/*
Copyright © 2025 ESO Maintainer Team

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

    https://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 vaultdynamic provides functionality for generating dynamic credentials from HashiCorp Vault.
package vaultdynamic

import (
	"context"
	"encoding/json"
	"errors"
	"fmt"

	vault "github.com/hashicorp/vault/api"
	apiextensions "k8s.io/apiextensions-apiserver/pkg/apis/apiextensions/v1"
	"k8s.io/client-go/kubernetes"
	typedcorev1 "k8s.io/client-go/kubernetes/typed/core/v1"
	"sigs.k8s.io/controller-runtime/pkg/client"
	ctrlcfg "sigs.k8s.io/controller-runtime/pkg/client/config"
	"sigs.k8s.io/yaml"

	genv1alpha1 "github.com/external-secrets/external-secrets/apis/generators/v1alpha1"
	provider "github.com/external-secrets/external-secrets/providers/v1/vault"
	"github.com/external-secrets/external-secrets/providers/v1/vault/util"
	"github.com/external-secrets/external-secrets/runtime/esutils"
)

// Generator implements credential generation using HashiCorp Vault's dynamic secrets.
type Generator struct{}

const (
	errNoSpec      = "no config spec provided"
	errParseSpec   = "unable to parse spec: %w"
	errVaultClient = "unable to setup Vault client: %w"
	errGetSecret   = "unable to get dynamic secret: %w"
)

// Generate creates dynamic credentials using HashiCorp Vault's secrets engines.
func (g *Generator) Generate(ctx context.Context, jsonSpec *apiextensions.JSON, kube client.Client, namespace string) (map[string][]byte, genv1alpha1.GeneratorProviderState, error) {
	c := &provider.Provider{NewVaultClient: provider.NewVaultClient}

	// controller-runtime/client does not support TokenRequest or other subresource APIs
	// so we need to construct our own client and use it to fetch tokens
	// (for Kubernetes service account token auth)
	restCfg, err := ctrlcfg.GetConfig()
	if err != nil {
		return nil, nil, err
	}
	clientset, err := kubernetes.NewForConfig(restCfg)
	if err != nil {
		return nil, nil, err
	}

	return g.generate(ctx, c, jsonSpec, kube, clientset.CoreV1(), namespace)
}

// Cleanup performs any necessary cleanup after token generation.
func (g *Generator) Cleanup(_ context.Context, _ *apiextensions.JSON, _ genv1alpha1.GeneratorProviderState, _ client.Client, _ string) error {
	return nil
}

func (g *Generator) generate(ctx context.Context, c *provider.Provider, jsonSpec *apiextensions.JSON, kube client.Client, corev1 typedcorev1.CoreV1Interface, namespace string) (map[string][]byte, genv1alpha1.GeneratorProviderState, error) {
	if jsonSpec == nil {
		return nil, nil, errors.New(errNoSpec)
	}
	spec, err := parseSpec(jsonSpec.Raw)
	if err != nil {
		return nil, nil, fmt.Errorf(errParseSpec, err)
	}
	if spec == nil || spec.Spec.Provider == nil {
		return nil, nil, errors.New("no Vault provider config in spec")
	}
	cl, err := c.NewGeneratorClient(ctx, kube, corev1, spec.Spec.Provider, namespace, spec.Spec.RetrySettings)
	if err != nil {
		return nil, nil, fmt.Errorf(errVaultClient, err)
	}

	result, err := g.fetchVaultSecret(ctx, spec, cl)
	if err != nil {
		return nil, nil, err
	}

	if result == nil && spec.Spec.AllowEmptyResponse {
		return nil, nil, nil
	}

	if result == nil {
		return nil, nil, fmt.Errorf(errGetSecret, errors.New("empty response from Vault"))
	}
	return g.prepareResponse(spec, result)
}

func (g *Generator) fetchVaultSecret(ctx context.Context, res *genv1alpha1.VaultDynamicSecret, cl vaultutil.Client) (*vault.Secret, error) {
	var (
		result *vault.Secret
		err    error
	)

	if res.Spec.Method == "" || res.Spec.Method == "GET" {
		result, err = cl.Logical().ReadWithDataWithContext(ctx, res.Spec.Path, nil)
	} else if res.Spec.Method == "LIST" {
		result, err = cl.Logical().ListWithContext(ctx, res.Spec.Path)
	} else if res.Spec.Method == "DELETE" {
		result, err = cl.Logical().DeleteWithContext(ctx, res.Spec.Path)
	} else {
		params := make(map[string]any)
		if res.Spec.Parameters != nil {
			if err := json.Unmarshal(res.Spec.Parameters.Raw, &params); err != nil {
				return nil, err
			}
		}

		result, err = cl.Logical().WriteWithContext(ctx, res.Spec.Path, params)
	}

	return result, err
}

func (g *Generator) prepareResponse(res *genv1alpha1.VaultDynamicSecret, result *vault.Secret) (map[string][]byte, genv1alpha1.GeneratorProviderState, error) {
	var err error
	data := make(map[string]any)
	response := make(map[string][]byte)
	if res.Spec.ResultType == genv1alpha1.VaultDynamicSecretResultTypeAuth {
		authJSON, err := json.Marshal(result.Auth)
		if err != nil {
			return nil, nil, err
		}
		err = json.Unmarshal(authJSON, &data)
		if err != nil {
			return nil, nil, err
		}
	} else if res.Spec.ResultType == genv1alpha1.VaultDynamicSecretResultTypeRaw {
		rawJSON, err := json.Marshal(result)
		if err != nil {
			return nil, nil, err
		}
		err = json.Unmarshal(rawJSON, &data)
		if err != nil {
			return nil, nil, err
		}
	} else {
		data = result.Data
	}

	for k := range data {
		response[k], err = esutils.GetByteValueFromMap(data, k)
		if err != nil {
			return nil, nil, err
		}
	}
	return response, nil, nil
}

func parseSpec(data []byte) (*genv1alpha1.VaultDynamicSecret, error) {
	var spec genv1alpha1.VaultDynamicSecret
	err := yaml.Unmarshal(data, &spec)
	return &spec, err
}

// NewGenerator creates a new Generator instance.
func NewGenerator() genv1alpha1.Generator {
	return &Generator{}
}

// Kind returns the generator kind.
func Kind() string {
	return string(genv1alpha1.GeneratorKindVaultDynamicSecret)
}