using System;
using System.Collections.Generic;
using System.IO;
using System.Linq;
using System.Runtime.Serialization.Formatters.Binary;
using UnityEngine;

/// <summary>
/// PersistentDataController singleton
/// </summary>
public class PersistentDataController
{
    /// <summary>
    /// The instance controlling the singleton
    /// </summary>
    private static PersistentDataController instance = null;

    /// <summary>
    /// Current implementation version of the PersistentDataController
    /// </summary>
    /// <remarks>MSB represent sprint version, LSB represent subversion</remarks>
    public const int VERSION = 0x04_03;

    /// <summary>
    /// Path of the <c>.json</c>-file to store all serialized data
    /// </summary>
    public static string PATH = null;

    /// <summary>
    /// Class to hold a list of data records
    /// </summary>
    [Serializable]
    public class PersistentDataContainer
    {
        /// <summary>
        /// A helper class for handling the stored progress
        /// </summary>
        [Serializable]
        public class PersistentDataEntry
        {
            /// <summary>
            /// The key, used to reference the data object
            /// </summary>
            public string key;

            /// <summary>
            /// The object, representated as a list of byte (which can be serialized)
            /// </summary>
            public List<byte> data = new List<byte>();

            /// <summary>
            /// Create a new PersistentDataEntry
            /// </summary>
            /// <param name="key"></param>
            /// <param name="data"></param>
            public PersistentDataEntry(string key, byte[] data) : this(key, data.ToList())
            { }

            /// <summary>
            /// Create a new PersistentDataEntry
            /// </summary>
            public PersistentDataEntry(string key, List<byte> data)
            {
                this.key = key;
                this.data = data;
            }
        }

        /// <summary>
        /// List of data records
        /// </summary>
        public List<PersistentDataEntry> entries = new List<PersistentDataEntry>();

        /// <summary>
        /// Update the value of a certain key,
        /// or add a new value if the key was not present.
        /// </summary>
        /// <typeparam name="T">The type of the data to be added/updated</typeparam>
        /// <param name="key">The key, used for referencing the data</param>
        /// <param name="data">The object of type <typeparamref name="T"/></param>
        /// <returns><c>true</c> if successful, <c>false</c> otherwise</returns>
        public bool Set<T>(string key, T data)
        {
            if (data == null)
                return false;

            PersistentDataEntry entry = entries.Find(x => x.key == key);

            // Hacky serialization stuff
            BinaryFormatter bf = new BinaryFormatter();
            using (MemoryStream ms = new MemoryStream())
            {
                bf.Serialize(ms, data);
                if (entry != null)
                {
                    entry.data.Clear();
                    entry.data.AddRange(ms.ToArray());
                }
                else
                {
                    entries.Add(new PersistentDataEntry(key, ms.ToArray()));
                }
                return true;
            }
        }

        /// <summary>
        /// Get the data object of a certain key
        /// </summary>
        /// <typeparam name="T">The type of the data object</typeparam>
        /// <param name="key">The key referencing the data object</param>
        /// <returns>The data, cast to a type <typeparamref name="T"/></returns>
        /// <exception cref="KeyNotFoundException"></exception>
        /// <exception cref="InvalidCastException"></exception>
        public T Get<T>(string key)
        {
            BinaryFormatter bf = new BinaryFormatter();
            using (MemoryStream ms = new MemoryStream())
            {
                // Find the correct key
                foreach (PersistentDataEntry entry in entries)
                {
                    if (entry.key == key)
                    {
                        // Hacky serialization stuff
                        byte[] data = entry.data.ToArray();
                        ms.Write(data, 0, data.Length);
                        ms.Seek(0, SeekOrigin.Begin);
                        return (T)bf.Deserialize(ms);
                    }
                }
            }

            // Raise an exception when key is not found
            throw new KeyNotFoundException();
        }

        /// <summary>
        /// Remove a key-value from the data.
        /// </summary>
        /// <param name="key">The key referencing the data object</param>
        /// <exception cref="KeyNotFoundException"></exception>
        public void Remove(string key)
        {
            if (!Has(key))
                throw new KeyNotFoundException();

            entries.Remove(entries.Find(x => x.key == key));
        }

        /// <summary>
        /// Remove and return value from the data.
        /// </summary>
        /// <typeparam name="T">The type of the data object</typeparam>
        /// <param name="key">The key referencing the data object</param>
        /// <param name="save">Whether the removal of the data should also be saved to disk</param>
        /// <returns></returns>
        public T Pop<T>(string key)
        {
            T data = Get<T>(key);
            Remove(key);
            return data;
        }

        /// <summary>
        /// Check whether a key is present
        /// </summary>
        /// <param name="key">The key to check</param>
        /// <returns>true if a item can be found with the specified key</returns>
        public bool Has(string key)
        {
            return entries.Find(x => x.key == key) != null;
        }
    }

    /// <summary>
    /// Stored user data record
    /// </summary>
    [Serializable]
    public class SavedUserData : PersistentDataContainer
    {
        /// <summary>
        /// The user's username
        /// </summary>
        public string username = null;

        /// <summary>
        /// The index of the user's avatar in the UserList.AVATARS list
        /// </summary>
        public int avatarIndex = -1;

        /// <summary>
        /// The total playtime of the user
        /// </summary>
        /// <remarks>Not implemented yet</remarks>
        public double playtime = 0.0;

        /// <summary>
        /// A list of progress on minigames the user has
        /// </summary>
        public List<SavedMinigameProgress> minigames = new List<SavedMinigameProgress>();

        /// <summary>
        /// A list of progress on courses the user has
        /// </summary>
        public List<SavedCourseProgress> courses = new List<SavedCourseProgress>();
    }

    /// <summary>
    /// Stored course progress data record
    /// </summary>
    [Serializable]
    public class SavedCourseProgress : PersistentDataContainer
    {

        /// <summary>
        /// Update the progress value of the SavedLearnableProgress with the given learnableName.
        /// </summary>
        /// <param name="learnableName"></param>
        /// <param name="addValue"></param>
        public void UpdateLearnable(string learnableName, float addValue)
        {
            SavedLearnableProgress learnable = learnables.Find(l => l.name == learnableName);
            if (learnable == null)
                throw new KeyNotFoundException();

            // Update the progress value of the SavedLearnableProgress
            learnable.progress += addValue;
            // crop the learnable progress around -5 and 5
            if (learnable.progress > 5.0f)
                learnable.progress = 5.0f;
            else if (learnable.progress < -5.0f)
                learnable.progress = -5.0f;

            // if learnable progress is big enough it is "completed"
            if (learnable.progress > 3)
                completedLearnables++;
        }

        /// <summary>
        /// Check whether there are enough inUse Learnables
        /// </summary>
        /// <returns></returns>
        private bool EnoughLearnables()
        {
            // There need to be more then 5 non completed learnables
            return inUseLearnables - completedLearnables > 5 || totalLearnables == inUseLearnables;
        }

        /// <summary>
        /// Find a SavedLearnableProgress with the given name
        /// </summary>
        /// <param name="name"></param>
        /// <returns> SavedLearnableProgress with the given name </returns>
        public SavedLearnableProgress FindLearnable(string name)
        {
            return learnables.Find(l => l.name == name);
        }

        /// <summary>
        /// Find learnable in learnables which is not yet in use, and set it active
        /// </summary>
        /// <returns> SavedLearnableProgress learnable </returns>
        private SavedLearnableProgress UseUnusedLearnable()
        {
            SavedLearnableProgress learnable = learnables.Find(l => !l.inUse);
            if (learnable == null)
                return null;

            learnable.inUse = true;
            inUseLearnables++;
            return learnable;
        }

        /// <summary>
        /// Gets a random inUse learnable
        /// </summary>
        /// <returns> a randomly selected inUse SavedLearnable which is not yet completed</returns>
        public SavedLearnableProgress GetRandomLearnable()
        {
            if (!EnoughLearnables())
                return UseUnusedLearnable();

            // only select inUse learnables which are not yet completed (progress < 3.5f)
            List<SavedLearnableProgress> inUseLearnables = learnables.FindAll(l => l.inUse && l.progress <= 3.5f);

            if (inUseLearnables.Count == 0)
                return null;

            // Select a random index from the in-use learnables list
            int randomIndex = UnityEngine.Random.Range(0, inUseLearnables.Count);
            return inUseLearnables[randomIndex];
        }

        /// <summary>
        /// Create new SavedLearnableProgress object and assigns the index and name values
        /// </summary>
        /// <param name="name"></param>
        /// <param name="index"></param>
        /// <returns> bool which indicates the success of the function</returns>
        public bool AddLearnable(string name, int index)
        {
            if (learnables.Any(learnable => learnable.name == name || learnable.index == index))
                return false;

            SavedLearnableProgress savedLearnableProgress = new SavedLearnableProgress();
            savedLearnableProgress.index = index;
            savedLearnableProgress.name = name;
            learnables.Add(savedLearnableProgress);
            totalLearnables++;
            return true;
        }

        public CourseIndex courseIndex;
        public float progress = -1.0f;
        public int completedLearnables = 0;
        public int inUseLearnables = 0;
        public int totalLearnables = 0;
        public List<SavedLearnableProgress> learnables = new List<SavedLearnableProgress>();
    }

    /// <summary>
    /// Stored individual learnable progress
    /// </summary>
    [Serializable]
    public class SavedLearnableProgress : PersistentDataContainer
    {
        /// <summary>
        /// Index of the Learnbable in its Theme
        /// </summary>
        public int index;

        /// <summary>
        /// Bool that indicated whether the user already started learning this Learnable
        /// </summary>
        public bool inUse = false;

        /// <summary>
        /// Display name of the Learnable
        /// </summary>
        public string name;

        /// <summary>
        /// Progress of the learnabe, a number between -5.0 and +5.0
        /// </summary>
        public float progress = 0.0f;
    }

    /// <summary>
    /// Stored minigame progress data record
    /// </summary>
    [Serializable]
    public class SavedMinigameProgress : PersistentDataContainer
    {
        /// <summary>
        /// Index of the minigame
        /// </summary>
        public MinigameIndex minigameIndex;

        /// <summary>
        /// The 10 last scores of a user
        /// </summary>
        public List<Score> latestScores = new List<Score>();

        /// <summary>
        /// Top 10 scores of a user
        /// </summary>
        public List<Score> highestScores = new List<Score>();
    }

    /// <summary>
    /// Stored WeSign data record
    /// </summary>
    [Serializable]
    private class SavedDataStructure
    {
        /// <summary>
        /// The version of the PersistentDataController with which this savefile is created
        /// </summary>
        public int version = VERSION;

        /// <summary>
        /// A list of all users
        /// </summary>
        public List<SavedUserData> users = new List<SavedUserData>();

        /// <summary>
        /// The index of the current user in the this.users list
        /// </summary>
        public int currentUser = -1;

        /// <summary>
        /// The index of the current minigame
        /// </summary>
        public MinigameIndex currentMinigame;

        /// <summary>
        /// The index of the current course
        /// </summary>
        public CourseIndex currentCourse;

        /// <summary>
        /// The index of the current theme
        /// </summary>
        public ThemeIndex currentTheme;

        /// <summary>
        /// The use hardware acceleration user preferences
        /// </summary>
        public bool useGPU = false;

        /// <summary>
        /// Initiate the SavedDataStructure, by setting the user preferences
        /// </summary>
        public SavedDataStructure()
        {
            RestoreSettings();
        }

        /// <summary>
        /// Reset the user preferences to the default values
        /// </summary>
        public void RestoreSettings()
        {
            useGPU = false;
        }
    }

    /// <summary>
    /// The object holding the data references
    /// </summary>
    private SavedDataStructure json = new SavedDataStructure();

    /// <summary>
    /// Get the instance loaded by the singleton
    /// </summary>
    /// <returns><c>PersistentDataController</c> instance</returns>
    public static PersistentDataController GetInstance()
    {
        // Create a new instance if non exists
        if (instance == null || PATH == null)
        {
            if (PATH == null)
                PersistentDataController.PATH = $"{Application.persistentDataPath}/wesign_saved_data.json";
            instance = new PersistentDataController();
        }
        return instance;
    }

    /// <summary>
    /// PersistentDataController contructor
    /// </summary>
    private PersistentDataController()
    {
        Load();
    }

    /// <summary>
    /// Clear everything stored in the PersistentDataController, won't save to disk
    /// </summary>
    public void Clear()
    {
        json.users.Clear();
        json.currentUser = -1;
        json.useGPU = false;
    }

    /// <summary>
    /// Save all data to disk
    /// </summary>
    public void Save()
    {
        string text = JsonUtility.ToJson(json);
        File.CreateText(PATH).Close();
        File.WriteAllText(PATH, text);
    }

    /// <summary>
    /// Override current data with the data from disk, will just clear if no data was found.
    /// </summary>
    /// <param name="overrideOnFail"><c>true</c> if you want to override the existing file if it exists and the loading failed.</param>
    /// <remarks>If the data on disk is outdated (version number is lower than the current version), the loading will also fail</remarks>
    /// <returns><c>true</c> if successful, <c>false</c> otherwise</returns>
    public bool Load(bool overrideOnFail = true)
    {
        Clear();
        if (!File.Exists(PATH))
            goto failed;

        try
        {
            string text = File.ReadAllText(PATH);
            SavedDataStructure newJson = JsonUtility.FromJson<SavedDataStructure>(text);
            if (newJson == null || newJson.version != VERSION)
                goto failed;

            json = newJson;
            return true;
        }
        catch (Exception) { goto failed; }

    failed:
        if (overrideOnFail)
            Save();
        return false;
    }

    /// <summary>
    /// Add a user to the WeSign data record
    /// </summary>
    /// <param name="user">User data record</param>
    /// <param name="save">Whether to save the addition immediately to disk</param>
    public void AddUser(SavedUserData user, bool save = true)
    {
        if (json.users.Count == 0)
            json.currentUser = 0;
        json.users.Add(user);

        if (save)
            Save();
    }

    /// <summary>
    /// Get a list of all user data records
    /// </summary>
    /// <returns></returns>
    public List<SavedUserData> GetUsers()
    {
        return json.users;
    }

    /// <summary>
    /// Get the index of the current user
    /// </summary>
    /// <returns></returns>
    public int GetCurrentUser()
    {
        return json.currentUser;
    }

    /// <summary>
    /// Set the index of the current record
    /// </summary>
    /// <param name="index">New index</param>
    /// <param name="save">Whether to save the change immediately to disk</param>
    /// <exception cref="IndexOutOfRangeException"></exception>
    public void SetCurrentUser(int index, bool save = true)
    {
        if (index < 0 || json.users.Count <= index)
            throw new IndexOutOfRangeException();
        json.currentUser = index;

        if (save)
            Save();
    }

    /// <summary>
    /// Remove a user data record
    /// </summary>
    /// <param name="index">Index of the user</param>
    /// <param name="save">Whether to save the deletion immediately to disk</param>
    /// <exception cref="IndexOutOfRangeException"></exception>
    public void DeleteUser(int index, bool save = true)
    {
        if (index < 0 || json.users.Count <= index)
            throw new IndexOutOfRangeException();

        if (0 < json.currentUser && index <= json.currentUser)
            json.currentUser--;
        json.users.RemoveAt(index);

        if (save)
            Save();
    }

    /// <summary>
    /// Get the current course
    /// </summary>
    /// <returns></returns>
    public CourseIndex GetCurrentCourse()
    {
        return json.currentCourse;
    }

    /// <summary>
    /// Set the current course
    /// </summary>
    /// <param name="course">New course index</param>
    /// <param name="save">Whether to save the change immediately to disk</param>
    public void SetCurrentCourse(CourseIndex course, bool save = true)
    {
        json.currentCourse = course;

        if (save)
            Save();
    }

    /// <summary>
    /// Get the current minigame
    /// </summary>
    /// <returns></returns>
    public MinigameIndex GetCurrentMinigame()
    {
        return json.currentMinigame;
    }

    /// <summary>
    /// Set the current minigame
    /// </summary>
    /// <param name="minigame">New minigame index</param>
    /// <param name="save">Whether to save the change immediately to disk</param>
    public void SetCurrentMinigame(MinigameIndex minigame, bool save = true)
    {
        json.currentMinigame = minigame;

        if (save)
            Save();
    }

    /// <summary>
    /// Get the current theme
    /// </summary>
    /// <returns></returns>
    public ThemeIndex GetCurrentTheme()
    {
        return json.currentTheme;
    }

    /// <summary>
    /// Set the current theme
    /// </summary>
    /// <param name="theme">New theme index</param>
    /// <param name="save">Whether to save the change immediately to disk</param>
    public void SetCurrentTheme(ThemeIndex theme, bool save = true)
    {
        json.currentTheme = theme;

        if (save)
            Save();
    }

    /// <summary>
    /// Whether the user wants to use hardware acceleration or not
    /// </summary>
    public bool IsUsingGPU()
    {
        return json.useGPU;
    }

    /// <summary>
    /// Set the preference of the user for hardware acceleration
    /// </summary>
    /// <param name="value">Value of the preference</param>
    /// <param name="save">Whether to save the change immediately to disk</param>
    public void SetGPUUsage(bool value, bool save = true)
    {
        json.useGPU = value;

        if (save)
            Save();
    }

    /// <summary>
    /// Restore preferences to default factory settings
    /// </summary>
    /// <param name="save">Whether to save the change immediately to disk</param>
    public void RestoreSettings(bool save = true)
    {
        json.RestoreSettings();

        if (save)
            Save();
    }
}