From 6f0e82fb7d25ba0e0a99c7affb6f18b5555473bc Mon Sep 17 00:00:00 2001
From: Igor Kashkuta <xrazont@gmail.com>
Date: Wed, 6 Jul 2016 11:16:51 +0100
Subject: [PATCH] Fix jolty transitions between input items. (#174)

---
 .../Source/Input/ChatInputBarPresenter.swift  | 57 ++++++++++++++++++-
 1 file changed, 55 insertions(+), 2 deletions(-)

diff --git a/ChattoAdditions/Source/Input/ChatInputBarPresenter.swift b/ChattoAdditions/Source/Input/ChatInputBarPresenter.swift
index dee4133..aa1103a 100644
--- a/ChattoAdditions/Source/Input/ChatInputBarPresenter.swift
+++ b/ChattoAdditions/Source/Input/ChatInputBarPresenter.swift
@@ -35,15 +35,27 @@ protocol ChatInputBarPresenter: class {
 @objc public class BasicChatInputBarPresenter: NSObject, ChatInputBarPresenter {
     let chatInputBar: ChatInputBar
     let chatInputItems: [ChatInputItemProtocol]
+    let notificationCenter: NSNotificationCenter
 
-    public init(chatInputBar: ChatInputBar, chatInputItems: [ChatInputItemProtocol], chatInputBarAppearance: ChatInputBarAppearance) {
+    public init(chatInputBar: ChatInputBar,
+                chatInputItems: [ChatInputItemProtocol],
+                chatInputBarAppearance: ChatInputBarAppearance,
+                notificationCenter: NSNotificationCenter = NSNotificationCenter.defaultCenter()) {
         self.chatInputBar = chatInputBar
         self.chatInputItems = chatInputItems
         self.chatInputBar.setAppearance(chatInputBarAppearance)
+        self.notificationCenter = notificationCenter
         super.init()
 
         self.chatInputBar.presenter = self
         self.chatInputBar.inputItems = self.chatInputItems
+        self.notificationCenter.addObserver(self, selector: #selector(BasicChatInputBarPresenter.keyboardDidChangeFrame), name: UIKeyboardDidChangeFrameNotification, object: nil)
+        self.notificationCenter.addObserver(self, selector: #selector(BasicChatInputBarPresenter.keyboardWillHide), name: UIKeyboardWillHideNotification, object: nil)
+        self.notificationCenter.addObserver(self, selector: #selector(BasicChatInputBarPresenter.keyboardWillShow), name: UIKeyboardWillShowNotification, object: nil)
+    }
+
+    deinit {
+        self.notificationCenter.removeObserver(self)
     }
 
     private(set) var focusedItem: ChatInputItemProtocol? {
@@ -57,8 +69,10 @@ protocol ChatInputBarPresenter: class {
 
     private func updateFirstResponderWithInputItem(inputItem: ChatInputItemProtocol) {
         let responder = self.chatInputBar.textView
-        responder.inputView = inputItem.inputView
+        let inputView = inputItem.inputView
+        responder.inputView = inputView
         if responder.isFirstResponder() {
+            self.setHeight(forInputView: inputView)
             responder.reloadInputViews()
         } else {
             responder.becomeFirstResponder()
@@ -75,6 +89,45 @@ protocol ChatInputBarPresenter: class {
         }
         return firstKeyboardInputItem
     }
+
+    private var lastKnownKeyboardHeight: CGFloat?
+
+    private func setHeight(forInputView inputView: UIView?) {
+        guard let inputView = inputView else { return }
+        guard let keyboardHeight = self.lastKnownKeyboardHeight else { return }
+
+        var mask = inputView.autoresizingMask
+        mask.remove(.FlexibleHeight)
+        inputView.autoresizingMask = mask
+
+        let accessoryViewHeight = self.chatInputBar.textView.inputAccessoryView?.bounds.height ?? 0
+        let inputViewHeight = keyboardHeight - accessoryViewHeight
+
+        if let heightConstraint = inputView.constraints.filter({ $0.firstAttribute == .Height }).first {
+            heightConstraint.constant = inputViewHeight
+        } else {
+            inputView.frame.size.height = inputViewHeight
+        }
+    }
+
+    private var allowListenToChangeFrameEvents = true
+
+    @objc
+    private func keyboardDidChangeFrame(notification: NSNotification) {
+        guard self.allowListenToChangeFrameEvents else { return }
+        guard let value = notification.userInfo?[UIKeyboardFrameEndUserInfoKey] as? NSValue else { return }
+        self.lastKnownKeyboardHeight = value.CGRectValue().height
+    }
+
+    @objc
+    private func keyboardWillHide(notification: NSNotification) {
+        self.allowListenToChangeFrameEvents = false
+    }
+
+    @objc
+    private func keyboardWillShow(notification: NSNotification) {
+        self.allowListenToChangeFrameEvents = true
+    }
 }
 
 // MARK: ChatInputBarPresenter