Fix parsing of keys that are prefix of others. (#58)

The ESC key generates sequences that are prefix of others. For instance:
- ESC => [27]
- F1 =>  [27, 79, 8]

As a result, we can't generate the ESC event when receiving [27],
because it might be the start of the [27, 79, 8] sequence (or not).

Application usually applies a timeout to help detecting the ESC key.
This patch introduce a timeout. It is set to 50ms.

Bug: https://github.com/ArthurSonzogni/FTXUI/issues/55

src/ftxui/component/terminal_input_parser_test.cpp

@@ -0,0 +1,71 @@
+#include "ftxui/component/terminal_input_parser.hpp"
+#include "ftxui/component/receiver.hpp"
+
+#include "gtest/gtest.h"
+
+using namespace ftxui;
+
+// Test char |c| to are trivially converted into |Event::Character(c)|.
+TEST(Event, Character) {
+  std::vector<char> basic_char;
+  for (char c = 'a'; c <= 'z'; ++c)
+    basic_char.push_back(c);
+  for (char c = 'A'; c <= 'Z'; ++c)
+    basic_char.push_back(c);
+
+  auto event_receiver = MakeReceiver<Event>();
+  {
+    auto parser = TerminalInputParser(event_receiver->MakeSender());
+    for (char c : basic_char)
+      parser.Add(c);
+  }
+
+  Event received;
+  for (char c : basic_char) {
+    EXPECT_TRUE(event_receiver->Receive(&received));
+    EXPECT_TRUE(received.is_character());
+    EXPECT_EQ(c, received.character());
+  }
+  EXPECT_FALSE(event_receiver->Receive(&received));
+}
+
+TEST(Event, EscapeKeyWithoutWaiting) {
+  auto event_receiver = MakeReceiver<Event>();
+  {
+    auto parser = TerminalInputParser(event_receiver->MakeSender());
+    parser.Add('\x1B');
+  }
+
+  Event received;
+  EXPECT_FALSE(event_receiver->Receive(&received));
+}
+
+TEST(Event, EscapeKeyNotEnoughWait) {
+  auto event_receiver = MakeReceiver<Event>();
+  {
+    auto parser = TerminalInputParser(event_receiver->MakeSender());
+    parser.Add('\x1B');
+    parser.Timeout(49);
+  }
+
+  Event received;
+  EXPECT_FALSE(event_receiver->Receive(&received));
+}
+
+TEST(Event, EscapeKeyEnoughWait) {
+  auto event_receiver = MakeReceiver<Event>();
+  {
+    auto parser = TerminalInputParser(event_receiver->MakeSender());
+    parser.Add('\x1B');
+    parser.Timeout(50);
+  }
+
+  Event received;
+  EXPECT_TRUE(event_receiver->Receive(&received));
+  EXPECT_EQ(received, Event::Escape);
+  EXPECT_FALSE(event_receiver->Receive(&received));
+}
+
+// Copyright 2020 Arthur Sonzogni. All rights reserved.
+// Use of this source code is governed by the MIT license that can be found in
+// the LICENSE file.