Param
(
    [Parameter(Mandatory = $false)]
    [Nullable[DateTime]]$StartDate,
    [Nullable[DateTime]]$EndDate,
    [switch]$NoMFA,
    [string]$UserName,
    [string]$Password
)

Function Connect_Modules
{
 #Check for EXO v2 module inatallation
 $Module = Get-Module ExchangeOnlineManagement -ListAvailable
 if($Module.count -eq 0) 
 { 
  Write-Host Exchange Online PowerShell V2 module is not available  -ForegroundColor yellow  
  $Confirm= Read-Host Are you sure you want to install module? [Y] Yes [N] No 
  if($Confirm -match "[yY]") 
  { 
   Write-host "Installing Exchange Online PowerShell module"
   Install-Module ExchangeOnlineManagement -Repository PSGallery -AllowClobber -Force
  } 
  else 
  { 
   Write-Host EXO V2 module is required to connect Exchange Online.Please install module using Install-Module ExchangeOnlineManagement cmdlet. 
   Exit
  }
 } 
 #Check for Azure AD module
 $Module = Get-Module AzureAD -ListAvailable
 if($Module.count -eq 0) 
 { 
  Write-Host Azure AD module is not available  -ForegroundColor yellow  
  $Confirm= Read-Host Are you sure you want to install the module? [Y] Yes [N] No 
  if($Confirm -match "[yY]") 
  { 
   Write-host "Installing AzureAD PowerShell module"
   Install-Module AzureAD -Repository PSGallery -AllowClobber -Force
  } 
  else 
  { 
   Write-Host AzureAD module is required to generate the report.Please install module using Install-Module AzureAD cmdlet. 
   Exit
  }
 }

 #Authentication using non-MFA
 if($NoMFA.IsPresent)
 {
  #Storing credential in script for scheduling purpose/ Passing credential as parameter
  if(($UserName -ne "") -and ($Password -ne ""))
  {
   $SecuredPassword = ConvertTo-SecureString -AsPlainText $Password -Force
   $Credential  = New-Object System.Management.Automation.PSCredential $UserName,$SecuredPassword
  }
  else
  {
   $Credential=Get-Credential -Credential $null
  }
  Write-Host "Connecting Azure AD..."
  Connect-AzureAD -Credential $Credential | Out-Null
  Write-Host "Connecting Exchange Online PowerShell..."
  Connect-ExchangeOnline -Credential $Credential
 }
 #Connect to Exchange Online and AzureAD module using MFA 
 else
 {
  Write-Host "Connecting Exchange Online PowerShell..."
  Connect-ExchangeOnline
  Write-Host "Connecting Azure AD..."
  Connect-AzureAD | Out-Null
 }
}

Function Get_TeamMeetings
{
 $Result=""   
 $Results=@()  
 $Count=0
 Search-UnifiedAuditLog -StartDate $StartDate -EndDate $EndDate -Operations "MeetingDetail" -ResultSize 5000 | ForEach-Object {
  $Count++
  Write-Progress -Activity "`n     Retrieving Teams meetings data from $StartDate to $EndDate.."`n" Processed Teams meetings count: $Count"
  $AuditData=$_.AuditData  | ConvertFrom-Json
  $MeetingID=$AuditData.ID
  $CreatedBy=$AuditData.UserId
  $StartTime=(Get-Date($AuditData.StartTime)).ToLocalTime()
  $EndTime=(Get-Date($AuditData.EndTime)).ToLocalTime()
  $MeetingURL=$AuditData.MeetingURL
  $MeetingType=$AuditData.ItemName
  $Result=@{'Meeting id'=$MeetingID;'Created By'=$CreatedBy;'Start Time'=$Star=$StartTime;'End Time'=$EndTime;'Meeting Type'=$MeetingType;'Meeting Link'=$MeetingURL;'More Info'=$AuditData}
  $Results= New-Object PSObject -Property $Result  
  $Results | Select-Object 'Meeting id','Created By','Start Time','End Time','Meeting Type','Meeting Link','More Info' | Export-Csv -Path $ExportCSV -Notype -Append 
 }
 Write-Host $Count meetings details are exported. -ForegroundColor Green
}

$MaxStartDate=((Get-Date).AddDays(-89)).Date
#Getting Teams meeting attendance report for past 90 days
if(($StartDate -eq $null) -and ($EndDate -eq $null))
{
 $EndDate=(Get-Date)#.Date
 $StartDate=$MaxStartDate
}
#Getting start date to generate Teams meetings attendance report
While($true)
{
 if ($StartDate -eq $null)
 {
  $StartDate=Read-Host Enter start time for report generation '(Eg:11/23/2021)'
 }
 Try
 {
  $Date=[DateTime]$StartDate
  if($Date -ge $MaxStartDate)
  { 
   break
  }
  else
  {
   Write-Host `nAudit can be retrieved only for past 90 days. Please select a date after $MaxStartDate -ForegroundColor Red
   return
  }
 }
 Catch
 {
  Write-Host `nNot a valid date -ForegroundColor Red
 }
}


#Getting end date for teams attendance report
While($true)
{
 if ($EndDate -eq $null)
 {
  $EndDate=Read-Host Enter End time for report generation '(Eg: 11/23/2021)'
 }
 Try
 {
  $Date=[DateTime]$EndDate
  if($EndDate -lt ($StartDate))
  {
   Write-Host End time should be later than start time -ForegroundColor Red
   return
  }
  break
 }
 Catch
 {
  Write-Host `nNot a valid date -ForegroundColor Red
 }
}

$OutputCSV=".\TeamsMeetingAttendanceReport_$((Get-Date -format yyyy-MMM-dd-ddd` hh-mm` tt).ToString()).csv" 
$ExportCSV=".\TeamsMeetingsReport_$((Get-Date -format yyyy-MMM-dd-ddd` hh-mm` tt).ToString()).csv" 
$IntervalTimeInMinutes=1440    #$IntervalTimeInMinutes=Read-Host Enter interval time period '(in minutes)'
$CurrentStart=$StartDate
$CurrentEnd=$CurrentStart.AddMinutes($IntervalTimeInMinutes)

#Check whether CurrentEnd exceeds EndDate
if($CurrentEnd -gt $EndDate)
{
 $CurrentEnd=$EndDate
}

if($CurrentStart -eq $CurrentEnd)
{
 Write-Host Start and end time are same.Please enter different time range -ForegroundColor Red
 Exit
}

Connect_Modules
Get_TeamMeetings
$CurrentResultCount=0
$AggregateResultCount=0
Write-Host `nGenerating Teams meeting attendance report from $StartDate to $EndDate...
$ProcessedAuditCount=0
$OutputEvents=0
$ExportResult=""   
$ExportResults=@()  
$RetriveOperation="MeetingParticipantDetail"
while($true)
{ 
 #Getting Teams meeting participants report for the given time range
 Search-UnifiedAuditLog -StartDate $CurrentStart -EndDate $CurrentEnd -Operations $RetriveOperation -SessionId s -SessionCommand ReturnLargeSet -ResultSize 5000 | ForEach-Object {
  $ResultCount++
  $ProcessedAuditCount++
  Write-Progress -Activity "`n     Retrieving Team meeting participant report from $CurrentStart to $CurrentEnd.."`n" Processed audit record count: $ProcessedAuditCount"
  $AuditData=$_.AuditData  | ConvertFrom-Json
  $MeetingID=$AuditData.MeetingDetailId
  $CreatedBy=$_.UserIDs
  $AttendeesInfo=($AuditData.Attendees)
  $Attendees=$AttendeesInfo.userObjectId
  $AttendeesType=$AttendeesInfo.RecipientType
  if($AttendeesType -ne "User")
  {
   $Attendees=$AttendeesInfo.DisplayName
  }
  else
  {
   $Attendees=(Get-AzureADUser -ObjectId $Attendees).UserPrincipalName
  }
  $JoinTime=(Get-Date($AuditData.JoinTime)).ToLocalTime()  #Get-Date($AuditData.JoinTime) Uncomment to view the Activity Time in UTC
  $LeaveTime=(Get-Date($AuditData.LeaveTime)).ToLocalTime()

   
  #Export result to csv
  $OutputEvents++
  $ExportResult=@{'Meeting id'=$MeetingID;'Created By'=$CreatedBy;'Attendees'=$Attendees;'Attendee Type'=$AttendeesType;'Joined Time'=$JoinTime;'Left Time'=$LeaveTime;'More Info'=$AuditData}
  $ExportResults= New-Object PSObject -Property $ExportResult  
  $ExportResults | Select-Object 'Meeting id','Created By','Attendees','Attendee Type','Joined Time','Left Time','More Info' | Export-Csv -Path $OutputCSV -Notype -Append 
 }

 $currentResultCount=$currentResultCount+$ResultCount
 if($CurrentResultCount -ge 50000)
 {
  Write-Host Retrieved max record for current range.Proceeding further may cause data loss or rerun the script with reduced time interval. -ForegroundColor Red
  $Confirm=Read-Host `nAre you sure you want to continue? [Y] Yes [N] No
  if($Confirm -match "[Y]")
  {
   Write-Host Proceeding audit log collection with data loss
   [DateTime]$CurrentStart=$CurrentEnd
   [DateTime]$CurrentEnd=$CurrentStart.AddMinutes($IntervalTimeInMinutes)
   $CurrentResultCount=0
   if($CurrentEnd -gt $EndDate)
   {
    $CurrentEnd=$EndDate
   }
  }
  else
  {
   Write-Host Please rerun the script with reduced time interval -ForegroundColor Red
   Exit
  }
 }

 if($ResultCount -lt 5000)
 { 
  if($CurrentEnd -eq $EndDate)
  {
   break
  }
  $CurrentStart=$CurrentEnd 
  if($CurrentStart -gt (Get-Date))
  {
   break
  }
  $CurrentEnd=$CurrentStart.AddMinutes($IntervalTimeInMinutes)
  $CurrentResultCount=0
  if($CurrentEnd -gt $EndDate)
  {
   $CurrentEnd=$EndDate
  }
 }                                                                                             
 $ResultCount=0
}

#Open output file after execution
If($OutputEvents -eq 0)
{
 Write-Host No records found
}
else
{
 Write-Host `nThe Teams meeting attendance report contains $OutputEvents audit records -ForegroundColor Green
 Write-Host `nFor more Office 365 related PowerShell scripts, check https://o365reports.com -ForegroundColor Cyan
 if((Test-Path -Path $OutputCSV) -eq "True") 
 {
  Write-Host `nThe Teams meetings attendance report available in $OutputCSV -ForegroundColor Cyan
  $Prompt = New-Object -ComObject wscript.shell   
  $UserInput = $Prompt.popup("Do you want to open output file?",`   
 0,"Open Output File",4)   
  If ($UserInput -eq 6)   
  {   
   Invoke-Item "$OutputCSV"   
   Invoke-Item "$ExportCSV"
  } 
 }
}

#Disconnect Exchange Online session
Disconnect-ExchangeOnline -Confirm:$false -InformationAction Ignore -ErrorAction SilentlyContinue

<#
=============================================================================================
Name:           Audit Microsoft Teams meetings using PowerShell
For detailed Script execution:  https://o365reports.com/2021/12/08/microsoft-teams-meeting-attendance-report
============================================================================================
#>