Param($url, $downloadDir, $sha1hash, $sha256hash)
if ($PSBoundParameters.Count -lt 4)  { Write-host "Error: -Url <url> -DownloadDir <path> -Sha1hash <hash> -Sha256hash <hash>" ;exit 1}
If ( -not (Test-Path $downloadDir)) { Write-host "Error: -DownloadDir <path> does not exist." ;exit 1}

function Write-Log {
  param (
      [string]$Message,
      [string]$LogPath = "$env:TEMP\downloadandcheck_updates.log"
    )
  #Output to Console
  Write-Host $Message
  $timestamp = Get-Date -Format "yyyy-MM-dd HH:mm:ss"
  $entry = "[$timestamp] $Message"
  Add-Content -Path $LogPath -Value $entry
}



$LogPath = ".\downloadandcheck_updates.logg"
if (Test-Path $logPath) {
  $logTime = (get-item $logPath).LastWriteTime
} else {
  $logTime = get-Date("1900/1/1")
}

Write-Log -Message "Start downloadandcheck_updates.ps1" -LogPath $LogPath

$downloadStatus = $false
$downloaduri = $url
$filename = Split-Path $downloaduri -Leaf
if (Test-Path (Join-Path $downloadDir $filename)) {
  Write-Log -Message "File $($filename) has already beed downloaded. Skip download." -LogPath $LogPath
} else {
  Write-Log -Message "Downloading $($filename) ..." -LogPath $LogPath
  Invoke-WebRequest -Uri $downloaduri -OutFile (Join-Path $downloadDir $filename) -UseBasicParsing
  if (Test-Path (Join-Path $downloadDir $filename)) {
    $downloadStatus = $true
    Write-Log -Message "Download completed." -LogPath $LogPath
  } else {
    Write-Log -Message "Download failed." -LogPath $LogPath
  }
}

$hashStatus = $true
$downloadedfile = Join-Path $downloadDir $filename
if ($downloadStatus) {
  $bytes  = [IO.File]::ReadAllBytes($downloadedfile)
  $sha256 = [Security.Cryptography.SHA256]::Create()
  $h256   = $sha256.ComputeHash($bytes)
  $h256_b64 = [Convert]::ToBase64String($h256)
  $sha1 = [Security.Cryptography.SHA1]::Create()
  $h1   = $sha1.ComputeHash($bytes)
  $h1_b64 = [Convert]::ToBase64String($h1)
  if ($sha1hash) {
    if (!($sha1hash -ceq $h1_b64)) {
      $hashStatus = $false
    }
    if($hashStatus) {
      Write-Log -Message "SHA1 Hash OK" -LogPath $LogPath
    } else {
      Write-Log -Message "SHA1 Hash NG" -LogPath $LogPath
    }
  }
  if ($sha256hash) {
    if ($sha256hash -ceq $h256_b64) {
      if (!($hashStatus)) {
        Write-Log -Message "SHA256 Hash NG" -LogPath $LogPath
        $hashStatus = $false
      }
    } else {
       $hashStatus = $false
    }
    if($hashStatus) {
      Write-Log -Message "SHA256 Hash OK" -LogPath $LogPath
    } else {
      Write-Log -Message "SHA256 Hash NG" -LogPath $LogPath
    }
  }
  if (!($hashStatus)) {
    Remove-Item $downloadedfile
    Write-Log -Message "Hash Check NG, Remove downloaded file." -LogPath $LogPath
  }  
}