// Runic Gateway Zones — a helper for ZoneManager, shipped beside the Runic Gateway bridge.
// Copyright (C) Runic Gateway contributors. GPL-3.0-or-later.
//
// ITS FIRST JOB (docs/modules/rust/PLAN_FIXES.md F12, D168, D181, D182):
//
// ZoneManager counts a player as inside a zone only when the zone's trigger fires on ENTRY. A
// zone created, updated or loaded around somebody who is already standing there never fires it,
// so ZoneManager says nobody is inside — and its flags, its enter message and `OnEnterZone` never
// happen for them. The first player walk found it twice: after a restart the org lead woke up
// eighteen metres inside an event zone the bridge had just re-created, and ZoneManager's
// `IsPlayerInZone` said no; and a zone opened around a player did the same. Every participant of
// an event that survives a restart scores nothing until they walk out and back in.
//
// ZoneManager has no public way to ask it to look again: the routine that does (`UpdatePlayerZones`)
// is private and runs only for a player who is connecting. So this helper patches ZoneManager with
// Harmony, which is the org lead's decision (D181):
//
//   * **The patch point is `Zone.InitializeZone`**, the one method a zone passes through when it is
//     created (`CreateOrUpdateZone`), updated (`Zone.Reset`) or loaded from ZoneManager's own data
//     file at startup. A postfix there sees every one of them.
//   * **It does not decide who is inside.** One tick later — when ZoneManager has finished
//     registering the zone — it asks ZoneManager's own public `IsPositionInZone` for each connected
//     player, and enters those it names through ZoneManager's own `OnPlayerEnterZone`. So ZoneManager's
//     flags, eject and kill rules, enter message and `OnEnterZone` all apply exactly as if the
//     player had walked in. A player ZoneManager already counts is skipped, and ZoneManager refuses
//     a second entry anyway, so a trigger that does fire after all changes nothing.
//   * **It fixes every zone on the server**, not only the bridge's. That is deliberate: the fault is
//     ZoneManager's, and it is the same fault for an arena another plugin made.
//
// A SECOND JOB (RunicNPC stage 9d walk, the org lead's call, 2026-10-07):
//
// ZoneManager subscribes the hooks that enforce its flags (`OnEntityTakeDamage` for PvpGod and the
// other damage flags, `OnEntityBuilt` for NoBuild, and so on) only for the flags some zone had when
// ZoneManager loaded, or when a flag is toggled by command. A zone made later through its API —
// which is every zone an event opens — never re-subscribes them, so on a server with no such zone
// already, an event's PvpGod or NoBuild zone enforces nothing: the 9d walk shot a player dead and
// built a foundation inside one. The same postfix that sees every zone made therefore also has
// ZoneManager run its own `UpdateHookSubscriptions` on the next tick. ZoneManager decides what to
// subscribe; this only asks it to look.
//
// It is optional. The bridge never depends on it to load: without it — deleted, or loaded but
// unable to find what it patches after a ZoneManager update — the bridge scores the zones it made
// by `IsPositionInZone` instead (D182), and reports this helper's state at hello so the site can
// say what is missing. `rgz.status` in the server console prints the same state.

using System;
using System.Collections.Generic;
using System.Reflection;
using HarmonyLib;
using Oxide.Core.Plugins;
using UnityEngine;

namespace Oxide.Plugins
{
    [Info("Runic Gateway Zones", "Runic Gateway", "0.2.0")]
    [Description("Helper for Runic Gateway: ZoneManager counts players already inside a zone when it is created, updated or loaded, and enforces a new zone's flags.")]
    public class RunicGatewayZones : RustPlugin
    {
        private const string HarmonyId = "runicgateway.zones";

        /// <summary>The instance the static postfix reports to. Null while unloaded.</summary>
        private static RunicGatewayZones _instance;

        private Harmony _harmony;
        private MethodInfo _patched;

        // Reflected once per ZoneManager load. A ZoneManager reload is a new assembly, so all of it
        // is looked up again then.
        private Plugin _zoneManager;
        private MethodInfo _enter;
        private MethodInfo _getZone;
        private FieldInfo _definition;
        private PropertyInfo _id;

        /// <summary>ZoneManager's private <c>UpdateHookSubscriptions</c>, or null when this ZoneManager has none (the second job is then off).</summary>
        private MethodInfo _updateHooks;

        /// <summary>
        ///     What the bridge reads through <see cref="State"/>: <c>patched</c>, <c>unsupported</c>
        ///     (ZoneManager is here but not the shape this helper patches), or <c>no-zonemanager</c>.
        /// </summary>
        private string _state = "no-zonemanager";
        private string _reason;

        /// <summary>Zones initialised this tick, swept once on the next. Main thread.</summary>
        private readonly Dictionary<string, object> _pending = new Dictionary<string, object>();
        private bool _sweepQueued;

        private void OnServerInitialized()
        {
            _instance = this;
            Patch();
        }

        private void Unload()
        {
            Unpatch();
            _instance = null;
        }

        private void OnPluginLoaded(Plugin plugin)
        {
            if (plugin != null && plugin.Name == "ZoneManager")
            {
                Unpatch();
                Patch();
            }
        }

        private void OnPluginUnloaded(Plugin plugin)
        {
            if (plugin != null && plugin.Name == "ZoneManager")
            {
                Unpatch();
                _state = "no-zonemanager";
                _reason = null;
            }
        }

        // ── The API the bridge calls ─────────────────────────────────────────────

        /// <summary><c>patched</c>, <c>unsupported</c> or <c>no-zonemanager</c>.</summary>
        private string State() => _state;

        /// <summary>Why the state is not <c>patched</c>, or null.</summary>
        private string StateReason() => _reason;

        /// <summary>The helper's own version, for hello.</summary>
        private string HelperVersion() => Version.ToString();

        // ── Patching ─────────────────────────────────────────────────────────────

        private void Patch()
        {
            _zoneManager = plugins.Find("ZoneManager");

            if (_zoneManager == null)
            {
                _state = "no-zonemanager";
                _reason = null;
                return;
            }

            const BindingFlags any = BindingFlags.Instance | BindingFlags.Public | BindingFlags.NonPublic;

            Type zmType = _zoneManager.GetType();
            Type zoneType = zmType.GetNestedType("Zone", BindingFlags.Public | BindingFlags.NonPublic);
            MethodInfo initialize = zoneType?.GetMethod("InitializeZone", any);

            _getZone = zmType.GetMethod("GetZoneByID", any, null, new[] { typeof(string) }, null);
            _updateHooks = zmType.GetMethod("UpdateHookSubscriptions", any, null, Type.EmptyTypes, null);
            _definition = zoneType?.GetField("definition", any);
            _id = _definition?.FieldType.GetProperty("Id", any);
            _enter = zoneType == null
                ? null
                : zmType.GetMethod("OnPlayerEnterZone", any, null, new[] { typeof(BasePlayer), zoneType }, null);

            string missing =
                zoneType == null ? "ZoneManager.Zone" :
                initialize == null ? "Zone.InitializeZone" :
                _definition == null || _id == null ? "Zone.definition.Id" :
                _enter == null ? "ZoneManager.OnPlayerEnterZone(BasePlayer, Zone)" :
                _getZone == null ? "ZoneManager.GetZoneByID(string)" :
                null;

            if (missing != null)
            {
                Fail($"this ZoneManager ({_zoneManager.Version}) has no {missing}");
                return;
            }

            try
            {
                _harmony = new Harmony(HarmonyId);
                _harmony.Patch(initialize, postfix: new HarmonyMethod(
                    typeof(RunicGatewayZones).GetMethod(nameof(AfterInitialize), BindingFlags.Static | BindingFlags.NonPublic)));
                _patched = initialize;
            }
            catch (Exception ex)
            {
                Fail($"Harmony could not patch Zone.InitializeZone: {ex.Message}");
                return;
            }

            _state = "patched";
            _reason = null;
            Puts($"patched ZoneManager {_zoneManager.Version}: a zone takes in the players already inside it" +
                 (_updateHooks != null ? ", and a new zone's flags are enforced" : ""));
            if (_updateHooks == null)
                PrintWarning($"this ZoneManager ({_zoneManager.Version}) has no UpdateHookSubscriptions: a zone made after it loaded may not enforce its flags until ZoneManager reloads");

            // The zones ZoneManager loaded before this helper did were initialised unwatched —
            // which, at a server start, is all of them. Sweep them once now.
            RefreshHooks();
            SweepAll();
        }

        private void Unpatch()
        {
            if (_harmony != null && _patched != null)
            {
                try
                {
                    _harmony.Unpatch(_patched, HarmonyPatchType.Postfix, HarmonyId);
                }
                catch (Exception ex)
                {
                    PrintWarning($"could not remove the ZoneManager patch: {ex.Message}");
                }
            }

            _harmony = null;
            _patched = null;
            _pending.Clear();
        }

        private void Fail(string reason)
        {
            Unpatch();
            _state = "unsupported";
            _reason = reason;
            PrintWarning($"{reason}. Runic Gateway scores its zones by position instead; ZoneManager's own flags will not apply to somebody already inside a new zone.");
        }

        // ── The patch ────────────────────────────────────────────────────────────

        /// <summary>
        ///     Harmony postfix on <c>ZoneManager.Zone.InitializeZone</c>. Static, as Harmony needs;
        ///     it only records the zone. Anything thrown here would surface inside ZoneManager, so
        ///     nothing is allowed to.
        /// </summary>
        private static void AfterInitialize(object __instance)
        {
            try
            {
                _instance?.Queue(__instance);
            }
            catch (Exception)
            {
                // Never ZoneManager's problem.
            }
        }

        private void Queue(object zone)
        {
            object definition = _definition.GetValue(zone);
            string id = definition == null ? null : _id.GetValue(definition) as string;

            if (string.IsNullOrEmpty(id))
                return;

            // The newest instance wins: a zone re-created in the same tick is one sweep.
            _pending[id] = zone;

            if (_sweepQueued)
                return;

            _sweepQueued = true;

            // A tick later, not now. `CreateOrUpdateZone` initialises a zone once with an empty
            // definition and again after the arguments are applied, and ZoneManager's startup load
            // registers the zone in its table only AFTER initialising it — so `IsPositionInZone`
            // answers correctly on the next tick and not before.
            NextTick(SweepPending);
        }

        private void SweepPending()
        {
            _sweepQueued = false;

            if (_state != "patched" || _pending.Count == 0)
            {
                _pending.Clear();
                return;
            }

            var batch = new List<KeyValuePair<string, object>>(_pending);
            _pending.Clear();

            // The second job first: the hooks that enforce the new zones' flags, then the players.
            RefreshHooks();

            foreach (KeyValuePair<string, object> entry in batch)
                Sweep(entry.Key, entry.Value);
        }

        /// <summary>
        ///     Main thread. Has ZoneManager subscribe the hooks its zones' flags now need. ZoneManager
        ///     only adds subscriptions here, and subscribing a hook twice is a no-op.
        /// </summary>
        private void RefreshHooks()
        {
            if (_updateHooks == null || _zoneManager == null)
                return;

            try
            {
                _updateHooks.Invoke(_zoneManager, null);
            }
            catch (Exception ex)
            {
                PrintWarning($"could not have ZoneManager refresh its hooks: {(ex.InnerException ?? ex).Message}");
            }
        }

        private void SweepAll()
        {
            var ids = _zoneManager.Call("GetZoneIDs") as string[];

            if (ids == null)
                return;

            foreach (string id in ids)
                Sweep(id, null);
        }

        /// <summary>
        ///     Main thread. Enters every connected player ZoneManager says is inside the zone and
        ///     does not yet count. <paramref name="zone"/> is the instance to enter them into, or null
        ///     to look it up (the startup sweep).
        /// </summary>
        private void Sweep(string id, object zone)
        {
            Plugin zm = _zoneManager;

            if (zm == null || zm.Call("CheckZoneID", id) == null)
                return;

            zone = zone ?? _getZone.Invoke(zm, new object[] { id });

            if (zone == null || (zone is UnityEngine.Object unity && unity == null))
                return;

            int entered = 0;

            // A copy: entering a player can eject or kill them, which changes the live list.
            // `activePlayerList` is Facepunch's ListHashSet, which has no ToArray.
            foreach (BasePlayer player in new List<BasePlayer>(BasePlayer.activePlayerList))
            {
                if (player == null || player.IsNpc || player.transform == null)
                    continue;

                if (zm.Call("IsPlayerInZone", id, player) is bool already && already)
                    continue;

                if (!(zm.Call("IsPositionInZone", id, player.transform.position) is bool inside) || !inside)
                    continue;

                try
                {
                    _enter.Invoke(zm, new[] { (object)player, zone });
                    entered++;
                }
                catch (Exception ex)
                {
                    PrintWarning($"could not enter {player.displayName} into zone {id}: {(ex.InnerException ?? ex).Message}");
                }
            }

            if (entered > 0)
                Puts($"zone {id}: {entered} player(s) already inside were counted in");
        }

        // ── Console ──────────────────────────────────────────────────────────────

        [ConsoleCommand("rgz.status")]
        private void StatusCommand(ConsoleSystem.Arg arg)
        {
            if (arg.Connection != null && !arg.IsAdmin)
                return;

            arg.ReplyWith($"Runic Gateway Zones {Version}: {_state}{(_reason != null ? $" ({_reason})" : "")}" +
                          $"; new zones' flags {(_updateHooks != null ? "enforced" : "NOT refreshed (no UpdateHookSubscriptions)")}");
        }
    }
}