package api

import (
	"crypto/rand"
	"crypto/rsa"
	"crypto/x509"
	"encoding/pem"
	"github.com/go-chi/jwtauth/v5"
	"log"
	"net/http"
	"os"
	"time"
)

var (
	jwtAuth *jwtauth.JWTAuth
)

// GetJWTAuth returns the JWT authorizer.
func GetJWTAuth() *jwtauth.JWTAuth {
	return jwtAuth
}

// InitJWT initializes JWT authentication.
func InitJWT() {
	generateRSAKeys()
	jwtAuth = jwtauth.New("RS256", loadRSAPrivateKey(), loadRSAPublicKey())
}

func Login(w http.ResponseWriter, r *http.Request) {
	req := struct {
		Username string `json:"username"`
		Password string `json:"password"`
	}{}

	if err := decodeJSON(w, r, &req); err != nil {
		return
	}

	// TODO
	t, tokenString, _ := jwtAuth.Encode(map[string]interface{}{"username": req.Username})
	encodeJSON(w, struct {
		AccessToken string    `json:"access_token"`
		ExpiresAt   time.Time `json:"expires_at"`
	}{
		tokenString,
		t.Expiration(),
	})
}

func generateRSAKeys() {
	err := os.Mkdir("secrets", 0755)

	if os.IsExist(err) {
		return
	} else if err != nil {
		log.Fatalf("Error creating secrets directory: %v", err)
	}

	key, err := rsa.GenerateKey(rand.Reader, 4096)

	if err != nil {
		log.Fatalf("Error generating RSA key: %v", err)
	}

	pub := key.Public()
	keyPEM := pem.EncodeToMemory(
		&pem.Block{
			Type:  "RSA PRIVATE KEY",
			Bytes: x509.MarshalPKCS1PrivateKey(key),
		},
	)
	pubPEM := pem.EncodeToMemory(
		&pem.Block{
			Type:  "RSA PUBLIC KEY",
			Bytes: x509.MarshalPKCS1PublicKey(pub.(*rsa.PublicKey)),
		},
	)

	if err := os.WriteFile("secrets/jwt.rsa", keyPEM, 0700); err != nil {
		log.Fatalf("Error writing private RSA key: %v", err)
	}

	if err := os.WriteFile("secrets/jwt.rsa.pub", pubPEM, 0755); err != nil {
		log.Fatalf("Error writing public RSA key: %v", err)
	}
}

func loadRSAPublicKey() *rsa.PublicKey {
	data, err := os.ReadFile("secrets/jwt.rsa.pub")

	if err != nil {
		log.Fatalf("Error loading RSA key: %v", err)
	}

	block, _ := pem.Decode(data)

	if block == nil {
		log.Fatalf("Error decoding RSA key: %v", err)
	}

	key, err := x509.ParsePKCS1PublicKey(block.Bytes)

	if err != nil {
		log.Fatalf("Error parsing RSA key: %v", err)
	}

	return key
}

func loadRSAPrivateKey() *rsa.PrivateKey {
	data, err := os.ReadFile("secrets/jwt.rsa")

	if err != nil {
		log.Fatalf("Error loading RSA key: %v", err)
	}

	block, _ := pem.Decode(data)

	if block == nil {
		log.Fatalf("Error decoding RSA key: %v", err)
	}

	key, err := x509.ParsePKCS1PrivateKey(block.Bytes)

	if err != nil {
		log.Fatalf("Error parsing RSA key: %v", err)
	}

	return key
}