BundleDelegates.kt

import android.os.Bundle
import kotlin.properties.ReadOnlyProperty
import kotlin.properties.ReadWriteProperty
import android.app.Fragment
import android.support.v4.app.Fragment as SupportFragment
import kotlin.properties.Delegates

public fun bundledBoolean(bundle: Bundle, key: String, default: Boolean = false): ReadWriteProperty<Any, Boolean> = bundleVar({ bundle }, key, default)
public fun bundledString(bundle: Bundle, key: String, default: String = ""): ReadWriteProperty<Any, String> = bundleVar({ bundle }, key, default)
public fun bundledInt(bundle: Bundle, key: String, default: Int = 0): ReadWriteProperty<Any, Int> = bundleVar({ bundle }, key, default)

public fun Fragment.booleanArgument(key: String, default: Boolean = false): ReadOnlyProperty<Any, Boolean> = bundleVal({ this.getArguments() }, key, default)
public fun Fragment.stringArgument(key: String, default: String = ""): ReadOnlyProperty<Any, String> = bundleVal({ this.getArguments() }, key, default)
public fun Fragment.intArgument(key: String, default: Int = 0): ReadOnlyProperty<Any, Int> = bundleVal({ this.getArguments() }, key, default)

public fun SupportFragment.booleanArgument(key: String, default: Boolean = false): ReadOnlyProperty<Any, Boolean> = bundleVal({ this.getArguments() }, key, default)
public fun SupportFragment.stringArgument(key: String, default: String = ""): ReadOnlyProperty<Any, String> = bundleVal({ this.getArguments() }, key, default)
public fun SupportFragment.intArgument(key: String, default: Int = 0): ReadOnlyProperty<Any, Int> = bundleVal({ this.getArguments() }, key, default)

private fun bundleVal(b: () -> Bundle, k: String, d: Boolean): ReadOnlyProperty<Any, Boolean> = BundleVal(b, k, d, { getBoolean(k) })
private fun bundleVar(b: () -> Bundle, k: String, d: Boolean): ReadWriteProperty<Any, Boolean> = BundleVar(b, k, d, { getBoolean(k) }, { v -> putBoolean(k, v) })
private fun bundleVal(b: () -> Bundle, k: String, d: String): ReadOnlyProperty<Any, String> = BundleVal(b, k, d, { getString(k) })
private fun bundleVar(b: () -> Bundle, k: String, d: String): ReadWriteProperty<Any, String> = BundleVar(b, k, d, { getString(k) }, { v -> putString(k, v) })
private fun bundleVal(b: () -> Bundle, k: String, d: Int): ReadOnlyProperty<Any, Int> = BundleVal(b, k, d, { getInt(k) })
private fun bundleVar(b: () -> Bundle, k: String, d: Int): ReadWriteProperty<Any, Int> = BundleVar(b, k, d, { getInt(k) }, { v -> putInt(k, v) })

private class BundleVal<T>(val bundleSource: () -> Bundle,
                           val key: String,
                           val default: T,
                           val read: Bundle.() -> T) : ReadOnlyProperty<Any, T> {
  val bundle: Bundle by Delegates.lazy { bundleSource() }

  override fun get(thisRef: Any, desc: PropertyMetadata): T =
      if (bundle.containsKey(key)) bundle.read()
      else default
}

private class BundleVar<T>(val bundleSource: () -> Bundle,
                           val key: String,
                           val default: T,
                           val read: Bundle.() -> T,
                           val write: Bundle.(v: T) -> Unit) : ReadWriteProperty<Any, T> {
  val bundle: Bundle by Delegates.lazy { bundleSource() }

  override fun set(thisRef: Any, desc: PropertyMetadata, value: T) = bundle.write(value)
  override fun get(thisRef: Any, desc: PropertyMetadata): T =
      if (bundle.containsKey(key)) bundle.read()
      else default
}