using System;
using System.Buffers.Binary;
using System.Text;

namespace AcDream.Core.Net.Messages;

/// <summary>
/// Parser + record types for the most-used <see cref="GameEventType"/>
/// sub-opcodes inside the <c>0xF7B0</c> envelope. Each parser takes the
/// <see cref="GameEventEnvelope.Payload"/> slice (header stripped) and
/// returns a typed record or null on malformed payload.
///
/// <para>
/// References: r08 protocol atlas §4 (wire specs) + ACE
/// <c>GameEventChat.cs</c>, <c>GameEventTell.cs</c>,
/// <c>GameEventUpdateHealth.cs</c>, <c>GameEventWeenieError.cs</c>,
/// <c>GameEventCommunicationTransientString.cs</c>.
/// </para>
/// </summary>
public static class GameEvents
{
    // ── Chat / communication ─────────────────────────────────────────────────

    /// <summary>0x0147 ChannelBroadcast payload.</summary>
    public readonly record struct ChannelBroadcast(
        uint ChannelId,
        string SenderName,
        string Message);

    public static ChannelBroadcast? ParseChannelBroadcast(ReadOnlySpan<byte> payload)
    {
        int pos = 0;
        if (payload.Length < 4) return null;
        uint channelId = BinaryPrimitives.ReadUInt32LittleEndian(payload);
        pos += 4;
        try
        {
            string sender  = ReadString16L(payload, ref pos);
            string message = ReadString16L(payload, ref pos);
            return new ChannelBroadcast(channelId, sender, message);
        }
        catch { return null; }
    }

    /// <summary>0x02BD Tell payload.</summary>
    public readonly record struct Tell(
        string Message,
        string SenderName,
        uint SenderGuid,
        uint TargetGuid,
        uint ChatType);

    public static Tell? ParseTell(ReadOnlySpan<byte> payload)
    {
        int pos = 0;
        try
        {
            string message = ReadString16L(payload, ref pos);
            string sender  = ReadString16L(payload, ref pos);
            if (payload.Length - pos < 12) return null;
            uint senderGuid = BinaryPrimitives.ReadUInt32LittleEndian(payload.Slice(pos)); pos += 4;
            uint targetGuid = BinaryPrimitives.ReadUInt32LittleEndian(payload.Slice(pos)); pos += 4;
            uint chatType   = BinaryPrimitives.ReadUInt32LittleEndian(payload.Slice(pos)); pos += 4;
            return new Tell(message, sender, senderGuid, targetGuid, chatType);
        }
        catch { return null; }
    }

    /// <summary>0x02EB CommunicationTransientString payload.</summary>
    public readonly record struct TransientMessage(string Message, uint ChatType);

    public static TransientMessage? ParseTransient(ReadOnlySpan<byte> payload)
    {
        int pos = 0;
        try
        {
            string message = ReadString16L(payload, ref pos);
            if (payload.Length - pos < 4) return null;
            uint chatType = BinaryPrimitives.ReadUInt32LittleEndian(payload.Slice(pos));
            return new TransientMessage(message, chatType);
        }
        catch { return null; }
    }

    /// <summary>0x0004 PopupString — modal dialog text.</summary>
    public static string? ParsePopupString(ReadOnlySpan<byte> payload)
    {
        int pos = 0;
        try { return ReadString16L(payload, ref pos); } catch { return null; }
    }

    // ── Errors ──────────────────────────────────────────────────────────────

    /// <summary>0x028A WeenieError: generic game-logic failure code.</summary>
    public static uint? ParseWeenieError(ReadOnlySpan<byte> payload)
    {
        if (payload.Length < 4) return null;
        return BinaryPrimitives.ReadUInt32LittleEndian(payload);
    }

    /// <summary>0x028B WeenieErrorWithString.</summary>
    public readonly record struct WeenieErrorWithString(uint ErrorCode, string Interpolation);

    public static WeenieErrorWithString? ParseWeenieErrorWithString(ReadOnlySpan<byte> payload)
    {
        if (payload.Length < 4) return null;
        uint code = BinaryPrimitives.ReadUInt32LittleEndian(payload);
        int pos = 4;
        try
        {
            string interp = ReadString16L(payload, ref pos);
            return new WeenieErrorWithString(code, interp);
        }
        catch { return null; }
    }

    // ── Vitals / combat ─────────────────────────────────────────────────────

    /// <summary>0x01C0 UpdateHealth: (guid, healthPercent 0..1).</summary>
    public readonly record struct UpdateHealth(uint TargetGuid, float HealthPercent);

    public static UpdateHealth? ParseUpdateHealth(ReadOnlySpan<byte> payload)
    {
        if (payload.Length < 8) return null;
        uint guid  = BinaryPrimitives.ReadUInt32LittleEndian(payload);
        float pct  = BinaryPrimitives.ReadSingleLittleEndian(payload.Slice(4));
        return new UpdateHealth(guid, pct);
    }

    // ── Pings / misc ────────────────────────────────────────────────────────

    /// <summary>0x01EA PingResponse: echoes the client ping id.</summary>
    public static uint? ParsePingResponse(ReadOnlySpan<byte> payload)
    {
        if (payload.Length < 4) return null;
        return BinaryPrimitives.ReadUInt32LittleEndian(payload);
    }

    // ── Spells / magic ──────────────────────────────────────────────────────

    /// <summary>0x02C1 MagicUpdateSpell: spell id added to spellbook.</summary>
    public static uint? ParseMagicUpdateSpell(ReadOnlySpan<byte> payload)
    {
        if (payload.Length < 4) return null;
        return BinaryPrimitives.ReadUInt32LittleEndian(payload);
    }

    // ── Combat notifications ────────────────────────────────────────────────

    /// <summary>0x01AC VictimNotification - death message for the victim.</summary>
    public readonly record struct VictimNotification(string DeathMessage);

    public static VictimNotification? ParseVictimNotification(ReadOnlySpan<byte> payload)
    {
        int pos = 0;
        try { return new VictimNotification(ReadString16L(payload, ref pos)); }
        catch { return null; }
    }

    /// <summary>0x01AD KillerNotification - death message for the killer.</summary>
    public readonly record struct KillerNotification(string DeathMessage);

    public static KillerNotification? ParseKillerNotification(ReadOnlySpan<byte> payload)
    {
        int pos = 0;
        try { return new KillerNotification(ReadString16L(payload, ref pos)); }
        catch { return null; }
    }

    /// <summary>0x01B1 AttackerNotification - "you hit X".</summary>
    public readonly record struct AttackerNotification(
        string DefenderName,
        uint DamageType,
        double HealthPercent,
        uint Damage,
        uint Critical,
        ulong AttackConditions);

    public static AttackerNotification? ParseAttackerNotification(ReadOnlySpan<byte> payload)
    {
        int pos = 0;
        try
        {
            string name = ReadString16L(payload, ref pos);
            if (payload.Length - pos < 28) return null;
            uint damageType = BinaryPrimitives.ReadUInt32LittleEndian(payload.Slice(pos)); pos += 4;
            double pct      = BinaryPrimitives.ReadDoubleLittleEndian(payload.Slice(pos)); pos += 8;
            uint damage     = BinaryPrimitives.ReadUInt32LittleEndian(payload.Slice(pos)); pos += 4;
            uint crit       = BinaryPrimitives.ReadUInt32LittleEndian(payload.Slice(pos)); pos += 4;
            ulong cond      = BinaryPrimitives.ReadUInt64LittleEndian(payload.Slice(pos)); pos += 8;
            return new AttackerNotification(name, damageType, pct, damage, crit, cond);
        }
        catch { return null; }
    }

    /// <summary>0x01B2 DefenderNotification - "X hit you".</summary>
    public readonly record struct DefenderNotification(
        string AttackerName,
        uint DamageType,
        double HealthPercent,
        uint Damage,
        uint HitQuadrant,
        uint Critical,
        ulong AttackConditions);

    public static DefenderNotification? ParseDefenderNotification(ReadOnlySpan<byte> payload)
    {
        int pos = 0;
        try
        {
            string name = ReadString16L(payload, ref pos);
            if (payload.Length - pos < 32) return null;
            uint dtype = BinaryPrimitives.ReadUInt32LittleEndian(payload.Slice(pos)); pos += 4;
            double pct = BinaryPrimitives.ReadDoubleLittleEndian(payload.Slice(pos)); pos += 8;
            uint dmg   = BinaryPrimitives.ReadUInt32LittleEndian(payload.Slice(pos)); pos += 4;
            uint quad  = BinaryPrimitives.ReadUInt32LittleEndian(payload.Slice(pos)); pos += 4;
            uint crit  = BinaryPrimitives.ReadUInt32LittleEndian(payload.Slice(pos)); pos += 4;
            ulong cond = BinaryPrimitives.ReadUInt64LittleEndian(payload.Slice(pos)); pos += 8;
            return new DefenderNotification(name, dtype, pct, dmg, quad, crit, cond);
        }
        catch { return null; }
    }

    /// <summary>0x01B3 EvasionAttackerNotification - "X evaded".</summary>
    public static string? ParseEvasionAttackerNotification(ReadOnlySpan<byte> payload)
    {
        int pos = 0;
        try { return ReadString16L(payload, ref pos); } catch { return null; }
    }

    /// <summary>0x01B4 EvasionDefenderNotification - "you evaded X".</summary>
    public static string? ParseEvasionDefenderNotification(ReadOnlySpan<byte> payload)
    {
        int pos = 0;
        try { return ReadString16L(payload, ref pos); } catch { return null; }
    }

    /// <summary>0x01B8 CombatCommenceAttack - empty payload.</summary>
    public static bool ParseCombatCommenceAttack(ReadOnlySpan<byte> payload) => payload.Length == 0;

    /// <summary>0x01A7 AttackDone - single WeenieError value.</summary>
    public readonly record struct AttackDone(uint AttackSequence, uint WeenieError);

    public static AttackDone? ParseAttackDone(ReadOnlySpan<byte> payload)
    {
        if (payload.Length < 4) return null;
        return new AttackDone(0u, BinaryPrimitives.ReadUInt32LittleEndian(payload));
    }

    // ── Spell enchantments ──────────────────────────────────────────────────

    /// <summary>
    /// 0x02C3 MagicRemoveEnchantment — (layerId, spellId).
    /// </summary>
    public readonly record struct MagicRemoveEnchantment(uint LayerId, uint SpellId);

    public static MagicRemoveEnchantment? ParseMagicRemoveEnchantment(ReadOnlySpan<byte> payload)
    {
        if (payload.Length < 8) return null;
        return new MagicRemoveEnchantment(
            BinaryPrimitives.ReadUInt32LittleEndian(payload),
            BinaryPrimitives.ReadUInt32LittleEndian(payload.Slice(4)));
    }

    /// <summary>0x01A8 MagicRemoveSpell — spell id removed from spellbook.</summary>
    public static uint? ParseMagicRemoveSpell(ReadOnlySpan<byte> payload)
    {
        if (payload.Length < 4) return null;
        return BinaryPrimitives.ReadUInt32LittleEndian(payload);
    }

    /// <summary>
    /// 0x02C2 MagicUpdateEnchantment — the Enchantment blob. Full layout
    /// (ACE <c>Enchantment.Pack</c>) is ~80+ bytes of spell metadata +
    /// stat mods. We expose the first few fields that drive the enchant
    /// bar UI; the rest is available via the raw payload view.
    /// </summary>
    public readonly record struct EnchantmentSummary(
        uint SpellId,
        uint LayerId,
        float Duration,
        uint CasterGuid);

    public static EnchantmentSummary? ParseMagicUpdateEnchantment(ReadOnlySpan<byte> payload)
    {
        // Layout (ACE Enchantment.Pack):
        //   u32 spellId
        //   u32 layerId
        //   f32 duration
        //   u32 casterGuid
        //   ... (stat mods, category, power, etc.)
        if (payload.Length < 16) return null;
        return new EnchantmentSummary(
            BinaryPrimitives.ReadUInt32LittleEndian(payload),
            BinaryPrimitives.ReadUInt32LittleEndian(payload.Slice(4)),
            BinaryPrimitives.ReadSingleLittleEndian(payload.Slice(8)),
            BinaryPrimitives.ReadUInt32LittleEndian(payload.Slice(12)));
    }

    /// <summary>
    /// 0x02C7 MagicDispelEnchantment — (layerId, spellId).
    /// Structure matches MagicRemoveEnchantment.
    /// </summary>
    public static MagicRemoveEnchantment? ParseMagicDispelEnchantment(ReadOnlySpan<byte> payload)
        => ParseMagicRemoveEnchantment(payload);

    // ── Appraise / identify ─────────────────────────────────────────────────

    /// <summary>0x00C9 IdentifyObjectResponse header.</summary>
    public readonly record struct IdentifyResponseHeader(
        uint Guid,
        uint AppraiseFlags,
        bool Success);

    /// <summary>
    /// Parse the header of an <c>IdentifyObjectResponse (0x00C9)</c>.
    /// Full property-bundle deserialization (int / bool / float / string
    /// tables per the AppraiseFlags bitfield) is a future pass; this
    /// header alone is enough for the UI to display "Appraise complete
    /// on target X" and to route into the repository.
    /// </summary>
    public static IdentifyResponseHeader? ParseIdentifyResponseHeader(ReadOnlySpan<byte> payload)
    {
        if (payload.Length < 12) return null;
        uint guid    = BinaryPrimitives.ReadUInt32LittleEndian(payload);
        uint flags   = BinaryPrimitives.ReadUInt32LittleEndian(payload.Slice(4));
        uint success = BinaryPrimitives.ReadUInt32LittleEndian(payload.Slice(8));
        return new IdentifyResponseHeader(guid, flags, success != 0);
    }

    /// <summary>0x0023 WieldObject: server-driven equip.</summary>
    public readonly record struct WieldObject(
        uint ItemGuid,
        uint EquipLoc,
        uint WielderGuid);

    public static WieldObject? ParseWieldObject(ReadOnlySpan<byte> payload)
    {
        if (payload.Length < 12) return null;
        return new WieldObject(
            BinaryPrimitives.ReadUInt32LittleEndian(payload),
            BinaryPrimitives.ReadUInt32LittleEndian(payload.Slice(4)),
            BinaryPrimitives.ReadUInt32LittleEndian(payload.Slice(8)));
    }

    /// <summary>0x0022 InventoryPutObjInContainer: server puts item into container slot.</summary>
    public readonly record struct InventoryPutObjInContainer(
        uint ItemGuid,
        uint ContainerGuid,
        uint Placement);

    public static InventoryPutObjInContainer? ParsePutObjInContainer(ReadOnlySpan<byte> payload)
    {
        if (payload.Length < 12) return null;
        return new InventoryPutObjInContainer(
            BinaryPrimitives.ReadUInt32LittleEndian(payload),
            BinaryPrimitives.ReadUInt32LittleEndian(payload.Slice(4)),
            BinaryPrimitives.ReadUInt32LittleEndian(payload.Slice(8)));
    }

    // ── Other small-payload events ──────────────────────────────────────────

    /// <summary>0x01C7 UseDone: the Use/UseWithTarget completion signal (WeenieError code).</summary>
    public static uint? ParseUseDone(ReadOnlySpan<byte> payload)
    {
        if (payload.Length < 4) return null;
        return BinaryPrimitives.ReadUInt32LittleEndian(payload);
    }

    /// <summary>0x019A InventoryPutObjectIn3D: server dropped item to ground.</summary>
    public static uint? ParsePutObjectIn3D(ReadOnlySpan<byte> payload)
    {
        if (payload.Length < 4) return null;
        return BinaryPrimitives.ReadUInt32LittleEndian(payload);
    }

    /// <summary>0x00A0 InventoryServerSaveFailed: revert a speculative local inventory op.</summary>
    public static uint? ParseInventoryServerSaveFailed(ReadOnlySpan<byte> payload)
    {
        if (payload.Length < 4) return null;
        return BinaryPrimitives.ReadUInt32LittleEndian(payload);
    }

    /// <summary>0x0052 CloseGroundContainer: server closed a ground container view.</summary>
    public static uint? ParseCloseGroundContainer(ReadOnlySpan<byte> payload)
    {
        if (payload.Length < 4) return null;
        return BinaryPrimitives.ReadUInt32LittleEndian(payload);
    }

    /// <summary>0x0207 TradeFailure: server trade error code.</summary>
    public static uint? ParseTradeFailure(ReadOnlySpan<byte> payload)
    {
        if (payload.Length < 4) return null;
        return BinaryPrimitives.ReadUInt32LittleEndian(payload);
    }

    /// <summary>0x0200 AddToTrade: (itemGuid, slotIndex).</summary>
    public readonly record struct AddToTrade(uint ItemGuid, uint SlotIndex);

    public static AddToTrade? ParseAddToTrade(ReadOnlySpan<byte> payload)
    {
        if (payload.Length < 8) return null;
        return new AddToTrade(
            BinaryPrimitives.ReadUInt32LittleEndian(payload),
            BinaryPrimitives.ReadUInt32LittleEndian(payload.Slice(4)));
    }

    /// <summary>0x0202 AcceptTrade: initiator guid.</summary>
    public static uint? ParseAcceptTrade(ReadOnlySpan<byte> payload)
    {
        if (payload.Length < 4) return null;
        return BinaryPrimitives.ReadUInt32LittleEndian(payload);
    }

    /// <summary>0x0264 QueryItemManaResponse: (itemGuid, manaPercent).</summary>
    public readonly record struct QueryItemManaResponse(uint ItemGuid, float ManaPercent);

    public static QueryItemManaResponse? ParseQueryItemManaResponse(ReadOnlySpan<byte> payload)
    {
        if (payload.Length < 8) return null;
        return new QueryItemManaResponse(
            BinaryPrimitives.ReadUInt32LittleEndian(payload),
            BinaryPrimitives.ReadSingleLittleEndian(payload.Slice(4)));
    }

    /// <summary>0x0274 CharacterConfirmationRequest — server-driven modal confirm.</summary>
    public readonly record struct CharacterConfirmationRequest(
        uint Type,
        uint ContextId,
        uint OtherGuid,
        string Message);

    public static CharacterConfirmationRequest? ParseCharacterConfirmationRequest(ReadOnlySpan<byte> payload)
    {
        if (payload.Length < 12) return null;
        int pos = 0;
        uint type      = BinaryPrimitives.ReadUInt32LittleEndian(payload);             pos += 4;
        uint contextId = BinaryPrimitives.ReadUInt32LittleEndian(payload.Slice(pos));  pos += 4;
        uint otherGuid = BinaryPrimitives.ReadUInt32LittleEndian(payload.Slice(pos));  pos += 4;
        try
        {
            string msg = ReadString16L(payload, ref pos);
            return new CharacterConfirmationRequest(type, contextId, otherGuid, msg);
        }
        catch { return null; }
    }

    // ── Shared string reader (matches LoginRequest.ReadString16L) ───────────

    private static string ReadString16L(ReadOnlySpan<byte> source, ref int pos)
    {
        if (source.Length - pos < 2) throw new FormatException("truncated String16L length");
        ushort length = BinaryPrimitives.ReadUInt16LittleEndian(source.Slice(pos));
        pos += 2;
        if (source.Length - pos < length) throw new FormatException("truncated String16L body");
        // Windows-1252 matches retail (and holtburger's encoding_rs::WINDOWS_1252).
        string result = Encoding.GetEncoding(1252).GetString(source.Slice(pos, length));
        pos += length;
        int recordSize = 2 + length;
        int padding = (4 - (recordSize & 3)) & 3;
        pos += padding;
        return result;
    }
}