namespace AcDream.UI.Abstractions.Panels.Vitals;

/// <summary>
/// First real UI panel — shows the local player's vitals as progress bars.
/// Backend-agnostic; renders exclusively through <see cref="IPanelRenderer"/>
/// so the same file works under ImGui.NET (D.2a) and the future custom
/// retail-look toolkit (D.2b).
///
/// <para>
/// D.2a shows only HP (percent). <see cref="VitalsVM.StaminaPercent"/> /
/// <see cref="VitalsVM.ManaPercent"/> return null until a
/// <c>LocalPlayerState</c> is wired (follow-up issue). When they start
/// returning non-null, this panel picks them up automatically.
/// </para>
/// </summary>
public sealed class VitalsPanel : IPanel
{
    private const float BarWidth = 200f;

    private readonly VitalsVM _vm;

    public VitalsPanel(VitalsVM vm)
    {
        _vm = vm ?? throw new ArgumentNullException(nameof(vm));
    }

    /// <inheritdoc />
    public string Id => "acdream.vitals";

    /// <inheritdoc />
    public string Title => "Vitals";

    /// <inheritdoc />
    public bool IsVisible { get; set; } = true;

    /// <inheritdoc />
    public void Render(PanelContext ctx, IPanelRenderer renderer)
    {
        if (!renderer.Begin(Title))
        {
            renderer.End();
            return;
        }

        // HP — always available from CombatState. If LocalPlayer has the
        // absolute values too, prefer "current/max (percent)" overlay.
        float hp = _vm.HealthPercent;
        renderer.Text("HP");
        renderer.SameLine();
        renderer.ProgressBar(hp, BarWidth, overlay: FormatOverlay(
            hp, _vm.HealthCurrent, _vm.HealthMax));

        // Stamina — show only when the VM has a real value.
        if (_vm.StaminaPercent is float stam)
        {
            renderer.Text("Stam");
            renderer.SameLine();
            renderer.ProgressBar(stam, BarWidth, overlay: FormatOverlay(
                stam, _vm.StaminaCurrent, _vm.StaminaMax));
        }

        // Mana — show only when the VM has a real value.
        if (_vm.ManaPercent is float mana)
        {
            renderer.Text("Mana");
            renderer.SameLine();
            renderer.ProgressBar(mana, BarWidth, overlay: FormatOverlay(
                mana, _vm.ManaCurrent, _vm.ManaMax));
        }

        renderer.End();
    }

    /// <summary>
    /// Format a vital-bar overlay. Prefers <c>current / max (percent%)</c>
    /// when absolute values are available; falls back to percent-only
    /// when not (e.g. HP pre-PlayerDescription, where only the
    /// CombatState percent has been wired).
    /// </summary>
    private static string FormatOverlay(float percent, uint? current, uint? max)
    {
        if (current is uint c && max is uint m && m > 0)
            return $"{c} / {m} ({percent * 100f:F0}%)";
        return $"{percent * 100f:F0}%";
    }
}