Imports System.Collections.Generic
Imports System.IO
Imports System.Net.Http
Imports System.Security.Cryptography
Imports System.Web.Script.Serialization
Imports System.Windows.Forms

' ---------------------------------------------------------------------------
' Updater.vb - self-update for Shipping Tracker
'
' Requires a project reference to: System.Web.Extensions  (for JavaScriptSerializer)
' Everything else is in the framework already.
'
' Wire-up (see notes at bottom of file):
'   Form1_Load  -> Updater.CleanupOldBinary() + Await Updater.CheckForUpdatesAsync(True)
'   Form3 btnUpdates -> Await Updater.CheckForUpdatesAsync(False)
' ---------------------------------------------------------------------------

Public Module Updater

    ' --- configuration -----------------------------------------------------

    Private Const ApiLatest As String =
        "https://gitea.apointless.space/api/v1/repos/bsncubed/ShippingTracker/releases/latest"

    Private Const ReleasesPage As String =
        "https://gitea.apointless.space/bsncubed/ShippingTracker/releases"

    ' Name of the .exe asset attached to each release. Must match exactly.
    Private Const AssetName As String = "Shipping Tracker.exe"

    ' Name of the checksum asset. sha256sum format: "<hash>  <filename>" per line.
    Private Const ChecksumAssetName As String = "checksums.txt"

    Private ReadOnly Http As New HttpClient() With {.Timeout = TimeSpan.FromSeconds(10)}

    ' --- public entry points -----------------------------------------------

    ''' <summary>
    ''' Checks for a newer release and offers to install it.
    ''' silent = True  -> startup check. Any failure (offline, DNS, timeout,
    '''                   bad response) returns quietly with no UI at all.
    ''' silent = False -> user clicked "Check for updates". Reports
    '''                   "up to date" and surfaces errors.
    ''' </summary>
    Public Async Function CheckForUpdatesAsync(silent As Boolean) As Task

        Dim rel As ReleaseInfo = Nothing

        Try
            rel = Await FetchLatestReleaseAsync()
        Catch ex As Exception
            ' Offline / DNS failure / timeout / non-200 / malformed JSON.
            If Not silent Then
                MessageBox.Show("Could not check for updates:" & vbCrLf & vbCrLf & ex.Message,
                                "Shipping Tracker", MessageBoxButtons.OK, MessageBoxIcon.Warning)
            End If
            Return
        End Try

        If rel Is Nothing OrElse rel.Version Is Nothing Then
            If Not silent Then
                MessageBox.Show("Could not read the latest version number.",
                                "Shipping Tracker", MessageBoxButtons.OK, MessageBoxIcon.Warning)
            End If
            Return
        End If

        Dim current As Version = Normalise(My.Application.Info.Version)

        If rel.Version <= current Then
            If Not silent Then
                MessageBox.Show("You're running the latest version (" & current.ToString() & ").",
                                "Shipping Tracker", MessageBoxButtons.OK, MessageBoxIcon.Information)
            End If
            Return
        End If

        ' --- newer version available ---------------------------------------

        Dim answer = MessageBox.Show(
            "A new version of Shipping Tracker is available." & vbCrLf & vbCrLf &
            "You have:  " & current.ToString() & vbCrLf &
            "Available: " & rel.Version.ToString() & vbCrLf & vbCrLf &
            "Update now?",
            "Update available", MessageBoxButtons.YesNo, MessageBoxIcon.Question)

        If answer <> DialogResult.Yes Then Return

        If String.IsNullOrEmpty(rel.AssetUrl) Then
            OfferManualDownload("This release doesn't contain a file named """ & AssetName & """.")
            Return
        End If

        ' Fail early if we can't write next to ourselves (e.g. Program Files,
        ' read-only network share) rather than half-applying the update.
        If Not CanWriteBesideExe() Then
            OfferManualDownload("Shipping Tracker doesn't have permission to update itself " &
                                "in this folder.")
            Return
        End If

        Await DownloadAndApplyAsync(rel)

    End Function

    ''' <summary>
    ''' Deletes the previous binary left behind by an update.
    ''' Call once, early, from Form1_Load. Never throws.
    ''' </summary>
    Public Sub CleanupOldBinary()
        Try
            Dim oldPath = Application.ExecutablePath & ".old"
            If File.Exists(oldPath) Then File.Delete(oldPath)
        Catch
            ' Still locked, or already gone. Harmless - try again next launch.
        End Try
    End Sub

    ' --- release metadata --------------------------------------------------

    Private Class ReleaseInfo
        Public Property Version As Version
        Public Property AssetUrl As String
        Public Property ChecksumUrl As String
    End Class

    Private Async Function FetchLatestReleaseAsync() As Task(Of ReleaseInfo)

        Using req As New HttpRequestMessage(HttpMethod.Get, ApiLatest)
            req.Headers.Add("User-Agent", "ShippingTracker")
            req.Headers.Add("Accept", "application/json")

            Using resp = Await Http.SendAsync(req)
                resp.EnsureSuccessStatusCode()
                Dim body = Await resp.Content.ReadAsStringAsync()

                Dim js As New JavaScriptSerializer()
                Dim root = TryCast(js.DeserializeObject(body), Dictionary(Of String, Object))
                If root Is Nothing Then Return Nothing

                Dim info As New ReleaseInfo()

                Dim tag As String = Nothing
                If root.ContainsKey("tag_name") Then tag = TryCast(root("tag_name"), String)
                info.Version = ParseVersion(tag)

                If root.ContainsKey("assets") Then
                    Dim assets = TryCast(root("assets"), Object())
                    If assets IsNot Nothing Then
                        For Each a In assets
                            Dim asset = TryCast(a, Dictionary(Of String, Object))
                            If asset Is Nothing Then Continue For

                            Dim name As String = Nothing
                            Dim url As String = Nothing
                            If asset.ContainsKey("name") Then name = TryCast(asset("name"), String)
                            If asset.ContainsKey("browser_download_url") Then _
                                url = TryCast(asset("browser_download_url"), String)

                            If name Is Nothing OrElse url Is Nothing Then Continue For

                            If String.Equals(name, AssetName, StringComparison.OrdinalIgnoreCase) Then
                                info.AssetUrl = url
                            ElseIf String.Equals(name, ChecksumAssetName, StringComparison.OrdinalIgnoreCase) Then
                                info.ChecksumUrl = url
                            End If
                        Next
                    End If
                End If

                Return info
            End Using
        End Using

    End Function

    ' --- version handling --------------------------------------------------

    ''' <summary>
    ''' Parses a tag like "1.2.0.0", "v1.2.0" or "1.2" into a 4-part Version.
    ''' Missing components become 0 so comparison against AssemblyVersion is sane
    ''' (an unset component in System.Version is -1, which would sort wrong).
    ''' </summary>
    Private Function ParseVersion(tag As String) As Version
        If String.IsNullOrEmpty(tag) Then Return Nothing

        Dim s = tag.Trim()
        If s.StartsWith("v", StringComparison.OrdinalIgnoreCase) Then s = s.Substring(1)

        Dim nums As New List(Of Integer)
        For Each part In s.Split("."c)
            Dim n As Integer
            If Not Integer.TryParse(part.Trim(), n) Then Exit For
            If n < 0 Then Exit For
            nums.Add(n)
            If nums.Count = 4 Then Exit For
        Next

        If nums.Count = 0 Then Return Nothing
        While nums.Count < 4
            nums.Add(0)
        End While

        Return New Version(nums(0), nums(1), nums(2), nums(3))
    End Function

    Private Function Normalise(v As Version) As Version
        Return New Version(Math.Max(v.Major, 0), Math.Max(v.Minor, 0),
                           Math.Max(v.Build, 0), Math.Max(v.Revision, 0))
    End Function

    ' --- download / verify / swap -----------------------------------------

    Private Async Function DownloadAndApplyAsync(rel As ReleaseInfo) As Task

        Dim exePath = Application.ExecutablePath
        Dim newPath = exePath & ".new"

        Dim prog As New UpdateProgressForm()
        prog.Show()

        Try
            ' 1. download the new binary
            prog.SetStatus("Downloading update...")
            Await DownloadToFileAsync(rel.AssetUrl, newPath, prog)

            ' 2. verify it, if the release published checksums
            If Not String.IsNullOrEmpty(rel.ChecksumUrl) Then
                prog.SetStatus("Verifying download...")
                prog.SetProgress(100)

                Dim expected = Await FetchExpectedHashAsync(rel.ChecksumUrl)
                If String.IsNullOrEmpty(expected) Then
                    Throw New Exception("The checksum file has no entry for """ & AssetName & """.")
                End If

                Dim actual = Sha256File(newPath)
                If Not String.Equals(expected, actual, StringComparison.OrdinalIgnoreCase) Then
                    Throw New Exception("Checksum mismatch - the download was corrupted or tampered with." &
                                        vbCrLf & vbCrLf &
                                        "Expected: " & expected & vbCrLf &
                                        "Got:      " & actual)
                End If
            End If

            ' 3. swap the binaries
            prog.SetStatus("Installing...")
            ApplyUpdate(newPath)

        Catch ex As Exception
            SafeDelete(newPath)
            prog.Close()
            OfferManualDownload("The update could not be installed:" & vbCrLf & vbCrLf & ex.Message)
            Return
        End Try

        prog.Close()

        MessageBox.Show("Update installed. Shipping Tracker will now restart.",
                        "Shipping Tracker", MessageBoxButtons.OK, MessageBoxIcon.Information)

        Try
            Process.Start(exePath)
        Catch
            ' If relaunch fails the update is still applied - next manual
            ' launch gets the new version.
        End Try

        Application.Exit()

    End Function

    Private Async Function DownloadToFileAsync(url As String, destPath As String,
                                               prog As UpdateProgressForm) As Task

        Using req As New HttpRequestMessage(HttpMethod.Get, url)
            req.Headers.Add("User-Agent", "ShippingTracker")

            ' ResponseHeadersRead so we stream to disk instead of buffering it all.
            Using resp = Await Http.SendAsync(req, HttpCompletionOption.ResponseHeadersRead)
                resp.EnsureSuccessStatusCode()

                Dim total As Long = -1
                If resp.Content.Headers.ContentLength.HasValue Then
                    total = resp.Content.Headers.ContentLength.Value
                End If

                Using src = Await resp.Content.ReadAsStreamAsync(),
                      dst = New FileStream(destPath, FileMode.Create, FileAccess.Write, FileShare.None)

                    Dim buffer(81919) As Byte
                    Dim readTotal As Long = 0
                    Dim n As Integer

                    Do
                        n = Await src.ReadAsync(buffer, 0, buffer.Length)
                        If n = 0 Then Exit Do
                        Await dst.WriteAsync(buffer, 0, n)
                        readTotal += n
                        If total > 0 Then
                            prog.SetProgress(CInt(Math.Min(100L, readTotal * 100L \ total)))
                        End If
                    Loop
                End Using
            End Using
        End Using

    End Function

    Private Async Function FetchExpectedHashAsync(checksumUrl As String) As Task(Of String)

        Using req As New HttpRequestMessage(HttpMethod.Get, checksumUrl)
            req.Headers.Add("User-Agent", "ShippingTracker")

            Using resp = Await Http.SendAsync(req)
                resp.EnsureSuccessStatusCode()
                Dim text = Await resp.Content.ReadAsStringAsync()

                ' sha256sum format: "<hash>  <filename>"  (two spaces, or " *")
                For Each line In text.Split({vbCr, vbLf}, StringSplitOptions.RemoveEmptyEntries)
                    Dim trimmed = line.Trim()
                    If trimmed.Length = 0 Then Continue For

                    Dim sep = trimmed.IndexOf(" "c)
                    If sep <= 0 Then Continue For

                    Dim hash = trimmed.Substring(0, sep).Trim()
                    Dim name = trimmed.Substring(sep).Trim().TrimStart("*"c).Trim()

                    If String.Equals(name, AssetName, StringComparison.OrdinalIgnoreCase) Then
                        Return hash
                    End If
                Next

                Return Nothing
            End Using
        End Using

    End Function

    Private Function Sha256File(path As String) As String
        Using sha = SHA256.Create(), fs = File.OpenRead(path)
            Return BitConverter.ToString(sha.ComputeHash(fs)).Replace("-", "").ToLowerInvariant()
        End Using
    End Function

    ''' <summary>
    ''' Windows won't let you delete a running .exe, but it will let you RENAME
    ''' one. So: current -> .old, downloaded -> current. The .old file is removed
    ''' by CleanupOldBinary() on the next launch.
    ''' </summary>
    Private Sub ApplyUpdate(newFile As String)

        Dim exePath = Application.ExecutablePath
        Dim oldPath = exePath & ".old"

        SafeDelete(oldPath)

        File.Move(exePath, oldPath)          ' running exe is now .old

        Try
            File.Move(newFile, exePath)      ' new binary takes its place
        Catch
            ' Roll back so the user isn't left without an application.
            Try
                File.Move(oldPath, exePath)
            Catch
            End Try
            Throw
        End Try

    End Sub

    ' --- helpers -----------------------------------------------------------

    Private Function CanWriteBesideExe() As Boolean
        Try
            Dim dir = Path.GetDirectoryName(Application.ExecutablePath)
            Dim probe = Path.Combine(dir, "." & Guid.NewGuid().ToString("N") & ".tmp")
            Using fs = New FileStream(probe, FileMode.CreateNew, FileAccess.Write, FileShare.None)
            End Using
            File.Delete(probe)
            Return True
        Catch
            Return False
        End Try
    End Function

    Private Sub SafeDelete(path As String)
        Try
            If File.Exists(path) Then File.Delete(path)
        Catch
        End Try
    End Sub

    Private Sub OfferManualDownload(message As String)
        Dim answer = MessageBox.Show(
            message & vbCrLf & vbCrLf & "Open the downloads page instead?",
            "Shipping Tracker", MessageBoxButtons.YesNo, MessageBoxIcon.Warning)

        If answer = DialogResult.Yes Then
            Try
                Process.Start(ReleasesPage)
            Catch
            End Try
        End If
    End Sub

End Module


''' <summary>
''' Minimal progress window, built in code so there's no extra .Designer.vb
''' to add to the project.
''' </summary>
Friend Class UpdateProgressForm
    Inherits Form

    Private ReadOnly _bar As ProgressBar
    Private ReadOnly _label As Label

    Public Sub New()
        Me.Text = "Updating Shipping Tracker"
        Me.FormBorderStyle = FormBorderStyle.FixedDialog
        Me.StartPosition = FormStartPosition.CenterScreen
        Me.MaximizeBox = False
        Me.MinimizeBox = False
        Me.ControlBox = False
        Me.ClientSize = New Drawing.Size(360, 90)

        _label = New Label() With {
            .Text = "Starting...",
            .AutoSize = False,
            .Location = New Drawing.Point(15, 15),
            .Size = New Drawing.Size(330, 20)
        }

        _bar = New ProgressBar() With {
            .Location = New Drawing.Point(15, 45),
            .Size = New Drawing.Size(330, 22),
            .Minimum = 0,
            .Maximum = 100
        }

        Me.Controls.Add(_label)
        Me.Controls.Add(_bar)
    End Sub

    Public Sub SetStatus(text As String)
        _label.Text = text
        _label.Refresh()
    End Sub

    Public Sub SetProgress(percent As Integer)
        If percent < 0 Then percent = 0
        If percent > 100 Then percent = 100
        _bar.Value = percent
    End Sub

End Class


' ---------------------------------------------------------------------------
' INTEGRATION
'
' 1. Project -> Add Reference -> Assemblies -> System.Web.Extensions
'
' 2. Form1.vb - replace the existing Form1_Load with:
'
'        Private Async Sub Form1_Load(sender As Object, e As EventArgs) Handles MyBase.Load
'            lblCoppiedNotifyer.Text = ""
'            Updater.CleanupOldBinary()
'            Await Updater.CheckForUpdatesAsync(True)
'        End Sub
'
'    (Async Sub is fine here - the await resumes on the UI thread, and the
'     window paints while the HTTP request is in flight.)
'
' 3. Form3.vb - replace the btnUpdates handler with:
'
'        Private Async Sub Button1_Click(sender As Object, e As EventArgs) Handles btnUpdates.Click
'            Await Updater.CheckForUpdatesAsync(False)
'        End Sub
'
' 4. Bump <Assembly: AssemblyVersion> and AssemblyFileVersion in
'    My Project\AssemblyInfo.vb before each release. This is what the updater
'    compares against - if you forget, users are told they're up to date.
'
' PUBLISHING A RELEASE
'
'   - Tag the release "1.2.0.0" (a leading "v" is also accepted).
'   - Attach the built binary, named exactly:  Shipping Tracker.exe
'   - Attach checksums.txt containing:
'         <sha256>  Shipping Tracker.exe
'     Generate it in PowerShell with:
'         (Get-FileHash ".\Shipping Tracker.exe" -Algorithm SHA256).Hash.ToLower() `
'             + "  Shipping Tracker.exe" | Out-File checksums.txt -Encoding ascii
'   - Don't mark it pre-release: /releases/latest skips drafts and pre-releases.
'
'   If checksums.txt is missing the update still installs, but unverified.
' ---------------------------------------------------------------------------