kotterresource.kt

import android.app.Activity
import android.app.Fragment
import android.support.annotation.BoolRes
import android.support.annotation.StringRes
import android.support.v4.app.DialogFragment
import kotlin.properties.ReadOnlyProperty
import kotlin.reflect.KProperty

//region Boolean
fun Activity.bindBool(@BoolRes id: Int) : ReadOnlyProperty<Activity, Boolean> =
    required(id, booleanGetter)

fun Fragment.bindBool(@BoolRes id: Int) : ReadOnlyProperty<Fragment, Boolean> =
    required(id, booleanGetter)

fun DialogFragment.bindBool(@BoolRes id: Int) : ReadOnlyProperty<DialogFragment, Boolean> =
    required(id, booleanGetter)

private val Activity.booleanGetter: Activity.(Int) -> Boolean
  get() = { resources.getBoolean(it) }
private val Fragment.booleanGetter: Fragment.(Int) -> Boolean
  get() = { resources.getBoolean(it) }
private val DialogFragment.booleanGetter: DialogFragment.(Int) -> Boolean
  get() = { resources.getBoolean(it) }
//endregion

// region String
fun Activity.bindString(@StringRes id: Int) : ReadOnlyProperty<Activity, String> =
    required(id, stringGetter)

fun Fragment.bindString(@StringRes id: Int) : ReadOnlyProperty<Fragment, String> =
    required(id, stringGetter)

fun DialogFragment.bindString(@StringRes id: Int) : ReadOnlyProperty<DialogFragment, String> =
    required(id, stringGetter)


private val Activity.stringGetter: Activity.(Int) -> String
  get() = { resources.getString(it) }
private val Fragment.stringGetter: Fragment.(Int) -> String
  get() = { resources.getString(it) }
private val DialogFragment.stringGetter: DialogFragment.(Int) -> String
  get() = { resources.getString(it) }

//endregion

//region utility
private fun <T, V> required(id: Int, getter: T.(Int) -> V)
    = Lazy { t: T, desc -> t.getter(id) ?: resourceNotFound(id, desc) }

private fun resourceNotFound(id:Int, desc: KProperty<*>): Nothing =
    throw IllegalStateException("Resource ID $id for '${desc.name}' not found.")

// Like Kotlin's lazy delegate but the initializer gets the target and metadata passed to it
// From kotterknife
private class Lazy<T, V>(private val initializer: (T, KProperty<*>) -> V) : ReadOnlyProperty<T, V> {
  private object EMPTY
  private var value: Any? = EMPTY

  override fun getValue(thisRef: T, property: KProperty<*>): V {
    if (value == EMPTY) {
      value = initializer(thisRef, property)
    }
    @Suppress("UNCHECKED_CAST")
    return value as V
  }
}
//endregion