package main

import (
	"crypto"
	"crypto/rand"
	"crypto/rsa"
	"crypto/sha1"
	"crypto/x509"
	"encoding/hex"
	"encoding/pem"
	"errors"
	"fmt"
	"log"
	"os"
	"os/signal"
	"path"

	"git.greysoh.dev/imterah/boron/bofs"
	"github.com/hanwen/go-fuse/v2/fs"
	"github.com/urfave/cli/v2"
)

func initializeFS(cCtx *cli.Context) error {
	privKeyPath := cCtx.String("key")
	allowKeyGeneration := cCtx.Bool("allow-keygeneration")

	srcFolder := cCtx.String("source-folder")
	destFolder := cCtx.String("dest-folder")

	privKeyRaw, err := os.ReadFile(privKeyPath)

	var privateKey *rsa.PrivateKey

	if err != nil && errors.Is(err, os.ErrNotExist) && allowKeyGeneration {
		log.Println("key not found. generating key...")
		privateKey, err = rsa.GenerateKey(rand.Reader, 4096)

		if err != nil {
			return fmt.Errorf("could not generate private key: %s", err.Error())
		}

		log.Println("getting key signature...")

		sha1Instance := sha1.New()
		keySignature := sha1Instance.Sum(nil)

		if _, err := rsa.SignPKCS1v15(rand.Reader, privateKey, crypto.SHA1, keySignature); err != nil {
			return fmt.Errorf("could not get key fingerprint/signature: %s", err.Error())
		}

		log.Println("saving public key...")

		if err := os.Mkdir(path.Join(srcFolder, "keys"), os.ModePerm); err != nil && !errors.Is(err, os.ErrExist) {
			return fmt.Errorf("failed to create keys folder: %s", err.Error())
		}

		pubKeyFile, err := os.Create(path.Join(srcFolder, "keys", hex.EncodeToString(keySignature)+".pub"))

		if err != nil {
			return fmt.Errorf("failed to open public key file: %s", err.Error())
		}

		// We're doing PCKS1 (todo: look into maybe changing to PCKS8?)
		err = pem.Encode(
			pubKeyFile,
			&pem.Block{
				Type:  "PUBLIC KEY",
				Bytes: x509.MarshalPKCS1PublicKey(&privateKey.PublicKey),
			},
		)

		if err != nil {
			return fmt.Errorf("failed to encode public key: %s", err.Error())
		}

		pubKeyFile.Close()

		privKeyFile, err := os.Create(privKeyPath)

		if err != nil {
			return fmt.Errorf("failed to open public key file: %s", err.Error())
		}

		log.Println("saving private key...")

		err = pem.Encode(
			privKeyFile,
			&pem.Block{
				Type:  "PRIVATE KEY",
				Bytes: x509.MarshalPKCS1PrivateKey(privateKey),
			},
		)

		if err != nil {
			return fmt.Errorf("failed to encode private key: %s", err.Error())
		}

		privKeyFile.Close()

		log.Println("finished key generation steps.")
	} else if err == nil {
		privKeyPem, _ := pem.Decode(privKeyRaw)

		if privKeyPem.Type != "RSA PRIVATE KEY" && privKeyPem.Type != "PRIVATE KEY" {
			return fmt.Errorf("decoded private key's header does not match RSA private key signature")
		}

		var parsedKey interface{}

		if parsedKey, err = x509.ParsePKCS1PrivateKey(privKeyPem.Bytes); err != nil {
			log.Println("failed to decode private key using PCKS1 format. trying PCKS8 next")

			if parsedKey, err = x509.ParsePKCS8PrivateKey(privKeyPem.Bytes); err != nil {
				return fmt.Errorf("failed to decode private key using PCKS8 format")
			}
		}

		var ok bool // Hack to make Go not complain
		privateKey, ok = parsedKey.(*rsa.PrivateKey)

		if !ok {
			return fmt.Errorf("failed to set privateKey variable (failed typecast)")
		}
	} else {
		return fmt.Errorf("could not read private key: %s", err.Error())
	}

	opts := &fs.Options{}
	log.Println("mounting filesystem...")

	server, err := fs.Mount(destFolder, &bofs.BoronInode{}, opts)

	if err != nil {
		return err
	}

	log.Println("successfully mounted filesystem.")

	c := make(chan os.Signal, 1)
	signal.Notify(c, os.Interrupt)

	go func() {
		for _ = range c {
			log.Println("unmounting filesystem...")
			err := server.Unmount()

			if err != nil {
				log.Println("failed to unmount filesystem.")
			}

			os.Exit(0)
		}
	}()

	server.Wait()

	return nil
}

func main() {
	app := &cli.App{
		Name:  "boron",
		Usage: "a collaborateive end-to-end-encrypted meta-filesystem",
		Flags: []cli.Flag{
			&cli.StringFlag{
				Name:     "key",
				Usage:    "armored private key to use",
				Required: true,
			},
			&cli.BoolFlag{
				Name:  "allow-keygeneration",
				Usage: "if true, allows keys to be generated if the keys do not exist",
			},
			&cli.StringFlag{
				Name:     "source-folder",
				Usage:    "source folder to use",
				Required: true,
			},
			&cli.StringFlag{
				Name:     "dest-folder",
				Usage:    "destination folder to use",
				Required: true,
			},
		},
		Action: initializeFS,
	}

	if err := app.Run(os.Args); err != nil {
		log.Fatal(err)
	}
}