Lab-Functions.ps1

# Function Add-Entity: Adds a blob file entity of a given type to a table.
function Add-Entity() {
  [CmdletBinding()]
  param(
    $Table,
    $Blob,
    $Type
  )

  # Use the Container name as the partition key
  $PartitionKey = $Blob.ICloudBlob.Container.Name
  # Use the blob name as the row key
  $RowKey = $Blob.Name

  $Entity = New-Object -TypeName Microsoft.WindowsAzure.Storage.Table.DynamicTableEntity
  $Entity.PartitionKey = $PartitionKey
  $Entity.RowKey = $RowKey
  $Entity.Properties.Add("Type", $Type)
  $Entity.Properties.Add("StorageUri", $Blob.ICloudBlob.StorageUri.PrimaryUri.AbsoluteUri)

  $Table.CloudTable.Execute([Microsoft.WindowsAzure.Storage.Table.TableOperation]::Insert($Entity))
}

# Add message to a queue
function Add-Message() {
  [CmdletBinding()]
  param(
    $Queue,
    $Blob
  )
  # Generate read-only SAS token for the blob
  $Sas = New-AzureStorageBlobSASToken -CloudBlob $Blob.ICloudBlob -Permission r

  # Message contains blob StorageUri and Name (what is needed to generate the thumbnail)
  $MessageHashTable = @{ StorageUri = $Blob.ICloudBlob.StorageUri.PrimaryUri;
                         Sas = $Sas;
                         Name = "$($Blob.ICloudBlob.Container.Name)\$($Blob.Name)" }

  # Convert the hash table to a JSON string
  $Message = ConvertTo-Json -InputObject $MessageHashTable

  # Construct a CloudQueueMessage with the serialized message
  $QueueMessage = New-Object -TypeName Microsoft.WindowsAzure.Storage.Queue.CloudQueueMessage `
                             -ArgumentList $Message

  # Add the message to the queue
  $Queue.CloudQueue.AddMessage($QueueMessage)
}

# Process a message if one is available and remove it when complete
function Process-Message() {
  [CmdletBinding()]
  param(
    $Queue
  )

  # Set the number of seconds to make a queue message invisible while processing
  $InvisibleTimeout = [System.TimeSpan]::FromSeconds(10)

  # Attempt to get a message from the queue
  $QueueMessage = $Queue.CloudQueue.GetMessage($InvisibleTimeout)

  if ($QueueMessage -eq $null) { 
    Write-Host "Empty queue"
    return
  }

  # Deserialize the JSON message
  $MessageHashTable = ConvertFrom-Json -InputObject $QueueMessage.AsString

  # Download the image to a temp file
  $TempFile = [System.IO.Path]::GetTempFileName()
  Invoke-WebRequest -Uri "$($MessageHashTable.StorageUri)$($MessageHashTable.Sas)" `
                    -OutFile $TempFile

  # Resize the image
  $ThumbnailFile = "$($TempFile)_thumb"
  Resize-Image -InputFile $TempFile -OutputFile $ThumbnailFile -Height 100 -Width 300

  # Upload the thumbnail to the thumbnails container
  Set-AzureStorageBlobContent -File $ThumbnailFile `
                              -Container thumbnails `
                              -Blob $MessageHashTable.Name

  Write-Host "Finished Processing"

  # Delete the message from the queue
  $Queue.CloudQueue.DeleteMessage($QueueMessage)
}