check register..just playing around

main.kt

fun main(){
    val user = User().apply {
        val account = Account("Capital One", 12345)
        createAccount(account)
        val cocaCola = Vendor("Coca Cola")
        createVendor(cocaCola)
        val beverages = Category("beverages")
        createCategory(beverages)
        writeCheck(account, 1, cocaCola, beverages, 113.30)
    }
    user.checks.forEach { println(it) }
}

data class Category(val name: String)

data class Account(val name: String, val id: Int){
    private val _checkRegister = CheckRegister()
    val checks: List<Check>
        get() = _checkRegister.checks

    fun addCheck(check: Check) = _checkRegister.checks.add(check)

    fun removeCheck(check: Check) = _checkRegister.checks.remove(check)
}

data class User(
    private val _accounts: MutableList<Account> = mutableListOf(),
    private val _vendors: MutableList<Vendor> = mutableListOf(),
    private val _categories: MutableList<Category> = mutableListOf()
){
    val checks: List<Check>
        get(){
            return mutableListOf<Check>().apply {
                _accounts.forEach { addAll(it.checks) }
            }
        }

    fun createAccount(vararg account: Account) = account.forEach { _accounts.add(it) }

    fun writeCheck(account: Account, id: Int, vendor: Vendor, category: Category, amount: Double){
        val newCheck = Check(id, vendor, category, amount, System.currentTimeMillis())
        this._accounts.first { it.equals(account) }.addCheck(newCheck)
    }

    fun createCategory(vararg category: Category) = category.forEach { _categories.add(it) }

    fun createVendor(vararg vendor: Vendor) = vendor.forEach { _vendors.add(it) }
}

@JvmInline
value class CheckRegister(val checks: MutableList<Check> = mutableListOf())

data class Check(
    val id: Int,
    val vendor: Vendor,
    val category: Category,
    val amount: Double,
    val date: Long
)

data class Vendor(val name: String)