package cmd

import (
	"crypto"
	"crypto/x509"
	"encoding/json"
	"encoding/pem"
	"errors"
	"net/url"
	"os"
	"path/filepath"
	"strings"

	"github.com/go-acme/lego/v4/certcrypto"
	"github.com/go-acme/lego/v4/lego"
	"github.com/go-acme/lego/v4/log"
	"github.com/go-acme/lego/v4/registration"
	"github.com/urfave/cli/v2"
)

const (
	baseAccountsRootFolderName = "accounts"
	baseKeysFolderName         = "keys"
	accountFileName            = "account.json"
)

// AccountsStorage A storage for account data.
//
// rootPath:
//
//	./.lego/accounts/
//	     │      └── root accounts directory
//	     └── "path" option
//
// rootUserPath:
//
//	./.lego/accounts/localhost_14000/hubert@hubert.com/
//	     │      │             │             └── userID ("email" option)
//	     │      │             └── CA server ("server" option)
//	     │      └── root accounts directory
//	     └── "path" option
//
// keysPath:
//
//	./.lego/accounts/localhost_14000/hubert@hubert.com/keys/
//	     │      │             │             │           └── root keys directory
//	     │      │             │             └── userID ("email" option)
//	     │      │             └── CA server ("server" option)
//	     │      └── root accounts directory
//	     └── "path" option
//
// accountFilePath:
//
//	./.lego/accounts/localhost_14000/hubert@hubert.com/account.json
//	     │      │             │             │             └── account file
//	     │      │             │             └── userID ("email" option)
//	     │      │             └── CA server ("server" option)
//	     │      └── root accounts directory
//	     └── "path" option
type AccountsStorage struct {
	userID          string
	rootPath        string
	rootUserPath    string
	keysPath        string
	accountFilePath string
	ctx             *cli.Context
}

// NewAccountsStorage Creates a new AccountsStorage.
func NewAccountsStorage(ctx *cli.Context) *AccountsStorage {
	// TODO: move to account struct? Currently MUST pass email.
	email := getEmail(ctx)

	serverURL, err := url.Parse(ctx.String(flgServer))
	if err != nil {
		log.Fatal(err)
	}

	rootPath := filepath.Join(ctx.String(flgPath), baseAccountsRootFolderName)
	serverPath := strings.NewReplacer(":", "_", "/", string(os.PathSeparator)).Replace(serverURL.Host)
	accountsPath := filepath.Join(rootPath, serverPath)
	rootUserPath := filepath.Join(accountsPath, email)

	return &AccountsStorage{
		userID:          email,
		rootPath:        rootPath,
		rootUserPath:    rootUserPath,
		keysPath:        filepath.Join(rootUserPath, baseKeysFolderName),
		accountFilePath: filepath.Join(rootUserPath, accountFileName),
		ctx:             ctx,
	}
}

func (s *AccountsStorage) ExistsAccountFilePath() bool {
	accountFile := filepath.Join(s.rootUserPath, accountFileName)
	if _, err := os.Stat(accountFile); os.IsNotExist(err) {
		return false
	} else if err != nil {
		log.Fatal(err)
	}
	return true
}

func (s *AccountsStorage) GetRootPath() string {
	return s.rootPath
}

func (s *AccountsStorage) GetRootUserPath() string {
	return s.rootUserPath
}

func (s *AccountsStorage) GetUserID() string {
	return s.userID
}

func (s *AccountsStorage) Save(account *Account) error {
	jsonBytes, err := json.MarshalIndent(account, "", "\t")
	if err != nil {
		return err
	}

	return os.WriteFile(s.accountFilePath, jsonBytes, filePerm)
}

func (s *AccountsStorage) LoadAccount(privateKey crypto.PrivateKey) *Account {
	fileBytes, err := os.ReadFile(s.accountFilePath)
	if err != nil {
		log.Fatalf("Could not load file for account %s: %v", s.userID, err)
	}

	var account Account
	err = json.Unmarshal(fileBytes, &account)
	if err != nil {
		log.Fatalf("Could not parse file for account %s: %v", s.userID, err)
	}

	account.key = privateKey

	if account.Registration == nil || account.Registration.Body.Status == "" {
		reg, err := tryRecoverRegistration(s.ctx, privateKey)
		if err != nil {
			log.Fatalf("Could not load account for %s. Registration is nil: %#v", s.userID, err)
		}

		account.Registration = reg
		err = s.Save(&account)
		if err != nil {
			log.Fatalf("Could not save account for %s. Registration is nil: %#v", s.userID, err)
		}
	}

	return &account
}

func (s *AccountsStorage) GetPrivateKey(keyType certcrypto.KeyType) crypto.PrivateKey {
	accKeyPath := filepath.Join(s.keysPath, s.userID+".key")

	if _, err := os.Stat(accKeyPath); os.IsNotExist(err) {
		log.Printf("No key found for account %s. Generating a %s key.", s.userID, keyType)
		s.createKeysFolder()

		privateKey, err := generatePrivateKey(accKeyPath, keyType)
		if err != nil {
			log.Fatalf("Could not generate RSA private account key for account %s: %v", s.userID, err)
		}

		log.Printf("Saved key to %s", accKeyPath)
		return privateKey
	}

	privateKey, err := loadPrivateKey(accKeyPath)
	if err != nil {
		log.Fatalf("Could not load RSA private key from file %s: %v", accKeyPath, err)
	}

	return privateKey
}

func (s *AccountsStorage) createKeysFolder() {
	if err := createNonExistingFolder(s.keysPath); err != nil {
		log.Fatalf("Could not check/create directory for account %s: %v", s.userID, err)
	}
}

func generatePrivateKey(file string, keyType certcrypto.KeyType) (crypto.PrivateKey, error) {
	privateKey, err := certcrypto.GeneratePrivateKey(keyType)
	if err != nil {
		return nil, err
	}

	certOut, err := os.Create(file)
	if err != nil {
		return nil, err
	}
	defer certOut.Close()

	pemKey := certcrypto.PEMBlock(privateKey)
	err = pem.Encode(certOut, pemKey)
	if err != nil {
		return nil, err
	}

	return privateKey, nil
}

func loadPrivateKey(file string) (crypto.PrivateKey, error) {
	keyBytes, err := os.ReadFile(file)
	if err != nil {
		return nil, err
	}

	keyBlock, _ := pem.Decode(keyBytes)

	switch keyBlock.Type {
	case "RSA PRIVATE KEY":
		return x509.ParsePKCS1PrivateKey(keyBlock.Bytes)
	case "EC PRIVATE KEY":
		return x509.ParseECPrivateKey(keyBlock.Bytes)
	}

	return nil, errors.New("unknown private key type")
}

func tryRecoverRegistration(ctx *cli.Context, privateKey crypto.PrivateKey) (*registration.Resource, error) {
	// couldn't load account but got a key. Try to look the account up.
	config := lego.NewConfig(&Account{key: privateKey})
	config.CADirURL = ctx.String(flgServer)
	config.UserAgent = getUserAgent(ctx)

	client, err := lego.NewClient(config)
	if err != nil {
		return nil, err
	}

	reg, err := client.Registration.ResolveAccountByKey()
	if err != nil {
		return nil, err
	}
	return reg, nil
}
