// Runic Gateway Domes — a helper for ZoneDomes, shipped beside the Runic Gateway bridge.
// Copyright (C) Runic Gateway contributors. GPL-3.0-or-later.
//
// ONE JOB (docs/modules/rust/PLAN_REDESIGNS.md §3.2, D168, D194):
//
// ZoneDomes draws a dome over a ZoneManager zone, and the bridge asks it to for an event zone
// whose step wants one. Its API was written for a person at a keyboard: `AddNewDome` and
// `RemoveExistingDome` both end by telling the player who asked how it went, with no check that
// there was one. Called by a plugin with no player, the dome is made and saved, and THEN the call
// throws — so the caller cannot tell a made dome from a failed one (plan §0.5, found on the rig).
//
// So this helper patches ZoneDomes with Harmony, the same way the zone helper patches ZoneManager
// (D181):
//
//   * **A message with no player is not sent.** A prefix on ZoneDomes' `TranslateMessage(BasePlayer,
//     string, string)` skips it when the player is null. Nothing else about the call changes, so
//     `AddNewDome` returns its true or false normally.
//   * **It says when ZoneDomes has finished starting.** ZoneDomes' own start (`InitializeDomes`)
//     drops every dome whose zone does not exist yet and draws every one that does. A dome added
//     BEFORE that is drawn a second time, and the first set of spheres stays in the world with
//     nothing holding it. A postfix there raises `OnRgDomesReady`, and the bridge puts its domes
//     back only after it.
//
// It is optional. Without it the bridge offers no dome and says why; the zones themselves are
// unaffected. `rgd.status` in the server console prints its state.

using System;
using System.Reflection;
using HarmonyLib;
using Oxide.Core;
using Oxide.Core.Plugins;

namespace Oxide.Plugins
{
    [Info("Runic Gateway Domes", "Runic Gateway", "0.1.0")]
    [Description("Helper for Runic Gateway: ZoneDomes can be called without a player, and says when it has started.")]
    public class RunicGatewayDomes : RustPlugin
    {
        private const string HarmonyId = "runicgateway.domes";

        /// <summary>The instance the static patches report to. Null while unloaded.</summary>
        private static RunicGatewayDomes _instance;

        private Harmony _harmony;
        private MethodInfo _message;
        private MethodInfo _initialize;

        /// <summary><c>patched</c>, <c>unsupported</c> (ZoneDomes is here but not the shape patched), or <c>no-zonedomes</c>.</summary>
        private string _state = "no-zonedomes";
        private string _reason;

        /// <summary>Whether ZoneDomes has finished its own start since it was patched. Main thread.</summary>
        private bool _ready;

        /// <summary>Set once the server is up, at this plugin's own <c>OnServerInitialized</c>.</summary>
        private bool _serverUp;

        // Patched as EARLY as possible — at load, or the moment ZoneDomes loads — so that at a real
        // server start the patch is in before ZoneDomes' `OnServerInitialized` runs its start.

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

        private void OnServerInitialized(bool initial)
        {
            _serverUp = true;

            // Loaded into a running server: ZoneDomes, if it is here, started long ago.
            if (!initial)
                MarkReadyNextTick();
        }

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

        private void OnPluginLoaded(Plugin plugin)
        {
            if (plugin == null || plugin.Name != "ZoneDomes")
                return;

            Unpatch();
            Patch();

            // A ZoneDomes loaded into a running server has run its start by now: the framework
            // calls a hot-loaded plugin's `OnServerInitialized` before it tells anybody else it
            // loaded. The tick is margin, and costs nothing.
            if (_serverUp)
                MarkReadyNextTick();
        }

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

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

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

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

        /// <summary>Whether ZoneDomes is patched and past its own start, so a dome may be added.</summary>
        private bool Ready() => _state == "patched" && _ready;

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

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

        private void Patch()
        {
            _ready = false;
            Plugin zoneDomes = plugins.Find("ZoneDomes");

            if (zoneDomes == null)
            {
                _state = "no-zonedomes";
                _reason = null;
                return;
            }

            const BindingFlags any = BindingFlags.Instance | BindingFlags.Public | BindingFlags.NonPublic;
            Type type = zoneDomes.GetType();

            _message = type.GetMethod("TranslateMessage", any, null, new[] { typeof(BasePlayer), typeof(string), typeof(string) }, null);
            _initialize = type.GetMethod("InitializeDomes", any, null, Type.EmptyTypes, null);

            string missing =
                _message == null ? "TranslateMessage(BasePlayer, string, string)" :
                _initialize == null ? "InitializeDomes()" :
                type.GetMethod("AddNewDome", any) == null ? "AddNewDome" :
                type.GetMethod("RemoveExistingDome", any) == null ? "RemoveExistingDome" :
                null;

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

            try
            {
                _harmony = new Harmony(HarmonyId);
                _harmony.Patch(_message, prefix: new HarmonyMethod(
                    typeof(RunicGatewayDomes).GetMethod(nameof(BeforeMessage), BindingFlags.Static | BindingFlags.NonPublic)));
                _harmony.Patch(_initialize, postfix: new HarmonyMethod(
                    typeof(RunicGatewayDomes).GetMethod(nameof(AfterInitialize), BindingFlags.Static | BindingFlags.NonPublic)));
            }
            catch (Exception ex)
            {
                Fail($"Harmony could not patch ZoneDomes: {ex.Message}");
                return;
            }

            _state = "patched";
            _reason = null;
            Puts($"patched ZoneDomes {zoneDomes.Version}: its API can be called without a player");
        }

        private void Unpatch()
        {
            if (_harmony != null)
            {
                try
                {
                    if (_message != null)
                        _harmony.Unpatch(_message, HarmonyPatchType.Prefix, HarmonyId);

                    if (_initialize != null)
                        _harmony.Unpatch(_initialize, HarmonyPatchType.Postfix, HarmonyId);
                }
                catch (Exception ex)
                {
                    PrintWarning($"could not remove the ZoneDomes patches: {ex.Message}");
                }
            }

            _harmony = null;
            _message = null;
            _initialize = null;
            _ready = false;
        }

        private void Fail(string reason)
        {
            Unpatch();
            _state = "unsupported";
            _reason = reason;
            PrintWarning($"{reason}. Runic Gateway will not offer a dome over its zones on this server.");
        }

        private void MarkReadyNextTick()
        {
            NextTick(() =>
            {
                if (_state != "patched" || _ready)
                    return;

                _ready = true;
                Interface.CallHook("OnRgDomesReady");
            });
        }

        // ── The patches ──────────────────────────────────────────────────────────

        /// <summary>
        ///     Harmony prefix on <c>ZoneDomes.TranslateMessage(BasePlayer, string, string)</c>.
        ///     Returning false skips the message; a real player still gets it.
        /// </summary>
        private static bool BeforeMessage(BasePlayer player)
        {
            return player != null;
        }

        /// <summary>
        ///     Harmony postfix on <c>ZoneDomes.InitializeDomes</c>. Anything thrown here would surface
        ///     inside ZoneDomes, so nothing is allowed to.
        /// </summary>
        private static void AfterInitialize()
        {
            try
            {
                RunicGatewayDomes self = _instance;

                if (self == null || self._state != "patched")
                    return;

                self._ready = true;
                Interface.CallHook("OnRgDomesReady");
            }
            catch (Exception)
            {
                // Never ZoneDomes' problem.
            }
        }

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

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

            arg.ReplyWith($"Runic Gateway Domes {Version}: {_state}{(_state == "patched" ? (_ready ? ", ready" : ", waiting for ZoneDomes to start") : "")}{(_reason != null ? $" ({_reason})" : "")}");
        }
    }
}