using System.Buffers.Binary;
using Ananta.SDK.Network;
using Ananta.SDK.Rpc;
using Ananta.Server.ClientData.Client4229938;
using Ananta.Server.Protocol.Client4229938;

namespace Ananta.Server.Handlers.Game;

/// <summary>
/// BBChat — AppId 27 "Message" (SystemId 146), the phone's NPC chat app. It is NOT the player IM:
/// its red dot comes from <c>gRedDotUtils.CheckNpcChatHasRedDot()</c> (MainPhoneUtils.lua:688) and
/// its panels are the <c>NpcChat*</c> stores, i.e. everything here is <c>gNpcChatManager</c>.
///
/// Content half: the conversation list is published by the login frame
/// (<c>InfoNpcCultivation.NpcChats</c> / <c>NpcGroupChats</c>, see RuntimePayloadFactory.FillNpcChats
/// and NpcChatCatalog4229938). Nothing here refills it — there is no pull request for that list.
///
/// Interaction half: every request below carries exactly one u32 (<c>chatid</c>) and the client
/// declares no reply reader for any of them (no <c>midToReader</c> entry in RPCDeserializeAuto for
/// 63013781 / 63098840 / 63137850 / 63203620 / 63266674 / 63082065), so the answer must be the
/// empty OK — anything else desynchronises nothing the client reads but wastes bytes. What actually
/// moves a conversation is the <c>SyncNpcChat</c> push: the next row of NPCChatConfig.
///
/// ⛑ The server owns no chat text. A row is "which config id is unlocked next"; the client resolves
/// speaker, side, avatar and body itself via <c>LTConfig.NPCChatConfig.GetConfig(chatItem.ChatId)</c>
/// (<c>NpcChatUtils.NewFromNpcChatItem</c>), which drops any id it does not know with a
/// "NPCChat表没有查到" error — hence NextChatId always comes from the catalogue's own map.
/// </summary>
internal sealed partial class GameRouter
{
    /// <summary>InteractNpcChatToEnd bursts get this many rows per gesture — see InteractNpcChatToEnd.</summary>
    private const int NpcChatSkipBatch = 24;

    /// <summary>Leading u32 of every request body here.</summary>
    private static uint NpcChatRequestId(UxRpcMessage msg)
        => msg.Body.Length >= 4 ? BinaryPrimitives.ReadUInt32LittleEndian(msg.Body) : 0u;

    // =================================================================================
    // Advancing a conversation
    //
    // Three different requests do the same thing from three different entry points, and all of them
    // mean "take the given row's NextMessage[0] and hand it to the client":
    //   InteractNpcChat(63098840)  NpcChatChattingPanelStore.lua:1035/1055 — tap to continue
    //   ChatToNpc(63013781)        :1169 — the player picked an authored reply
    //   InviteNpcChat(63137850)    :1142 — the player accepted an invite row
    // The client arms a timeout before sending (StartChatTimeout) and clears it when the push lands,
    // so pushing nothing would leave the panel spinning for its timeout window; pushing the same row
    // back would be worse, hence the explicit unknown-row branch below.
    // =================================================================================

    [Handler(MethodId.InteractNpcChat, HandlerPacketKind.Invoke)]
    private Task InteractNpcChat(Connection conn, UxRpcMessage msg)
        => AdvanceNpcChatAsync(conn, msg, "interact");

    [Handler(MethodId.ChatToNpc, HandlerPacketKind.Invoke)]
    private Task ChatToNpc(Connection conn, UxRpcMessage msg)
        => AdvanceNpcChatAsync(conn, msg, "chatToNpc");

    [Handler(MethodId.InviteNpcChat, HandlerPacketKind.Invoke)]
    private Task InviteNpcChat(Connection conn, UxRpcMessage msg)
        => AdvanceNpcChatAsync(conn, msg, "invite");

    private async Task AdvanceNpcChatAsync(Connection conn, UxRpcMessage msg, string via)
    {
        var id = NpcChatRequestId(msg);
        if (!NpcChatCatalog4229938.Knows(id))
        {
            conn.Log.Info($"[NPCCHAT] {via} id={id} -> unknown row, nothing to push");
            await conn.ReturnEmptyOkAsync(msg);
            return;
        }

        var next = NpcChatCatalog4229938.NextOf(id);
        if (next == 0)
        {
            // End of the conversation. The client's own contract for that is the NpcChatFinished
            // error code; it is left as OK because returning an unexpected code path here closes the
            // phone panel (NpcChatChattingPanelStore.lua:1064-1078) even mid-conversation.
            conn.Log.Info($"[NPCCHAT] {via} id={id} -> end of thread");
            await conn.ReturnEmptyOkAsync(msg);
            return;
        }

        await conn.NotifyAsync(MethodId.SyncNpcChat, BuildNpcChatItem(next, id, read: false));
        conn.Log.Info($"[NPCCHAT] {via} id={id} -> pushed {next}");
        await conn.ReturnEmptyOkAsync(msg);
    }

    /// <summary>
    /// InteractNpcChatToEnd(63203620) — "skip to the end" button. The whole remaining tail of the
    /// thread is pushed as one burst so the panel can render it as history.
    ///
    /// Capped at <see cref="NpcChatSkipBatch"/> rows: the rows are pushed one SyncNpcChat at a time
    /// because that is the only framing the client reads for this, and a 60-message thread would
    /// otherwise hold the gesture hostage for a full row-by-row animation queue.
    /// </summary>
    [Handler(MethodId.InteractNpcChatToEnd, HandlerPacketKind.Invoke)]
    private async Task InteractNpcChatToEnd(Connection conn, UxRpcMessage msg)
    {
        var id = NpcChatRequestId(msg);
        if (!NpcChatCatalog4229938.Knows(id))
        {
            conn.Log.Info($"[NPCCHAT] skipToEnd id={id} -> unknown row");
            await conn.ReturnEmptyOkAsync(msg);
            return;
        }

        var pushed = 0;
        var current = id;
        while (pushed < NpcChatSkipBatch)
        {
            var next = NpcChatCatalog4229938.NextOf(current);
            if (next == 0)
                break;
            await conn.NotifyAsync(MethodId.SyncNpcChat, BuildNpcChatItem(next, current, read: true));
            current = next;
            pushed++;
        }

        conn.Log.Info($"[NPCCHAT] skipToEnd id={id} -> pushed {pushed} rows");
        await conn.ReturnEmptyOkAsync(msg);
    }

    // =================================================================================
    // Bookkeeping requests — nothing persists, everything answers OK
    // =================================================================================

    /// <summary>AskMarkNpcChatRead(63266674) — NpcChatChattingPanelStore.lua:132/818, NpcChatN2NChattingPanel.lua:217.</summary>
    [Handler(MethodId.AskMarkNpcChatRead, HandlerPacketKind.Invoke)]
    private Task AskMarkNpcChatRead(Connection conn, UxRpcMessage msg)
    {
        conn.Log.Info($"[NPCCHAT] markRead id={NpcChatRequestId(msg)}");
        return conn.ReturnEmptyOkAsync(msg);
    }

    /// <summary>
    /// RequestNpcChatList(63082065) — ChatNpcsPhoneManager.lua:229 / ChattingToNpcPanelStore.lua:375.
    ///
    /// Used by the GM "pull this conversation" route; the player-facing list already arrived in the
    /// login frame, so there is nothing to stream back — **but the reply still has a shape**:
    /// ⛑⛑ 2026-09-29 修正：客户端 `midToReturnMessageReader[63082065]` 是
    ///    `Base.ReadList7Bit(reader, …Complex[372])`，即 RET 是 **List&lt;T&gt; 而不是 void**。
    ///    原来 `ReturnEmptyOkAsync` 是 **0 字节载荷**（Connection.cs:32 `Array.Empty<byte>()`）
    ///    ⇒ 客户端 reader 读不到 presence 字节。实测 [NPCCHAT] 有触发（今日累计 2 次）。
    ///    ⇒ 回**空列表** `FF 01`（0xFF=presence，0x01=Int7(0) 的 +1 偏置，硬规则"空列表 2B"）。
    ///    数据本身仍为空（列表确实走登录包），但 wire 形状正确，客户端不会读空 buffer。
    ///    ⛑ 回滚：把 return 换回 `conn.ReturnEmptyOkAsync(msg)`。
    /// </summary>
    [Handler(MethodId.RequestNpcChatList, HandlerPacketKind.Invoke)]
    private Task RequestNpcChatList(Connection conn, UxRpcMessage msg)
    {
        conn.Log.Info($"[NPCCHAT] requestList id={NpcChatRequestId(msg)} " +
                      $"(list rides the login frame) -> empty list(ff 01)");
        return conn.ReturnRawAsync(msg, new byte[] { 0xFF, 0x01 });
    }

    /// <summary>AskCloseNpcChatWnd(67994672) — NpcChatChattingPanelStore.lua:635/1240, sent on the scene delegate.</summary>
    [Handler(MethodId.AskCloseNpcChatWnd, HandlerPacketKind.Invoke)]
    private Task AskCloseNpcChatWnd(Connection conn, UxRpcMessage msg)
    {
        conn.Log.Info($"[NPCCHAT] closeWnd id={NpcChatRequestId(msg)}");
        return conn.ReturnEmptyOkAsync(msg);
    }

    /// <summary>AskClearSpiritGroupChat(63527240) / AskClearNpcUncompletedInviteChat(63639364) — one-shot cleanups.</summary>
    [Handler(MethodId.AskClearSpiritGroupChat, HandlerPacketKind.Invoke)]
    private Task AskClearSpiritGroupChat(Connection conn, UxRpcMessage msg)
    {
        conn.Log.Info($"[NPCCHAT] clearSpiritGroupChat id={NpcChatRequestId(msg)}");
        return conn.ReturnEmptyOkAsync(msg);
    }

    [Handler(MethodId.AskClearNpcUncompletedInviteChat, HandlerPacketKind.Invoke)]
    private Task AskClearNpcUncompletedInviteChat(Connection conn, UxRpcMessage msg)
    {
        conn.Log.Info($"[NPCCHAT] clearUncompletedInvite id={NpcChatRequestId(msg)}");
        return conn.ReturnEmptyOkAsync(msg);
    }

    // =================================================================================
    // Row construction
    // =================================================================================

    /// <summary>
    /// One pushed/downloaded history row. Field order and the complex root come from the client's own
    /// reader — <c>Auto.Reader[372]</c> read via <c>Base.ReadComplex</c>, so the push starts with a
    /// 0xFF marker and no other framing is involved.
    /// </summary>
    private static Ananta.Server.RpcTypes.Client4229938.Auto.NpcChatItem BuildNpcChatItem(
        uint chatId, uint fromChatId, bool read)
    {
        return new Ananta.Server.RpcTypes.Client4229938.Auto.NpcChatItem
        {
            Timestamp = (uint)DateTimeOffset.UtcNow.ToUnixTimeSeconds(),
            ChatId = chatId,
            NextChatId = NpcChatCatalog4229938.NextOf(chatId),
            // No emoji / hyperlink payload: bubbles come from NPCChatConfig, not from us.
            ChatContext = null,
            // A pushed row is new to the player, so it must stay unread for the notify path; the
            // skip-to-end burst marks them read so opening a skipped thread does not leave 20 dots.
            IsRead = read,
            // AddNewNpcChatItem falls back to BelongNpc for the dictionary key when the row's
            // AsNpcCultivation is 0, so it has to be the row's own owner rather than anything we invent.
            BelongNpc = OwnerOf(chatId, fromChatId),
            ChatActionTriggeredTime = 0,
        };
    }

    /// <summary>
    /// Best-effort owner for a pushed row. The catalogue only stores owners for published threads, so
    /// anything else falls back to the owner of the row the player came from — what really matters is
    /// that it is non-zero and stable for a conversation, because it becomes the dictionary key.
    /// </summary>
    private static uint OwnerOf(uint chatId, uint fromChatId)
    {
        if (FindOwner(chatId) is { } direct)
            return direct;
        if (fromChatId != 0 && FindOwner(fromChatId) is { } viaCaller)
            return viaCaller;
        return 0;

        static uint? FindOwner(uint rowId)
        {
            foreach (var owner in NpcChatCatalog4229938.Npcs)
                foreach (var thread in owner.Threads)
                    foreach (var node in thread.Items)
                        if (node.Id == rowId)
                            return owner.Id;
            foreach (var owner in NpcChatCatalog4229938.Groups)
                foreach (var thread in owner.Threads)
                    foreach (var node in thread.Items)
                        if (node.Id == rowId)
                            return owner.Id;
            return null;
        }
    }
}