Adapter Pattern

// Demo Adapter Pattern: wraps incompatible interface; extension function as adapter.

// === Target interface yang diharapkan klien ===
interface LoggerModern {
    fun log(level: String, message: String)
    fun error(message: String) = log("ERROR", message)
    fun info(message: String) = log("INFO", message)
    fun warn(message: String) = log("WARN", message)
}

// === Adaptee: library lama dengan interface berbeda ===
class LegacyLogger {
    fun writeLog(priority: Int, message: String) {
        val level = when (priority) {
            1 -> "INFO"
            2 -> "WARN"
            3 -> "ERROR"
            else -> "UNKNOWN"
        }
        println("[legacy] $level: $message")
    }
}

// === Adapter: class yang mengimplementasi Target dan membungkus Adaptee ===
class LegacyLoggerAdapter(private val legacy: LegacyLogger) : LoggerModern {
    override fun log(level: String, message: String) {
        val priority = when (level.uppercase()) {
            "INFO" -> 1
            "WARN" -> 2
            "ERROR" -> 3
            else -> 0
        }
        legacy.writeLog(priority, message)
    }
}

// === Extension function as adapter (idiomatic Kotlin) ===
fun LegacyLogger.logModern(level: String, message: String) {
    val priority = when (level.uppercase()) {
        "INFO" -> 1
        "WARN" -> 2
        "ERROR" -> 3
        else -> 0
    }
    writeLog(priority, message)
}

// === Adapter untuk collection: List<Int> -> JSON array string ===
class ListToJsonAdapter(private val list: List<Int>) {
    fun toJson(): String = "[" + list.joinToString(",") + "]"
}

// === Adapter untuk Map<String, Any> -> data class instance ===
data class Pengguna(val id: Int, val nama: String, val email: String)

class MapToPenggunaAdapter(private val map: Map<String, Any>) {
    fun toPengguna(): Pengguna {
        @Suppress("UNCHECKED_CAST")
        return Pengguna(
            id = (map["id"] as Number).toInt(),
            nama = map["nama"] as String,
            email = map["email"] as String
        )
    }
}

// === Adapter untuk third-party JSON library (simulated) ===
// Misalkan kita punya library JSON yang mengembalikan String, padahal kita butuh Map
class JsonStringAdapter(private val json: String) {
    // Parser sangat sederhana untuk JSON seperti {"id":1,"nama":"Budi","email":"[email protected]"}
    fun toMap(): Map<String, Any> {
        val body = json.trim().removeSurrounding("{", "}")
        return body.split(",").associate { pair ->
            val (k, v) = pair.split(":", limit = 2)
            val key = k.trim().trim('"')
            val rawVal = v.trim()
            val value: Any = if (rawVal.startsWith("\"")) rawVal.trim('"')
            else rawVal.toIntOrNull() ?: rawVal
            key to value
        }
    }
}

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

    println("--- 1. Class Adapter (LegacyLogger -> LoggerModern) ---")
    val modern: LoggerModern = LegacyLoggerAdapter(LegacyLogger())
    modern.info("Aplikasi dimulai")
    modern.error("Koneksi gagal")
    modern.warn("Stok menipis")

    println()
    println("--- 2. Extension function as adapter ---")
    val legacy = LegacyLogger()
    legacy.logModern("INFO", "via extension function")
    legacy.logModern("ERROR", "via extension function")

    println()
    println("--- 3. List -> JSON ---")
    val daftar = listOf(1, 2, 3, 4, 5)
    val json = ListToJsonAdapter(daftar).toJson()
    println("List: $daftar -> JSON: $json")

    println()
    println("--- 4. Map -> data class ---")
    val map = mapOf("id" to 1, "nama" to "Budi", "email" to "[email protected]")
    val pengguna = MapToPenggunaAdapter(map).toPengguna()
    println("Map: $map -> Pengguna: $pengguna")

    println()
    println("--- 5. JSON string -> Map -> data class ---")
    val jsonString = """{"id":42,"nama":"Siti","email":"[email protected]"}"""
    val parsed = JsonStringAdapter(jsonString).toMap()
    println("JSON: $jsonString")
    println("Map: $parsed")
    val p = MapToPenggunaAdapter(parsed).toPengguna()
    println("Pengguna: $p")
}

=== Demo Adapter Pattern ===
--- 1. Class Adapter (LegacyLogger -> LoggerModern) ---
[legacy] INFO: Aplikasi dimulai
[legacy] ERROR: Koneksi gagal
[legacy] WARN: Stok menipis

--- 2. Extension function as adapter ---
[legacy] INFO: via extension function
[legacy] ERROR: via extension function

--- 3. List -> JSON ---
List: [1, 2, 3, 4, 5] -> JSON: [1,2,3,4,5]

--- 4. Map -> data class ---
Map: {id=1, nama=Budi, [email protected]} -> Pengguna: Pengguna(id=1, nama=Budi, [email protected])

--- 5. JSON string -> Map -> data class ---
JSON: {"id":42,"nama":"Siti","email":"[email protected]"}
Map: {id=42, nama=Siti, [email protected]}
Pengguna: Pengguna(id=42, nama=Siti, [email protected])