package acme

import (
	"crypto"
	"crypto/ecdsa"
	"crypto/elliptic"
	"crypto/rand"
	"crypto/x509"
	"encoding/json"
	"encoding/pem"
	"io/ioutil"
	"log"
	"net/http"
	"os"
	"path/filepath"
	"strconv"
	"strings"
	"time"

	"github.com/go-acme/lego/v4/certcrypto"
	"github.com/go-acme/lego/v4/certificate"
	"github.com/go-acme/lego/v4/challenge/http01"
	"github.com/go-acme/lego/v4/lego"
	"github.com/go-acme/lego/v4/registration"
	"imuslab.com/zoraxy/mod/utils"
)

// You'll need a user or account type that implements acme.User
type ACMEUser struct {
	Email        string
	Registration *registration.Resource
	key          crypto.PrivateKey
}

func (u *ACMEUser) GetEmail() string {
	return u.Email
}
func (u ACMEUser) GetRegistration() *registration.Resource {
	return u.Registration
}
func (u *ACMEUser) GetPrivateKey() crypto.PrivateKey {
	return u.key
}

type ACMEHandler struct {
	email      string
	acmeServer string
	port       string
}

func NewACME(email string, acmeServer string, port string) *ACMEHandler {

	return &ACMEHandler{
		email:      email,
		acmeServer: acmeServer,
		port:       port,
	}
}

func (a *ACMEHandler) ObtainCert(domains []string, certificateName string) (bool, error) {
	log.Println("Obtaining certificate...")

	privateKey, err := ecdsa.GenerateKey(elliptic.P256(), rand.Reader)
	if err != nil {
		log.Println(err)
		return false, err
	}

	log.Println(a.acmeServer)
	adminUser := ACMEUser{
		Email: a.email,
		key:   privateKey,
	}

	config := lego.NewConfig(&adminUser)

	config.CADirURL = a.acmeServer
	config.Certificate.KeyType = certcrypto.RSA2048

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

	err = client.Challenge.SetHTTP01Provider(http01.NewProviderServer("", a.port))
	if err != nil {
		log.Println(err)
		return false, err
	}

	// New users will need to register
	reg, err := client.Registration.Register(registration.RegisterOptions{TermsOfServiceAgreed: true})
	if err != nil {
		log.Println(err)
		return false, err
	}
	adminUser.Registration = reg

	request := certificate.ObtainRequest{
		Domains: domains,
		Bundle:  true,
	}
	certificates, err := client.Certificate.Obtain(request)
	if err != nil {
		log.Println(err)
		return false, err
	}

	// Each certificate comes back with the cert bytes, the bytes of the client's
	// private key, and a certificate URL. SAVE THESE TO DISK.
	err = ioutil.WriteFile("./certs/"+certificateName+".crt", certificates.Certificate, 0777)
	if err != nil {
		log.Println(err)
		return false, err
	}
	err = ioutil.WriteFile("./certs/"+certificateName+".key", certificates.PrivateKey, 0777)

	if err != nil {
		log.Println(err)
		return false, err
	}

	return true, nil
}

// Return a list of domains that is in expired certificates
func (a *ACMEHandler) CheckCertificate() []string {

	filenames, err := os.ReadDir("./certs/")

	expiredCerts := []string{}

	if err != nil {
		log.Println(err)
		return []string{}
	}

	for _, filename := range filenames {
		certFilepath := filepath.Join("./certs/", filename.Name())

		certBtyes, err := os.ReadFile(certFilepath)
		if err != nil {
			//Unable to load this file
			continue
		} else {
			//Cert loaded. Check its expire time
			block, _ := pem.Decode(certBtyes)
			if block != nil {
				cert, err := x509.ParseCertificate(block.Bytes)
				if err == nil {
					elapsed := time.Since(cert.NotAfter)
					//approxMonths := -int(elapsed.Hours() / (24 * 30.44))
					//approxDays := -int(elapsed.Hours()/24) % 30
					if elapsed > 0 {
						//log.Println("Certificate", certFilepath, " expired")
						for _, dnsName := range cert.DNSNames {
							if !contains(expiredCerts, dnsName) {
								expiredCerts = append(expiredCerts, dnsName)
							}
						}
						if !contains(expiredCerts, cert.Subject.CommonName) {
							expiredCerts = append(expiredCerts, cert.Subject.CommonName)
						}
					} else {
						//log.Println("Certificate", certFilepath, " will still vaild for the next ", approxMonths, "m", approxDays, "d")
					}
				}
			}
		}

	}

	return expiredCerts
}

func (a *ACMEHandler) Getport() string {
	return a.port
}

func contains(slice []string, str string) bool {
	for _, s := range slice {
		if s == str {
			return true
		}
	}
	return false
}

func (a *ACMEHandler) HandleGetExpiredDomains(w http.ResponseWriter, r *http.Request) {
	type ExpiredDomains struct {
		Domain []string `json:"domain"`
	}

	info := ExpiredDomains{
		Domain: a.CheckCertificate(),
	}

	js, _ := json.MarshalIndent(info, "", " ")
	utils.SendJSONResponse(w, string(js))
}

func (a *ACMEHandler) HandleRenewCertificate(w http.ResponseWriter, r *http.Request) {
	domainPara, err := utils.GetPara(r, "domains")
	if err != nil {
		utils.SendErrorResponse(w, jsonEscape(err.Error()))
		return
	}
	filename, err := utils.GetPara(r, "filename")
	if err != nil {
		utils.SendErrorResponse(w, jsonEscape(err.Error()))
		return
	}
	domains := strings.Split(domainPara, ",")
	result, err := a.ObtainCert(domains, filename)
	if err != nil {
		utils.SendErrorResponse(w, jsonEscape(err.Error()))
		return
	}
	utils.SendJSONResponse(w, strconv.FormatBool(result))
}

func jsonEscape(i string) string {
	b, err := json.Marshal(i)
	if err != nil {
		panic(err)
	}
	s := string(b)
	return s[1 : len(s)-1]
}