using System;
using System.Threading;

namespace AcDream.Core.Chat;

/// <summary>
/// Retail's per-chat-window text-type filter and open/visible state — window
/// id <c>0</c> is the main chat window, ids <c>1</c>-<c>4</c> are the four
/// floating chat windows (Campaign CH slice CH6b,
/// <c>docs/research/2026-08-09-chat-retail-window-shell.md</c> §1.2 and
/// <c>docs/research/2026-08-09-chat-retail-color-table.md</c> §4). These are
/// acdream's OWN compact indices, not retail's raw <c>m_eWindowID</c> values:
/// retail's actual main window is <c>m_eWindowID == 8</c>, its floaties are
/// <c>2</c>-<c>5</c>, and <c>m_eWindowID == 0</c> is retail's ctor-default
/// "unauthored" sentinel — none of that is <c>0</c>-<c>4</c> (CH6a/b
/// REJECT-review SHOULD-FIX 2,
/// <c>docs/research/2026-08-10-ch6ab-review-findings.md</c>).
///
/// <para>
/// Ports two retail mechanisms exactly:
/// <list type="bullet">
///   <item><c>ChatInterface::PostInit @0x004F3DD0</c>'s <c>m_oldState</c>
///   switch seeds each window's default 64-bit
///   <c>m_llTextTypeFilter</c> (color-table doc §4's table — the constants
///   below are byte-identical to that table; retail's own main-window default
///   0xFBFFFFFF is shared by <c>m_eWindowID</c> 1 AND 8, and the floaty
///   defaults come from retail <c>m_eWindowID</c> 2-5, one higher than
///   acdream's compact 1-4).</item>
///   <item><c>ChatInterface::RecvNotice_DisplayFinalStringInfo
///   @0x004F4640</c>'s display predicate: a line shows in window
///   <c>W</c> when the message's target window id equals <c>W</c>
///   (explicit addressing) OR the message is broadcast
///   (<see cref="BroadcastTargetWindow"/>) AND <c>W</c>'s filter accepts the
///   line's <see cref="RetailLogTextType"/> (<c>ChatInterface::TypeIsActive
///   @0x004F2F10</c>).</item>
/// </list>
/// </para>
///
/// <para>
/// <see cref="BroadcastTargetWindow"/> is a sentinel distinct from every real
/// window id (<c>0</c>-<c>4</c>) — the acdream-internal analogue of retail's
/// wire <c>arg5 == 0</c> broadcast marker, deliberately kept separate from
/// window id <c>0</c> (main). Earlier CH6b code conflated the two (both were
/// literal <c>0</c>), so <see cref="ShouldDisplay"/>'s explicit-addressing
/// branch (<c>targetWindowId == windowId</c>) short-circuited true for EVERY
/// broadcast line evaluated against the main window, regardless of its own
/// filter — the CH6a/b REJECT-review BLOCKER. With the sentinel separated
/// out, the main window's filter is genuinely consulted for broadcast lines,
/// <see cref="SetFilter"/> is a real (not inert) write for window <c>0</c>
/// too, and a future explicit <c>targetWindowId == MainWindowId</c> (AP-180's
/// <c>m_idCurrentCommandSource</c> per-window echo) stays distinguishable
/// from an ordinary broadcast line. <see cref="SetOpen"/>/<see cref="Toggle"/>
/// keep their own, UNRELATED no-op for window <c>0</c> — retail's main window
/// is simply never closable, independent of the broadcast-sentinel fix.
/// </para>
///
/// <para>
/// No production <see cref="ChatEntry"/> carries an explicit target window
/// id yet (register row AP-180 — the <c>windowId</c> dual-destination echo
/// is deferred); every current line is effectively broadcast
/// (<c>targetWindowId == </c><see cref="BroadcastTargetWindow"/>).
/// <see cref="ShouldDisplay"/> still accepts the full retail shape so the
/// routing predicate does not need to change shape when AP-180 lands.
/// </para>
/// </summary>
public sealed class ChatWindowState
{
    public const int MainWindowId = 0;
    public const int MinFloatingWindowId = 1;
    public const int MaxFloatingWindowId = 4;

    /// <summary>
    /// Retail's authored per-window text-type filter defaults
    /// (<c>gmChatOptionsUI::InitOptions @0x0049FC60</c> /
    /// <c>AddCheckboxBitfield64Option @0x0049EDA0</c>'s <c>SetDefaultValue</c> calls,
    /// <c>docs/research/2026-08-10-options-panel-structure.md</c> §5.2). Named here
    /// (rather than only as the private literals in <see cref="ResetToDefaults"/>)
    /// because Campaign OP slice OP5's Chat-tab Defaults button needs the SAME
    /// values <see cref="ResetToDefaults"/> seeds — one source, not two independently
    /// literal tables that could drift.
    /// </summary>
    public const ulong MainWindowDefaultFilter = 0xFBFFFFFFul;
    public const ulong Floaty1DefaultFilter = 0x0000101Cul;
    public const ulong Floaty2DefaultFilter = 0x00040C00ul;
    public const ulong Floaty3DefaultFilter = 0x00080000ul;
    public const ulong Floaty4DefaultFilter = 0x78000000ul;

    /// <summary>
    /// Sentinel <c>targetWindowId</c> meaning "broadcast to every window,
    /// subject to each window's own filter" — the acdream-internal analogue
    /// of retail's wire <c>arg5 == 0</c>. Deliberately outside the
    /// <c>0</c>-<c>4</c> real-window-id range (see the class doc) so it can
    /// never collide with <see cref="MainWindowId"/>.
    /// </summary>
    public const uint BroadcastTargetWindow = uint.MaxValue;

    private const int WindowCount = MaxFloatingWindowId + 1;

    private readonly object _gate = new();
    private readonly ulong[] _filters = new ulong[WindowCount];
    private readonly bool[] _open = new bool[WindowCount];
    private long _revision;

    public ChatWindowState() => ResetToDefaults();

    /// <summary>
    /// Monotonic counter bumped on every filter or open-state change.
    /// Lets presentation caches (per-window transcript layout) detect a
    /// filter/visibility change without re-deriving it from the raw arrays.
    /// </summary>
    public long Revision => Interlocked.Read(ref _revision);

    /// <summary>
    /// Reset every window to retail's <c>PostInit</c> defaults (color-table
    /// doc §4). The high dword is always <c>0</c> for every window — Society
    /// (<c>0x20</c>) and the reserved slot (<c>0x21</c>) are opt-in only,
    /// matching retail. Windows 1-4 start closed; window 0 (main) is always
    /// open.
    /// </summary>
    public void ResetToDefaults()
    {
        lock (_gate)
        {
            // "everything 0x00-0x1F except 0x1A" (m_oldState 1/8) — genuinely
            // consulted for broadcast lines now that BroadcastTargetWindow is
            // distinct from MainWindowId (see class doc).
            _filters[0] = MainWindowDefaultFilter;
            // Speech, Tell, Speech_Direct_Send, Emote (m_oldState 2).
            _filters[1] = Floaty1DefaultFilter;
            // Social, Social_Send, Allegiance (m_oldState 3).
            _filters[2] = Floaty2DefaultFilter;
            // Fellowship (m_oldState 4).
            _filters[3] = Floaty3DefaultFilter;
            // Turbine General/Trade/LFG/Roleplay (m_oldState 5).
            _filters[4] = Floaty4DefaultFilter;

            _open[0] = true;
            for (int i = MinFloatingWindowId; i <= MaxFloatingWindowId; i++)
                _open[i] = false;

            Interlocked.Increment(ref _revision);
        }
    }

    public ulong GetFilter(int windowId)
    {
        ValidateWindowId(windowId);
        lock (_gate) return _filters[windowId];
    }

    /// <summary>
    /// Set window <paramref name="windowId"/>'s 64-bit type filter — including
    /// the main window (id <c>0</c>): CH6a/b REJECT-review SHOULD-FIX 2 drops
    /// the old no-op (see the class doc's <see cref="BroadcastTargetWindow"/>
    /// paragraph). Retail's main window IS user-settable through the options
    /// page; only the settings UI to drive this is future work.
    /// </summary>
    public void SetFilter(int windowId, ulong filter)
    {
        ValidateWindowId(windowId);
        lock (_gate)
        {
            if (_filters[windowId] == filter) return;
            _filters[windowId] = filter;
            Interlocked.Increment(ref _revision);
        }
    }

    /// <summary>Main window (id 0) is always open.</summary>
    public bool IsOpen(int windowId)
    {
        ValidateWindowId(windowId);
        if (windowId == MainWindowId) return true;
        lock (_gate) return _open[windowId];
    }

    /// <summary>No-op for the main window — it cannot be closed.</summary>
    public void SetOpen(int windowId, bool open)
    {
        ValidateWindowId(windowId);
        if (windowId == MainWindowId) return;
        lock (_gate)
        {
            if (_open[windowId] == open) return;
            _open[windowId] = open;
            Interlocked.Increment(ref _revision);
        }
    }

    /// <summary>
    /// Flip window <paramref name="windowId"/>'s open state and return the
    /// new value. Always returns <see langword="true"/> for the main window
    /// (it cannot be toggled closed).
    /// </summary>
    public bool Toggle(int windowId)
    {
        ValidateWindowId(windowId);
        if (windowId == MainWindowId) return true;
        lock (_gate)
        {
            bool next = !_open[windowId];
            _open[windowId] = next;
            Interlocked.Increment(ref _revision);
            return next;
        }
    }

    /// <summary>
    /// <c>ChatInterface::TypeIsActive @0x004F2F10</c>: does window
    /// <paramref name="windowId"/>'s filter accept retail
    /// <see cref="RetailLogTextType"/> <paramref name="logTextType"/>?
    /// Types <c>&gt;= 64</c> are never active (there is no such bit).
    /// </summary>
    public bool TypeIsActive(int windowId, uint logTextType)
    {
        ValidateWindowId(windowId);
        if (logTextType >= 64u) return false;
        ulong filter;
        lock (_gate) filter = _filters[windowId];
        return ((1UL << (int)logTextType) & filter) != 0UL;
    }

    /// <summary>
    /// <c>ChatInterface::RecvNotice_DisplayFinalStringInfo @0x004F4640</c>'s
    /// exact display predicate — see the class doc for the two branches.
    /// <paramref name="targetWindowId"/> is either a real window id
    /// (<c>0</c>-<c>4</c>, explicit addressing) or
    /// <see cref="BroadcastTargetWindow"/> (broadcast, filtered per window).
    /// </summary>
    public bool ShouldDisplay(int windowId, uint targetWindowId, uint logTextType)
    {
        ValidateWindowId(windowId);
        if (targetWindowId == (uint)windowId) return true;
        return targetWindowId == BroadcastTargetWindow && TypeIsActive(windowId, logTextType);
    }

    private static void ValidateWindowId(int windowId)
    {
        if (windowId < MainWindowId || windowId > MaxFloatingWindowId)
            throw new ArgumentOutOfRangeException(
                nameof(windowId), windowId, "chat window id must be 0 (main) through 4 (floating).");
    }
}