using AcDream.Core.Combat;
using AcDream.Core.Player;

namespace AcDream.UI.Abstractions.Panels.Vitals;

/// <summary>
/// ViewModel for the vitals HUD panel. Reads live health percentage for the
/// local player from <see cref="CombatState"/> (which is fed by the server's
/// <c>UpdateHealth (0x01C0)</c> GameEvent).
///
/// <para>
/// <b>Sources:</b>
/// </para>
///
/// <list type="bullet">
///   <item>HP — <see cref="CombatState.GetHealthPercent"/> (percent-only,
///         updated by <c>UpdateHealth (0x01C0)</c>).</item>
///   <item>Stamina / Mana — <see cref="LocalPlayerState"/>'s
///         <c>StaminaPercent</c> / <c>ManaPercent</c>, populated from the
///         <c>CreatureProfile</c> embedded in <c>PlayerDescription
///         (0x0013)</c>. When no <see cref="LocalPlayerState"/> is wired
///         (older constructor / tests), both stay <c>null</c> and
///         <c>VitalsPanel</c> simply skips those bars.</item>
/// </list>
///
/// <para>
/// <b>GUID timing:</b> the local player's server GUID isn't known at
/// <c>OnLoad</c> (pre-login). Construct with <see cref="SetLocalPlayerGuid"/>
/// left as 0; <c>GameWindow</c> calls the setter when the live session
/// receives its guid at <c>EnterWorld</c>. Before the GUID is set,
/// <see cref="HealthPercent"/> returns 1.0 (via <c>CombatState</c>'s safe
/// default for unknown guids) — the bar reads "full", which is harmless.
/// </para>
/// </summary>
public sealed class VitalsVM
{
    private readonly CombatState _combat;
    private readonly LocalPlayerState? _local;
    private uint _localPlayerGuid;

    /// <summary>
    /// Build a VitalsVM bound to a <see cref="CombatState"/> and (optionally)
    /// a <see cref="LocalPlayerState"/>. The GUID starts at 0; call
    /// <see cref="SetLocalPlayerGuid"/> once the live session assigns it.
    /// When <paramref name="localPlayer"/> is <c>null</c> (back-compat),
    /// stamina + mana stay <c>null</c> and <c>VitalsPanel</c> skips those bars.
    /// </summary>
    public VitalsVM(CombatState combat, LocalPlayerState? localPlayer = null)
    {
        _combat = combat ?? throw new ArgumentNullException(nameof(combat));
        _local = localPlayer;
        _localPlayerGuid = 0;
    }

    /// <summary>
    /// Push the authoritative local-player GUID from <c>WorldSession</c>.
    /// One-way setter — only <c>GameWindow</c> should call it, exactly once
    /// per live session.
    /// </summary>
    public void SetLocalPlayerGuid(uint guid) => _localPlayerGuid = guid;

    /// <summary>
    /// Current health percent (0..1) for the local player. Returns 1.0
    /// before login or if the server has never sent an UpdateHealth for
    /// this GUID.
    /// </summary>
    public float HealthPercent => _combat.GetHealthPercent(_localPlayerGuid);

    /// <summary>
    /// Stamina percent (0..1), or <c>null</c> when no
    /// <see cref="LocalPlayerState"/> is wired or it hasn't received a
    /// <c>PlayerDescription</c> with both current and max yet. Reads
    /// through to the cache every access — no VM-side caching.
    /// </summary>
    public float? StaminaPercent => _local?.StaminaPercent;

    /// <summary>
    /// Mana percent (0..1), or <c>null</c> under the same conditions as
    /// <see cref="StaminaPercent"/>.
    /// </summary>
    public float? ManaPercent => _local?.ManaPercent;

    // ── Absolute values for HUD overlays ──────────────────────────────────

    /// <summary>Current health value (server-authoritative absolute) or
    /// <c>null</c> if <see cref="LocalPlayerState"/> hasn't received the
    /// vital snapshot yet.</summary>
    public uint? HealthCurrent => _local?.Get(LocalPlayerState.VitalKind.Health)?.Current;

    /// <summary>Max health value, accounting for attribute contribution
    /// + active enchantment buffs + vitae. <c>null</c> if no vital
    /// snapshot yet.</summary>
    public uint? HealthMax => _local?.GetMaxApprox(LocalPlayerState.VitalKind.Health);

    /// <summary>Current stamina value.</summary>
    public uint? StaminaCurrent => _local?.Get(LocalPlayerState.VitalKind.Stamina)?.Current;

    /// <summary>Max stamina including buffs + vitae.</summary>
    public uint? StaminaMax => _local?.GetMaxApprox(LocalPlayerState.VitalKind.Stamina);

    /// <summary>Current mana value.</summary>
    public uint? ManaCurrent => _local?.Get(LocalPlayerState.VitalKind.Mana)?.Current;

    /// <summary>Max mana including buffs + vitae.</summary>
    public uint? ManaMax => _local?.GetMaxApprox(LocalPlayerState.VitalKind.Mana);
}