/*
Copyright 2021 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 validation

import (
	"strings"

	machinery "k8s.io/apimachinery/pkg/api/validation"
	"k8s.io/apimachinery/pkg/util/sets"
	"k8s.io/apimachinery/pkg/util/validation/field"
	admissionapi "k8s.io/pod-security-admission/admission/api"
	"k8s.io/pod-security-admission/api"
)

// ValidatePodSecurityConfiguration validates a given PodSecurityConfiguration.
func ValidatePodSecurityConfiguration(configuration *admissionapi.PodSecurityConfiguration) field.ErrorList {
	allErrs := field.ErrorList{}

	// validate defaults
	allErrs = append(allErrs, validateLevel(field.NewPath("defaults", "enforce"), configuration.Defaults.Enforce)...)
	allErrs = append(allErrs, validateVersion(field.NewPath("defaults", "enforce-version"), configuration.Defaults.EnforceVersion)...)
	allErrs = append(allErrs, validateLevel(field.NewPath("defaults", "warn"), configuration.Defaults.Warn)...)
	allErrs = append(allErrs, validateVersion(field.NewPath("defaults", "warn-version"), configuration.Defaults.WarnVersion)...)
	allErrs = append(allErrs, validateLevel(field.NewPath("defaults", "audit"), configuration.Defaults.Audit)...)
	allErrs = append(allErrs, validateVersion(field.NewPath("defaults", "audit-version"), configuration.Defaults.AuditVersion)...)

	// validate exemptions
	allErrs = append(allErrs, validateNamespaces(configuration)...)
	allErrs = append(allErrs, validateRuntimeClasses(configuration)...)
	allErrs = append(allErrs, validateUsernames(configuration)...)

	return allErrs
}

// validateLevel validates a level
func validateLevel(p *field.Path, value string) field.ErrorList {
	errs := field.ErrorList{}
	_, err := api.ParseLevel(value)
	if err != nil {
		errs = append(errs, field.Invalid(p, value, err.Error()))
	}
	return errs
}

// validateVersion validates a version
func validateVersion(p *field.Path, value string) field.ErrorList {
	errs := field.ErrorList{}
	_, err := api.ParseVersion(value)
	if err != nil {
		errs = append(errs, field.Invalid(p, value, err.Error()))
	}
	return errs
}

func validateNamespaces(configuration *admissionapi.PodSecurityConfiguration) field.ErrorList {
	errs := field.ErrorList{}
	validSet := sets.NewString()
	for i, ns := range configuration.Exemptions.Namespaces {
		err := machinery.ValidateNamespaceName(ns, false)
		if len(err) > 0 {
			path := field.NewPath("exemptions", "namespaces").Index(i)
			errs = append(errs, field.Invalid(path, ns, strings.Join(err, ", ")))
			continue
		}
		if validSet.Has(ns) {
			path := field.NewPath("exemptions", "namespaces").Index(i)
			errs = append(errs, field.Duplicate(path, ns))
			continue
		}
		validSet.Insert(ns)
	}
	return errs
}

func validateRuntimeClasses(configuration *admissionapi.PodSecurityConfiguration) field.ErrorList {
	errs := field.ErrorList{}
	validSet := sets.NewString()
	for i, rc := range configuration.Exemptions.RuntimeClasses {
		err := machinery.NameIsDNSSubdomain(rc, false)
		if len(err) > 0 {
			path := field.NewPath("exemptions", "runtimeClasses").Index(i)
			errs = append(errs, field.Invalid(path, rc, strings.Join(err, ", ")))
			continue
		}
		if validSet.Has(rc) {
			path := field.NewPath("exemptions", "runtimeClasses").Index(i)
			errs = append(errs, field.Duplicate(path, rc))
			continue
		}
		validSet.Insert(rc)
	}
	return errs
}

func validateUsernames(configuration *admissionapi.PodSecurityConfiguration) field.ErrorList {
	errs := field.ErrorList{}
	validSet := sets.NewString()
	for i, uname := range configuration.Exemptions.Usernames {
		if uname == "" {
			path := field.NewPath("exemptions", "usernames").Index(i)
			errs = append(errs, field.Invalid(path, uname, "username must not be empty"))
			continue
		}
		if validSet.Has(uname) {
			path := field.NewPath("exemptions", "usernames").Index(i)
			errs = append(errs, field.Duplicate(path, uname))
			continue
		}
		validSet.Insert(uname)
	}

	return errs
}