cozystack/pkg/specschema/specschema.go

/*
Copyright 2024 The Cozystack 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 specschema turns the OpenAPI schema an ApplicationDefinition embeds
// into a structural schema and applies its defaults to application values the
// way kube-apiserver defaults a custom resource.
package specschema

import (
	"encoding/json"
	"fmt"
	"strings"

	internalapiext "k8s.io/apiextensions-apiserver/pkg/apis/apiextensions"
	apiextv1 "k8s.io/apiextensions-apiserver/pkg/apis/apiextensions/v1"
	structuralschema "k8s.io/apiextensions-apiserver/pkg/apiserver/schema"
	"k8s.io/apimachinery/pkg/runtime"
)

// Build parses an OpenAPI-v3 JSON schema string and returns the
// structural-schema form used for defaulting. Returns (nil, nil) when raw
// is empty after trimming. Returns (nil, error) for malformed JSON,
// v1→internal conversion failures, or structural-schema construction
// errors — callers can decide whether to log-and-continue (NewREST does)
// or fail hard (tests do).
func Build(raw string) (*structuralschema.Structural, error) {
	raw = strings.TrimSpace(raw)
	if raw == "" {
		return nil, nil
	}
	var v1js apiextv1.JSONSchemaProps
	if err := json.Unmarshal([]byte(raw), &v1js); err != nil {
		return nil, fmt.Errorf("unmarshal v1 OpenAPI schema: %w", err)
	}
	scheme := runtime.NewScheme()
	_ = internalapiext.AddToScheme(scheme)
	_ = apiextv1.AddToScheme(scheme)
	var ijs internalapiext.JSONSchemaProps
	if err := scheme.Convert(&v1js, &ijs, nil); err != nil {
		return nil, fmt.Errorf("convert v1->internal JSONSchemaProps: %w", err)
	}
	s, err := structuralschema.NewStructural(&ijs)
	if err != nil {
		return nil, fmt.Errorf("build structural schema: %w", err)
	}
	return s, nil
}

// ApplyDefaults fills root in place with the schema's defaults, as
// kube-apiserver would default a custom resource: a property default lands
// only where the property is absent, and an object default never creates keys
// in a map that exists.
func ApplyDefaults(root *map[string]any, s *structuralschema.Structural) error {
	v := any(*root)
	nv, err := applyDefaults(v, s, true)
	if err != nil {
		return err
	}
	obj, ok := nv.(map[string]any)
	if !ok && nv != nil {
		return fmt.Errorf("internal error: applyDefaults returned non-map type %T for object root", nv)
	}
	if obj == nil {
		obj = map[string]any{}
	}
	*root = obj
	return nil
}

func applyDefaults(v any, s *structuralschema.Structural, top bool) (any, error) {
	if s == nil {
		return v, nil
	}

	effType := s.Type
	if effType == "" {
		switch {
		case len(s.Properties) > 0 || (s.AdditionalProperties != nil && s.AdditionalProperties.Structural != nil):
			effType = "object"
		case s.Items != nil:
			effType = "array"
		default:
			// scalar
		}
	}

	switch effType {
	case "object":
		mv, isMap := v.(map[string]any)
		if !isMap || v == nil {
			if s.Default.Object != nil && !top {
				if dm, ok := s.Default.Object.(map[string]any); ok {
					mv = cloneMap(dm)
				}
			}
			if mv == nil {
				mv = map[string]any{}
			}
		}

		for name, ps := range s.Properties {
			if _, ok := mv[name]; !ok {
				if ps.Default.Object != nil {
					mv[name] = clone(ps.Default.Object)
				}
			}
			if cur, ok := mv[name]; ok {
				cv, err := applyDefaults(cur, &ps, false)
				if err != nil {
					return nil, err
				}
				mv[name] = cv
			}
		}

		if s.AdditionalProperties != nil && s.AdditionalProperties.Structural != nil {
			ap := s.AdditionalProperties.Structural
			for k, cur := range mv {
				if _, isKnown := s.Properties[k]; isKnown {
					continue
				}
				cv, err := applyDefaults(cur, ap, false)
				if err != nil {
					return nil, err
				}
				mv[k] = cv
			}
		}
		return mv, nil

	case "array":
		sl, isSlice := v.([]any)
		if !isSlice || v == nil {
			if s.Default.Object != nil {
				if ds, ok := s.Default.Object.([]any); ok {
					sl = cloneSlice(ds)
				}
			}
			if sl == nil {
				sl = []any{}
			}
		}
		if s.Items != nil {
			for i := range sl {
				cv, err := applyDefaults(sl[i], s.Items, false)
				if err != nil {
					return nil, err
				}
				sl[i] = cv
			}
		}
		return sl, nil

	default:
		if v == nil && s.Default.Object != nil {
			return clone(s.Default.Object), nil
		}
		return v, nil
	}
}

func clone(x any) any {
	switch t := x.(type) {
	case map[string]any:
		return cloneMap(t)
	case []any:
		return cloneSlice(t)
	default:
		return t
	}
}

func cloneMap(m map[string]any) map[string]any {
	out := make(map[string]any, len(m))
	for k, v := range m {
		out[k] = clone(v)
	}
	return out
}

func cloneSlice(s []any) []any {
	out := make([]any, len(s))
	for i := range s {
		out[i] = clone(s[i])
	}
	return out
}