namespace tgcli.Tests;

public class MessagePaging {
	[Theory]
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	public void Test1(int offset) {
		const string testMessage =
			"this is a test string please ignore 1, this is a test string please ignore 2, this is a test string please ignore 3, this is a test string please ignore 4, this is a test string please ignore 5, this is a test string please ignore 6, this is a test string please ignore 7, this is a test str.";
		const int testBufferWidth = 80;
		Assert.Equal(ReferenceMethods.GetViewIntoMessageBuffer(testMessage, offset, testBufferWidth),
					 Util.GetViewIntoMessageBuffer(testMessage, offset, testBufferWidth));
	}

	private static class ReferenceMethods {
		internal static (string messageBuffer, int relativeCursorPosition)
			GetViewIntoMessageBuffer(string message, int absoluteCursorPosition, int bufferWidth) {
			const int wraparoundOffsetPre  = 2; // number of "untouchable" characters moving the cursor onto will cause a wrap on the right screen edge
			const int wraparoundOffsetPost = 5; // number of "untouchable" characters moving the cursor onto will cause a wrap on the left screen edge

			const int wraparoundOffsetPreW  = wraparoundOffsetPre + 1;  // offset + 1 (character on the edge), for easier calculations
			const int wraparoundOffsetPostW = wraparoundOffsetPost + 1; // offset + 1 (character on the edge), for easier calculations

			if (absoluteCursorPosition > message.Length)
				throw new ArgumentOutOfRangeException();

			if (message.Length < bufferWidth)
				return (message, absoluteCursorPosition);

			if (absoluteCursorPosition < bufferWidth - wraparoundOffsetPre - 1)
				return (Util.TruncateString(message, bufferWidth, $"{Util.Ansi.Inverse}>{Util.Ansi.InverseOff}"), absoluteCursorPosition);

			// now we can be sure the message needs at least one wrap

			// first wrap
			// get rid of the content shown on the zeroth wrap, which is buf width minus wraparoundPreW (respects > character on screen edge)
			var finalMessage   = message[(bufferWidth - wraparoundOffsetPreW - wraparoundOffsetPost)..];
			var finalCursorPos = absoluteCursorPosition - bufferWidth + wraparoundOffsetPreW + wraparoundOffsetPostW;

			// successive wraps
			// repeat above steps (but counting the new < character) until the string fits into the buffer
			// it fits into the buffer when cursorPos >= bufferwidth minus wraparound (this time respecting > character absent on first wrap)
			while (finalCursorPos >= bufferWidth - wraparoundOffsetPreW) {
				finalMessage   = finalMessage[(bufferWidth - wraparoundOffsetPreW - wraparoundOffsetPostW)..];
				finalCursorPos = finalCursorPos - bufferWidth + wraparoundOffsetPreW + wraparoundOffsetPostW;
			}

			finalMessage = Util.TruncateString(finalMessage, bufferWidth - 1, $"{Util.Ansi.Inverse}>{Util.Ansi.InverseOff}");

			return ($"{Util.Ansi.Inverse}<{Util.Ansi.InverseOff}" + finalMessage, finalCursorPos);
		}
	}
}