Imports System.IO

Imports Newtonsoft.Json

Public Class SettingsManager
    Implements ISettingsManager

    Public Shared Event InitializingManager As EventHandler

    Public Event AutoSavingSettings As EventHandler
    Public Event SavingSettings As EventHandler
    Public Event SavedSettings As EventHandler

    Protected ReadOnly settingsProvider As New List(Of ISettingsProvider)
    Protected defaultInstance As ISettings = Nothing
    Protected enableAutoSave As Boolean = False
    Protected addedHandler As Boolean = False

    Public Property ConfigFilePath As String

    Public ReadOnly Property Instance As ISettings Implements ISettingsManager.Instance
        Get
            If defaultInstance Is Nothing Then
                Load()
            End If
            Return defaultInstance
        End Get
    End Property

    Public Property AutoSaveOnExit As Boolean
        Get
            Return enableAutoSave
        End Get
        Set
            If enableAutoSave <> Value Then
                enableAutoSave = Value
                Select Case enableAutoSave
                    Case True
                        If Not addedHandler Then
                            AddAutoSaveHandler()
                        End If
                    Case False
                        If addedHandler Then
                            RemoveAutoSaveHandler()
                        End If
                End Select
            End If
        End Set
    End Property

    Public Sub New()
        RaiseEvent InitializingManager(Me, EventArgs.Empty)
    End Sub

    Public Sub New(fileName As String, autoSaveOnExit As Boolean)
        Me.New
        ConfigFilePath = fileName
        Me.AutoSaveOnExit = autoSaveOnExit
    End Sub

    Public Sub RegisterProvider(provider As ISettingsProvider)
        settingsProvider.Add(provider)
    End Sub

    Protected Sub AddAutoSaveHandler()
        AddHandler AppDomain.CurrentDomain.ProcessExit, AddressOf AutoSaveSettingsOnExit
        addedHandler = True
    End Sub

    Protected Sub RemoveAutoSaveHandler()
        RemoveHandler AppDomain.CurrentDomain.ProcessExit, AddressOf AutoSaveSettingsOnExit
        addedHandler = False
    End Sub

    Private Sub AutoSaveSettingsOnExit(sender As Object, e As EventArgs)
        RaiseEvent AutoSavingSettings(Me, New EventArgs)
        Save()
    End Sub

    Public Sub Save() Implements ISettingsManager.Save
        If Not String.IsNullOrEmpty(ConfigFilePath) AndAlso defaultInstance IsNot Nothing Then
            SaveInternal()
        End If
    End Sub

    Public Sub Load() Implements ISettingsManager.Load
        If Not String.IsNullOrEmpty(ConfigFilePath) AndAlso File.Exists(ConfigFilePath) Then
            LoadInternal()
        Else
            CreateNewInstance()
        End If
    End Sub

    Public Sub Reset() Implements ISettingsManager.Reset
        Instance.Reset()
    End Sub

    Protected Overridable Sub CreateNewInstance()
        defaultInstance = New Settings
        defaultInstance.Initialize(settingsProvider)
        defaultInstance.Reset()
    End Sub

    Protected Overridable Sub LoadInternal()
        defaultInstance = JsonConvert.DeserializeObject(Of Settings)(File.ReadAllText(ConfigFilePath), CreateJsonSerializerSettings)
        defaultInstance.Initialize(settingsProvider)
    End Sub

    Protected Overridable Sub SaveInternal()
        RaiseEvent SavingSettings(Me, EventArgs.Empty)
        File.WriteAllText(ConfigFilePath, JsonConvert.SerializeObject(defaultInstance, CreateJsonSerializerSettings))
        RaiseEvent SavedSettings(Me, EventArgs.Empty)
    End Sub

    Protected Overridable Function CreateJsonSerializerSettings() As JsonSerializerSettings
        Return New JsonSerializerSettings With {
            .Formatting = Formatting.Indented,
            .TypeNameHandling = TypeNameHandling.Auto
        }
    End Function

End Class