using System;
using System.Collections.Concurrent;

namespace AcDream.Core.Combat;

/// <summary>
/// Client-side combat state — tracks per-entity health percent and
/// emits typed events when UpdateHealth / Victim / Attacker / Defender
/// notifications arrive. Powers target HP bars, damage floaters, combat
/// log panel.
///
/// <para>
/// Retail client-side combat responsibilities (r02 §7):
/// <list type="bullet">
///   <item><description>
///     Maintain a cache of "last known health percent" per entity guid.
///     UpdateHealth (0x01C0) is sent when the player queries or the
///     server broadcasts a change.
///   </description></item>
///   <item><description>
///     Convert raw damage events into UI-ready notifications (colored
///     floating numbers, "Critical!" flashes, body-part locations).
///   </description></item>
///   <item><description>
///     Track self-centered notifications (you hit / you got hit / you
///     evaded / you were evaded) so the log panel can format them
///     correctly.
///   </description></item>
/// </list>
/// </para>
///
/// <para>
/// The server is authoritative: this class does NOT simulate damage
/// locally (exception: a predictive-ish "estimated damage" display for
/// the attack bar UI, which can use <see cref="CombatMath"/>).
/// </para>
/// </summary>
public sealed class CombatState
{
    private readonly ConcurrentDictionary<uint, float> _healthByGuid = new();

    public CombatMode CurrentMode { get; private set; } = CombatMode.NonCombat;

    /// <summary>Fires when a target's health percent changes (from UpdateHealth).</summary>
    public event Action<uint /*guid*/, float /*percent*/>? HealthChanged;

    /// <summary>You (the player) got hit for some damage.</summary>
    public event Action<DamageIncoming>? DamageTaken;

    /// <summary>You (the player) dealt some damage.</summary>
    public event Action<DamageDealt>? DamageDealtAccepted;

    /// <summary>You (the player) evaded an incoming hit.</summary>
    public event Action<string>? EvadedIncoming;

    /// <summary>The target evaded your hit.</summary>
    public event Action<string>? MissedOutgoing;

    /// <summary>An attack commit completed (0x01A7). WeenieError = 0 on success.</summary>
    public event Action<uint /*attackSeq*/, uint /*weenieError*/>? AttackDone;

    /// <summary>The server accepted the attack and the power bar/animation can begin.</summary>
    public event Action? AttackCommenced;

    /// <summary>The locally requested or server-confirmed combat mode changed.</summary>
    public event Action<CombatMode>? CombatModeChanged;

    /// <summary>
    /// Fires when the server confirms the player landed a killing blow
    /// (GameEvent <c>KillerNotification (0x01AD)</c>). Event payload is
    /// the victim's display name + their server GUID. Used by killfeed UI
    /// (future panel) and any plugin scoring kill counts.
    /// </summary>
    public event Action<string /*victimName*/, uint /*victimGuid*/>? KillLanded;

    public readonly record struct DamageIncoming(
        string AttackerName,
        uint AttackerGuid,
        uint DamageType,
        uint Damage,
        uint HitQuadrant,
        bool Critical,
        uint AttackType);

    public readonly record struct DamageDealt(
        string DefenderName,
        uint DamageType,
        uint Damage,
        float DamagePercent);

    /// <summary>Retrieve last known health percent for a guid, or 1.0 if unknown.</summary>
    public float GetHealthPercent(uint guid) =>
        _healthByGuid.TryGetValue(guid, out var pct) ? pct : 1f;

    public int TrackedTargetCount => _healthByGuid.Count;

    // ── Inbound handlers (wired from WorldSession.GameEvents) ────────────────

    public void OnUpdateHealth(uint targetGuid, float healthPercent)
    {
        _healthByGuid[targetGuid] = healthPercent;
        HealthChanged?.Invoke(targetGuid, healthPercent);
    }

    public void SetCombatMode(CombatMode mode)
    {
        if (CurrentMode == mode)
            return;

        CurrentMode = mode;
        CombatModeChanged?.Invoke(mode);
    }

    public void OnVictimNotification(
        string attackerName, uint attackerGuid, uint damageType, uint damage,
        uint hitQuadrant, uint critical, uint attackType)
    {
        DamageTaken?.Invoke(new DamageIncoming(
            attackerName, attackerGuid, damageType, damage, hitQuadrant,
            critical != 0, attackType));
    }

    public void OnDefenderNotification(
        string attackerName, uint attackerGuid, uint damageType, uint damage,
        uint hitQuadrant, uint critical)
    {
        // DefenderNotification is semantically the same as VictimNotification
        // from the defender's POV — the client log merges them.
        DamageTaken?.Invoke(new DamageIncoming(
            attackerName, attackerGuid, damageType, damage, hitQuadrant,
            critical != 0, 0));
    }

    public void OnAttackerNotification(
        string defenderName, uint damageType, uint damage, float damagePercent)
    {
        DamageDealtAccepted?.Invoke(new DamageDealt(
            defenderName, damageType, damage, damagePercent));
    }

    public void OnEvasionAttackerNotification(string defenderName)
        => MissedOutgoing?.Invoke(defenderName);

    /// <summary>
    /// Server confirmation that the player landed a killing blow on a
    /// target. Wire source: GameEvent <c>KillerNotification (0x01AD)</c>
    /// — the parser at <c>GameEvents.ParseKillerNotification</c> shipped
    /// alongside victim/defender notifications but was never registered
    /// for dispatch until 2026-04-25 (per ISSUES.md #10).
    /// </summary>
    public void OnKillerNotification(string victimName, uint victimGuid)
        => KillLanded?.Invoke(victimName, victimGuid);

    public void OnEvasionDefenderNotification(string attackerName)
        => EvadedIncoming?.Invoke(attackerName);

    public void OnAttackDone(uint attackSequence, uint weenieError)
        => AttackDone?.Invoke(attackSequence, weenieError);

    public void OnCombatCommenceAttack()
        => AttackCommenced?.Invoke();

    public void Clear() => _healthByGuid.Clear();
}