using UIKit;

namespace VoiceCat.iOS;

internal static class UiHelpers
{
    internal static void ShowError(UIViewController owner, Exception exception) => ShowMessage(owner, "VoiceCat", exception.Message);
    internal static void ShowMessage(UIViewController owner, string title, string message)
    {
        UIAlertController alert = UIAlertController.Create(title, message, UIAlertControllerStyle.Alert);
        alert.AddAction(UIAlertAction.Create("OK", UIAlertActionStyle.Default, null)); owner.PresentViewController(alert, true, null);
    }

    internal static UITextField Field(string placeholder, bool secure = false)
    {
        var field = new UITextField { Placeholder = placeholder, BorderStyle = UITextBorderStyle.RoundedRect,
            SecureTextEntry = secure, TranslatesAutoresizingMaskIntoConstraints = false };
        field.AccessibilityLabel = placeholder; return field;
    }
}

// VoiceOver rebuilds its element tree from scratch on every UITableView.ReloadData. The model
// notifies far more often than any list's content actually changes - the microphone level timer
// alone ticks at 20 Hz - so reloading unconditionally re-announces the row under an exploring
// finger and destroys the element a double tap was aimed at. Reload only when the rendered text
// actually differs, and only while the view is on screen, so an off-screen or popped controller
// stops reloading instead of holding a subscription for the lifetime of the connection.
internal sealed class ListRefresher(UITableViewController owner, Func<string> signature, Action<Action> subscribe, Action<Action> unsubscribe)
{
    // Null means nothing has been rendered yet. A signature is never null, so the first
    // Refresh after Start or Invalidate always reloads.
    private string? rendered;
    private bool observing;

    internal void Start()
    {
        if (observing) return;
        observing = true; subscribe(Refresh); Refresh();
    }

    internal void Stop()
    {
        if (!observing) return;
        observing = false; unsubscribe(Refresh);
    }

    // Forces the next Refresh to reload even when the signature is unchanged, for state the
    // signature cannot see.
    internal void Invalidate() => rendered = null;

    internal void Refresh()
    {
        if (!observing || !owner.IsViewLoaded) return;
        string next = signature();
        if (next == rendered) return;
        rendered = next; owner.TableView.ReloadData();
    }
}