SmartField.kt

import android.text.Editable
import android.text.TextWatcher
import android.view.View
import android.widget.EditText

/**
 * Created by Konstantin Tskhovrebov (aka @terrakok) on 18.09.17.
 */
class SmartField<T: Any>(
        private val editText: EditText,
        defaultValue: T,
        private val formatter: (T) -> String,
        private val extractor: (String) -> T,
        private val changeListener: (T) -> Unit,
        private val isLiveUpdate: Boolean = false
) {
    val currentValue get() = extractor(editText.text.toString())

    private val watcher = object : TextWatcher {
        private var v = ""

        override fun beforeTextChanged(p0: CharSequence?, p1: Int, p2: Int, p3: Int) {
            v = editText.text.toString()
        }

        override fun onTextChanged(p0: CharSequence?, p1: Int, p2: Int, p3: Int) { }

        override fun afterTextChanged(p0: Editable?) {
            val newVal = extractor(editText.text.toString())
            if (isLiveUpdate && extractor(v) != newVal) {
                changeListener(newVal)
            }
        }
    }

    init {
        editText.setText(formatter(defaultValue))
        if (!isLiveUpdate) {
            editText.onFocusChangeListener = View.OnFocusChangeListener { view, focus ->
                if (!focus) changeListener(extractor(editText.text.toString()))
            }
        }
        enableWatcher()
    }

    fun setValue(value: T) {
        disableWatcher()
        with(formatter(value)) {
            editText.setText(this)
            editText.setSelection(this.length)
        }
        enableWatcher()
    }

    private fun enableWatcher() = editText.addTextChangedListener(watcher)
    private fun disableWatcher() = editText.removeTextChangedListener(watcher)
}