namespace WxAgent.Core;

public enum WechatScrollDirection { Up, Down }

public sealed record WechatSessionScrollResult(
    int Scrolls, bool ViewportChanged, IReadOnlyList<WechatSessionSnapshot> Sessions);

public sealed record WechatMessagePosition(ChatMessageSnapshot Message, int Scrolls);

public static class WechatNavigationRules
{
    public static void ValidateScrollLimit(int pages)
    {
        if (pages is < 1 or > 100)
            throw new WxAgentException(WxAgentErrorCode.InvalidArgument, "Scroll limit must be between 1 and 100.");
    }

    public static ChatMessageSnapshot? FindMessage(IReadOnlyList<ChatMessageSnapshot> messages, string fingerprint)
    {
        if (fingerprint.Length != 64 || !fingerprint.All(char.IsAsciiHexDigit))
            throw new WxAgentException(WxAgentErrorCode.InvalidArgument, "A 64-character visible-message fingerprint is required.");
        var matches = messages.Where(message => string.Equals(message.Fingerprint, fingerprint, StringComparison.OrdinalIgnoreCase)).Take(2).ToArray();
        if (matches.Length > 1)
            throw new WxAgentException(WxAgentErrorCode.InvalidOperationState, "More than one visible message matches the fingerprint.");
        return matches.SingleOrDefault();
    }
}