using WxAgent.Core;
using Xunit;

namespace WxAgent.Core.Tests;

public sealed class WechatTextInputSegmentationTests
{
    [Fact]
    public void SplitForSendSplitsLongTextAtTheSingleMessageBoundary()
    {
        var text = new string('x', WechatTextInput.MaxSegmentLength + 1);

        var segments = WechatTextInput.SplitForSend(text);

        Assert.Equal(2, segments.Count);
        Assert.Equal(WechatTextInput.MaxSegmentLength, segments[0].Length);
        Assert.Equal(1, segments[1].Length);
        Assert.Equal(text, string.Concat(segments));
        Assert.Throws<WxAgentException>(() => WechatTextInput.Prepare(text));
    }

    [Fact]
    public void SplitForSendDoesNotBreakACombiningTextElement()
    {
        var prefix = new string('x', WechatTextInput.MaxSegmentLength - 1);
        var combiningElement = "e\u0301";
        var text = prefix + combiningElement + "tail";

        var segments = WechatTextInput.SplitForSend(text);

        Assert.Equal(2, segments.Count);
        Assert.Equal(prefix, segments[0]);
        Assert.StartsWith(combiningElement, segments[1], StringComparison.Ordinal);
        Assert.All(segments, segment => Assert.InRange(segment.Length, 1, WechatTextInput.MaxSegmentLength));
        Assert.Equal(text, string.Concat(segments));
    }

    [Fact]
    public void SplitForSendRejectsTextBeyondTheBoundedTotalLength()
    {
        var text = new string('x', WechatTextInput.MaxTextLength + 1);

        var exception = Assert.Throws<WxAgentException>(() => WechatTextInput.SplitForSend(text));

        Assert.Equal(WxAgentErrorCode.InvalidArgument, exception.Code);
    }
}