Use homegrown solution to check for base image update (#98)

This change replaces the actions I was using to check if the image was
up to date because none of the solutions were working properly.

.github/workflows/Rolling.yml

@@ -10,18 +10,10 @@ on:
 jobs:
   check:
     name: Container Image Update Check
-    runs-on: ubuntu-latest
-    outputs:
-      needs-updating: ${{ steps.check.outputs.needs-updating }}
-    steps:
-      # https://github.com/giggio/docker-image-update-checker
-      - name: Check if container update available
-        id: check
-        uses: giggio/docker-image-update-checker@v2
-        with:
-          base-image: mcr.microsoft.com/dotnet/aspnet:7.0-cbl-mariner2.0-distroless
-          image: ${{ secrets.DOCKERHUB_USERNAME }}/synologyddnsupdater:latest
-          os: linux
+    uses: ./.github/workflows/workflow_image-update-check.yml
+    with:
+      base-image: mcr.microsoft.com/dotnet/aspnet:7.0-cbl-mariner2.0-distroless
+      image: craigktreasure/synologyddnsupdater:latest
 
   build_rolling:
     name: Build

.github/workflows/workflow_image-update-check.yml

@@ -0,0 +1,33 @@
+name: Check for image updates
+
+on:
+  workflow_call:
+    inputs:
+      image:
+        type: string
+        required: true
+        description: The container image to verify against the base image.
+      base-image:
+        type: string
+        required: true
+        description: The container base image.
+    outputs:
+      needs-updating:
+        description: Whether the image needs updating.
+        value: ${{ jobs.image-update-check.steps.update-check.outputs.needsBaseUpdate }}
+
+jobs:
+  image-update-check:
+    runs-on: ubuntu-latest
+
+    steps:
+      - uses: actions/checkout@v4
+        with:
+          fetch-depth: 0
+
+      - name: Check base image
+        id: update-check
+        shell: pwsh
+        run: |
+          $imageNeedsUpdate = ./scripts/CheckImageNeedsBaseUpdate.ps1 -Image ${{ inputs.image }} -BaseImage ${{ inputs.base-image }} -CheckDateCreated
+          "needsBaseUpdate=$imageNeedsUpdate" >> $env:GITHUB_ENV

scripts/CheckImageNeedsBaseUpdate.ps1

@@ -0,0 +1,110 @@
+#Requires -PSEdition Core
+
+<#
+.SYNOPSIS
+Checks if the image needs to be updated due to changes in the specified base image.
+Returns `true` if the image needs to be updated and `false` if the image is up to date.
+.PARAMETER BaseImageName
+The name of the base image to check against.
+.PARAMETER ImageName
+The name of the image to check.
+.PARAMETER CheckDateCreated
+If specified, the image creation date will be checked to ensure the image was created after the base image.
+#>
+[CmdletBinding()]
+param (
+    [string] $BaseImageName = 'mcr.microsoft.com/dotnet/aspnet:7.0-cbl-mariner2.0-distroless',
+
+    [string] $ImageName = 'craigktreasure/synologyddnsupdater:latest',
+
+    [switch] $CheckDateCreated
+)
+
+Set-StrictMode -Version 2.0
+$ErrorActionPreference = 'Stop'
+
+function CheckLastExitCode($message) {
+    if ($LASTEXITCODE -ne 0) {
+        Write-Error "Command failed with $LASTEXITCODE. $message"
+    }
+}
+
+function PullImage($imageName) {
+    Write-Host "Pulling image $imageName..." -ForegroundColor Magenta
+    docker pull $imageName
+    CheckLastExitCode "Failed to pull image $imageName"
+}
+
+function GetDateCreated($imageName) {
+    Write-Host "Getting image creation date for $imageName..." -ForegroundColor Magenta
+    $imageCreated = docker image inspect $imageName --format='{{.Created}}'
+    CheckLastExitCode "Failed to get image creation date for $imageName"
+    return $imageCreated
+}
+
+function CompareImageCreationDates($baseImageName, $imageName) {
+    Write-Host 'Comparing image creation dates...' -ForegroundColor Magenta
+
+    $baseImageCreated = GetDateCreated $baseImageName
+    $imageCreated = GetDateCreated $imageName
+
+    $baseImageCreatedDate = [DateTime]::Parse($baseImageCreated)
+    $imageCreatedDate = [DateTime]::Parse($imageCreated)
+
+    if ($baseImageCreatedDate -gt $imageCreatedDate) {
+        Write-Verbose "Base image was created on $baseImageCreatedDate, but image was created on $imageCreatedDate."
+
+        return $false
+    }
+
+    return $true
+}
+
+function GetImageLayers($imageName) {
+    Write-Host "Getting image layers for $imageName..." -ForegroundColor Magenta
+    $imageLayers = docker image inspect $imageName --format='{{range .RootFS.Layers}}{{println .}}{{end}}'
+    CheckLastExitCode "Failed to get image layers for $imageName"
+    return $imageLayers | Where-Object { $_ -ne '' }
+}
+
+function CheckImageContainsBaseLayers($baseImageLayers, $imageLayers) {
+    Write-Host 'Comparing image layers...' -ForegroundColor Magenta
+
+    for ($i = 0; $i -lt $baseImageLayers.Length; $i++) {
+        if ($baseImageLayers[$i] -ne $imageLayers[$i]) {
+            Write-Verbose "Image layers do not match. Base image layer $i is $($baseImageLayers[$i]), but image layer $i is $($imageLayers[$i])."
+
+            return $false
+        }
+    }
+
+    return $true
+}
+
+PullImage $BaseImageName
+PullImage $ImageName
+
+if ($CheckDateCreated) {
+    if (CompareImageCreationDates $BaseImageName $ImageName) {
+        Write-Host 'Image was created after base image.' -ForegroundColor Green
+    }
+    else {
+        Write-Host 'Image was created before base image. Image needs an update.' -ForegroundColor Red
+
+        return $true
+    }
+}
+
+$baseImageLayers = GetImageLayers $BaseImageName
+$imageLayers = GetImageLayers $ImageName
+
+$imageIsUpToDate = CheckImageContainsBaseLayers $baseImageLayers $imageLayers
+
+if ($imageIsUpToDate) {
+    Write-Host 'Image contains base layers. Image is up to date.' -ForegroundColor Green
+}
+else {
+    Write-Host 'Image does NOT contain all base layers. Image needs an update.' -ForegroundColor Red
+}
+
+return !$imageIsUpToDate