package api

import (
	"crypto/ecdsa"
	"crypto/elliptic"
	"crypto/rand"
	"crypto/x509"
	"crypto/x509/pkix"
	"encoding/pem"
	"math/big"
	"net"
	"os"
	"path/filepath"
	"time"
)

func EnsureSelfSignedCert(certFile, keyFile string) error {
	if _, err := os.Stat(certFile); err == nil {
		if _, err := os.Stat(keyFile); err == nil {
			return nil
		}
	}

	priv, err := ecdsa.GenerateKey(elliptic.P256(), rand.Reader)
	if err != nil {
		return err
	}

	serial, err := rand.Int(rand.Reader, new(big.Int).Lsh(big.NewInt(1), 128))
	if err != nil {
		return err
	}

	tmpl := &x509.Certificate{
		SerialNumber: serial,
		Subject: pkix.Name{
			Organization: []string{"AI-Status-Light"},
			CommonName:   "localhost",
		},
		NotBefore:             time.Now(),
		NotAfter:              time.Now().Add(10 * 365 * 24 * time.Hour),
		KeyUsage:              x509.KeyUsageKeyEncipherment | x509.KeyUsageDigitalSignature,
		ExtKeyUsage:           []x509.ExtKeyUsage{x509.ExtKeyUsageServerAuth},
		BasicConstraintsValid: true,
		DNSNames:              []string{"localhost"},
		IPAddresses:           []net.IP{net.ParseIP("127.0.0.1")},
	}

	certDER, err := x509.CreateCertificate(rand.Reader, tmpl, tmpl, &priv.PublicKey, priv)
	if err != nil {
		return err
	}

	if err := os.MkdirAll(filepath.Dir(certFile), 0700); err != nil {
		return err
	}

	certOut, err := os.Create(certFile)
	if err != nil {
		return err
	}
	if err := pem.Encode(certOut, &pem.Block{Type: "CERTIFICATE", Bytes: certDER}); err != nil {
		certOut.Close()
		return err
	}
	certOut.Close()

	keyOut, err := os.Create(keyFile)
	if err != nil {
		return err
	}
	privBytes, err := x509.MarshalECPrivateKey(priv)
	if err != nil {
		keyOut.Close()
		return err
	}
	if err := pem.Encode(keyOut, &pem.Block{Type: "EC PRIVATE KEY", Bytes: privBytes}); err != nil {
		keyOut.Close()
		return err
	}
	keyOut.Close()

	return nil
}