package i2pkeys

import (
	"bytes"
	"crypto"
	"encoding/base32"
	"encoding/base64"
	"errors"
	"fmt"
	"io"
	"os"
	"strings"
)

var (
	i2pB64enc *base64.Encoding = base64.NewEncoding("ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789-~")
	i2pB32enc *base32.Encoding = base32.NewEncoding("abcdefghijklmnopqrstuvwxyz234567")
)

// If you set this to true, Addr will return a base64 String()
var StringIsBase64 bool

// The public and private keys associated with an I2P destination. I2P hides the
// details of exactly what this is, so treat them as blobs, but generally: One
// pair of DSA keys, one pair of ElGamal keys, and sometimes (almost never) also
// a certificate. String() returns you the full content of I2PKeys and Addr()
// returns the public keys.
type I2PKeys struct {
	Address I2PAddr // only the public key
	Both    string  // both public and private keys
}

// Creates I2PKeys from an I2PAddr and a public/private keypair string (as
// generated by String().)
func NewKeys(addr I2PAddr, both string) I2PKeys {
	log.WithField("addr", addr).Debug("Creating new I2PKeys")
	return I2PKeys{addr, both}
}

// fileExists checks if a file exists and is not a directory before we
// try using it to prevent further errors.
func fileExists(filename string) (bool, error) {
	info, err := os.Stat(filename)
	if os.IsNotExist(err) {
		log.WithField("filename", filename).Debug("File does not exist")
		return false, nil
	} else if err != nil {
		log.WithError(err).WithField("filename", filename).Error("Error checking file existence")
		return false, fmt.Errorf("error checking file existence: %w", err)
	}
	exists := !info.IsDir()
	if exists {
		log.WithField("filename", filename).Debug("File exists")
	} else {
		log.WithField("filename", filename).Debug("File is a directory")
	}
	return !info.IsDir(), nil
}

// LoadKeysIncompat loads keys from a non-standard format
func LoadKeysIncompat(r io.Reader) (I2PKeys, error) {
	log.Debug("Loading keys from reader")
	var buff bytes.Buffer
	_, err := io.Copy(&buff, r)
	if err != nil {
		log.WithError(err).Error("Error copying from reader, did not load keys")
		return I2PKeys{}, fmt.Errorf("error copying from reader: %w", err)
	}

	parts := strings.Split(buff.String(), "\n")
	if len(parts) < 2 {
		err := errors.New("invalid key format: not enough data")
		log.WithError(err).Error("Error parsing keys")
		return I2PKeys{}, err
	}

	k := I2PKeys{I2PAddr(parts[0]), parts[1]}
	log.WithField("keys", k).Debug("Loaded keys")
	return k, nil
}

// load keys from non-standard format by specifying a text file.
// If the file does not exist, generate keys, otherwise, fail
// closed.
func LoadKeys(r string) (I2PKeys, error) {
	log.WithField("filename", r).Debug("Loading keys from file")
	exists, err := fileExists(r)
	if err != nil {
		log.WithError(err).Error("Error checking if file exists")
		return I2PKeys{}, err
	}
	if !exists {
		// File doesn't exist so we'll generate new keys
		log.WithError(err).Debug("File does not exist, attempting to generate new keys")
		k, err := NewDestination()
		if err != nil {
			log.WithError(err).Error("Error generating new keys")
			return I2PKeys{}, err
		}
		// Save the new keys to the file
		err = StoreKeys(*k, r)
		if err != nil {
			log.WithError(err).Error("Error saving new keys to file")
			return I2PKeys{}, err
		}
		return *k, nil
	}
	fi, err := os.Open(r)
	if err != nil {
		log.WithError(err).WithField("filename", r).Error("Error opening file")
		return I2PKeys{}, fmt.Errorf("error opening file: %w", err)
	}
	defer fi.Close()
	log.WithField("filename", r).Debug("File opened successfully")
	return LoadKeysIncompat(fi)
}

// store keys in non standard format
func StoreKeysIncompat(k I2PKeys, w io.Writer) error {
	log.Debug("Storing keys")
	_, err := io.WriteString(w, k.Address.Base64()+"\n"+k.Both)
	if err != nil {
		log.WithError(err).Error("Error writing keys")
		return fmt.Errorf("error writing keys: %w", err)
	}
	log.WithField("keys", k).Debug("Keys stored successfully")
	return nil
}

func StoreKeys(k I2PKeys, r string) error {
	log.WithField("filename", r).Debug("Storing keys to file")
	if _, err := os.Stat(r); err != nil {
		if os.IsNotExist(err) {
			log.WithField("filename", r).Debug("File does not exist, creating new file")
			fi, err := os.Create(r)
			if err != nil {
				log.WithError(err).Error("Error creating file")
				return err
			}
			defer fi.Close()
			return StoreKeysIncompat(k, fi)
		}
	}
	fi, err := os.Open(r)
	if err != nil {
		log.WithError(err).Error("Error opening file")
		return err
	}
	defer fi.Close()
	return StoreKeysIncompat(k, fi)
}

func (k I2PKeys) Network() string {
	return k.Address.Network()
}

// Returns the public keys of the I2PKeys in Addr form
func (k I2PKeys) Addr() I2PAddr {
	return k.Address
}

// Returns the public keys of the I2PKeys.
func (k I2PKeys) Public() crypto.PublicKey {
	return k.Address
}

func (k I2PKeys) Private() []byte {
	log.Debug("Extracting private key")
	src := strings.Split(k.String(), k.Addr().String())[0]
	var dest []byte
	_, err := i2pB64enc.Decode(dest, []byte(src))
	if err != nil {
		log.WithError(err).Error("Error decoding private key")
		panic(err)
	}
	return dest
}

// Returns the keys (both public and private), in I2Ps base64 format. Use this
// when you create sessions.
func (k I2PKeys) String() string {
	return k.Both
}