package main

import (
  "fmt"
  "strings"
  "gopkg.in/ldap.v2"
)

const (
  ldapServer = "ad.example.com:389"
  ldapBind = "search@example.com"
  ldapPassword = "Password123!"

  filterDN = "(&(objectClass=person)(memberOf:1.2.840.113556.1.4.1941:=CN=Chat,CN=Users,DC=example,DC=com)(|(sAMAccountName={username})(mail={username})))"
  baseDN = "CN=Users,DC=example,DC=com"

  loginUsername = "tboerger"
  loginPassword = "password"
)

func main() {
  conn, err := connect()

  if err != nil {
    fmt.Printf("Failed to connect. %s", err)
    return
  }

  defer conn.Close()

  if err := list(conn); err != nil {
    fmt.Printf("%v", err)
    return
  }

  if err := auth(conn); err != nil {
    fmt.Printf("%v", err)
    return
  }
}

func connect() (*ldap.Conn, error) {
  conn, err := ldap.Dial("tcp", ldapServer)

  if err != nil {
    return nil, fmt.Errorf("Failed to connect. %s", err)
  }

  if err := conn.Bind(ldapBind, ldapPassword); err != nil {
    return nil, fmt.Errorf("Failed to bind. %s", err)
  }

  return conn, nil
}

func list(conn *ldap.Conn) error {
  result, err := conn.Search(ldap.NewSearchRequest(
    baseDN,
    ldap.ScopeWholeSubtree,
    ldap.NeverDerefAliases,
    0,
    0,
    false,
    filter("*"),
    []string{"dn", "sAMAccountName", "mail", "sn", "givenName"},
    nil,
  ))

  if err != nil {
    return fmt.Errorf("Failed to search users. %s", err)
  }

  for _, entry := range result.Entries {
    fmt.Printf(
      "%s: %s %s -- %v -- %v\n",
      entry.DN,
      entry.GetAttributeValue("givenName"),
      entry.GetAttributeValue("sn"),
      entry.GetAttributeValue("sAMAccountName"),
      entry.GetAttributeValue("mail"),
    )
  }

  return nil
}

func auth(conn *ldap.Conn) error {
  result, err := conn.Search(ldap.NewSearchRequest(
    baseDN,
    ldap.ScopeWholeSubtree,
    ldap.NeverDerefAliases,
    0,
    0,
    false,
    filter(loginUsername),
    []string{"dn"},
    nil,
  ))

  if err != nil {
    return fmt.Errorf("Failed to find user. %s", err)
  }

  if len(result.Entries) < 1 {
    return fmt.Errorf("User does not exist")
  }

  if len(result.Entries) > 1 {
    return fmt.Errorf("Too many entries returned")
  }

  if err := conn.Bind(result.Entries[0].DN, loginPassword); err != nil {
    fmt.Printf("Failed to auth. %s", err)
  } else {
    fmt.Printf("Authenticated successfuly!")
  }

  return nil
}

func filter(needle string) string {
  res := strings.Replace(
    filterDN,
    "{username}",
    needle,
    -1,
  )

  return res
}