package main

import (
	"fmt"
	"log"
	mrand "math/rand"
	"net/http"
	"os"
	"path"
	"strings"
	"text/template"
	"time"

	"github.com/gorilla/mux"
	"github.com/tredoe/osutil/v2/userutil/crypt/sha512_crypt"

	"git.teamworkapps.com/shortcut/forms"
	"github.com/knadh/go-pop3"
)

// We use my forms package to create a password change form which on success executes a docker call to change the password

type tplData struct {
	Time int64
	Body string
}

func mwLog(next http.Handler) http.Handler {
	return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
		log.Printf("%s %s", r.RemoteAddr, r.URL.String())
		next.ServeHTTP(w, r)
	})
}

func main() {

	f := forms.NewForm()
	f.ContainerClasses = "relative mx-auto gap-x-16 bg-slate-100 w-full lg-w-1/2 lg:px-8 lg:pt-16"
	f.Classes = " py-2 text-indigo-300 md:px-10 lg:col-start-2 lg:row-start-1 lg:mx-auto lg:w-full lg:max-w-lg lg:bg-transparent lg:px-0 "
	f.InputClasses = " w-full mr-12 pr-12  rounded-md border-gray-300 shadow-sm focus:border-indigo-500 focus:ring-indigo-500 sm:text-sm"
	f.LabelClasses = "block text-sm font-medium text-gray-700"
	f.ErrorClasses = "text-red-800 font-bold"
	f.Autocomplete = "one-time-code"

	e := forms.NewElement()
	e.Label = "Email Address"
	e.Type = "text"
	e.Validator = "email"
	e.FailMessage = "Must be a valid email address"
	e.Name = "field1"
	f.Add(e)

	e = forms.NewElement()
	e.Label = "Old"
	e.Type = "password"
	e.Validator = ""
	e.FailMessage = "Passsword Incorrect"
	e.Name = "field2"
	f.Add(e)

	e = forms.NewElement()
	e.Label = "New"
	e.Type = "password"
	e.FailMessage = "Password must be at least 8 characters long and contain at least one uppercase letter, one lowercase letter and one digit"
	e.Validator = "minlength=8;haslowercase;hasuppercase;hasdigit"
	e.Name = "field3"
	f.Add(e)

	e = forms.NewElement()
	e.Label = "Confirm "
	e.Type = "password"
	e.FailMessage = "Passwords do not match"
	e.Validator = "mustmatch=field3"
	e.Name = "field4"
	f.Add(e)

	e = forms.NewElement()
	e.Label = "Change Password"
	e.Type = "submit"
	e.InputClasses = "flex w-full justify-center rounded-md bg-indigo-600 px-3 py-1.5 text-sm font-semibold leading-6 text-white shadow-sm hover:bg-indigo-500 focus-visible:outline focus-visible:outline-2 focus-visible:outline-offset-2 focus-visible:outline-indigo-600"
	f.Add(e)

	f.Route = "/chpass/changepassword"
	out, err := f.ToJSON()
	if err == nil {
		os.WriteFile("form.json", out, 0644)
	}

	tmpFile := "template.html"
	tmpl, err := template.New(path.Base(tmpFile)).ParseFiles(tmpFile)
	if err != nil {
		log.Fatal(err)
	}
	var d tplData

	r := mux.NewRouter()
	r.Use(mwLog)

	r.HandleFunc("/style.css", http.FileServer(http.Dir("./")).ServeHTTP)
	r.HandleFunc("/", func(w http.ResponseWriter, r *http.Request) {
		d.Body = f.Render(false)
		tmpl.Execute(w, d)
	})
	r.HandleFunc("/changepassword", func(w http.ResponseWriter, r *http.Request) {
		if f.Validate(r) != nil {
			d.Body = f.Render(true)
			tmpl.Execute(w, d)
			return
		}
		// Test if the given username ans password can authenticate via pop3
		// If so, change the password

		p := pop3.New(pop3.Opt{Host: "teamworkapps.com", Port: 995, TLSEnabled: true})

		c, err := p.NewConn()
		if err != nil {
			log.Println(err)
			d.Body = "Internal error"
			tmpl.Execute(w, d)
			return
		}
		defer c.Quit()

		// Authenticate.
		if err := c.Auth(f.GetValue("field1"), f.GetValue("field2")); err != nil {
			f.MakeInvalid("theoldpassword", "Invalid password")
			d.Body = f.Render(true)
			tmpl.Execute(w, d)
			return
		}
		// Change the password
		if !modifyPasswordFile(f.GetValue("field1"), f.GetValue("field3")) {
			log.Println(err)
			d.Body = "Internal error"
			tmpl.Execute(w, d)
			return
		}
		d.Body = "Password changed. You will need to login again."
		tmpl.Execute(w, d)
	})
	d.Time = time.Now().Unix()
	d.Body = f.Render(true)
	tmpl.Execute(os.Stdout, d)
	http.ListenAndServe("127.0.0.1:8910", r)
}

/*
example password entry:
recreation@pinnaclelake.com|{SHA512-CRYPT}$6$uTiy7Q5xn1CIN22w$3VAElns3TFfejtdTCTJMcz8k2UPPwAmlUIoXC4NgPJRnDcgo3CnI91EsB6irgwuecCrolxAx7i4mjvTxPaAlf0

*/

// createPasswordEntry: input email and plain text password, output a password entry with sha512-crypt.

func modifyPasswordFile(email, password string) bool {
	email = strings.ToLower(email)
	log.Printf("Changing password for %s", email)
	// read the password file
	// find the entry with the given email
	// replace the password with the new password
	// write the file back
	in, err := os.ReadFile("/root/docker/mail/config/postfix-accounts.cf")
	if err != nil {
		log.Println(err)
		return false
	}
	out, err := os.Create("/root/docker/mail/config/postfix-accounts.cf.tmp")
	if err != nil {
		log.Println(err)
		return false
	}

	lines := strings.Split(string(in), "\n")
	for _, line := range lines {
		tmp := strings.Split(line, "|")
		if len(tmp) != 2 {
			continue
		}
		if tmp[0] == email {
			line = createPasswordEntry(email, password)
		}
		out.WriteString(line)
		out.WriteString("\n")
	}
	out.Close()
	os.Rename("/root/docker/mail/config/postfix-accounts.cf", "/root/docker/mail/config/postfix-accounts.cf.old")
	os.Rename("/root/docker/mail/config/postfix-accounts.cf.tmp", "/root/docker/mail/config/postfix-accounts.cf")
	log.Println("Successfully changed password")
	return true
}

func createPasswordEntry(email, password string) string {
	salt := RandStringBytesMaskImprSrc(16)

	c := sha512_crypt.New()
	hash, err := c.Generate([]byte(password), []byte("$6$"+salt))
	if err != nil {
		log.Println(err)
		return ""
	}

	return fmt.Sprintf("%s|{SHA512-CRYPT}%s", email, hash)
}

const letterBytes = "abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ"
const (
	letterIdxBits = 6                    // 6 bits to represent a letter index
	letterIdxMask = 1<<letterIdxBits - 1 // All 1-bits, as many as letterIdxBits
	letterIdxMax  = 63 / letterIdxBits   // # of letter indices fitting in 63 bits
)

// http://stackoverflow.com/questions/22892120/how-to-generate-a-random-string-of-a-fixed-length-in-golang
func RandStringBytesMaskImprSrc(n int) string {
	var src = mrand.NewSource(time.Now().UnixNano())
	b := make([]byte, n)
	// A src.Int63() generates 63 random bits, enough for letterIdxMax characters!
	for i, cache, remain := n-1, src.Int63(), letterIdxMax; i >= 0; {
		if remain == 0 {
			cache, remain = src.Int63(), letterIdxMax
		}
		if idx := int(cache & letterIdxMask); idx < len(letterBytes) {
			b[i] = letterBytes[idx]
			i--
		}
		cache >>= letterIdxBits
		remain--
	}

	return string(b)
}