Turn AWS ServiceManager configuration into nested JSON

AwsSsmToAppSettings.ps1

#!/usr/bin/env powershell
param (
    [ValidateScript({
        if ($_ -eq $null) {
            return $true
        }
        if (-Not ($_ | Test-Path -PathType Leaf) ) {
            throw "Input file is a directory or does not exist"
        }
        return $true
    })]
    [Parameter(Position=0,Mandatory,ParameterSetName="FileInput")]
    [string]$InputFile = $null,
    [Parameter(ValueFromPipeline,ParameterSetName="PipeInput")]
    [string[]]$InputJson,
    [Parameter(Mandatory,ParameterSetName="AwsInput")]
    [string]$AwsPath = $null,
    [ValidateScript({
        if ($_ -eq $null) {
            return $true
        }
        if ($_ | Test-Path -PathType Container) {
            throw "Cannot write to a directory"
        }
        if (-Not ($_.Directory | Test-Path -PathType Container) ) {
            throw "The output file's directory must exist"
        }
        return $true
    })]
    [string]$OutputFile = $null,
    [Parameter(ParameterSetName="FileInput")]
    [Parameter(ParameterSetName="PipeInput")]
    [string]$KeyPrefix = "/"
)

Switch ($PSCmdlet.ParameterSetName) {
    "FileInput" {
        $InputJson = (Get-Content $InputFile)
    }
    "PipeInput" {
        if ($null -eq $InputJson -Or 0 -eq $InputJson.Length) {
            throw "No JSON input provided"
        }
    }
    "AwsInput" {
        $KeyPrefix = $AwsPath
        $InputJson = (aws "--no-cli-auto-prompt" "ssm" "get-parameters-by-path" "--recursive" "--no-cli-pager" "--path" $AwsPath)
    }
}

$json = [string]::Join([System.Environment]::NewLine, $InputJson) |`
    ConvertFrom-Json

if ($null -eq $json -Or `
    $null -eq $json.Parameters -Or `
    -Not [System.Array] -eq $json.Parameters.GetType().BaseType) {
    throw "Missing or invalid JSON input"
}

if (-Not $KeyPrefix.StartsWith("/")) {
    $KeyPrefix = "/$KeyPrefix"
}
if (-Not $KeyPrefix.EndsWith("/")) {
    $KeyPrefix = "$KeyPrefix/"
}

$output = @{}
$longest = 0

foreach ($kv in $json.Parameters) {
    $key = $kv.Name
    $value = $kv.Value
    if ($key.StartsWith($KeyPrefix)) {
        $key = $key.Substring($KeyPrefix.Length)
    }
    Write-Debug "$key = $value"
    [System.Collections.Generic.Queue[string]]$keyPath = `
        $key.Split("/", [System.StringSplitOptions]::RemoveEmptyEntries)
    if ($keyPath.Count -gt $longest) {
        $longest = $keyPath.Count
    }
    $parentDict = $output
    while ($keyPath.Count -gt 1) {
        $segment = $keyPath.Dequeue()
        if (-Not $parentDict.ContainsKey($segment)) {
            $parentDict[$segment] = @{}
        }
        $parentDict = $parentDict[$segment]
    }
    $parentDict[$keyPath.Dequeue()] = $value
}

if (-Not $null -eq $OutputFile) {
    ConvertTo-Json $output -Depth $longest | Set-Content $OutputFile
} else {
    ConvertTo-Json $output -Depth $longest
}