/*
Copyright 2022 CAcert Inc.
SPDX-License-Identifier: Apache-2.0

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 hsm

import (
	"errors"
	"fmt"
	"log"
	"os"
	"strings"
	"syscall"

	"github.com/ThalesIgnite/crypto11"
	"golang.org/x/term"
)

func (a *Access) prepareCrypto11Context(label string) (*crypto11.Context, error) {
	var (
		err        error
		p11Context *crypto11.Context
	)

	storage, err := a.GetSignerConfig().GetKeyStorage(label)
	if err != nil {
		return nil, fmt.Errorf("key storage %s not available: %w", label, err)
	}

	p11Config := &crypto11.Config{
		Path:       storage.Module,
		TokenLabel: storage.Label,
	}

	a.infoLog.Printf("using PKCS#11 module %s", p11Config.Path)
	a.infoLog.Printf("looking for token with label %s", p11Config.TokenLabel)

	p11Config.Pin, err = getPin(p11Config, a.infoLog)
	if err != nil {
		return nil, err
	}

	p11Context, err = crypto11.Configure(p11Config)
	if err != nil {
		return nil, fmt.Errorf("could not configure PKCS#11 library: %w", err)
	}

	return p11Context, nil
}

func getPin(p11Config *crypto11.Config, infoLog *log.Logger) (string, error) {
	var err error

	tokenPinEnv := strings.NewReplacer(
		"-", "_",
		" ", "_",
		"(", "_",
		")", "_",
	).Replace(p11Config.TokenLabel)
	tokenPinEnv = strings.ToUpper(tokenPinEnv)
	tokenPinEnv = fmt.Sprintf("TOKEN_PIN_%s", tokenPinEnv)

	pin, found := os.LookupEnv(tokenPinEnv)
	if !found {
		infoLog.Printf("environment variable %s has not been set", tokenPinEnv)

		if !term.IsTerminal(syscall.Stdin) {
			return "", errors.New("stdin is not a terminal")
		}

		_, err = fmt.Fprintf(os.Stdout, "Enter PIN for token %s: ", p11Config.TokenLabel)
		if err != nil {
			return "", fmt.Errorf("could not write PIN prompt: %w", err)
		}

		bytePin, err := term.ReadPassword(syscall.Stdin)
		if err != nil {
			return "", fmt.Errorf("could not read PIN: %w", err)
		}

		_, err = fmt.Fprintln(os.Stdout)
		if err != nil {
			return "", fmt.Errorf("could not write to stdout: %w", err)
		}

		pin = string(bytePin)
	}

	return strings.TrimSpace(pin), nil
}