#
# Install/Upgrade Check-MK-Agent from URL
#

function get_installed_software_info {
	param (
		[string]$pattern
	)
    $data = Get-ItemProperty $global:reg_key_sw_uninstall  | 
        Select-Object DisplayName, DisplayVersion          |
        Where-Object{$_.DisplayName -match $pattern}
    if ($data) {
        return @{ 
            name    = $data.DisplayName.Trim()
            version = $data.DisplayVersion.Trim()
            }
    }
}

function get_msi_db_property {
    param (
        $msidb,                       # opened msi database object System.__ComObject
        [string]$wanted_property      # wanted property of the MSI file
    )
    $view=$null
    $query = "SELECT Value FROM Property WHERE Property = '$($wanted_property)'"
    
    $view = $msidb.GetType().InvokeMember('OpenView', 'InvokeMethod', $null, $msidb, ($query))

    $view.GetType().InvokeMember('Execute', 'InvokeMethod', $null, $view, $null)

    $record = $view.
        GetType().
        InvokeMember('Fetch', 'InvokeMethod', $null, $view, $null)

    $value  = $record.
        GetType().
        InvokeMember('StringData', 'GetProperty', $null, $record, 1)

    return $value

}

function get_msi_product_info {
    param (
        [string]$msi_path
    )

    $installer = New-Object -ComObject WindowsInstaller.Installer
    $msidb= $installer.GetType().InvokeMember('OpenDatabase', 'InvokeMethod', $null, $installer, @($msi_path, 0))

    $product_version = get_msi_db_property -msidb $msidb -wanted_property "ProductVersion" | Out-String
    $product_name    = get_msi_db_property -msidb $msidb -wanted_property "ProductName"    | Out-String
    
    return @{
                name=$product_name.Trim()
             version=$product_version.Trim()
             }
}

function get_installed_checkmk_agent_info {
    $c = get_installed_software_info -pattern "Check MK Agent.*"
    return $c
}

function uninstall_checkmk_agent {
    $application = Get-WmiObject -Class Win32_Product | Where-Object {$_.Name -match "Check MK Agent.*"}
    if ($application) {
        $application.Uninstall()
    }
}

function install_msi_package {
    param(
        [string]$msi_path
    )
    msiexec /I $msi_path /qn

}

function mylog {
    $logline = ( $(Get-Date -Format "yyyy-MM-dd HH:mm:ss") + " " + $args[0] )
    Write-Host $logline
    Add-Content -Path $global:log_path -Value "$logline"
}

function main {
    param (
        [string]$msi_path,
        [string]$msi_url
    )

    mylog "Check-MK Installer/Updater starting"
    mylog "deleting $($msi_path)"
    # delete and redownload msi
    if (Remove-Item -Path $msi_path -ErrorAction SilentlyContinue) {
        mylog "Can not delete file $($msi_path): Aborting!"
        exit 1
    }

    mylog "downloading $($msi_url) to $($msi_path)"
    $global:progressPreference = 'silentlyContinue'
    for($i=1;$i -le 10;$i++) {
        mylog "trying download #$($i)"
        try {
            Invoke-WebRequest -Uri $msi_url -OutFile $msi_path
            $res = $?
        } catch {
            mylog "Error while downloading: $_"
            $res = $false
        }
        # mylog ('$?: ' + ">" + $res + "<")
        if($res -eq $True) { break }
        Start-Sleep -Seconds 10
    }
    if ($res -eq $false) {
        mylog "Giving up download. Aborting!"
        exit 1
    }
    
    Start-Sleep -Seconds 2

    mylog "examining msi file $($msi_file)"
    $msi_data       = get_msi_product_info -msi_path $msi_path

    mylog "checking installed version of check_mk"
    $installed_data = get_installed_checkmk_agent_info

    if ( $msi_data -and $msi_data.version ) {
       if ( $installed_data ) {
          if ( $installed_data.version ) {
            $installed_data_cversion = [System.Version] ($installed_data.version -replace 'p', '.')
            $msi_data_cversion       = [System.Version] ($msi_data.version -replace 'p', '.')
            if ( $installed_data_cversion -lt $msi_data_cversion ) {
                mylog "Installed Version $($installed_data.version) older than MSI-Version $($msi_data.version): Uninstalling old and Installing new"
                uninstall_checkmk_agent
                install_msi_package -msi_path $msi_path
            } else {
                mylog "Installed Version ($($installed_data.version)) is at least the same Version as MSI-Version ($($msi_data.version)): Doing nothing"
            }
          }
       } else {
            mylog "Check-MK not installed: Installing MSI-Package"
            install_msi_package -msi_path $msi_path
       }
    }
    mylog "Check-MK Installer/Updater finished"
}

# todo: implement check if download is really necessary (avoid bandwidth wasting)

# program starts here

$global:reg_key_sw_uninstall = "HKLM:\Software\Wow6432Node\Microsoft\Windows\CurrentVersion\Uninstall\*"
$base_path         = "$($env:LOCALAPPDATA)\check_mk_updater"
$msi_path          = "$base_path\check_mk_agent.msi"
$global:log_path   = "$base_path\install.log"
$msi_url           = "https://download.mydomain.de/repo/check_mk_agent.msi"

New-Item -ItemType Directory -Path $base_path -Force | Out-Null
main -msi_path $msi_path -msi_url $msi_url