[Powershell] Update-UserInstalledModules

[cmdletbinding()]
param(
    [Switch]
    $UninstallOldVersions
)

# Load required modules
$requiredModules = @(
    'PowerShellGet'
)
$modCheckFail = $false
foreach ($modName in $requiredModules) {
    if (!(Get-Module -Name $modName)) {
        if (!(Get-Module -Name $modName -ListAvailable)) {
            Write-Warning "'$modName' module required. Please install prior to running"
            $modCheckFail = $true
        }
        else {
            Import-Module -Name $modName
        }
    }
}
if ($modCheckFail) { Return }

# Validate required commands (failure may indicate too old a version of required modules)
$requiredCommands = @(
    'Find-Module',
    'Get-InstalledModule',
    'Install-Module',
    'Uninstall-Module'
)
$cmdCheckFail = $false
foreach ($cmdName in $requiredCommands) {
    if (!(Get-Command -Name $cmdName -ErrorAction Ignore)) {
        Write-Warning "Required command '$cmdName' not found after loading required modules"
        $cmdCheckFail = $true
    }
}
if ($cmdCheckFail) {
    Write-Warning "Check you have the latest versions of all required modules"
    foreach ($modName in $requiredModules) {
        Write-Warning "$modName"
    }
    Return
}

# Dependent functions
function Test-VersionString {
    [cmdletbinding()]
    param(
        [parameter(Mandatory = $true)]
        [ValidateNotNullOrEmpty()]
        [String]
        $VersionString
    )

    if ($VersionString -match '^[\d]+\.[\d]+\.[\d]+$') { $true }
    if ($VersionString -match '^[\d]+\.[\d]+\.[\d]+\.[\d]+$') { $true }
    else { $false }
}

function Test-ModuleVersionPresent {
    [cmdletbinding()]
    param(
        [parameter(Mandatory = $true)]
        [ValidateNotNullOrEmpty()]
        [String]
        $ModuleName,

        [parameter(Mandatory = $true)]
        [ValidateNotNullOrEmpty()]
        [String]
        $Version
    )

    $list = [System.Collections.Generic.List[String]]::new()

    $moduleList = Get-Module -Name $ModuleName -ListAvailable

    foreach ($module in $moduleList) {
        $list.Add($module.Version.ToString())
    }

    if ($Version -in $list) { $true }
    else { $false }
}

# MAIN
$installedModules = Get-InstalledModule

$x = 1
foreach ($installedModule in $installedModules) {
    Write-Progress -Activity 'Processing modules' -Status "($x/$($installedModules.Count)) - '$($installedModule.Name)'" -PercentComplete ($x/$installedModules.Count*100)

    $latestModule = Find-Module -Name $installedModule.Name -Repository $installedModule.Repository
    if (!$latestModule) {
        Write-Warning "Unable to find latest module '$($installedModule.Name)' at repository '$($installedModule.Repository)'. Skipping module."
        Continue
    }

    if (!(Test-VersionString -VersionString $installedModule.Version) -or !(Test-VersionString -VersionString $latestModule.Version)) {
        Write-Warning "Unhandled version string syntax in source or latest module. Version must 4 segments of digits only. Skipping module."
        Write-Warning "Source: '$($installedModule.Name)' - '$($installedModule.Version)' -- Latest: '$($latestModule.Name)' - '$($latestModule.Version)'"
        Continue
    }
    else {
        if ([System.Version]$installedModule.Version -lt [System.Version]$latestModule.Version) {
            Write-Output "'$($installedModule.Name)' - Higher version '$($latestModule.Version)' found (local version '$($installedModule.Version)'). Installing."

            Install-Module -Name $installedModule.Name -Repository $installedModule.Repository -RequiredVersion $latestModule.Version -Scope CurrentUser -Force
            if (!(Test-ModuleVersionPresent -ModuleName $installedModule.Name -Version $latestModule.Version)) {
                Write-Warning "'$($installedModule.Name)' - Latest version not found after installation attempt."
                if ($UninstallOldVersions) { Write-Warning "Uninstall of old versions will not proceed" }
                Continue
            }
            else {
                if ($UninstallOldVersions) {
                    Write-Output "'$($installedModule.Name)' - Uninstalling old versions"

                    $installedModuleMatches = Get-Module -Name $installedModule.Name -ListAvailable

                    foreach ($moduleMatch in $installedModuleMatches) {
                        if ($moduleMatch.Version.ToString() -eq $latestModule.Version) { Continue }
                        else {
                            Uninstall-Module -Name $moduleMatch.Name -RequiredVersion $moduleMatch.Version -Force
                        }
                    }
                }
            }
        }
        elseif ([System.Version]$installedModule.Version -eq [System.Version]$latestModule.Version) {
            Write-Output "'$($installedModule.Name)' - Same version '$($latestModule.Version)' found (local version '$($installedModule.Version)'). Skipping install."

            if ($UninstallOldVersions) {
                Write-Output "'$($installedModule.Name)' - Uninstalling old versions"

                $installedModuleMatches = Get-Module -Name $installedModule.Name -ListAvailable

                foreach ($moduleMatch in $installedModuleMatches) {
                    if ($moduleMatch.Version.ToString() -eq $latestModule.Version) { Continue }
                    else {
                        Uninstall-Module -Name $moduleMatch.Name -RequiredVersion $moduleMatch.Version -Force
                    }
                }
            }
        }
        elseif ([System.Version]$installedModule.Version -gt [System.Version]$latestModule.Version) {
            Write-Warning "'$($installedModule.Name)' - Local version '$($installedModule.Version)' found as higher (repository version '$($latestModule.Version)'). No action taken due to anomaly."
            Continue
        }
    }

    $x++
}