Capistrano-style IIS deployment helper

update_deployment.ps1

param(
    [switch] $Rollback
)

################################################################################
# Config
################################################################################

$WebsiteName = "FIXME: IIS WEBSITE NAME"
$WaitForWebsiteTimeoutSeconds = 60
$NumReleasesToKeep = 5
$ReleasesDir = (Join-Path "." releases)


################################################################################
# Helpers
################################################################################

function WriteInfo {
    param([Parameter(Mandatory = $true)][string] $Msg)

    Write-Host $Msg
}

function WriteWarn {
    param([Parameter(Mandatory = $true)][string] $Msg)

    Write-Host -ForegroundColor Yellow $Msg
}

function WriteError {
    param([Parameter(Mandatory = $true)][string] $Msg)

    Write-Host -ForegroundColor Red $Msg
}

function FailWithMessage {
    param([Parameter(Mandatory = $true)][string] $Msg)

    WriteError $Msg
    [System.Console]::ReadKey()
    exit 1
}

function WaitForState() {
    param([Parameter(Mandatory = $true)][string] $State)

    $Timeout = (Get-Date).AddSeconds($WaitForWebsiteTimeoutSeconds)

    while ($State -ne (Get-IISSite -name $WebsiteName).State) {
        if ((Get-Date) -gt $Timeout) {
            return $false
        }
        Start-Sleep -Seconds 1
    }

    return $true
}

function LoadIISModule() {
    Import-Module IISAdministration
    if (-not $?) {
        FailWithMessage "Error while loading IISAdministration module. Exiting."
    }
}

function UpdateCurrentTo() {
    param([Parameter(Mandatory = $true)][string] $TargetPath)

    $CurrentPath = (Join-Path "." "current")
    if (Test-Path $CurrentPath) {
        Remove-Item $CurrentPath
    }

    New-Item -ItemType SymbolicLink -Path $CurrentPath -Target $TargetPath | Out-Null
    WriteInfo "   Updated $CurrentPath to point at [$TargetPath]"
}

function GetRollbackTarget() {
    $CurrentTarget = (Get-ChildItem -Filter "current").Target
    $Releases = (Get-ChildItem $ReleasesDir | Sort-Object -Descending)
    $ReturnNext = $false
    foreach ($Release in $Releases) {
        if ($ReturnNext) {
            return $Release
        }

        if ($Release.ToString() -eq $CurrentTarget.ToString()) {
            $ReturnNext = $true
        }
    }
    return $null
}

function RemoveOldReleases() {
    $ReleasesToDelete = (Get-ChildItem $ReleasesDir -exclude ".revision" | Sort-Object -Descending | Select-Object -Skip $NumReleasesToKeep)
    $CurrentTarget = (Get-ChildItem -Filter "current").Target
    foreach ($Release in $ReleasesToDelete) {
        if ($Release.ToString() -eq $CurrentTarget.ToString()) {
            WriteInfo "   Skipping current release [$Release]"
        } else {
            WriteInfo "   Removing old release at [$Release]"
            Remove-Item $Release -Force -Recurse
        }
    }
}

function CheckIfRunningAsAdmin() {
    # https://megamorf.gitlab.io/2020/05/26/check-if-powershell-is-running-as-administrator/
    [Security.Principal.WindowsIdentity]::GetCurrent().Groups -contains 'S-1-5-32-544'
}

################################################################################
# Main
################################################################################

if (-not ("Core" -eq $PSVersionTable.PSEdition)) {
    FailWithMessage "This script requires Powershell Core. Exiting."
}

if (-not (CheckIfRunningAsAdmin)) {
    FailWithMessage "This script requires being run as Admin. Exiting."
}

if (-not (Test-Path $ReleasesDir)) {
    FailWithMessage "No releases found in [$ReleasesDir]. Exiting."
}

$NewestRelease = Get-ChildItem $ReleasesDir | Sort-Object -Descending | Select-Object -First 1
if ($null -eq $NewestRelease) {
    FailWithMessage "No releases found in [$ReleasesDir]. Exiting."
}
$NewestReleasePath = $NewestRelease

function Main() {
    WriteInfo " > Loading IISAdministration PS module"
    LoadIISModule

    WriteInfo " > Checking if website is stopped"
    if ("Stopped" -ne (Get-IISSite -name $WebsiteName).State) {
        WriteWarn "You must stop the website named [$WebsiteName] in IIS.`n`nWaiting..."
        if (-not (WaitForState "Stopped")) {
            FailWithMessage "`nTimed out waiting for [$WebsiteName] to be stopped. Exiting."
        }
    }
    WriteInfo "   Stopped"

    WriteInfo " > Updating current link"
    if ($Rollback) {
        $Target = GetRollbackTarget
        if ($null -eq $Target) {
            WriteInfo "   No target for rollback"
        } else {
            WriteInfo "   Rolling back to [$Target]"
            UpdateCurrentTo $Target
        }
    } else {
        UpdateCurrentTo $NewestReleasePath

        WriteInfo " > Checking for old releases"
        RemoveOldReleases
    }

    WriteWarn "Release updated. You must start the website named [$WebsiteName] in IIS.`n`nWaiting..."
    if ("Started" -ne (Get-IISSite -name $WebsiteName).State) {
        if (-not (WaitForState "Started")) {
            FailWithMessage "`nTimed out waiting for [$WebsiteName] to be started. Exiting."
        }
    }
    WriteInfo "   Started"

    WriteInfo "`nDone!"
    [System.Console]::ReadKey()
}

Main