Used flatMap(), filter() and singleOnError() for email verification

Used flatMap(), just() and singleOnError() to check length of enter text
Used retryWhen() and FlatMap() for error handling

Author: AnkitDroidGit

RxBinding/src/main/java/com/freeankit/rxbinding/MainActivity.kt

@@ -2,11 +2,91 @@ package com.freeankit.rxbinding
 
 import android.support.v7.app.AppCompatActivity
 import android.os.Bundle
+import android.util.Patterns
+import com.jakewharton.rxbinding2.widget.RxTextView
+import io.reactivex.Observable
+import io.reactivex.ObservableTransformer
+import io.reactivex.Single
+import io.reactivex.android.schedulers.AndroidSchedulers
+import kotlinx.android.synthetic.main.activity_main.*
+import java.util.concurrent.TimeUnit
 
 class MainActivity : AppCompatActivity() {
 
     override fun onCreate(savedInstanceState: Bundle?) {
         super.onCreate(savedInstanceState)
         setContentView(R.layout.activity_main)
+
+        RxTextView.afterTextChangeEvents(editTextEmail)
+                .skipInitialValue()
+                .map {
+                    emailWrapper.error = null
+                    it.view().text.toString()
+                }
+                .debounce(1, TimeUnit.SECONDS).observeOn(AndroidSchedulers.mainThread())
+                .compose(lengthGreaterThanSix)
+                .compose(verifyEmailPattern)
+                .compose(retryWhenError {
+                    emailWrapper.error = it.message
+                })
+                .subscribe()
+
+        RxTextView.afterTextChangeEvents(editTextPassword)
+                .skipInitialValue()
+                .map {
+                    passwordWrapper.error = null
+                    it.view().text.toString()
+                }
+                .debounce(1, TimeUnit.SECONDS).observeOn(AndroidSchedulers.mainThread())
+                .compose(lengthGreaterThanSix)
+                .compose(retryWhenError {
+                    passwordWrapper.error = it.message
+                })
+                .subscribe()
+    }
+    private inline fun retryWhenError(crossinline onError: (ex: Throwable) -> Unit): ObservableTransformer<String, String> = ObservableTransformer { observable ->
+        observable.retryWhen { errors ->
+            errors.flatMap {
+                onError(it)
+                Observable.just("")
+            }
+        }
+    }
+
+    private val lengthGreaterThanSix = ObservableTransformer<String, String> { observable ->
+        observable.flatMap {
+            Observable.just(it).map { it.trim() } // - abcdefg - |
+                    .filter { it.length > 6 }
+                    .singleOrError()
+                    .onErrorResumeNext {
+                        if (it is NoSuchElementException) {
+                            Single.error(Exception("Length should be greater than 6"))
+                        } else {
+                            Single.error(it)
+                        }
+                    }
+                    .toObservable()
+        }
     }
+
+    private val verifyEmailPattern = ObservableTransformer<String, String> { observable ->
+        observable.flatMap {
+            Observable.just(it).map { it.trim() }
+                    .filter {
+                        Patterns.EMAIL_ADDRESS.matcher(it).matches()
+                    }
+                    .singleOrError()
+                    .onErrorResumeNext {
+                        if (it is NoSuchElementException) {
+                            Single.error(Exception("Email not valid"))
+                        } else {
+                            Single.error(it)
+                        }
+                    }
+                    .toObservable()
+        }
+    }
+
+
+
 }