GameSession.cs

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using Engine.Models;
using Engine.Factories;
using System.ComponentModel;
using Engine.EventArgs;

namespace Engine.ViewModels
{
    public class GameSession : BaseNotificationClass
    {
        public event EventHandler<GameMessageEventArgs> OnMessageRaised;

        #region Properties
        private Location _currentLocation;
        private Monster _currentMonster;
        private Trader _currentTrader;

        public World CurrentWorld { get; set; }
        public Player CurrentPlayer { get; set; }
        public Location CurrentLocation
        {
            get { return _currentLocation; }
            set
            {
                _currentLocation = value;
                OnPropertyChanged(nameof(CurrentLocation));
                OnPropertyChanged(nameof(HasLocationToNorth));
                OnPropertyChanged(nameof(HasLocationToWest));
                OnPropertyChanged(nameof(HasLocationToEast));
                OnPropertyChanged(nameof(HasLocationToSouth));

                CompleteQuestsAtLocation();
                GivePlayerQuestsAtLocation();
                GetMonsterAtLocation(); //TODO maybe at a timer so even if a player stays in the same area monsters will respawn.

                _currentTrader = CurrentLocation.TraderHere;
            }
        }

       

        public Monster CurrentMonster
        {
            get { return _currentMonster; }
            set
            {
                _currentMonster = value;
                OnPropertyChanged(nameof(CurrentMonster));
                OnPropertyChanged(nameof(HasMonster));

                if(CurrentMonster != null)
                {
                    RaiseMessage("");
                    RaiseMessage($"You see a {CurrentMonster.Name} here!");
                }
            }
        }

        public Trader CurrentTrader
        {
            get { return _currentTrader; }
            set
            {
                _currentTrader = value;
                OnPropertyChanged(nameof(CurrentTrader));
                OnPropertyChanged(nameof(HasTrader));
            }
        }

        //TODO might be away to simplify this..
        public bool HasLocationToNorth =>
            CurrentWorld.LocationAt(CurrentLocation.XCoordinate, CurrentLocation.YCoordinate + 1) != null; 

        public bool HasLocationToWest =>
            CurrentWorld.LocationAt(CurrentLocation.XCoordinate - 1, CurrentLocation.YCoordinate) != null; 
        
        public bool HasLocationToEast =>
            CurrentWorld.LocationAt(CurrentLocation.XCoordinate + 1, CurrentLocation.YCoordinate) != null; 
        
        public bool HasLocationToSouth =>
            CurrentWorld.LocationAt(CurrentLocation.XCoordinate, CurrentLocation.YCoordinate - 1) != null; 
        

        public bool HasMonster => CurrentMonster != null;

        public bool HasTrader => CurrentTrader != null;

        #endregion

        public GameSession()
        {
            CurrentPlayer = new Player
            {
                Name = "Jack",
                CharacterClass = "Fighter",
                HitPoints = 10,
                ExperiencePoints = 0,
                Level = 1,
                Gold = 1000000
            };

            if(!CurrentPlayer.Weapons.Any())
            {
                CurrentPlayer.AddItemToInventory(ItemFactory.CreateGameItem(1001));

            }

            CurrentWorld = WorldFactory.CreateWorld();

            CurrentLocation = CurrentWorld.LocationAt(0, 0);
        }

        public void MoveNorth()
        {
            if (HasLocationToNorth)
            {
                CurrentLocation = CurrentWorld.LocationAt(CurrentLocation.XCoordinate, CurrentLocation.YCoordinate + 1);
            }
        }
        public void MoveWest()
        {
            if (HasLocationToWest)
            {
                CurrentLocation = CurrentWorld.LocationAt(CurrentLocation.XCoordinate - 1, CurrentLocation.YCoordinate);
            }
        }      
        public void MoveEast()
        {
            if (HasLocationToEast)
            {
                CurrentLocation = CurrentWorld.LocationAt(CurrentLocation.XCoordinate + 1, CurrentLocation.YCoordinate);
            }
        }
        public void MoveSouth()
        {
            if (HasLocationToSouth)
            {
                CurrentLocation = CurrentWorld.LocationAt(CurrentLocation.XCoordinate, CurrentLocation.YCoordinate - 1);
            }
        }


        private void CompleteQuestsAtLocation()
        {
            foreach(Quest quest in CurrentLocation.QuestAvailableHere)
            {
                QuestStatus questToComplete =
                    CurrentPlayer.Quests.FirstOrDefault(q => q.PlayerQuest.ID == quest.ID && !q.IsCompleted);

                if(questToComplete != null)
                {
                    if(CurrentPlayer.HasAllTheseItems(quest.ItemsToComplete))
                    {
                        //remove quest items from player's inventory
                        foreach (ItemQuantity itemQuantity in quest.ItemsToComplete)
                        {
                            for(int i = 0; i < itemQuantity.Quantity; i++)
                            {
                                CurrentPlayer.RemoveItemFromInventory(CurrentPlayer.Inventory.First(item => item.ItemTypeID == itemQuantity.ItemID));

                            }
                        }

                        RaiseMessage("");
                        RaiseMessage($"You completed the '{quest.Name}' quest");

                        //Give rewards
                        CurrentPlayer.ExperiencePoints += quest.RewardExperiencePoints;
                        RaiseMessage($"You recieve {quest.RewardExperiencePoints} experience");

                        CurrentPlayer.Gold += quest.RewardGold;
                        RaiseMessage($"You recieve {quest.RewardGold} gold");

                        foreach(ItemQuantity itemQuantity in quest.RewardItems)
                        {
                            GameItem rewardItem = ItemFactory.CreateGameItem(itemQuantity.ItemID);
                            CurrentPlayer.AddItemToInventory(rewardItem);
                            RaiseMessage($"You recieve {rewardItem.Name}");
                        }

                        //Mark quest as completed
                        questToComplete.IsCompleted = true;

                    }
                }
            }
        }
        private void GivePlayerQuestsAtLocation()
        {
            foreach(Quest quest in CurrentLocation.QuestAvailableHere)
            {
                if (!CurrentPlayer.Quests.Any(q => q.PlayerQuest.ID == quest.ID)) // USing LINQ to search through the player's quest list and see if any quests avaible at this location are not in the current player's quest list.
                {
                    CurrentPlayer.Quests.Add(new QuestStatus(quest));
                    RaiseMessage("");
                    RaiseMessage($"You recieve the '{quest.Name}' quest");
                    RaiseMessage(quest.Description);

                    RaiseMessage("Return with:");
                    foreach (ItemQuantity itemQuantity in quest.ItemsToComplete)
                    {
                        RaiseMessage($"    {itemQuantity.Quantity} {ItemFactory.CreateGameItem(itemQuantity.ItemID).Name}");

                    }
                    RaiseMessage("And you will recieve:");
                    RaiseMessage($"    {quest.RewardExperiencePoints} experience points");
                    RaiseMessage($"    {quest.RewardGold} gold");
                    foreach (ItemQuantity itemQuantity in quest.RewardItems)
                    {
                        RaiseMessage($"    {itemQuantity.Quantity} {ItemFactory.CreateGameItem(itemQuantity.ItemID).Name}");
                    }
                }
            }
        }

        private void GetMonsterAtLocation()
        {
            CurrentMonster = CurrentLocation.GetMonster();
        }

        public void AttackCurrentMonster()
        {
            //TODO change to fists? But type of logic is guard clause called early exit.
            if (CurrentPlayer.CurrentWeapon == null)
            {
                RaiseMessage("You Must select a weapon, to attack.");
                return;
            }

            //Determine damage to monster
            int damageToMonster = RandomNumberGenerator.NumberBetween(CurrentPlayer.CurrentWeapon.MinimumDamge, CurrentPlayer.CurrentWeapon.MaximumDamge);

            if(damageToMonster == 0)
            {
                RaiseMessage($"You missed the {CurrentMonster.Name}");
            }
            else
            {
                CurrentMonster.HitPoints -= damageToMonster;
                RaiseMessage($"You hit the {CurrentMonster.Name} for {damageToMonster}.");
            }

            if(CurrentMonster.HitPoints <= 0)
            {
                RaiseMessage("");
                RaiseMessage($"You defeated the {CurrentMonster.Name}");

                CurrentPlayer.ExperiencePoints += CurrentMonster.RewardExperiencePoints;
                RaiseMessage($"You recieved {CurrentMonster.RewardExperiencePoints} expierence points.");

                CurrentPlayer.Gold += CurrentMonster.RewardGold;
                RaiseMessage($"You recieved {CurrentMonster.RewardGold} gold.");

                foreach(ItemQuantity itemQuantity in CurrentMonster.Inventory)
                {
                    GameItem item = ItemFactory.CreateGameItem(itemQuantity.ItemID);
                    CurrentPlayer.AddItemToInventory(item);
                    RaiseMessage($"You recieved {itemQuantity.Quantity} {item.Name}.");
                }

                //Get another monster to fight
                GetMonsterAtLocation();
            }
            else
            {
                // If monster is still alive, let the monster attack
                int damageToPlayer = RandomNumberGenerator.NumberBetween(CurrentMonster.MinimumDamage, CurrentMonster.MaximumHitPoints);
                if(damageToPlayer <= 0 )
                {
                    RaiseMessage($"The {CurrentMonster.Name} missed you!");
                }
                else if (damageToPlayer > 0)
                {
                    CurrentPlayer.HitPoints -= damageToPlayer;
                    RaiseMessage($"The {CurrentMonster.Name} hit you for {damageToPlayer} points.");
                }

                if (CurrentPlayer.HitPoints <= 0)
                {
                    RaiseMessage("");
                    RaiseMessage($"The {CurrentMonster.Name} killed you");

                    CurrentLocation = CurrentWorld.LocationAt(0, -1); //return player to home
                    CurrentPlayer.HitPoints = CurrentPlayer.Level * 10; //completely heal the player
                }
            }
        }

        private void RaiseMessage(string message)
        {
            OnMessageRaised?.Invoke(this, new GameMessageEventArgs(message));
        }

    }
}