Replace Either with Kotlin Result and optimize ListUtils (#4443)

Using `Either<Throwable, T>` is basically the same as `Result<T>` with a
less friendly API. Futhermore, `Either` is currently only used in a
single component.

- Replace `Either` with `Result` in `AccountsInListFragment` and
`AccountsInListViewModel`.
- Add a method to convert a `NetworkResult` to a `Result` in
`AccountsInListViewModel`. Alternatively, `NetworkResult` could be used
everywhere in the code but other classes are already using `Result`.
- Replace `updateState()` method with `MutableStateFlow.update()` in
`AccountsInListViewModel`.
- Store the current search query in a `MutableStateFlow` collected by a
coroutine. This allows automatically cancelling the previous search when
a new query arrives, instead of launching a new coroutine for each query
which may conflict with the previous ones.
- Optimize `ListUtils`.

app/src/main/java/com/keylesspalace/tusky/util/Either.kt

@@ -1,49 +0,0 @@
-/* Copyright 2017 Andrew Dawson
- *
- * This file is a part of Tusky.
- *
- * This program is free software; you can redistribute it and/or modify it under the terms of the
- * GNU General Public License as published by the Free Software Foundation; either version 3 of the
- * License, or (at your option) any later version.
- *
- * Tusky is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even
- * the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General
- * Public License for more details.
- *
- * You should have received a copy of the GNU General Public License along with Tusky; if not,
- * see <http://www.gnu.org/licenses>. */
-
-package com.keylesspalace.tusky.util
-
-/**
- * Created by charlag on 05/11/17.
- *
- * Class to represent sum type/tagged union/variant/ADT e.t.c.
- * It is either Left or Right.
- */
-sealed interface Either<out L, out R> {
-    data class Left<out L, out R>(val value: L) : Either<L, R>
-    data class Right<out L, out R>(val value: R) : Either<L, R>
-
-    fun isRight(): Boolean = this is Right
-
-    fun isLeft(): Boolean = this is Left
-
-    fun asLeftOrNull(): L? = (this as? Left<L, R>)?.value
-
-    fun asRightOrNull(): R? = (this as? Right<L, R>)?.value
-
-    fun asLeft(): L = (this as Left<L, R>).value
-
-    fun asRight(): R = (this as Right<L, R>).value
-
-    companion object {
-        inline fun <L, R, N> Either<L, R>.map(mapper: (R) -> N): Either<L, N> {
-            return if (this.isLeft()) {
-                Left(this.asLeft())
-            } else {
-                Right(mapper(this.asRight()))
-            }
-        }
-    }
-}

app/src/main/java/com/keylesspalace/tusky/util/ListUtils.kt

@@ -17,31 +17,36 @@
 
 package com.keylesspalace.tusky.util
 
-import java.util.ArrayList
-import java.util.LinkedHashSet
+/**
+ * Copies elements to destination, removing duplicates and preserving original order.
+ */
+fun <T, C : MutableCollection<in T>> Iterable<T>.removeDuplicatesTo(destination: C): C {
+    return filterTo(destination, HashSet<T>()::add)
+}
 
 /**
- * @return a new ArrayList containing the elements without duplicates in the same order
+ * Copies elements to a new list, removing duplicates and preserving original order.
  */
-fun <T> removeDuplicates(list: List<T>): ArrayList<T> {
-    val set = LinkedHashSet(list)
-    return ArrayList(set)
+fun <T> Iterable<T>.removeDuplicates(): List<T> {
+    return removeDuplicatesTo(ArrayList())
 }
 
 inline fun <T> List<T>.withoutFirstWhich(predicate: (T) -> Boolean): List<T> {
-    val newList = toMutableList()
-    val index = newList.indexOfFirst(predicate)
-    if (index != -1) {
-        newList.removeAt(index)
+    val index = indexOfFirst(predicate)
+    if (index == -1) {
+        return this
     }
+    val newList = toMutableList()
+    newList.removeAt(index)
     return newList
 }
 
 inline fun <T> List<T>.replacedFirstWhich(replacement: T, predicate: (T) -> Boolean): List<T> {
-    val newList = toMutableList()
-    val index = newList.indexOfFirst(predicate)
-    if (index != -1) {
-        newList[index] = replacement
+    val index = indexOfFirst(predicate)
+    if (index == -1) {
+        return this
     }
+    val newList = toMutableList()
+    newList[index] = replacement
     return newList
 }