How to make a Rust treasure hunt plugin (Oxide/Carbon)

using System.Linq;
using System;
using System.Collections.Generic;
using Newtonsoft.Json;
using Oxide.Core;
using UnityEngine;

namespace Oxide.Plugins
{
    [Info("TreasureHunt", "RustPluginGenerator", "1.0.0")]
    [Description("Spawns a loot crate at a random land position, announces its grid hint and rewards the first player to loot it.")]
    public class TreasureHunt : RustPlugin
    {
        private const string PermUse = "treasurehunt.use";

        private PluginConfig config;
        private Timer timeoutTimer;
        private BaseEntity treasure;

        private class LootEntry
        {
            [JsonProperty("Shortname")]
            public string Shortname = "scrap";

            [JsonProperty("Min Amount")]
            public int MinAmount = 50;

            [JsonProperty("Max Amount")]
            public int MaxAmount = 200;
        }

        private class PluginConfig
        {
            [JsonProperty("Crate Prefab")]
            public string CratePrefab = "assets/prefabs/misc/supply drop/supply_drop.prefab";

            [JsonProperty("Loot Items")]
            public List<LootEntry> LootItems = new List<LootEntry>
            {
                new LootEntry { Shortname = "scrap", MinAmount = 200, MaxAmount = 600 },
                new LootEntry { Shortname = "rifle.ak", MinAmount = 1, MaxAmount = 1 },
                new LootEntry { Shortname = "ammo.rifle", MinAmount = 60, MaxAmount = 120 },
                new LootEntry { Shortname = "metal.refined", MinAmount = 50, MaxAmount = 150 }
            };

            [JsonProperty("Map Radius")]
            public float MapRadius = 2000f;

            [JsonProperty("Minimum Altitude")]
            public float MinimumAltitude = 1f;

            [JsonProperty("Grid Cell Size")]
            public float GridCellSize = 150f;

            [JsonProperty("Max Placement Attempts")]
            public int MaxAttempts = 30;

            [JsonProperty("Hunt Duration Minutes")]
            public float DurationMinutes = 20f;
        }

        protected override void LoadDefaultConfig() => config = new PluginConfig();

        protected override void LoadConfig()
        {
            base.LoadConfig();
            try
            {
                config = Config.ReadObject<PluginConfig>();
                if (config == null) throw new Exception();
            }
            catch
            {
                PrintWarning("Configuration file is invalid, using defaults");
                LoadDefaultConfig();
            }
            SaveConfig();
        }

        protected override void SaveConfig() => Config.WriteObject(config);

        protected override void LoadDefaultMessages()
        {
            lang.RegisterMessages(new Dictionary<string, string>
            {
                ["HuntStarted"] = "A treasure crate has been dropped near grid {0}. First player to open it wins.",
                ["HuntWon"] = "{0} found the treasure crate in grid {1}!",
                ["HuntExpired"] = "The treasure crate was never found and has been removed.",
                ["HuntStopped"] = "The active treasure hunt has been cancelled.",
                ["NoHunt"] = "There is no active treasure hunt.",
                ["NoSpawnFound"] = "Could not find a valid land position. Increase Map Radius or lower Minimum Altitude.",
                ["AlreadyActive"] = "A treasure hunt is already running. Use /treasure stop to cancel it first.",
                ["NoPermission"] = "You do not have permission to use this command."
            }, this);
        }

        private string Msg(string key, string userId = null, params object[] args)
        {
            return string.Format(lang.GetMessage(key, this, userId), args);
        }

        private void Init()
        {
            permission.RegisterPermission(PermUse, this);
        }

        [ChatCommand("treasure")]
        private void CmdTreasure(BasePlayer player, string command, string[] args)
        {
            if (player != null && !permission.UserHasPermission(player.UserIDString, PermUse))
            {
                SendReply(player, Msg("NoPermission", player.UserIDString));
                return;
            }

            if (args != null && args.Length > 0 && args[0].ToLower() == "stop")
            {
                if (treasure == null)
                {
                    Reply(player, Msg("NoHunt"));
                    return;
                }
                EndHunt(false);
                Reply(player, Msg("HuntStopped"));
                return;
            }

            if (treasure != null)
            {
                Reply(player, Msg("AlreadyActive"));
                return;
            }

            if (!StartHunt())
            {
                Reply(player, Msg("NoSpawnFound"));
            }
        }

        private void Reply(BasePlayer player, string message)
        {
            if (player != null) SendReply(player, message);
            else Puts(message);
        }

        private bool StartHunt()
        {
            Vector3 position = FindSpawnPosition();
            if (position == Vector3.zero) return false;

            var entity = GameManager.server.CreateEntity(config.CratePrefab, position, Quaternion.identity);
            if (entity == null) return false;

            entity.Spawn();
            treasure = entity;

            var container = entity as StorageContainer;
            if (container != null) FillLoot(container);

            string grid = GetGrid(position);
            Server.Broadcast(Msg("HuntStarted", null, grid));

            if (config.DurationMinutes > 0f)
            {
                timeoutTimer = timer.Once(config.DurationMinutes * 60f, () =>
                {
                    if (treasure != null)
                    {
                        EndHunt(false);
                        Server.Broadcast(Msg("HuntExpired"));
                    }
                });
            }

            return true;
        }

        private Vector3 FindSpawnPosition()
        {
            for (int attempt = 0; attempt < config.MaxAttempts; attempt++)
            {
                float x = UnityEngine.Random.Range(-config.MapRadius, config.MapRadius);
                float z = UnityEngine.Random.Range(-config.MapRadius, config.MapRadius);
                float y = TerrainMeta.HeightMap.GetHeight(new Vector3(x, 0f, z));
                if (y < config.MinimumAltitude) continue;
                return new Vector3(x, y + 0.5f, z);
            }
            return Vector3.zero;
        }

        private void FillLoot(StorageContainer container)
        {
            if (container.inventory == null || config.LootItems == null) return;

            foreach (var entry in config.LootItems)
            {
                if (entry == null || string.IsNullOrEmpty(entry.Shortname)) continue;
                int amount = UnityEngine.Random.Range(entry.MinAmount, entry.MaxAmount + 1);
                if (amount < 1) amount = 1;

                var item = ItemManager.CreateByName(entry.Shortname, amount);
                if (item == null) continue;

                if (!item.MoveToContainer(container.inventory))
                {
                    item.Remove();
                }
            }
            container.inventory.MarkDirty();
        }

        private string GetGrid(Vector3 position)
        {
            int col = Mathf.FloorToInt((position.x + config.MapRadius) / config.GridCellSize);
            int row = Mathf.FloorToInt((position.z + config.MapRadius) / config.GridCellSize);
            col = Mathf.Max(0, col);
            row = Mathf.Max(0, row);
            char letter = (char)('A' + (col % 26));
            return letter + row.ToString();
        }

        private void OnLootEntity(BasePlayer player, BaseEntity targetEntity)
        {
            if (treasure == null || player == null || targetEntity == null) return;
            if (player.IsNpc) return;
            if (targetEntity.net == null) return;
            if (targetEntity.net.ID.Value != treasure.net.ID.Value) return;

            string grid = GetGrid(treasure.transform.position);
            Server.Broadcast(Msg("HuntWon", null, player.displayName, grid));
            EndHunt(true);
        }

        private void EndHunt(bool destroyNow)
        {
            if (timeoutTimer != null)
            {
                timeoutTimer.Destroy();
                timeoutTimer = null;
            }

            if (treasure != null)
            {
                if (!treasure.IsDestroyed) treasure.Kill();
                treasure = null;
            }
        }

        private void Unload()
        {
            if (timeoutTimer != null)
            {
                timeoutTimer.Destroy();
                timeoutTimer = null;
            }
            if (treasure != null)
            {
                if (!treasure.IsDestroyed) treasure.Kill();
                treasure = null;
            }
        }
    }
}