map)
+	VisitPrimitive(*Primitive)
+	VisitKind(*Kind)
+	VisitReference(Reference)
+}
+
+// SchemaVisitorArbitrary is an additional visitor interface which handles
+// arbitrary types. For backwards compatibility, it's a separate interface
+// which is checked for at runtime.
+type SchemaVisitorArbitrary interface {
+	SchemaVisitor
+	VisitArbitrary(*Arbitrary)
+}
+
+// Schema is the base definition of an openapi type.
+type Schema interface {
+	// Giving a visitor here will let you visit the actual type.
+	Accept(SchemaVisitor)
+
+	// Pretty print the name of the type.
+	GetName() string
+	// Describes how to access this field.
+	GetPath() *Path
+	// Describes the field.
+	GetDescription() string
+	// Default for that schema.
+	GetDefault() interface{}
+	// Returns type extensions.
+	GetExtensions() map[string]interface{}
+}
+
+// Path helps us keep track of type paths
+type Path struct {
+	parent *Path
+	key    string
+}
+
+func NewPath(key string) Path {
+	return Path{key: key}
+}
+
+func (p *Path) Get() []string {
+	if p == nil {
+		return []string{}
+	}
+	if p.key == "" {
+		return p.parent.Get()
+	}
+	return append(p.parent.Get(), p.key)
+}
+
+func (p *Path) Len() int {
+	return len(p.Get())
+}
+
+func (p *Path) String() string {
+	return strings.Join(p.Get(), "")
+}
+
+// ArrayPath appends an array index and creates a new path
+func (p *Path) ArrayPath(i int) Path {
+	return Path{
+		parent: p,
+		key:    fmt.Sprintf("[%d]", i),
+	}
+}
+
+// FieldPath appends a field name and creates a new path
+func (p *Path) FieldPath(field string) Path {
+	return Path{
+		parent: p,
+		key:    fmt.Sprintf(".%s", field),
+	}
+}
+
+// BaseSchema holds data used by each types of schema.
+type BaseSchema struct {
+	Description string
+	Extensions  map[string]interface{}
+	Default     interface{}
+
+	Path Path
+}
+
+func (b *BaseSchema) GetDescription() string {
+	return b.Description
+}
+
+func (b *BaseSchema) GetExtensions() map[string]interface{} {
+	return b.Extensions
+}
+
+func (b *BaseSchema) GetDefault() interface{} {
+	return b.Default
+}
+
+func (b *BaseSchema) GetPath() *Path {
+	return &b.Path
+}
+
+// Array must have all its element of the same `SubType`.
+type Array struct {
+	BaseSchema
+
+	SubType Schema
+}
+
+var _ Schema = &Array{}
+
+func (a *Array) Accept(v SchemaVisitor) {
+	v.VisitArray(a)
+}
+
+func (a *Array) GetName() string {
+	return fmt.Sprintf("Array of %s", a.SubType.GetName())
+}
+
+// Kind is a complex object. It can have multiple different
+// subtypes for each field, as defined in the `Fields` field. Mandatory
+// fields are listed in `RequiredFields`. The key of the object is
+// always of type `string`.
+type Kind struct {
+	BaseSchema
+
+	// Lists names of required fields.
+	RequiredFields []string
+	// Maps field names to types.
+	Fields map[string]Schema
+	// FieldOrder reports the canonical order for the fields.
+	FieldOrder []string
+}
+
+var _ Schema = &Kind{}
+
+func (k *Kind) Accept(v SchemaVisitor) {
+	v.VisitKind(k)
+}
+
+func (k *Kind) GetName() string {
+	properties := []string{}
+	for key := range k.Fields {
+		properties = append(properties, key)
+	}
+	return fmt.Sprintf("Kind(%v)", properties)
+}
+
+// IsRequired returns true if `field` is a required field for this type.
+func (k *Kind) IsRequired(field string) bool {
+	for _, f := range k.RequiredFields {
+		if f == field {
+			return true
+		}
+	}
+	return false
+}
+
+// Keys returns a alphabetically sorted list of keys.
+func (k *Kind) Keys() []string {
+	keys := make([]string, 0)
+	for key := range k.Fields {
+		keys = append(keys, key)
+	}
+	sort.Strings(keys)
+	return keys
+}
+
+// Map is an object who values must all be of the same `SubType`.
+// The key of the object is always of type `string`.
+type Map struct {
+	BaseSchema
+
+	SubType Schema
+}
+
+var _ Schema = &Map{}
+
+func (m *Map) Accept(v SchemaVisitor) {
+	v.VisitMap(m)
+}
+
+func (m *Map) GetName() string {
+	return fmt.Sprintf("Map of %s", m.SubType.GetName())
+}
+
+// Primitive is a literal. There can be multiple types of primitives,
+// and this subtype can be visited through the `subType` field.
+type Primitive struct {
+	BaseSchema
+
+	// Type of a primitive must be one of: integer, number, string, boolean.
+	Type   string
+	Format string
+}
+
+var _ Schema = &Primitive{}
+
+func (p *Primitive) Accept(v SchemaVisitor) {
+	v.VisitPrimitive(p)
+}
+
+func (p *Primitive) GetName() string {
+	if p.Format == "" {
+		return p.Type
+	}
+	return fmt.Sprintf("%s (%s)", p.Type, p.Format)
+}
+
+// Arbitrary is a value of any type (primitive, object or array)
+type Arbitrary struct {
+	BaseSchema
+}
+
+var _ Schema = &Arbitrary{}
+
+func (a *Arbitrary) Accept(v SchemaVisitor) {
+	if visitor, ok := v.(SchemaVisitorArbitrary); ok {
+		visitor.VisitArbitrary(a)
+	}
+}
+
+func (a *Arbitrary) GetName() string {
+	return "Arbitrary value (primitive, object or array)"
+}
+
+// Reference implementation depends on the type of document.
+type Reference interface {
+	Schema
+
+	Reference() string
+	SubSchema() Schema
+}