Azure App Settings to local.settings.json converter

ConvertAzureAppSettingsToLocalSettings

<#

Azure App Settings / Environment Variables to local.settings.json Converter
| v1.0.1 |-----------------------------------------------------------------

This script will take an Azure App Settings JSON file and convert it to a 
local.settings.json file for use with Azure Functions.

It also moves some of the Azure specific settings to the top of the file.

Usage:
    .\Convert-AzureAppSettingsToLocalSettings.ps1 "appsettings.json" "local.settings.json"

Example:

appsettings.json:
[
  {
    "name": "XkcdApiKey",
    "value": "cd39809326cc",
    "slotSetting": false
  },
  {
    "name": "FUNCTIONS_WORKER_RUNTIME",
    "value": "dotnet-isolated",
    "slotSetting": false
  },
  {
    "name": "FUNCTIONS_EXTENSION_VERSION",
    "value": "~4",
    "slotSetting": false
  },
  {
    "name": "APPINSIGHTS_INSTRUMENTATIONKEY",
    "value": "ABCDSFDKJSDKGLSJDKLGJSDG",
    "slotSetting": false
  }
]

local.settings.json:

{
  "IsEncrypted": false,
  "Values": {
    "FUNCTIONS_WORKER_RUNTIME": "dotnet-isolated",
    "FUNCTIONS_EXTENSION_VERSION": "~4",
    "APPINSIGHTS_INSTRUMENTATIONKEY": "ABCDSFDKJSDKGLSJDKLGJSDG",
    "XkcdApiKey": "cd39809326cc",
  }
}

#>
$azureAppSettingsFilePath = $args[0]
$outputLocalSettingsFPath = if ($args[1]) { $args[1] } else { "local.settings.json" }

# We don't need these from Azures in our local settings
$ignoredKeys = @(
    "AZURE_FUNCTIONS_ENVIRONMENT",
    "WEBSITE_RUN_FROM_PACKAGE"
)

# Make the script neater by having these up the top.
$headerKeys = @(
    "FUNCTIONS_WORKER_RUNTIME", "FUNCTIONS_EXTENSION_VERSION",
    "APPINSIGHTS_INSTRUMENTATIONKEY", "AzureWebJobsStorage",
    "WEBSITE_CONTENTAZUREFILECONNECTIONSTRING", "WEBSITE_CONTENTSHARE"
)

$filterOutKeys = $ignoredKeys + $headerKeys

$azureAppSettings = Get-Content -Path $azureAppSettingsFilePath | ConvertFrom-Json
$sortedAzureAppSettings = $azureAppSettings.GetEnumerator() | Sort-Object Name

$localSettings = [ordered]@{}
$headerSettings = [ordered]@{}

foreach ($setting in $sortedAzureAppSettings) {
    if ($setting.Name -notin $filterOutKeys) {
        $localSettings[$setting.Name] = $setting.Value
    } elseif ($setting.Name -in $headerKeys) {
        $headerSettings[$setting.Name] = $setting.Value
    }
}

$localSettingsJson = @{
    "IsEncrypted" = $false
    "Values" = $headerSettings + $localSettings
}

$localSettingsJsonString = $localSettingsJson | ConvertTo-Json -Depth 100
$localSettingsJsonString | Out-File -FilePath $outputLocalSettingsFPath