'
' Notes:
'   The real challenge is error handling. Only the simplest is done here.
'   The database is defined to prevent duplicate student & class names
'   The database is defined to enforce relational integrity
'
Sub DoPost()
    Dim buf As String
    Dim buf2 As String

    
    On Error GoTo OnPostError       ' We need to handle errors here

    Select Case sSelector
        Case "ENROLL":      ' Enroll a student
            buf = GetSmallField("Name")
            Set ds = db!Students.OpenRecordset(dbOpenTable)
            ds.AddNew
            ds("Name") = buf
            ds("Major") = GetSmallField("Major")
            ds.Update
            ds.Close                    ' ** THIS IS EASY TO FORGET! **
            Send ("<H2>" & buf & " enrolled successfully</H2>")

        Case "DISMISS":     ' Dismiss a student
            buf = GetSmallField("Student")
            Set qd = db.QueryDefs!DismissStudent
            qd.Parameters!pName = buf
            qd.Execute
            qd.Close
            Send ("<H2>" & buf & " dismissed successfully</H2>")

        Case "ADD":
            buf = GetSmallField("ClassName")
            Set ds = db!Classes.OpenRecordset(dbOpenDynaset)
            ds.AddNew
            ds("ClassName") = buf
            ds("Instructor") = GetSmallField("Instructor")
            ds.Update
            ds.Close
            Send ("<H2>" & buf & " added successfully</H2>")

        Case "DEL":
            buf = GetSmallField("Class")
            Set qd = db.QueryDefs!DeleteClass
            qd.Parameters!pClass = buf
            qd.Execute
            qd.Close
            Send ("<H2>" & buf & " deleted successfully</H2>")

        Case "CL4ST":
            buf = GetSmallField("Student")
            Send ("<H2>Classes for " & buf & ":</H2>")
            Set qd = db.QueryDefs!ClassesForStudent
            qd.Parameters!pName = buf
            Set ds = qd.OpenRecordset(dbOpenDynaset)
            Do Until ds.EOF
                Send (ds("ClassName") & " (" & ds("Instructor") & ")<BR>")
                ds.MoveNext
            Loop
            ds.Close
            qd.Close
                
        Case "ST4CL"
            buf = GetSmallField("Class")
            Send ("<H2>Students in " & buf & ":</H2>")
            Set qd = db.QueryDefs!StudentsInClass
            qd.Parameters!pClass = buf
            Set ds = qd.OpenRecordset(dbOpenDynaset)
            Do Until ds.EOF
                Send (ds("Name") & " (" & ds("Major") & ")<BR>")
                ds.MoveNext
            Loop
            ds.Close
            qd.Close

        Case "TAKE":
            buf = GetSmallField("Student")
            buf2 = GetSmallField("Class")
            Set qd = db.QueryDefs!TakeClass
            qd.Parameters!pName = buf
            qd.Parameters!pClass = buf2
            qd.Execute
            qd.Close
            Send ("<H2>" & buf & " is now taking " & buf2 & "</H2>")
        
        Case "DROP":
            buf = GetSmallField("Student")
            buf2 = GetSmallField("Class")
            Set qd = db.QueryDefs!DropClass
            qd.Parameters!pName = buf
            qd.Parameters!pClass = buf2
            qd.Execute
            qd.Close
            Send ("<H2>" & buf & " has dropped " & buf2 & "</H2>")
        
        Case Else:
            Send ("<H2>Unknown POST selector """ & sSelector & """</H2>")

    End Select

DoPostFinish:                   ' Can come here via error,
                                ' State of ds & qd unknown
    On Error Resume Next        ' Make damn sure ds and qd are closed
    ds.Close                    ' else db.Close will fail and you lose
    qd.Close

    Exit Sub

' =================
' Exception Handler
' =================
'
OnPostError:
    
    If Err >= CGI_ERR_START Then Error Err  ' Resignal if a CGI.BAS error

    Send ("<H2>There was a problem:</H2>")
    Send ("VB reports: <CODE>" & Error$ & " (error #" & Err & ")</CODE><H3>Best Guess:")

    Select Case sSelector
        Case "ENROLL":      ' Probably a duplicate name (enforced by database)
            Send ("Already enrolled")

        Case "DISMISS":     ' This is ugly, name came from dropbox
            Send ("?? This is ugly ??")

        Case "ADD":
            Send ("Class already exists")
        
        Case "DEL":
            Send ("?? This is ugly ??")
        
        Case "CL4ST":
            Send ("?? This is ugly ??")
        
        Case "ST4CL"
            Send ("?? This is ugly ??")
        
        Case "TAKE":
            Send ("Already taking this class")
        
        Case "DROP":
            Send ("Not in this class")
        
        Case Else:
            Send ("Programmer error: Unknown selector in POST exception handler.")
    End Select
    
    Send ("</H3>")
    
    Resume DoPostFinish

End Sub