using JetBrains.Annotations;
using PkmnLib.Dynamic.Events;
using PkmnLib.Dynamic.Libraries;
using PkmnLib.Dynamic.ScriptHandling;
using PkmnLib.Static;
using PkmnLib.Static.Species;
using PkmnLib.Static.Utils;

namespace PkmnLib.Dynamic.Models;

/// <summary>
/// The data of a Pokemon.
/// </summary>
public interface IPokemon : IScriptSource
{
    /// <summary>
    /// The library data of the Pokemon.
    /// </summary>
    IDynamicLibrary Library { get; }

    /// <summary>
    /// The species of the Pokemon.
    /// </summary>
    ISpecies Species { get; }

    /// <summary>
    /// The form of the Pokemon.
    /// </summary>
    IForm Form { get; }

    /// <summary>
    /// An optional display species of the Pokemon. If this is set, the client should display this
    /// species. An example of usage for this is the Illusion ability.
    /// </summary>
    ISpecies? DisplaySpecies { get; }

    /// <summary>
    /// An optional display form of the Pokemon. If this is set, the client should display this
    /// form. An example of usage for this is the Illusion ability.
    /// </summary>
    IForm? DisplayForm { get; }

    /// <summary>
    /// The current level of the Pokemon.
    /// </summary>
    LevelInt Level { get; }

    /// <summary>
    /// The amount of experience of the Pokemon.
    /// </summary>
    uint Experience { get; }

    /// <summary>
    /// The personality value of the Pokemon.
    /// </summary>
    uint PersonalityValue { get; }

    /// <summary>
    /// The gender of the Pokemon.
    /// </summary>
    Gender Gender { get; }

    /// <summary>
    /// The coloring of the Pokemon. Value 0 is the default, value 1 means shiny. Other values are
    /// currently not used, and can be used for other implementations.
    /// </summary>
    byte Coloring { get; }

    /// <summary>
    /// The held item of the Pokemon.
    /// </summary>
    IItem? HeldItem { get; }

    /// <summary>
    /// The remaining health points of the Pokemon.
    /// </summary>
    uint CurrentHealth { get; }

    /// <summary>
    /// The weight of the Pokemon in kilograms.
    /// </summary>
    float WeightInKm { get; set; }

    /// <summary>
    /// The height of the Pokemon in meters.
    /// </summary>
    float HeightInMeters { get; set; }

    /// <summary>
    /// The happiness of the Pokemon. Also known as friendship.
    /// </summary>
    byte Happiness { get; }

    /// <summary>
    /// The stats of the Pokemon when disregarding any stat boosts.
    /// </summary>
    StatisticSet<uint> FlatStats { get; }

    /// <summary>
    /// The statistics boosts of the Pokemon. Will prevent the value from going above 6, and below
    /// -6.
    /// </summary>
    StatBoostStatisticSet StatBoost { get; }

    /// <summary>
    /// The stats of the Pokemon including the stat boosts
    /// </summary>
    StatisticSet<uint> BoostedStats { get; }

    /// <summary>
    /// The individual values of the Pokemon.
    /// </summary>
    IndividualValueStatisticSet IndividualValues { get; }

    /// <summary>
    /// The effort values of the Pokemon.
    /// </summary>
    EffortValueStatisticSet EffortValues { get; }

    /// <summary>
    /// The nature of the Pokemon.
    /// </summary>
    INature Nature { get; }

    /// <summary>
    /// An optional nickname of the Pokemon.
    /// </summary>
    string? Nickname { get; }

    /// <summary>
    /// An index of the ability to find the actual ability on the form.
    /// </summary>
    AbilityIndex AbilityIndex { get; }

    /// <summary>
    /// An ability can be overriden to an arbitrary ability. This is for example used for the Mummy
    /// ability.
    /// </summary>
    IAbility? OverrideAbility { get; }

    /// <summary>
    /// If in battle, we have additional data.
    /// </summary>
    IPokemonBattleData? BattleData { get; }

    /// <summary>
    /// The moves the Pokemon has learned. This is of a set length of <see cref="Const.MovesCount"/>. Empty move slots
    /// are null.
    /// </summary>
    IReadOnlyList<ILearnedMove?> Moves { get; }

    /// <summary>
    /// Whether or not the Pokemon is allowed to gain experience.
    /// </summary>
    bool AllowedExperience { get; }

    /// <summary>
    /// The current types of the Pokemon.
    /// </summary>
    IReadOnlyList<TypeIdentifier> Types { get; }

    /// <summary>
    /// Whether or not this Pokemon is an egg.
    /// </summary>
    bool IsEgg { get; }

    /// <summary>
    /// Whether or not this Pokemon was caught this battle.
    /// </summary>
    bool IsCaught { get; }

    /// <summary>
    /// The script for the held item.
    /// </summary>
    ScriptContainer HeldItemTriggerScript { get; }

    /// <summary>
    /// The script for the ability.
    /// </summary>
    ScriptContainer AbilityScript { get; }

    /// <summary>
    /// The script for the status.
    /// </summary>
    ScriptContainer StatusScript { get; }

    /// <summary>
    /// The volatile status scripts of the Pokemon.
    /// </summary>
    IScriptSet Volatile { get; }

    /// <summary>
    /// Checks whether the Pokemon is holding an item with a specific name.
    /// </summary>
    bool HasHeldItem(StringKey itemName);

    /// <summary>
    /// Changes the held item of the Pokemon. Returns the previously held item.
    /// </summary>
    [MustUseReturnValue]
    IItem? SetHeldItem(IItem? item);

    /// <summary>
    /// Removes the held item from the Pokemon. Returns the previously held item.
    /// </summary>
    [MustUseReturnValue]
    IItem? RemoveHeldItem();

    /// <summary>
    /// Makes the Pokemon uses its held item. Returns whether the item was consumed.
    /// </summary>
    bool ConsumeHeldItem();

    /// <summary>
    /// Change a boosted stat by a certain amount.
    /// </summary>
    /// <param name="stat">The stat to be changed</param>
    /// <param name="change">The amount to change the stat by</param>
    /// <param name="selfInflicted">Whether the change was self-inflicted. This can be relevant in scripts.</param>
    bool ChangeStatBoost(Statistic stat, sbyte change, bool selfInflicted);

    /// <summary>
    /// Returns the currently active ability.
    /// </summary>
    IAbility ActiveAbility { get; }

    /// <summary>
    /// Calculates the flat stats on the Pokemon. This should be called when for example the base
    /// stats, level, nature, IV, or EV changes. This has a side effect of recalculating the boosted
    /// stats, as those depend on the flat stats.
    /// </summary>
    void RecalculateFlatStats();

    /// <summary>
    /// Calculates the boosted stats on the Pokemon, _without_ recalculating the flat stats.
    /// This should be called when a stat boost changes.
    /// </summary>
    void RecalculateBoostedStats();

    /// <summary>
    /// Change the species of the Pokemon.
    /// </summary>
    void ChangeSpecies(ISpecies species, IForm form);

    /// <summary>
    /// Change the form of the Pokemon.
    /// </summary>
    void ChangeForm(IForm form);

    /// <summary>
    /// Whether the Pokemon is useable in a battle.
    /// </summary>
    bool IsUsable { get; }

    /// <summary>
    /// Whether the Pokemon is fainted.
    /// </summary>
    bool IsFainted { get; }

    /// <summary>
    /// Damages the Pokemon by a certain amount of damage, from a damage source.
    /// </summary>
    void Damage(uint damage, DamageSource source, EventBatchId batchId);

    /// <summary>
    /// Heals the Pokemon by a specific amount. Unless allow_revive is set to true, this will not
    /// heal if the Pokemon has 0 health. If the amount healed is 0, this will return false.
    /// </summary>
    bool Heal(uint heal, bool allowRevive);

    /// <summary>
    /// Learn a move by name.
    /// </summary>
    void LearnMove(string moveName, MoveLearnMethod method, byte index);

    /// <summary>
    /// Removes the current non-volatile status from the Pokemon.
    /// </summary>
    void ClearStatus();

    /// <summary>
    /// Modifies the level by a certain amount
    /// </summary>
    void ChangeLevelBy(int change);

    /// <summary>
    /// Sets the current battle the Pokémon is in.
    /// </summary>
    void SetBattleData(IBattle battle, byte sideIndex);

    /// <summary>
    /// Sets whether the Pokémon is on the battlefield.
    /// </summary>
    void SetOnBattlefield(bool onBattleField);

    /// <summary>
    /// Sets the position the Pokémon has within its side.
    /// </summary>
    /// <param name="position"></param>
    void SetBattleSidePosition(byte position);

    /// <summary>
    /// Marks a Pokemon as seen in the battle.
    /// </summary>
    void MarkOpponentAsSeen(IPokemon pokemon);

    // TODO: (de)serialize
}

/// <summary>
/// The data of the Pokemon related to being in a battle.
/// This is only set when the Pokemon is on the field in a battle.
/// </summary>
public interface IPokemonBattleData
{
    /// <summary>
    /// The battle the Pokemon is in.
    /// </summary>
    IBattle Battle { get; internal set; }

    /// <summary>
    /// The index of the side of the Pokemon
    /// </summary>
    byte SideIndex { get; internal set; }

    /// <summary>
    /// The index of the position of the Pokemon on the field
    /// </summary>
    byte Position { get; internal set; }

    /// <summary>
    /// A list of opponents the Pokemon has seen this battle.
    /// </summary>
    IReadOnlyList<IPokemon> SeenOpponents { get; }
    
    /// <summary>
    /// Whether the Pokemon is on the battlefield.
    /// </summary>
    bool IsOnBattlefield { get; set; }

    /// <summary>
    /// Adds an opponent to the list of seen opponents.
    /// </summary>
    void MarkOpponentAsSeen(IPokemon opponent);
}

/// <inheritdoc cref="IPokemon"/>
public class PokemonImpl : ScriptSource, IPokemon
{
    /// <inheritdoc cref="PokemonImpl"/>
    public PokemonImpl(IDynamicLibrary library, ISpecies species, IForm form, AbilityIndex abilityIndex, LevelInt level,
        uint personalityValue, Gender gender, byte coloring, StringKey natureName)
    {
        Library = library;
        Species = species;
        Form = form;
        AbilityIndex = abilityIndex;
        Level = level;
        PersonalityValue = personalityValue;
        Gender = gender;
        Coloring = coloring;
        Types = form.Types.ToList();

        Experience = library.StaticLibrary.GrowthRates.CalculateExperience(species.GrowthRate, level);
        WeightInKm = form.Weight;
        HeightInMeters = form.Height;
        Happiness = species.BaseHappiness;
        if (!library.StaticLibrary.Natures.TryGet(natureName, out var nature))
            throw new KeyNotFoundException($"Nature {natureName} not found.");
        Nature = nature;

        RecalculateFlatStats();
        CurrentHealth = BoostedStats.Hp;
    }

    /// <inheritdoc />
    public IDynamicLibrary Library { get; }

    /// <inheritdoc />
    public ISpecies Species { get; }

    /// <inheritdoc />
    public IForm Form { get; }

    /// <inheritdoc />
    public ISpecies? DisplaySpecies { get; set; }

    /// <inheritdoc />
    public IForm? DisplayForm { get; set; }

    /// <inheritdoc />
    public LevelInt Level { get; private set; }

    /// <inheritdoc />
    public uint Experience { get; }

    /// <inheritdoc />
    public uint PersonalityValue { get; }

    /// <inheritdoc />
    public Gender Gender { get; }

    /// <inheritdoc />
    public byte Coloring { get; }

    /// <inheritdoc />
    public IItem? HeldItem { get; private set; }

    /// <inheritdoc />
    public uint CurrentHealth { get; private set; }

    /// <inheritdoc />
    public float WeightInKm { get; set; }

    /// <inheritdoc />
    public float HeightInMeters { get; set; }

    /// <inheritdoc />
    public byte Happiness { get; }

    /// <inheritdoc />
    public StatisticSet<uint> FlatStats { get; } = new();

    /// <inheritdoc />
    public StatBoostStatisticSet StatBoost { get; } = new();

    /// <inheritdoc />
    public StatisticSet<uint> BoostedStats { get; } = new();

    /// <inheritdoc />
    public IndividualValueStatisticSet IndividualValues { get; } = new();

    /// <inheritdoc />
    public EffortValueStatisticSet EffortValues { get; } = new();

    /// <inheritdoc />
    public INature Nature { get; }

    /// <inheritdoc />
    public string? Nickname { get; set; }

    /// <inheritdoc />
    public AbilityIndex AbilityIndex { get; }

    /// <inheritdoc />
    public IAbility? OverrideAbility { get; private set; }

    /// <inheritdoc />
    public IPokemonBattleData? BattleData { get; private set; }

    private readonly ILearnedMove?[] _learnedMoves = new ILearnedMove[Const.MovesCount];

    /// <inheritdoc />
    public IReadOnlyList<ILearnedMove?> Moves => _learnedMoves;

    /// <inheritdoc />
    public bool AllowedExperience { get; set; }

    /// <inheritdoc />
    public IReadOnlyList<TypeIdentifier> Types { get; private set; }

    /// <inheritdoc />
    public bool IsEgg { get; private set; }

    /// <inheritdoc />
    public bool IsCaught { get; private set; }

    /// <inheritdoc />
    public ScriptContainer HeldItemTriggerScript { get; } = new();

    /// <inheritdoc />
    public ScriptContainer AbilityScript { get; } = new();

    /// <inheritdoc />
    public ScriptContainer StatusScript { get; } = new();

    /// <inheritdoc />
    public IScriptSet Volatile { get; } = new ScriptSet();

    /// <inheritdoc />
    public bool HasHeldItem(StringKey itemName) => HeldItem?.Name == itemName;

    /// <inheritdoc />
    public IItem? SetHeldItem(IItem? item)
    {
        var previous = HeldItem;
        HeldItem = item;
        return previous;
    }

    /// <inheritdoc />
    public IItem? RemoveHeldItem()
    {
        var previous = HeldItem;
        HeldItem = null;
        return previous;
    }

    /// <inheritdoc />
    public bool ConsumeHeldItem()
    {
        if (HeldItem is null)
            return false;
        if (!Library.ScriptResolver.TryResolveItemScript(HeldItem, out _))
            return false;
        // TODO: actually consume the item
        throw new NotImplementedException();
    }

    /// <inheritdoc />
    public bool ChangeStatBoost(Statistic stat, sbyte change, bool selfInflicted)
    {
        var prevented = false;
        this.RunScriptHook(script => script.PreventStatBoostChange(this, stat, change, selfInflicted, ref prevented));
        if (prevented)
            return false;
        this.RunScriptHook(script => script.ChangeStatBoostChange(this, stat, selfInflicted, ref change));
        if (change == 0)
            return false;
        var changed = false;
        var oldBoost = StatBoost.GetStatistic(stat);
        changed = change switch
        {
            > 0 => StatBoost.IncreaseStatistic(stat, change),
            < 0 => StatBoost.DecreaseStatistic(stat, change),
            _ => changed,
        };
        if (!changed)
            return false;
        if (BattleData != null)
        {
            var newBoost = StatBoost.GetStatistic(stat);
            BattleData.Battle.EventHook.Invoke(new StatBoostEvent(this, stat, oldBoost, newBoost));
        }

        RecalculateBoostedStats();
        return true;
    }

    /// <inheritdoc />
    public IAbility ActiveAbility
    {
        get
        {
            if (OverrideAbility != null)
                return OverrideAbility;
            var ability = Form.GetAbility(AbilityIndex);
            if (!Library.StaticLibrary.Abilities.TryGet(ability, out var abilityObj))
                throw new KeyNotFoundException($"Ability {ability} not found.");
            return abilityObj;
        }
    }

    /// <inheritdoc />
    public void RecalculateFlatStats()
    {
        Library.StatCalculator.CalculateFlatStats(this, FlatStats);
        RecalculateBoostedStats();
    }

    /// <inheritdoc />
    public void RecalculateBoostedStats() => Library.StatCalculator.CalculateBoostedStats(this, BoostedStats);

    /// <inheritdoc />
    public void ChangeSpecies(ISpecies species, IForm form)
    {
        throw new NotImplementedException();
    }

    /// <inheritdoc />
    public void ChangeForm(IForm form)
    {
        throw new NotImplementedException();
    }

    /// <inheritdoc />
    /// <remarks>
    /// Currently this checks the Pokemon is not an egg, not caught, and not fainted.
    /// </remarks>
    public bool IsUsable => !IsCaught && !IsEgg && !IsFainted;

    /// <inheritdoc />
    public bool IsFainted => CurrentHealth == 0;

    /// <inheritdoc />
    public void Damage(uint damage, DamageSource source, EventBatchId batchId)
    {
        // If the Pokemon is already fainted, we don't need to do anything.
        if (IsFainted)
            return;
        // If the damage is more than the current health, we cap it at the current health, to prevent
        // underflow.
        if (damage >= CurrentHealth)
            damage = CurrentHealth;
        // Calculate the new health.
        var newHealth = CurrentHealth - damage;
        if (BattleData is not null)
        {
            // If the Pokémon is in a battle, we trigger an event to the front-end.
            BattleData.Battle.EventHook.Invoke(new DamageEvent(this, CurrentHealth, newHealth, source)
            {
                BatchId = batchId,
            });
            // And allow scripts to execute.
            this.RunScriptHook(script => script.OnDamage(this, source, CurrentHealth, newHealth));
        }

        CurrentHealth = newHealth;

        // If the Pokémon is now fainted, we also run faint handling.
        if (IsFainted)
        {
            OnFaint(source);
        }
    }

    private void OnFaint(DamageSource source)
    {
        // If the Pokémon is not in a battle, we don't need to do anything.
        if (BattleData is null)
            return;

        // Trigger the faint event to the front-end.
        BattleData.Battle.EventHook.Invoke(new FaintEvent(this));

        // Allow scripts to trigger based on the faint.
        this.RunScriptHook(script => script.OnFaint(this, source));
        // Make sure the OnRemove script is run.
        this.RunScriptHook(script => script.OnRemove());

        // Mark the position as unfillable if it can't be filled by any party.
        if (!BattleData.Battle.CanSlotBeFilled(BattleData.SideIndex, BattleData.Position))
        {
            BattleData.Battle.Sides[BattleData.SideIndex].MarkPositionAsUnfillable(BattleData.Position);
        }

        // Validate the battle state to see if the battle is over.
        BattleData.Battle.ValidateBattleState();
    }

    /// <inheritdoc />
    public bool Heal(uint heal, bool allowRevive)
    {
        if (IsFainted && !allowRevive)
            return false;
        var maxAmount = this.BoostedStats.Hp - CurrentHealth;
        if (heal > maxAmount)
            heal = maxAmount;
        if (heal == 0)
            return false;
        var newHealth = CurrentHealth + heal;
        BattleData?.Battle.EventHook.Invoke(new HealEvent(this, CurrentHealth, newHealth));
        CurrentHealth = newHealth;
        return true;
    }

    /// <inheritdoc />
    /// <remarks>
    /// If the index is 255, it will try to find the first empty move slot.
    /// </remarks>
    public void LearnMove(string moveName, MoveLearnMethod method, byte index)
    {
        if (index == 255)
        {
            for (byte i = 0; i < Moves.Count; i++)
            {
                if (Moves[i] is not null) continue;
                index = i;
                break;
            }
        }

        if (index >= Moves.Count)
            throw new InvalidOperationException("No empty move slot found.");
        if (!Library.StaticLibrary.Moves.TryGet(moveName, out var move))
            throw new KeyNotFoundException($"Move {moveName} not found.");

        _learnedMoves[index] = new LearnedMoveImpl(move, method);
    }

    /// <inheritdoc />
    public void ClearStatus() => StatusScript.Clear();

    /// <inheritdoc />
    public void ChangeLevelBy(int change)
    {
        var newLevel = Level + change;
        Level = (LevelInt)Math.Clamp(newLevel, 1, Library.StaticLibrary.Settings.MaxLevel);
        RecalculateFlatStats();
    }

    /// <inheritdoc />
    public void SetBattleData(IBattle battle, byte sideIndex)
    {
        if (BattleData is not null)
        {
            BattleData.Battle = battle;
            BattleData.SideIndex = sideIndex;
        }
        else
        {
            BattleData = new PokemonBattleDataImpl(battle, sideIndex);
        }
    }

    /// <inheritdoc />
    public void SetOnBattlefield(bool onBattleField)
    {
        if (BattleData is not null)
        {
            BattleData.IsOnBattlefield = onBattleField;
            if (!onBattleField)
            {
                Volatile.Clear();
                WeightInKm = Form.Weight;
                HeightInMeters = Form.Height;
            }
        }
    }

    /// <inheritdoc />
    public void SetBattleSidePosition(byte position)
    {
        if (BattleData is not null)
        {
            BattleData.Position = position;
        }
    }

    /// <inheritdoc />
    public void MarkOpponentAsSeen(IPokemon pokemon) => BattleData?.MarkOpponentAsSeen(pokemon);

    /// <inheritdoc />
    public override int ScriptCount
    {
        get
        {
            var c = 4;
            if (BattleData != null)
            {
                var side = BattleData.Battle.Sides[BattleData.SideIndex];
                c += side.ScriptCount;
            }

            return c;
        }
    }

    /// <inheritdoc />
    public override void GetOwnScripts(List<IEnumerable<ScriptContainer>> scripts)
    {
        scripts.Add(HeldItemTriggerScript);
        scripts.Add(AbilityScript);
        scripts.Add(StatusScript);
        scripts.Add(Volatile);
    }

    /// <inheritdoc />
    public override void CollectScripts(List<IEnumerable<ScriptContainer>> scripts)
    {
        GetOwnScripts(scripts);
        if (BattleData != null)
        {
            var side = BattleData.Battle.Sides[BattleData.SideIndex];
            side.CollectScripts(scripts);
        }
    }
}

/// <inheritdoc />
public class PokemonBattleDataImpl : IPokemonBattleData
{
    /// <inheritdoc cref="PokemonBattleDataImpl"/>
    public PokemonBattleDataImpl(IBattle battle, byte sideIndex)
    {
        Battle = battle;
        SideIndex = sideIndex;
    }

    /// <inheritdoc />
    public IBattle Battle { get; set; }

    /// <inheritdoc />
    public byte SideIndex { get; set; }

    /// <inheritdoc />
    public byte Position { get; set; }

    private readonly List<IPokemon> _seenOpponents = [];
    /// <inheritdoc />
    public IReadOnlyList<IPokemon> SeenOpponents => _seenOpponents;

    /// <inheritdoc />
    public bool IsOnBattlefield { get; set; }

    /// <inheritdoc />
    public void MarkOpponentAsSeen(IPokemon opponent)
    {
        _seenOpponents.Add(opponent);
    }
}