File I/O & JSON

Imports System.IO

' --- Safe base folder (no admin rights needed) ---
Dim dataDir = Application.LocalUserAppDataPath
Directory.CreateDirectory(dataDir)   ' ensure it exists
Dim filePath = Path.Combine(dataDir, "notes.txt")

' ═══ ONE-SHOT (small files) ═══
File.WriteAllText(filePath, txtNotes.Text)                         ' write whole file
Dim content = File.ReadAllText(filePath)                          ' read whole file
Dim lines() = File.ReadAllLines(filePath)                         ' read into String array
File.AppendAllText(filePath, Environment.NewLine & "New line")  ' append

' ═══ STREAMING (large files, line-by-line) ═══
Using sw As New StreamWriter(filePath, append:=False)  ' overwrite
    sw.WriteLine("StudentID,Name,Grade,Class")         ' header
    For Each s In students
        sw.WriteLine($"{s.StudentID},{s.Name},{s.Grade},{s.Class}")
    Next
End Using   ' file closed here even if exception occurs

Using sr As New StreamReader(filePath)
    Dim header = sr.ReadLine()     ' skip header row
    Dim line = sr.ReadLine()
    Do While line IsNot Nothing
        Dim parts = line.Split(","c)
        If parts.Length = 4 Then
            Dim s As New Student With {
                .Name  = parts(1).Trim(),
                .Grade = CDbl(parts(2)),
                .Class = parts(3).Trim()
            }
            students.Add(s)
        End If
        line = sr.ReadLine()
    Loop
End Using

' --- Check existence before reading ---
If File.Exists(filePath) Then
    content = File.ReadAllText(filePath)
Else
    MessageBox.Show("File not found.")
End If

' --- Export List(Of Student) to CSV ---
Private Sub ExportCSV(path As String, students As List(Of Student))
    Using sw As New StreamWriter(path, append:=False, encoding:=Text.Encoding.UTF8)
        sw.WriteLine("StudentID,Name,Grade,Class")
        For Each s In students
            ' Quote name in case it contains a comma
            sw.WriteLine($'{s.StudentID},"{s.Name}",{s.Grade},{s.Class}')
        Next
    End Using
    MessageBox.Show($"Exported {students.Count} rows to {path}")
End Sub

' --- Import CSV → List(Of Student) ---
Private Function ImportCSV(path As String) As List(Of Student)
    Dim result As New List(Of Student)
    Dim lines = File.ReadAllLines(path)
    For i = 1 To lines.Length - 1   ' skip header (index 0)
        Dim parts = lines(i).Split(","c)
        If parts.Length < 4 Then Continue For
        Dim grade As Double
        If Not Double.TryParse(parts(2), grade) Then Continue For
        result.Add(New Student With {
            .StudentID = CInt(parts(0)),
            .Name      = parts(1).Trim(""""c),  ' strip surrounding quotes
            .Grade     = grade,
            .Class     = parts(3).Trim()
        })
    Next
    Return result
End Function

' --- OpenFileDialog integration ---
Private Sub btnImport_Click(...)
    Using dlg As New OpenFileDialog()
        dlg.Filter  = "CSV files|*.csv|All files|*.*"
        dlg.Title   = "Import Students from CSV"
        If dlg.ShowDialog() = DialogResult.OK Then
            students = ImportCSV(dlg.FileName)
            _bs.DataSource = students.ToList()
            MessageBox.Show($"Imported {students.Count} students.")
        End If
    End Using
End Sub

Imports System.Text.Json

' --- Serialize: object → JSON string ---
Dim opts As New JsonSerializerOptions() With {.WriteIndented = True}
Dim json = JsonSerializer.Serialize(students, opts)
' Result:
' [
'   { "StudentID": 1, "Name": "Ahmad Farid", "Grade": 88, "Class": "4A" },
'   ...
' ]

' --- Write to file ---
File.WriteAllText(Path.Combine(dataDir, "students.json"), json)

' --- Deserialize: JSON string → typed object ---
Dim loaded = JsonSerializer.Deserialize(Of List(Of Student))(
    File.ReadAllText(Path.Combine(dataDir, "students.json")))

' --- Application settings pattern ---
Public Class AppSettings
    Public Property LastOpenedFile As String
    Public Property Theme          As String = "Light"
    Public Property MaxResults     As Integer = 100
End Class

Private _settingsPath = Path.Combine(Application.LocalUserAppDataPath, "settings.json")

Function LoadSettings() As AppSettings
    If Not File.Exists(_settingsPath) Then Return New AppSettings()
    Try
        Return JsonSerializer.Deserialize(Of AppSettings)(File.ReadAllText(_settingsPath))
    Catch
        Return New AppSettings()   ' corrupt file → fresh defaults
    End Try
End Function

Sub SaveSettings(s As AppSettings)
    File.WriteAllText(_settingsPath,
        JsonSerializer.Serialize(s, New JsonSerializerOptions With {.WriteIndented=True}))
End Sub