Builder Pattern

// Demo Builder Pattern: data class + copy, type-safe builder with apply, idiomatic Kotlin.

// === Java-style Builder (verbose, tidak idiomatic di Kotlin) ===
class PesananBuilder {
    private var id: Int = 0
    private var pelanggan: String = ""
    private var item: MutableList<String> = mutableListOf()
    private var total: Double = 0.0

    fun id(v: Int) = apply { id = v }
    fun pelanggan(v: String) = apply { pelanggan = v }
    fun tambahItem(nama: String, harga: Double) = apply {
        item.add(nama)
        total += harga
    }
    fun build() = PesananBuilt(id, pelanggan, item.toList(), total)
}
data class PesananBuilt(val id: Int, val pelanggan: String, val item: List<String>, val total: Double)

// === Idiomatic Kotlin: data class dengan default parameter + named arguments ===
data class Pesanan(
    val id: Int,
    val pelanggan: String,
    val item: List<String> = emptyList(),
    val total: Double = 0.0
)

// === Builder dengan apply untuk konfigurasi kompleks ===
class ServerConfig {
    var host: String = "localhost"
    var port: Int = 8080
    var timeoutMs: Int = 5000
    var ssl: Boolean = false
    var maxConnection: Int = 100
    var enableCors: Boolean = false

    override fun toString() = "ServerConfig(host=$host, port=$port, timeout=${timeoutMs}ms, ssl=$ssl, maxConn=$maxConnection, cors=$enableCors)"
}

class DatabaseConfig {
    var url: String = "jdbc:h2:mem:test"
    var user: String = "sa"
    var password: String = ""
    var poolSize: Int = 10

    override fun toString() = "DatabaseConfig(url=$url, user=$user, poolSize=$poolSize)"
}

class AppConfig {
    var server: ServerConfig = ServerConfig()
        private set
    var database: DatabaseConfig = DatabaseConfig()
        private set

    fun server(block: ServerConfig.() -> Unit) = apply { server.apply(block) }
    fun database(block: DatabaseConfig.() -> Unit) = apply { database.apply(block) }

    override fun toString() = "AppConfig(\n  $server,\n  $database\n)"
}

fun main() {
    println("=== Demo Builder Pattern ===")

    println("--- 1. Java-style Builder ---")
    val p1 = PesananBuilder()
        .id(101)
        .pelanggan("Budi")
        .tambahItem("Buku", 15000.0)
        .tambahItem("Pulpen", 5000.0)
        .build()
    println(p1)

    println()
    println("--- 2. Idiomatic Kotlin: named arguments + default ---")
    val p2 = Pesanan(
        id = 102,
        pelanggan = "Siti",
        item = listOf("Penggaris", "Buku"),
        total = 20000.0
    )
    println(p2)

    println()
    println("--- 3. Builder dengan apply ---")
    val cfg = ServerConfig().apply {
        host = "production.example.com"
        port = 443
        ssl = true
        maxConnection = 1000
    }
    println(cfg)

    println()
    println("--- 4. Nested DSL-like config ---")
    val app = AppConfig()
        .server {
            host = "api.example.com"
            port = 443
            ssl = true
            enableCors = true
        }
        .database {
            url = "jdbc:postgresql://db.example.com/app"
            user = "app_user"
            poolSize = 20
        }
    println(app)
}

=== Demo Builder Pattern ===
--- 1. Java-style Builder ---
PesananBuilt(id=101, pelanggan=Budi, item=[Buku, Pulpen], total=20000.0)

--- 2. Idiomatic Kotlin: named arguments + default ---
Pesanan(id=102, pelanggan=Siti, item=[Penggaris, Buku], total=20000.0)

--- 3. Builder dengan apply ---
ServerConfig(host=production.example.com, port=443, timeout=5000ms, ssl=true, maxConn=1000, cors=false)

--- 4. Nested DSL-like config ---
AppConfig(
  ServerConfig(host=api.example.com, port=443, timeout=5000ms, ssl=true, maxConn=100, cors=true),
  DatabaseConfig(url=jdbc:postgresql://db.example.com/app, user=app_user, poolSize=20)
)