/*
Copyright © The ESO 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

    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 sts implements a generator for AWS STS session tokens
package sts

import (
	"context"
	"errors"
	"fmt"
	"strconv"

	"github.com/aws/aws-sdk-go-v2/aws"
	"github.com/aws/aws-sdk-go-v2/service/sts"
	apiextensions "k8s.io/apiextensions-apiserver/pkg/apis/apiextensions/v1"
	"sigs.k8s.io/controller-runtime/pkg/client"
	"sigs.k8s.io/yaml"

	esv1 "github.com/external-secrets/external-secrets/apis/externalsecrets/v1"
	genv1alpha1 "github.com/external-secrets/external-secrets/apis/generators/v1alpha1"
	awsauth "github.com/external-secrets/external-secrets/providers/v1/aws/auth"
)

// stsAPI defines the methods needed for the STS generator.
type stsAPI interface {
	GetSessionToken(ctx context.Context, params *sts.GetSessionTokenInput, optFns ...func(*sts.Options)) (*sts.GetSessionTokenOutput, error)
}

// Generator implements a generator for AWS STS session tokens.
type Generator struct{}

// const error messages.
const (
	errNoSpec     = "no config spec provided"
	errParseSpec  = "unable to parse spec: %w"
	errCreateSess = "unable to create aws session: %w"
	errGetToken   = "unable to get authorization token: %w"
)

// Generate creates AWS STS session tokens and returns credentials.
func (g *Generator) Generate(ctx context.Context, jsonSpec *apiextensions.JSON, kube client.Client, namespace string) (map[string][]byte, genv1alpha1.GeneratorProviderState, error) {
	return g.generate(ctx, jsonSpec, kube, namespace, stsFactory)
}

func (g *Generator) generate(
	ctx context.Context,
	jsonSpec *apiextensions.JSON,
	kube client.Client,
	namespace string,
	stsFunc stsFactoryFunc,
) (map[string][]byte, genv1alpha1.GeneratorProviderState, error) {
	if jsonSpec == nil {
		return nil, nil, errors.New(errNoSpec)
	}
	res, err := parseSpec(jsonSpec.Raw)
	if err != nil {
		return nil, nil, fmt.Errorf(errParseSpec, err)
	}
	if res.Spec.Auth.JWTAuth != nil {
		return nil, nil, errors.New("jwt auth cannot be used for STS Session Token generation")
	}
	cfg, err := awsauth.NewGeneratorSession(
		ctx,
		esv1.AWSAuth{
			SecretRef: (*esv1.AWSAuthSecretRef)(res.Spec.Auth.SecretRef),
		},
		res.Spec.Role,
		res.Spec.Region,
		kube,
		namespace,
		awsauth.DefaultSTSProvider,
		awsauth.DefaultJWTProvider)
	if err != nil {
		return nil, nil, fmt.Errorf(errCreateSess, err)
	}
	api := stsFunc(cfg)
	input := &sts.GetSessionTokenInput{}
	if res.Spec.RequestParameters != nil {
		input.DurationSeconds = res.Spec.RequestParameters.SessionDuration
		input.TokenCode = res.Spec.RequestParameters.TokenCode
		input.SerialNumber = res.Spec.RequestParameters.SerialNumber
	}
	out, err := api.GetSessionToken(ctx, input)
	if err != nil {
		return nil, nil, fmt.Errorf(errGetToken, err)
	}
	if out.Credentials == nil {
		return nil, nil, errors.New("no credentials found")
	}

	return map[string][]byte{
		"access_key_id":     []byte(*out.Credentials.AccessKeyId),
		"expiration":        []byte(strconv.FormatInt(out.Credentials.Expiration.Unix(), 10)),
		"secret_access_key": []byte(*out.Credentials.SecretAccessKey),
		"session_token":     []byte(*out.Credentials.SessionToken),
	}, nil, nil
}

// Cleanup is a no-op for STS generator as it doesn't require any cleanup.
func (g *Generator) Cleanup(_ context.Context, _ *apiextensions.JSON, _ genv1alpha1.GeneratorProviderState, _ client.Client, _ string) error {
	return nil
}

type stsFactoryFunc func(cfg *aws.Config) stsAPI

func stsFactory(cfg *aws.Config) stsAPI {
	return sts.NewFromConfig(*cfg)
}

func parseSpec(data []byte) (*genv1alpha1.STSSessionToken, error) {
	var spec genv1alpha1.STSSessionToken
	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.GeneratorKindSTSSessionToken)
}