/*
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 password provides functionality for generating secure random passwords.
package password

import (
	"context"
	"encoding/base32"
	"encoding/base64"
	"encoding/hex"
	"errors"
	"fmt"

	"github.com/sethvargo/go-password/password"
	apiextensions "k8s.io/apiextensions-apiserver/pkg/apis/apiextensions/v1"
	"sigs.k8s.io/controller-runtime/pkg/client"
	"sigs.k8s.io/yaml"

	genv1alpha1 "github.com/external-secrets/external-secrets/apis/generators/v1alpha1"
)

// Generator implements secure random password generation functionality.
type Generator struct{}

const (
	defaultLength      = 24
	defaultSymbolChars = "~!@#$%^&*()_+`-={}|[]\\:\"<>?,./"
	digitFactor        = 0.25
	symbolFactor       = 0.25

	errNoSpec    = "no config spec provided"
	errParseSpec = "unable to parse spec: %w"
	errGetToken  = "unable to get authorization token: %w"
)

type generateFunc func(
	length int,
	symbols int,
	symbolCharacters string,
	digits int,
	noUpper bool,
	allowRepeat bool,
) (string, error)

// Generate creates a secure random password based on the provided configuration.
func (g *Generator) Generate(_ context.Context, jsonSpec *apiextensions.JSON, _ client.Client, _ string) (map[string][]byte, genv1alpha1.GeneratorProviderState, error) {
	return g.generate(
		jsonSpec,
		generateSafePassword,
	)
}

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

func (g *Generator) generate(jsonSpec *apiextensions.JSON, passGen generateFunc) (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)
	}
	symbolCharacters := defaultSymbolChars
	if res.Spec.SymbolCharacters != nil {
		symbolCharacters = *res.Spec.SymbolCharacters
	}
	passLen := defaultLength
	if res.Spec.Length > 0 {
		passLen = res.Spec.Length
	}
	digits := int(float32(passLen) * digitFactor)
	if res.Spec.Digits != nil {
		digits = *res.Spec.Digits
	}
	symbols := int(float32(passLen) * symbolFactor)
	if res.Spec.Symbols != nil {
		symbols = *res.Spec.Symbols
	}
	pass, err := passGen(
		passLen,
		symbols,
		symbolCharacters,
		digits,
		res.Spec.NoUpper,
		res.Spec.AllowRepeat,
	)
	if err != nil {
		return nil, nil, err
	}

	// Apply encoding
	encoding := "raw"
	if res.Spec.Encoding != nil {
		encoding = *res.Spec.Encoding
	}

	encodedPass := encodePassword([]byte(pass), encoding)

	return map[string][]byte{
		"password": encodedPass,
	}, nil, nil
}

func generateSafePassword(
	passLen int,
	symbols int,
	symbolCharacters string,
	digits int,
	noUpper bool,
	allowRepeat bool,
) (string, error) {
	gen, err := password.NewGenerator(&password.GeneratorInput{
		Symbols: symbolCharacters,
	})
	if err != nil {
		return "", err
	}
	return gen.Generate(
		passLen,
		digits,
		symbols,
		noUpper,
		allowRepeat,
	)
}

func encodePassword(b []byte, encoding string) []byte {
	var encodedString string
	switch encoding {
	case "base64url":
		encodedString = base64.URLEncoding.EncodeToString(b)
	case "raw":
		return b
	case "base32":
		encodedString = base32.StdEncoding.EncodeToString(b)
	case "hex":
		encodedString = hex.EncodeToString(b)
	case "base64":
		encodedString = base64.StdEncoding.EncodeToString(b)
	default:
		return b
	}
	return []byte(encodedString)
}

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