using NUnit.Framework;
using NUnit.Framework.Internal;
using System;
using System.Collections.Generic;
using System.IO;
using UnityEngine;

/// <summary>
/// Test the PersistentDataController class
/// </summary>
[TestFixture]
public class PersistentDataControllerTests
{
    /// <summary>
    /// Create a new path so the existing .json file will not be overwritten
    /// </summary>
    private static string PATH = $"{Application.persistentDataPath}/wesign_unit_test.json";

    /// <summary>
    /// Reference to the pdc to perform tests on
    /// </summary>
    private PersistentDataController pdc = null;

    /// <summary>
    /// A dummy serializable struct to perform test operations on
    /// </summary>
    [Serializable]
    private struct Struct
    {
        public int r, g, b;
        public float x, y, z;
    }

    /// <summary>
    /// A dummy serializable enum to perform test operations on
    /// </summary>
    private enum Enum
    {
        SQUARE,
        TRIANBLE,
        CIRCLE
    }

    [SetUp]
    public void Setup_PersistentDataController()
    {
        Assert.IsNull(PersistentDataController.PATH);
        PersistentDataController.PATH = PersistentDataControllerTests.PATH;
        pdc = PersistentDataController.GetInstance();
    }

    [TearDown]
    public void TearDown_PersistentDataController()
    {
        PersistentDataController.PATH = null;
    }

    [Test]
    public void Test_PersistentDataController_GetInstance()
    {
        PersistentDataController.PATH = null;
        Assert.IsNotNull(PersistentDataController.GetInstance());
        Assert.AreEqual(0x04_03, PersistentDataController.VERSION);
        Assert.AreEqual($"{Application.persistentDataPath}/wesign_saved_data.json", PersistentDataController.PATH);
    }

    [Test]
    public void Test_PersistentDataController_Clear()
    {
        pdc.Load();
        pdc.Clear();
        Assert.Zero(pdc.GetUsers().Count);
        Assert.AreEqual(-1, pdc.GetCurrentUser());
    }

    [Test]
    public void Test_PersistentDataController_Save_Empty()
    {
        pdc.Load();
        pdc.Clear();

        pdc.Save();
        FileAssert.Exists(PATH);

        string content = File.ReadAllText(PATH);
        string expected = "{\"version\":1027,\"users\":[],\"currentUser\":-1,\"currentMinigame\":0,\"currentCourse\":0,\"currentTheme\":0,\"useGPU\":false}";
        Assert.AreEqual(expected, content);
    }

    [Test]
    public void Test_PersistentDataController_Save_New()
    {
        pdc.Load();
        pdc.Clear();

        if (File.Exists(PATH))
            File.Delete(PATH);
        pdc.Save();
        FileAssert.Exists(PATH);

        string content = File.ReadAllText(PATH);
        string expected = "{\"version\":1027,\"users\":[],\"currentUser\":-1,\"currentMinigame\":0,\"currentCourse\":0,\"currentTheme\":0,\"useGPU\":false}";
        Assert.AreEqual(expected, content);
    }

    [Test]
    public void Test_PersistentDataController_Load_Existing()
    {
        string content = "{\"version\":1027,\"users\":[],\"currentUser\":-1,\"currentMinigame\":0,\"currentCourse\":0,\"currentTheme\":0,\"useGPU\":false}";
        File.WriteAllText(PATH, content);
        Assert.IsTrue(pdc.Load(false));
    }

    [Test]
    public void Test_PersistentDataController_Load_OlderVersion()
    {
        string content = "{\"version\":1026,\"users\":[],\"currentUser\":-1,\"currentMinigame\":0,\"currentCourse\":0,\"currentTheme\":0,\"useGPU\":false}";
        File.WriteAllText(PATH, content);
        Assert.IsFalse(pdc.Load(false));
    }

    [Test]
    public void Test_PersistentDataController_Load_NewerVersion()
    {
        string content = "{\"version\":1028,\"users\":[],\"currentUser\":-1,\"currentMinigame\":0,\"currentCourse\":0,\"currentTheme\":0,\"useGPU\":false}";
        File.WriteAllText(PATH, content);
        Assert.IsFalse(pdc.Load(false));
    }

    [Test]
    public void Test_PersistentDataController_Load_New()
    {
        if (File.Exists(PATH))
            File.Delete(PATH);
        Assert.IsFalse(pdc.Load(false));
        FileAssert.DoesNotExist(PATH);
    }

    [Test]
    public void Test_PersistentDataController_Load_Exception()
    {
        File.WriteAllText(PATH, "https://www.youtube.com/watch?v=dQw4w9WgXcQ");
        Assert.IsFalse(pdc.Load(false));
        Assert.AreEqual("https://www.youtube.com/watch?v=dQw4w9WgXcQ", File.ReadAllText(PATH));
    }

    [Test]
    public void Test_PersistentDataController_Load_Override()
    {
        File.WriteAllText(PATH, "https://www.youtube.com/watch?v=dQw4w9WgXcQ");
        Assert.IsFalse(pdc.Load(true));
        string content = File.ReadAllText(PATH);
        string expected = "{\"version\":1027,\"users\":[],\"currentUser\":-1,\"currentMinigame\":0,\"currentCourse\":0,\"currentTheme\":0,\"useGPU\":false}";
        Assert.AreEqual(expected, content);
    }

    [Test]
    public void Test_PersistentDataController_Version()
    {
        const int VERSION = 0x04_03;
        Assert.AreEqual(VERSION, PersistentDataController.VERSION);
    }

    [Test]
    public void Test_PersistentDataController_AddUser()
    {
        pdc.Load();
        pdc.Clear();
        var d = new PersistentDataController.SavedUserData()
        {
            username = "username",
            avatarIndex = 0
        };

        pdc.AddUser(d);
        string content = File.ReadAllText(PATH);
        string expected = "{\"version\":1027,\"users\":[{\"entries\":[],\"username\":\"username\",\"avatarIndex\":0,\"playtime\":0.0,\"minigames\":[],\"courses\":[]}],\"currentUser\":0,\"currentMinigame\":0,\"currentCourse\":0,\"currentTheme\":0,\"useGPU\":false}";
        Assert.AreEqual(expected, content);
    }

    [Test]
    public void Test_PersistentDataController_GetUsers()
    {
        pdc.Load();
        pdc.Clear();
        var d = new PersistentDataController.SavedUserData()
        {
            username = "username",
            avatarIndex = 0
        };

        pdc.AddUser(d);
        var users = pdc.GetUsers();
        Assert.AreEqual(1, users.Count);
        Assert.AreEqual("username", users[0].username);
        Assert.AreEqual(0, users[0].avatarIndex);
    }

    [Test]
    public void Test_PersistentDataController_GetCurrentUser()
    {
        pdc.Load();
        pdc.Clear();

        Assert.AreEqual(-1, pdc.GetCurrentUser());
        pdc.AddUser(new PersistentDataController.SavedUserData()
        {
            username = "username",
            avatarIndex = 0
        });
        Assert.AreEqual(0, pdc.GetCurrentUser());
    }

    [Test]
    public void Test_PersistentDataController_SetCurrentUser()
    {
        pdc.Load();
        pdc.Clear();

        for (int i = 0; i < 5; i++)
            pdc.AddUser(new PersistentDataController.SavedUserData()
            {
                username = $"username_{i}",
                avatarIndex = i
            });
        pdc.SetCurrentUser(3);
        Assert.AreEqual(3, pdc.GetCurrentUser());
    }

    [Test]
    public void Test_PersistentDataController_SetCurrentUser_Invalid()
    {
        pdc.Load();
        pdc.Clear();

        pdc.AddUser(new PersistentDataController.SavedUserData()
        {
            username = $"username",
            avatarIndex = 0
        });
        Assert.Throws<IndexOutOfRangeException>(delegate { pdc.SetCurrentUser(3); });
    }

    [Test]
    public void Test_PersistentDataController_SetCurrentUser_Empty()
    {
        pdc.Load();
        pdc.Clear();
        Assert.Throws<IndexOutOfRangeException>(delegate { pdc.SetCurrentUser(0); });
    }

    [Test]
    public void Test_PersistentDataController_DeleteUser_BeforeCurrent()
    {
        pdc.Load();
        pdc.Clear();

        var users = new List<PersistentDataController.SavedUserData>();
        for (int i = 0; i < 5; i++)
        {
            var d = new PersistentDataController.SavedUserData()
            {
                username = $"username_{i}",
                avatarIndex = i
            };
            pdc.AddUser(d);
            users.Add(d);
        }
        pdc.SetCurrentUser(0);
        users.RemoveAt(2);
        pdc.DeleteUser(2);

        var vsers = pdc.GetUsers();
        Assert.AreEqual(0, pdc.GetCurrentUser());
        Assert.AreEqual(users.Count, vsers.Count);
        for (int i = 0; i < 4; i++)
        {
            Assert.AreEqual(users[i].username, vsers[i].username);
            Assert.AreEqual(users[i].avatarIndex, vsers[i].avatarIndex);
        }
    }

    [Test]
    public void Test_PersistentDataController_DeleteUser_Current()
    {
        pdc.Load();
        pdc.Clear();

        var users = new List<PersistentDataController.SavedUserData>();
        for (int i = 0; i < 5; i++)
        {
            var d = new PersistentDataController.SavedUserData()
            {
                username = $"username_{i}",
                avatarIndex = i
            };
            pdc.AddUser(d);
            users.Add(d);
        }
        pdc.SetCurrentUser(2);
        users.RemoveAt(2);
        pdc.DeleteUser(2);

        var vsers = pdc.GetUsers();
        Assert.AreEqual(1, pdc.GetCurrentUser());
        Assert.AreEqual(users.Count, vsers.Count);
        for (int i = 0; i < 4; i++)
        {
            Assert.AreEqual(users[i].username, vsers[i].username);
            Assert.AreEqual(users[i].avatarIndex, vsers[i].avatarIndex);
        }
    }

    [Test]
    public void Test_PersistentDataController_DeleteUser_AfterCurrent()
    {
        pdc.Load();
        pdc.Clear();

        var users = new List<PersistentDataController.SavedUserData>();
        for (int i = 0; i < 5; i++)
        {
            var d = new PersistentDataController.SavedUserData()
            {
                username = $"username_{i}",
                avatarIndex = i
            };
            pdc.AddUser(d);
            users.Add(d);

        }
        pdc.SetCurrentUser(4);
        users.RemoveAt(2);
        pdc.DeleteUser(2);

        var vsers = pdc.GetUsers();
        Assert.AreEqual(3, pdc.GetCurrentUser());
        Assert.AreEqual(users.Count, vsers.Count);
        for (int i = 0; i < 4; i++)
        {
            Assert.AreEqual(users[i].username, vsers[i].username);
            Assert.AreEqual(users[i].avatarIndex, vsers[i].avatarIndex);
        }
    }

    [Test]
    public void Test_PersistentDataController_DeleteUser_Invalid()
    {
        pdc.Load();
        pdc.Clear();

        pdc.AddUser(new PersistentDataController.SavedUserData()
        {
            username = $"username",
            avatarIndex = 0
        });
        Assert.Throws<IndexOutOfRangeException>(delegate { pdc.SetCurrentUser(3); });
    }

    [Test]
    public void Test_PersistentDataController_DeleteUser_Empty()
    {
        pdc.Load();
        pdc.Clear();
        Assert.Throws<IndexOutOfRangeException>(delegate { pdc.DeleteUser(0); });
    }

    [Test]
    public void Test_PersistentDataController_CurrentCourse()
    {
        pdc.Load();
        pdc.Clear();
        pdc.SetCurrentCourse(CourseIndex.FINGERSPELLING);
        Assert.AreEqual(CourseIndex.FINGERSPELLING, pdc.GetCurrentCourse());
    }

    [Test]
    public void Test_PersistentDataController_CurrentMinigame()
    {
        pdc.Load();
        pdc.Clear();
        pdc.SetCurrentMinigame(MinigameIndex.SPELLING_BEE);
        Assert.AreEqual(MinigameIndex.SPELLING_BEE, pdc.GetCurrentMinigame());
    }

    [Test]
    public void Test_PersistentDataController_CurrentTheme()
    {
        pdc.Load();
        pdc.Clear();
        pdc.SetCurrentTheme(ThemeIndex.SIGN_ALPHABET);
        Assert.AreEqual(ThemeIndex.SIGN_ALPHABET, pdc.GetCurrentTheme());
    }

    /// <summary>
    /// Test whether hardware acceleration preference is saved correctly
    /// </summary>
    [Test]
    public void Test_PersistentDataController_UseGPU()
    {
        pdc.Load();
        pdc.Clear();
        Assert.IsFalse(pdc.IsUsingGPU());
        pdc.SetGPUUsage(true);
        Assert.IsTrue(pdc.IsUsingGPU());
        pdc.SetGPUUsage(false);
        Assert.IsFalse(pdc.IsUsingGPU());
    }

    /// <summary>
    /// Test whether restoring user preference is done correctly
    /// </summary>
    [Test]
    public void Test_PersistentDataController_RestoreSettings()
    {
        pdc.Load();
        pdc.Clear();
        pdc.SetGPUUsage(true);
        pdc.RestoreSettings();
        Assert.IsFalse(pdc.IsUsingGPU());
    }

    [Test]
    public void Test_New_PersistentDataContainer()
    {
        var c = new PersistentDataController.PersistentDataContainer();
        Assert.IsNotNull(c);
        Assert.Zero(c.entries.Count);
    }

    [Test]
    public void Test_PersistentDataContainer_Set_Invalid()
    {
        var c = new PersistentDataController.PersistentDataContainer();
        Assert.IsFalse(c.Set<object>("key", null));
    }

    [Test]
    public void Test_PersistentDataContainer_Set_DuplicateKey()
    {
        var c = new PersistentDataController.PersistentDataContainer();
        Assert.IsTrue(c.Set<int>("key", 123));
        Assert.IsTrue(c.Set<int>("key", 321));
    }

    [Test]
    public void Test_PersistentDataContainer_Set_Int()
    {
        var c = new PersistentDataController.PersistentDataContainer();
        Assert.IsTrue(c.Set<int>("key", 123));
    }

    [Test]
    public void Test_PersistentDataContainer_Set_String()
    {
        var c = new PersistentDataController.PersistentDataContainer();
        Assert.IsTrue(c.Set<string>("key", "abc"));
    }

    [Test]
    public void Test_PersistentDataContainer_Set_Struct()
    {
        var c = new PersistentDataController.PersistentDataContainer();
        Assert.IsTrue(c.Set<Struct>("key", new Struct()));
    }

    [Test]
    public void Test_PersistentDataContainer_Set_Enum()
    {
        var c = new PersistentDataController.PersistentDataContainer();
        Assert.IsTrue(c.Set<Enum>("key", new Enum()));
    }

    [Test]
    public void Test_PersistentDataContainer_Get_InvalidType()
    {
        var c = new PersistentDataController.PersistentDataContainer();
        c.Set<Struct>("key", new Struct() { r = 255, g = 127, b = 63, x = 31, y = 15, z = 7 });
        Assert.Throws<InvalidCastException>(delegate { c.Get<int>("key"); });
        c.Set<int>("key", 123);
        Assert.Throws<InvalidCastException>(delegate { c.Get<Struct>("key"); });
    }

    [Test]
    public void Test_PersistentDataContainer_Get_KeyNotFound()
    {
        var c = new PersistentDataController.PersistentDataContainer();
        c.Set<int>("key", 123);
        Assert.Throws<KeyNotFoundException>(delegate { c.Get<int>("KEY"); });
    }

    [Test]
    public void Test_PersistentDataContainer_Get_Empty()
    {
        var c = new PersistentDataController.PersistentDataContainer();
        Assert.Throws<KeyNotFoundException>(delegate { c.Get<int>("key"); });
    }

    [Test]
    public void Test_PersistentDataContainer_Get_Int()
    {
        var c = new PersistentDataController.PersistentDataContainer();
        c.Set<int>("key", 123);
        Assert.AreEqual(123, c.Get<int>("key"));
    }

    [Test]
    public void Test_PersistentDataContainer_Get_String()
    {
        var c = new PersistentDataController.PersistentDataContainer();
        c.Set<string>("key", "value");
        Assert.AreEqual("value", c.Get<string>("key"));
    }

    [Test]
    public void Test_PersistentDataContainer_Get_Struct()
    {
        var c = new PersistentDataController.PersistentDataContainer();
        var s = new Struct() { r = 255, g = 127, b = 63, x = 31, y = 15, z = 7 };
        c.Set<Struct>("key", s);
        Assert.AreEqual(s, c.Get<Struct>("key"));
    }

    [Test]
    public void Test_PersistentDataContainer_Get_Enum()
    {
        var c = new PersistentDataController.PersistentDataContainer();
        var e = Enum.CIRCLE;
        c.Set<Enum>("key", e);
        Assert.AreEqual(e, c.Get<Enum>("key"));
    }

    [Test]
    public void Test_PersistentDataContainer_Remove_Invalid()
    {
        var c = new PersistentDataController.PersistentDataContainer();
        c.Set<int>("key", 123);
        Assert.Throws<KeyNotFoundException>(delegate { c.Remove("KEY"); });
    }

    [Test]
    public void Test_PersistentDataContainer_Remove_Empty()
    {
        var c = new PersistentDataController.PersistentDataContainer();
        Assert.Throws<KeyNotFoundException>(delegate { c.Remove("key"); });
    }

    [Test]
    public void Test_PersistentDataContainer_Remove_Int()
    {
        var c = new PersistentDataController.PersistentDataContainer();
        c.Set<int>("key", 123);
        c.Remove("key");
        Assert.Throws<KeyNotFoundException>(delegate { c.Get<int>("key"); });
    }

    [Test]
    public void Test_PersistentDataContainer_Remove_String()
    {
        var c = new PersistentDataController.PersistentDataContainer();
        c.Set<string>("key", "value");
        c.Remove("key");
        Assert.Throws<KeyNotFoundException>(delegate { c.Get<string>("key"); });
    }

    [Test]
    public void Test_PersistentDataContainer_Remove_Struct()
    {
        var c = new PersistentDataController.PersistentDataContainer();
        var s = new Struct() { r = 255, g = 127, b = 63, x = 31, y = 15, z = 7 };
        c.Set<Struct>("key", s);
        c.Remove("key");
        Assert.Throws<KeyNotFoundException>(delegate { c.Get<Struct>("key"); });
    }

    [Test]
    public void Test_PersistentDataContainer_Remove_Enum()
    {
        var c = new PersistentDataController.PersistentDataContainer();
        c.Set<Enum>("key", Enum.CIRCLE);
        c.Remove("key");
        Assert.Throws<KeyNotFoundException>(delegate { c.Get<Enum>("key"); });
    }

    [Test]
    public void Test_PersistentDataContainer_Pop_Invalid()
    {
        var c = new PersistentDataController.PersistentDataContainer();
        c.Set<int>("key", 123);
        Assert.Throws<KeyNotFoundException>(delegate { c.Remove("KEY"); });
    }

    [Test]
    public void Test_PersistentDataContainer_Pop_Empty()
    {
        var c = new PersistentDataController.PersistentDataContainer();
        Assert.Throws<KeyNotFoundException>(delegate { c.Remove("KEY"); });
    }

    [Test]
    public void Test_PersistentDataContainer_Pop_Int()
    {
        var c = new PersistentDataController.PersistentDataContainer();
        c.Set<int>("key", 123);
        Assert.AreEqual(123, c.Pop<int>("key"));
        Assert.Throws<KeyNotFoundException>(delegate { c.Get<int>("key"); });
    }

    [Test]
    public void Test_PersistentDataContainer_Pop_String()
    {
        var c = new PersistentDataController.PersistentDataContainer();
        c.Set<string>("key", "value");
        Assert.AreEqual("value", c.Pop<string>("key"));
        Assert.Throws<KeyNotFoundException>(delegate { c.Get<string>("key"); });
    }

    [Test]
    public void Test_PersistentDataContainer_Pop_Struct()
    {
        var c = new PersistentDataController.PersistentDataContainer();
        var s = new Struct() { r = 255, g = 127, b = 63, x = 31, y = 15, z = 7 };
        c.Set<Struct>("key", s);
        Assert.AreEqual(s, c.Pop<Struct>("key"));
        Assert.Throws<KeyNotFoundException>(delegate { c.Get<Struct>("key"); });
    }

    [Test]
    public void Test_PersistentDataContainer_Pop_Enum()
    {
        var c = new PersistentDataController.PersistentDataContainer();
        c.Set<Enum>("key", Enum.CIRCLE);
        Assert.AreEqual(Enum.CIRCLE, c.Pop<Enum>("key"));
        Assert.Throws<KeyNotFoundException>(delegate { c.Get<Enum>("key"); });
    }

    [Test]
    public void Test_PersistentDataContainer_Has_ValidKey()
    {
        var c = new PersistentDataController.PersistentDataContainer();
        Assert.IsFalse(c.Has("key"));
        c.Set<int>("key", 123);
        Assert.IsTrue(c.Has("key"));
    }

    [Test]
    public void Test_PersistentDataContainer_Has_InvalidKey()
    {
        var c = new PersistentDataController.PersistentDataContainer();
        Assert.IsFalse(c.Has("KEY"));
        c.Set<int>("key", 123);
        Assert.IsFalse(c.Has("KEY"));
    }

    [Test]
    public void Test_SavedCourseProgress_AddLearnable_Valid()
    {
        PersistentDataController.SavedCourseProgress progress = new PersistentDataController.SavedCourseProgress();
        Assert.Zero(progress.learnables.Count);

        bool added = progress.AddLearnable("learnable", 0);
        Assert.IsTrue(added);
        Assert.AreEqual(1, progress.learnables.Count);
        Assert.AreEqual("learnable", progress.learnables[0].name);
        Assert.AreEqual(0, progress.FindLearnable("learnable").index);
    }

    [Test]
    public void Test_SavedCourseProgress_AddLearnable_DuplicateName()
    {
        PersistentDataController.SavedCourseProgress progress = new PersistentDataController.SavedCourseProgress();

        progress.AddLearnable("learnable", 0);

        Assert.AreEqual(1, progress.learnables.Count);
        Assert.IsFalse(progress.AddLearnable("learnable", 1));
        Assert.AreEqual(1, progress.learnables.Count);
    }

    [Test]
    public void Test_SavedCourseProgress_AddLearnable_DuplicateIndex()
    {
        PersistentDataController.SavedCourseProgress progress = new PersistentDataController.SavedCourseProgress();

        progress.AddLearnable("learnable", 0);

        Assert.AreEqual(1, progress.learnables.Count);
        Assert.IsFalse(progress.AddLearnable("LEARNABLE", 0));
        Assert.AreEqual(1, progress.learnables.Count);
    }


    [Test]
    public void Test_SavedCourseProgress_UpdateLearnable_InvalidName()
    {
        PersistentDataController.SavedCourseProgress progress = new PersistentDataController.SavedCourseProgress();

        progress.AddLearnable("learnable", 0);
        Assert.AreEqual(0.0f, progress.FindLearnable("learnable").progress);
        Assert.Throws<KeyNotFoundException>(delegate { progress.UpdateLearnable("LEARNABLE", 3.0f); });
        Assert.AreEqual(0.0f, progress.FindLearnable("learnable").progress);
    }


    [Test]
    public void Test_SavedCourseProgress_UpdateLearnable_UpdatesProgress()
    {
        PersistentDataController.SavedCourseProgress progress = new PersistentDataController.SavedCourseProgress();

        progress.AddLearnable("learnable", 0);
        Assert.AreEqual(0.0f, progress.FindLearnable("learnable").progress);
        progress.UpdateLearnable("learnable", 3.0f);
        Assert.AreEqual(3.0f, progress.FindLearnable("learnable").progress);
    }

    [Test]
    public void Test_SavedCourseProgress_UpdateLearnable_CropsProgressAtFive()
    {
        PersistentDataController.SavedCourseProgress progress = new PersistentDataController.SavedCourseProgress();

        progress.AddLearnable("learnable", 0);
        Assert.AreEqual(0, progress.completedLearnables);
        progress.UpdateLearnable("learnable", 10.0f);
        Assert.AreEqual(5.0f, progress.FindLearnable("learnable").progress);
        Assert.AreEqual(1, progress.completedLearnables);
    }

    [Test]
    public void Test_SavedCourseProgress_UpdateLearnable_CropsProgressAtNegativeFive()
    {
        PersistentDataController.SavedCourseProgress progress = new PersistentDataController.SavedCourseProgress();

        progress.AddLearnable("learnable", 0);
        Assert.AreEqual(0, progress.completedLearnables);
        progress.UpdateLearnable("learnable", -10.0f);
        Assert.AreEqual(-5.0f, progress.FindLearnable("learnable").progress);
        Assert.AreEqual(0, progress.completedLearnables);
    }

    [Test]
    public void Test_SavedCourseProgress_FindLearnable()
    {
        PersistentDataController.SavedCourseProgress progress = new PersistentDataController.SavedCourseProgress();
        progress.AddLearnable("learnable 1", 0);

        Assert.IsNull(progress.FindLearnable("learnable 2"));
        progress.AddLearnable("learnable 2", 1);
        Assert.IsNotNull(progress.FindLearnable("learnable 2"));
    }

    [Test]
    public void Test_SavedCourseProgress_GetRandomLearnable_NoLearnables()
    {
        PersistentDataController.SavedCourseProgress progress = new PersistentDataController.SavedCourseProgress();
        Assert.IsNull(progress.GetRandomLearnable());
    }

    [Test]
    public void Test_SavedCourseProgress_GetRandomLearnable_NoUnusedLearnables()
    {
        PersistentDataController.SavedCourseProgress progress = new PersistentDataController.SavedCourseProgress();
        progress.AddLearnable("learnable", 0);
        progress.FindLearnable("learnable").inUse = true;
        progress.completedLearnables = 1;
        progress.inUseLearnables = 0;

        Assert.IsNull(progress.GetRandomLearnable());
    }

    [Test]
    public void Test_SavedCourseProgress_GetRandomLearnable_OnlyCompletedLearnables()
    {
        PersistentDataController.SavedCourseProgress progress = new PersistentDataController.SavedCourseProgress();
        for (int i = 0; i < 2; i++)
        {
            progress.AddLearnable($"learnable {i}", i);
            var learnable = progress.FindLearnable($"learnable {i}");
            learnable.progress = 4.0f;
            learnable.inUse = true;
        }
        progress.completedLearnables = 2;
        progress.inUseLearnables = 0;

        Assert.IsNull(progress.GetRandomLearnable());
    }

    [Test]
    public void Test_SavedCourseProgress_GetRandomLearnable_Valid()
    {
        PersistentDataController.SavedCourseProgress progress = new PersistentDataController.SavedCourseProgress();
        for (int i = 0; i < 10; i++)
        {
            progress.AddLearnable($"learnable {i}", i);
            progress.FindLearnable($"learnable {i}").inUse = true;
        }
        progress.completedLearnables = 0;
        progress.inUseLearnables = 10;

        Assert.AreEqual(10, progress.inUseLearnables);
        Assert.AreEqual(0, progress.completedLearnables);
        Assert.IsNotNull(progress.GetRandomLearnable());
        Assert.AreEqual(10, progress.inUseLearnables);
        Assert.AreEqual(0, progress.completedLearnables);
    }
}