// Assets/_Project/Scripts/Gameplay/SpellSlot.cs
using System;
using Unity.Netcode;
using TD.Core;

namespace TD.Gameplay
{
    /// <summary>
    /// One granted builder spell in a <see cref="PlayerSpellLoadout"/>. Replicated as part of
    /// a <see cref="NetworkList{T}"/>; the entry's index in that list IS the hotkey slot
    /// (grant order == key order), so no separate slot index field is needed.
    /// </summary>
    /// <remarks>
    /// <b>One struct, not parallel lists.</b> <see cref="Kind"/> is set once at grant time;
    /// <see cref="CooldownEndServerTime"/> is rewritten on every cast. <c>NetworkList{T}</c>'s
    /// indexer setter (<c>spells[i] = newValue</c>) short-circuits the write when
    /// <c>Equals</c> on the old value returns true (see <see cref="BuildJob"/> for the
    /// documented case that first surfaced this). Comparing only <see cref="Kind"/> would mean
    /// a cooldown update — same Kind, new CooldownEndServerTime — never actually replicates.
    /// <see cref="Equals"/> therefore compares every field.
    /// </remarks>
    [Serializable]
    public struct SpellSlot : INetworkSerializable, IEquatable<SpellSlot>
    {
        /// <summary>Which spell occupies this slot. Fixed for the slot's lifetime.</summary>
        public BuilderSpellKind Kind;

        /// <summary>
        /// <c>NetworkManager.ServerTime.Time</c> at which this slot is next ready to cast.
        /// 0 (or any value &lt;= current server time) means ready now.
        /// </summary>
        public double CooldownEndServerTime;

        public static SpellSlot CreateReady(BuilderSpellKind kind)
        {
            return new SpellSlot { Kind = kind, CooldownEndServerTime = 0d };
        }

        // ----- INetworkSerializable ---------------------------------------

        public void NetworkSerialize<T>(BufferSerializer<T> serializer) where T : IReaderWriter
        {
            byte kindByte = (byte)Kind;
            serializer.SerializeValue(ref kindByte);
            Kind = (BuilderSpellKind)kindByte;

            serializer.SerializeValue(ref CooldownEndServerTime);
        }

        // ----- IEquatable -------------------------------------------------
        //
        // Full-field comparison — see remarks above. Without this, cooldown writes
        // (Kind unchanged, only CooldownEndServerTime updated) would be silently dropped
        // by NetworkList's indexer setter.

        public bool Equals(SpellSlot other) =>
            Kind == other.Kind && CooldownEndServerTime == other.CooldownEndServerTime;

        public override bool Equals(object obj) => obj is SpellSlot other && Equals(other);

        public override int GetHashCode() => (int)Kind;
    }
}