using Blacklight.Core.Keyboard;

namespace Blacklight.Core.UnitTests.Keyboard
{
    public class CharAssemblerTests : UnitTestSharp.TestFixture
    {
        public static readonly char HighSurrogate = '\uD842';
        public static readonly char LowSurrogate = '\uDFB7';

        public class AddTests : UnitTestSharp.TestFixture
        {
            public void PlainCharacter_IsReturnedAsText()
            {
                CheckEqual("a", new CharAssembler().Add('a'));
            }

            public void Space_IsText()
            {
                CheckEqual(" ", new CharAssembler().Add(' '));
            }

            public void CharacterOutsideAscii_IsText()
            {
                string text = char.ConvertFromUtf32(0x65E5);

                CheckEqual(text, new CharAssembler().Add(text[0]));
            }

            public void ControlCharacters_AreDropped()
            {
                var assembler = new CharAssembler();

                foreach (char control in new[] { '\0', '\b', '\t', '\r', '\n', (char)0x1A, (char)0x1B, (char)0x7F })
                {
                    CheckNull(assembler.Add(control));
                }
            }

            public void LatinOneControlCharacters_AreDropped()
            {
                CheckNull(new CharAssembler().Add((char)0x85));
            }

            public void SurrogatePair_IsJoinedOnTheSecondHalf()
            {
                var assembler = new CharAssembler();

                CheckNull(assembler.Add(HighSurrogate));
                CheckEqual(char.ConvertFromUtf32(0x20BB7), assembler.Add(LowSurrogate));
            }

            public void CompletedPair_LeavesNothingBehind()
            {
                var assembler = new CharAssembler();
                assembler.Add(HighSurrogate);
                assembler.Add(LowSurrogate);

                CheckNull(assembler.Add(LowSurrogate));
                CheckEqual("a", assembler.Add('a'));
            }

            public void LoneLowSurrogate_IsDropped()
            {
                CheckNull(new CharAssembler().Add(LowSurrogate));
            }

            public void HighSurrogateFollowedByAPlainCharacter_DropsTheHighSurrogate()
            {
                var assembler = new CharAssembler();
                assembler.Add(HighSurrogate);

                CheckEqual("a", assembler.Add('a'));
                CheckNull(assembler.Add(LowSurrogate));
            }

            public void HighSurrogateFollowedByAControlCharacter_DropsBoth()
            {
                var assembler = new CharAssembler();
                assembler.Add(HighSurrogate);

                CheckNull(assembler.Add('\r'));
                CheckNull(assembler.Add(LowSurrogate));
            }

            public void HighSurrogateFollowedByAnother_KeepsTheLater()
            {
                var assembler = new CharAssembler();
                assembler.Add((char)0xD800);
                assembler.Add(HighSurrogate);

                CheckEqual(char.ConvertFromUtf32(0x20BB7), assembler.Add(LowSurrogate));
            }
        }
    }
}