namespace Htmx.ApiDemo.Templates.Components;

/// <summary>
/// shadcn-style Pagination. Generates prev/next and page-number buttons.
/// urlPattern: format string where {0} is replaced by the page number, e.g. "/items?page={0}"
/// </summary>
public sealed class Pagination : PaginationBase
{
    private const string BtnBase =
        "inline-flex items-center justify-center rounded-md border border-input bg-background " +
        "px-3 h-9 text-sm font-medium ring-offset-background transition-colors " +
        "hover:bg-accent hover:text-accent-foreground " +
        "focus-visible:outline-none focus-visible:ring-2 focus-visible:ring-ring focus-visible:ring-offset-2 " +
        "disabled:pointer-events-none disabled:opacity-50";

    private const string ActiveBtn =
        "inline-flex items-center justify-center rounded-md bg-primary text-primary-foreground " +
        "px-3 h-9 text-sm font-medium ring-offset-background " +
        "focus-visible:outline-none focus-visible:ring-2 focus-visible:ring-ring focus-visible:ring-offset-2";

    private readonly byte[] _prevData;
    private readonly byte[] _pagesData;
    private readonly byte[] _nextData;

    public Pagination(int current, int total, string urlPattern = "?page={0}")
    {
        _prevData = current <= 1
            ? $"""<button type="button" class="{BtnBase}" disabled aria-label="Previous page">&#8249;</button>""".ToUtf8Bytes()
            : $"""<a href="{string.Format(urlPattern, current - 1)}" class="{BtnBase}" aria-label="Previous page">&#8249;</a>""".ToUtf8Bytes();

        _nextData = current >= total
            ? $"""<button type="button" class="{BtnBase}" disabled aria-label="Next page">&#8250;</button>""".ToUtf8Bytes()
            : $"""<a href="{string.Format(urlPattern, current + 1)}" class="{BtnBase}" aria-label="Next page">&#8250;</a>""".ToUtf8Bytes();

        var sb = new System.Text.StringBuilder();
        for (int p = 1; p <= total; p++)
        {
            if (p == current)
                sb.Append($"""<span class="{ActiveBtn}" aria-current="page">{p}</span>""");
            else
                sb.Append($"""<a href="{string.Format(urlPattern, p)}" class="{BtnBase}">{p}</a>""");
        }
        _pagesData = sb.ToString().ToUtf8Bytes();
    }

    protected override void RenderPrev(HtmxRenderContext ctx)  => ctx.Writer.WriteUtf8(_prevData);
    protected override void RenderPages(HtmxRenderContext ctx) => ctx.Writer.WriteUtf8(_pagesData);
    protected override void RenderNext(HtmxRenderContext ctx)  => ctx.Writer.WriteUtf8(_nextData);
}