using Amphora;
using System;
using UnitTestSharp;

namespace Blacklight.Core.UnitTests
{
    public class HostClipboardExtensionsTests : TestFixture
    {
        public class RecordingClipboard : IHostClipboard
        {
            public string Held { get; private set; }
            public bool Accepts { get; set; } = true;

            public StringHostClipboardText Opened { get; private set; }

            // Handed out in place of the held text when set.
            public IHostClipboardText Override { get; set; }

            public bool TryOpenText(out IHostClipboardText text)
            {
                text = Override;
                if (text != null)
                {
                    return true;
                }

                if (Held == null)
                {
                    return false;
                }

                Opened = new StringHostClipboardText(Held);
                text = Opened;

                return true;
            }

            public bool SetText(IChunkedText text)
            {
                if (Accepts)
                {
                    Held = text.ToText();
                }

                return Accepts;
            }
        }

        public class OutOfMemoryText : IHostClipboardText
        {
            public bool IsDisposed { get; private set; }

            public int Length => 1;

            public StringView GetChunk(int start)
            {
                throw new OutOfMemoryException();
            }

            public void Dispose()
            {
                IsDisposed = true;
            }
        }

        public class TryGetTextTests : TestFixture
        {
            public void ReturnsTheTextTheHostHolds()
            {
                var clipboard = new RecordingClipboard();
                clipboard.SetText("hello");

                CheckTrue(clipboard.TryGetText(out string text));

                CheckEqual("hello", text);
            }

            public void AnEmptyText_IsReturnedAsEmpty()
            {
                var clipboard = new RecordingClipboard();
                clipboard.SetText("");

                CheckTrue(clipboard.TryGetText(out string text));

                CheckEqual("", text);
            }

            public void WithNothingOnTheHost_ReturnsFalseAndNull()
            {
                CheckFalse(new RecordingClipboard().TryGetText(out string text));

                CheckNull(text);
            }

            public void DisposesTheTextItOpened()
            {
                var clipboard = new RecordingClipboard();
                clipboard.SetText("hello");

                clipboard.TryGetText(out string _);

                CheckTrue(clipboard.Opened.IsDisposed);
            }

            public void ATextTooBigToBuild_ReturnsFalseAndNull()
            {
                var clipboard = new RecordingClipboard { Override = new OutOfMemoryText() };

                CheckFalse(clipboard.TryGetText(out string text));

                CheckNull(text);
            }

            public void ATextTooBigToBuild_IsStillDisposed()
            {
                var big = new OutOfMemoryText();
                var clipboard = new RecordingClipboard { Override = big };

                clipboard.TryGetText(out string _);

                CheckTrue(big.IsDisposed);
            }
        }

        public class SetTextTests : TestFixture
        {
            public void AString_ReachesTheHostAsItsText()
            {
                var clipboard = new RecordingClipboard();

                clipboard.SetText("hello");

                CheckEqual("hello", clipboard.Held);
            }

            public void AnEmptyString_ReachesTheHostAsAnEmptyText()
            {
                var clipboard = new RecordingClipboard();

                clipboard.SetText("");

                CheckEqual("", clipboard.Held);
            }

            public void ReturnsWhatTheHostReturns()
            {
                var clipboard = new RecordingClipboard();

                CheckTrue(clipboard.SetText("a"));

                clipboard.Accepts = false;

                CheckFalse(clipboard.SetText("b"));
            }

            public void ANullString_Throws()
            {
                CheckThrow(typeof(ArgumentNullException));
                new RecordingClipboard().SetText((string)null);
            }
        }
    }
}