# This code is subject to the MIT Licence shown at https://geekwolf.cloud/licence


param(
	[string]$TargetFolderPath = '~\Downloads\BTStatistics',
	[datetime]$StartDateTime = (Get-Date).AddDays(-1),
	[datetime]$EndDateTime = (Get-Date),
	[string]$MailboxFolder = 'Inbox'
)

if( $Null -eq (Get-MGContext) ) {
	Connect-MGGraph
}
 
function Get-MGGraphAllResults {
param( $Uri )
	$Values = @()
	do{
		$Results = Invoke-MgGraphRequest -Uri $Uri
		$Values += $Results.Value
		$Uri = $Results."@odata.nextLink"
	} while( $Uri )
	write-output $Values
}

$MailFolders = Get-MGGraphAllResults -Uri https://graph.microsoft.com/v1.0/me/mailFolders/delta
$MailboxFolderParts = $MailboxFolder.Split('\')
$FoundFolder = $MailFolders | ? { $_.DisplayName -eq $MailboxFolderParts[0] }
for( $i = 1; $i -lt $MailboxFolderParts.Count; $i++ ) {
	$FoundFolder = $MailFolders | ? { $_.DisplayName -eq $MailboxFolderParts[$i] -and $_.ParentFolderId -eq $FoundFolder.Id }
}


if( $FoundFolder ) {
	$Messages = Get-MGGraphAllResults -Uri "https://graph.microsoft.com/v1.0/me/mailFolders/$($FoundFolder.Id)/messages?`$filter=(contains(subject, 'Migration Statistics for Project ')) and (createdDateTime ge $($StartDateTime.ToString("yyyy-MM-ddTHH:mm:ssZ"))) and (createdDateTime le $($EndDateTime.ToString("yyyy-MM-ddTHH:mm:ssZ")))"
 
	if( -not (Test-Path $TargetFolderPath -Type Container) ) { New-Item $TargetFolderPath -Type Container | Out-Null}
	$TargetFolder = Get-Item $TargetFolderPath

	if( $TargetFolder.Attributes -contains 'Directory' ) {
		Foreach( $Message in $Messages ) {
			$ProjectName = $Message.Subject -replace 'Migration Statistics for Project ', ''
			$FileDate = $Message.createdDateTime.ToString( 'yyyyMMdd-HHmmss' )

			$Attachments =  Get-MGGraphAllResults -Uri "https://graph.microsoft.com/v1.0/me/messages/$($Message.Id)/attachments"
			Foreach( $Attachment in $Attachments ){
				if( $Attachment.Name -eq 'ProjectStats.zip' ) {
					$FilePath = $TargetFolder.FullName + '\' + $ProjectName + '-' + $FileDate

					# Ensure the folder exists
					if( -not (Test-Path $FilePath -Type Container) ) { New-Item $FilePath -Type Container }

					# create and expand the zip file
					[IO.File]::WriteAllBytes( ($FilePath + '.zip'), ([Convert]::FromBase64String($Attachment.contentBytes))) | Out-Null
					Expand-Archive ($FilePath + '.zip') -DestinationPath $FilePath -Force | Out-Null

					# Rename the extracted CSV file
					$ExtractedCsvFile = Join-Path -Path $TargetFolder.FullName -ChildPath 'ProjectStats.csv'
					if (Test-Path $ExtractedCsvFile) {
						Rename-Item -Path $ExtractedCsvFile -NewName ($FilePath + '.csv')
					}
 
					Remove-item $FilePath -Force -Recurse
					Remove-item ($FilePath + '.zip') -Force
				}
			}
		}
	} else {
		Write-Host "Folder $TargetFolderPath is not a valid folder" -fore red
	}

	# Merge the csv files and then export to Excel
	$Files = Get-ChildItem $TargetFolder -Recurse | Where-Object { $_.Name -like "*.csv"}
	$ItemResultHeaders = @()
	$ItemResultExports = @()
 
	foreach ( $File in $Files  ) {
		if( $File.VersionInfo.FileName -like "*.csv" ) {
			$ItemResults = @(Import-CSV $File.VersionInfo.FileName | select @{name="SourceFile";Expression={$File.Name}},*)
			$CsvHeader = Get-Content -Path $File.VersionInfo.FileName -TotalCount 1
			# try to find the previous set of header columns
			$ItemResultExportIndex = -1
			for( $i = 0; $i -lt $ItemResultHeaders.count; $i++ ) {
				if( $ItemResultHeaders[$i] -eq $CsvHeader ) {
					$ItemResultExportIndex = $i
				}
			}

			# if the header is new then add a new exports array element
			if( $ItemResultExportIndex -eq -1 ) {
				$ItemResultsExportIndex = $ItemResultHeaders.Count
				$ItemResultHeaders += @($CsvHeader)
				$ItemResultExports += ''
				$ItemResultExports[$ItemResultsExportIndex] = $ItemResults
			} else {
				$ItemResultExports[$ItemResultsExportIndex] += $ItemResults
			}
		}
	}

	for( $i = 0; $i -lt $ItemResultHeaders.count; $i++ ) {
		$ItemResultExports[$i] | Export-Excel "$($TargetFolder.FullName)-MigWizStats.xlsx" -WorksheetName "MigWizStats-$($i)" -Append -AutoSize -FreezeTopRow -BoldTopRow
	}
} else {
	write-Host "Folder $MailboxFolder cannot be found" -fore Red
}