using System;
using System.Collections.Concurrent;
using System.Collections.Generic;

namespace AcDream.Core.Spells;

/// <summary>
/// Client-side spellbook mirror. Tracks which spells the player has
/// learned (<c>UpdateSpell</c> 0x02C1) + a parallel active-enchantment
/// table keyed by layer id (<c>UpdateEnchantment</c> 0x02C2 etc.).
///
/// <para>
/// The UI binds to the collection-changed events so the spellbook
/// panel + active-buff bar redraw automatically when the server
/// pushes changes.
/// </para>
/// </summary>
public sealed class Spellbook
{
    private readonly HashSet<uint> _learnedSpells = new();
    private readonly ConcurrentDictionary<uint, ActiveEnchantmentRecord> _activeByLayer = new();
    private readonly SpellTable _table;

    /// <summary>
    /// Build a Spellbook with an optional <see cref="SpellTable"/>
    /// metadata source. When provided, <see cref="TryGetMetadata"/>
    /// returns the static spell descriptor (name / school / family /
    /// icon / mana / duration / etc.). When absent (back-compat for
    /// existing constructors / tests), <see cref="TryGetMetadata"/>
    /// always returns <c>false</c>.
    /// </summary>
    public Spellbook(SpellTable? table = null)
    {
        _table = table ?? SpellTable.Empty;
    }

    /// <summary>
    /// Look up static spell metadata. Closes ISSUES.md #11 — feeds the
    /// buff bar UI labels + icons + the family-stacking aggregation in
    /// <c>EnchantmentMath</c> (issue #6).
    /// </summary>
    public bool TryGetMetadata(uint spellId, out SpellMetadata meta) =>
        _table.TryGet(spellId, out meta);

    /// <summary>The spell-metadata table this spellbook was built with.
    /// Returns <see cref="SpellTable.Empty"/> if none was provided.</summary>
    public SpellTable Metadata => _table;

    /// <summary>
    /// Issue #6 — combined buff modifier for a vital stat. Aggregates
    /// over <see cref="ActiveEnchantments"/> through
    /// <see cref="EnchantmentMath.GetMod"/> with family-stacking dedup
    /// from the spell metadata table. Returns
    /// <see cref="EnchantmentMath.VitalMod.Identity"/> when no buffs
    /// apply (or when no SpellTable was wired).
    /// </summary>
    public EnchantmentMath.VitalMod GetVitalMod(uint statKey) =>
        EnchantmentMath.GetMod(ActiveEnchantments, _table, statKey);

    /// <summary>Fires when a spell is added to the player's spellbook.</summary>
    public event Action<uint>? SpellLearned;

    /// <summary>Fires when a spell is removed (rare — usually on respec / admin).</summary>
    public event Action<uint>? SpellForgotten;

    /// <summary>Fires when an enchantment is added / refreshed.</summary>
    public event Action<ActiveEnchantmentRecord>? EnchantmentAdded;

    /// <summary>Fires when an enchantment is removed (expired / dispelled).</summary>
    public event Action<ActiveEnchantmentRecord>? EnchantmentRemoved;

    /// <summary>All currently learned spell ids.</summary>
    public IReadOnlyCollection<uint> LearnedSpells => _learnedSpells;

    /// <summary>All currently-active enchantments.</summary>
    public IEnumerable<ActiveEnchantmentRecord> ActiveEnchantments => _activeByLayer.Values;

    public int LearnedCount => _learnedSpells.Count;
    public int ActiveCount  => _activeByLayer.Count;

    public bool Knows(uint spellId) => _learnedSpells.Contains(spellId);

    // ── Inbound handlers ─────────────────────────────────────────────────────

    /// <summary>0x02C1 MagicUpdateSpell: learn a spell.</summary>
    public void OnSpellLearned(uint spellId)
    {
        if (_learnedSpells.Add(spellId))
            SpellLearned?.Invoke(spellId);
    }

    /// <summary>0x01A8 MagicRemoveSpell: forget a spell.</summary>
    public void OnSpellForgotten(uint spellId)
    {
        if (_learnedSpells.Remove(spellId))
            SpellForgotten?.Invoke(spellId);
    }

    /// <summary>0x02C2 MagicUpdateEnchantment: enchantment added / refreshed.</summary>
    public void OnEnchantmentAdded(uint spellId, uint layerId, float duration, uint casterGuid)
    {
        var record = new ActiveEnchantmentRecord(spellId, layerId, duration, casterGuid);
        _activeByLayer[layerId] = record;
        EnchantmentAdded?.Invoke(record);
    }

    /// <summary>
    /// Issue #7 / #12 — accept a fully-populated record from
    /// <c>PlayerDescription</c>'s enchantment block (which carries
    /// the StatMod triad + bucket). Used when the wire-format extension
    /// gives us the full per-enchantment payload, rather than the
    /// 4-field summary from <c>MagicUpdateEnchantment</c>.
    /// </summary>
    public void OnEnchantmentAdded(ActiveEnchantmentRecord record)
    {
        _activeByLayer[record.LayerId] = record;
        EnchantmentAdded?.Invoke(record);
    }

    /// <summary>0x02C3 / 0x02C7 MagicRemove/DispelEnchantment.</summary>
    public void OnEnchantmentRemoved(uint layerId, uint spellId)
    {
        if (_activeByLayer.TryRemove(layerId, out var record))
            EnchantmentRemoved?.Invoke(record);
        else
            EnchantmentRemoved?.Invoke(new ActiveEnchantmentRecord(spellId, layerId, 0f, 0));
    }

    /// <summary>0x02C6 MagicPurgeEnchantments: clear all active buffs.</summary>
    public void OnPurgeAll()
    {
        foreach (var rec in _activeByLayer.Values)
            EnchantmentRemoved?.Invoke(rec);
        _activeByLayer.Clear();
    }

    public void Clear()
    {
        _learnedSpells.Clear();
        _activeByLayer.Clear();
    }
}

/// <summary>
/// Summary of one active enchantment layer on the player. The
/// optional StatMod fields (issue #12) carry the wire-level
/// `_smod` triad <c>(type, key, val)</c> when available — only
/// `PlayerDescription`'s enchantment block currently populates these
/// (<see cref="AcDream.Core.Net.Messages.PlayerDescriptionParser"/>).
/// `MagicUpdateEnchantment` events still produce records with these
/// fields null until the wire parser is extended.
///
/// <para>
/// <see cref="Bucket"/> tells <c>EnchantmentMath</c> whether this
/// enchantment's StatMod is multiplicative (<c>0x01</c>), additive
/// (<c>0x02</c>), cooldown (<c>0x04</c>), or vitae (<c>0x08</c>) per
/// the retail <c>EnchantmentMask</c> classification.
/// </para>
/// </summary>
public readonly record struct ActiveEnchantmentRecord(
    uint   SpellId,
    uint   LayerId,
    float  Duration,
    uint   CasterGuid,
    uint?  StatModType   = null,
    uint?  StatModKey    = null,
    float? StatModValue  = null,
    uint   Bucket        = 0);