btcpayserver/BTCPayServer/Components/Pager/Default.cshtml

@using System.Web
@using BTCPayServer.TagHelpers
@model BasePagingViewModel

@{
	var pageSizeOptions = new[] { 50, 100, 250, 500 };
}

@if (Model.Total is null || Model.Total.Value > pageSizeOptions.Min())
{
    <nav aria-label="..." class="d-flex flex-wrap gap-3 justify-content-between">
        @if (Model.Total is null || Model.Total.Value > Model.Count)
        {
            <ul class="pagination me-auto">
                @if (Model.Skip > 0)
                {
                    <li class="page-item">
                        <a class="page-link" tabindex="-1" href="@NavigatePages(-1, Model.Count)" text-translate="true">Prev</a>
                    </li>
                }
                <li class="page-item disabled">
                    <span class="page-link @(Model.Total is null ? "px-0" : (Model.Skip == 0 ? "ps-0" : null))">
                    @if (Model.Total is null)
                    {
                        @($"{Model.Skip + 1} – {Model.Skip + Model.Count}")
                    }
                    else if (Model.Total.Value <= Model.Count)
                    {
                        @($"1 – {Model.Total.Value}")
                    }
                    else
                    {
                        @($"{Model.Skip + 1} – {Model.Skip + Model.Count}, Total: {Model.Total.Value}")
                    }
                    </span>
                </li>
                @if ((Model.Total is null && Model.CurrentPageCount >= Model.Count) || (Model.Total is not null && Model.Total.Value > Model.Skip + Model.Count))
                {
                    <li class="page-item">
                        <a class="page-link" href="@NavigatePages(1, Model.Count)" text-translate="true">Next</a>
                    </li>
                }
            </ul>
        }

        @if (Model.Total is null || Model.Total.Value >= pageSizeOptions.Min())
        {
            <ul class="pagination ms-auto">
                <li class="page-item disabled">
                    <span class="page-link" text-translate="true">Page Size</span>
                </li>
                @foreach (var pageSize in pageSizeOptions)
                {
                    if (Model.Total is null || Model.Total.Value >= pageSize)
                    {
                        <li class="page-item @(Model.Count == pageSize ? "active" : null)">
                            <a class="page-link @(Model.Count != pageSize && pageSize == pageSizeOptions.Max() ? "pe-0" : null)" href="@NavigatePages(0, pageSize)">@pageSize</a>
                        </li>
                    }
                }
            </ul>
        }
    </nav>
}
@{
    string NavigatePages(int prevNext, int count)
    {
        var skip = Model.Skip;
        if (prevNext == -1)
        {
            skip = Math.Max(0, Model.Skip - Model.Count);
        }
        else if (prevNext == 1)
        {
            skip = Model.Skip + count;
        }

        var query = new Dictionary<string, object>
        {
            { "searchTerm", Model.SearchTerm },
            { "timezoneOffset", Model.TimezoneOffset },
            { "skip", skip },
            { "count", count }
        };

        if (Model.PaginationQuery != null)
        {
            // merge both, preferring the `query` properties in case of duplicate keys
            query = query.Concat(Model.PaginationQuery)
                .Where(e => e.Value != null)
                .GroupBy(e => e.Key)
                .ToDictionary(g => g.Key, g => g.First().Value);
        }

        return ReplaceQueryParameters(query);
    }
    
    string ReplaceQueryParameters(Dictionary<string, object> query)
    {
        var uri = new Uri(ViewContext.HttpContext.Request.GetCurrentUrlWithQueryString());
        var queryParams = HttpUtility.ParseQueryString(uri.Query);
        foreach (var (key, value) in query)
        {
            if (value != null) queryParams[key] = value?.ToString();
        }
        var uriBuilder = new UriBuilder(uri)
        {
            Query = queryParams.ToString()!
        };
        return uriBuilder.ToString();
    }
}