AbstractUser.kt

package com.erezbiox1

import java.nio.charset.StandardCharsets
import java.security.MessageDigest
import java.sql.DriverManager
import java.sql.ResultSet
import java.util.*
import kotlin.reflect.KProperty

@Suppress("NullableBooleanElvis", "unused", "MemberVisibilityCanPrivate")

/**
 * Created by Erezbiox1 on 30/11/2017.
 * (C) 2017 Erez Rotem All Rights Reserved.
 */

abstract class AbstractUser(val id: Int) {

    var username: String by SQL()
    var email: String by SQL()
    var password: String
        get() = error("Cannot access hashed password")
        set(pass) = sql("UPDATE users SET password = ?", hash(password))

    companion object {
        fun sql(query: String, vararg objects: Any, function: ((ResultSet?) -> Unit)? = null) {
            Class.forName("com.mysql.jdbc.Driver")

            val db = DriverManager.getConnection("jdbc:mysql://localhost:3306/main", "erez", "Pizza123")
            val statement = db.prepareStatement(query)
            objects.withIndex().forEach {
                when(it.value){
                    is Int -> statement.setInt(it.index + 1, it.value as Int)
                    is Boolean -> statement.setBoolean(it.index + 1, it.value as Boolean)
                    else -> statement.setString(it.index + 1, it.value.toString())
                }
            }
            val result =
                    if(statement.execute() && statement.resultSet.next())
                        statement.resultSet
                    else null

            function?.invoke(result)

            result?.close()
            statement.close()
            db.close()
        }

        inline fun <reified T> ResultSet?.get(column: Int = 1) : T? {
            if(this == null)
                return null

            return when(T::class){
                java.lang.Integer::class -> this.getInt(column) as T
                java.lang.Integer::class.java -> this.getInt(column) as T
                java.lang.Boolean::class -> this.getBoolean(column) as T
                java.lang.Boolean::class.java -> this.getBoolean(column) as T
                else -> this.getString(column) as T
            }
        }

        private fun createHash(password: String) : String {
            val random = UUID.randomUUID().toString()
            return random + ":" + hash(random + password)
        }

        private fun matchHash(password: String, hash: String) : Boolean {
            val split = hash.split(":")
            val salt = split[0]
            val hashed = split[1]
            return hash(salt + password) == hashed
        }

        private fun hash(password: String): String {
            return Base64.getEncoder().encodeToString(MessageDigest.getInstance("SHA-256").digest(password.toByteArray(StandardCharsets.UTF_8)))
        }

        @JvmStatic
        protected fun registerUser(username: String, email: String, password: String) : Int {
            var userId = -1
            sql("SELECT id, password FROM users WHERE username = ?", username.toLowerCase()){
                val pass = it?.get<String>(2)
                if(pass != null){
                    userId =
                            if(hash(password.toLowerCase()) == pass)
                                it.get(1)!!
                            else -2
                }

            }

            if(userId == -1){
                sql("INSERT INTO users (username, email, password) VALUES (?, ?, ?)",
                        username.toLowerCase(),
                        email.toLowerCase(),
                        createHash(password.toLowerCase()))

                sql("SELECT id FROM users WHERE username = ?", username.toLowerCase()){
                    userId = it?.get() ?: -1 // Cannot really be -1, but what the heck.
                }
            }

            return userId
        }

        @JvmStatic
        protected fun loginUser(username: String, password: String) : Int {
            var userId = -1
            sql("SELECT id, password FROM users WHERE username = ?", username.toLowerCase()){
                val pass = it?.get<String>(2)
                if(pass != null)
                    userId = if(matchHash(password.toLowerCase(), pass))
                        it.get(1) ?: -1
                    else -2
            }
            return userId
        }
    }

    inner class SQL(val name: String? = null) {
        inline operator fun <reified T> getValue(ref: Any?, property: KProperty<*>) : T {
            var value: T? = null
            sql("SELECT ${name ?: property.name} FROM users where id = ?", id){
                value = it.get()
            }
            return value ?: error("Database Connection Error. value is null.")
        }

        operator fun <T> setValue(ref: Any?, property: KProperty<*>, value: T) {
            sql("UPDATE users SET ${name ?: property.name} = ? WHERE id = ?", value!!, id)
        }
    }
}