param(
    [Parameter(Mandatory=$true, HelpMessage="The guid for the subscription you'll be deploying to.")]
    [string]$azureSubscriptionId,
    [Parameter(Mandatory=$true, HelpMessage="The name of the azure app service that you'll be deploying to.")]
    [string]$appServiceName
)

$ErrorActionPreference = 'Stop'

Import-Module Az
Import-Module Az.Resources

# this is the friendly-ish name and info for your application
# NOTE: this is the name of the Active Directory Application not the AppService
$appServiceDefaultDomain = "$appServiceName.azurewebsites.net"
$activeDirectoryApplicationDisplayName = $appServiceName
$activeDirectoryApplicationHomePage = "https://$appServiceDefaultDomain"
$credentialStartTime = [DateTime]::Now
$credentialEndTime = $credentialStartTime.AddYears(1)

# Login to Azure
Connect-AzAccount
 
Write-Output "Getting subscription using Get-AzSubscription..."
Write-Output "Requested subscription: $azureSubscriptionId"

$subscription = 
    (Get-AzSubscription -SubscriptionId $azureSubscriptionId)

if ($null -eq $subscription) {
    Write-Output "Subscription is null"
    exit
}
else {
    Write-Output "Got subscription using Get-AzSubscription..."
}

$subscriptionId = $subscription.Id
$subscriptionName = $subscription.Name
$tenantId = $subscription.tenantId

Write-Output "Subscription Id: $subscriptionId"
Write-Output "Subscription Name: $subscriptionName"
Write-Output "Tenant Id: $tenantId"

Write-Output "Calling Set-AzContext..."
Set-AzContext -SubscriptionId $subscriptionId -TenantId $tenantId

# create application in AAD
Write-Output "Calling New-AzADApplication..."

New-AzADApplication -DisplayName $activeDirectoryApplicationDisplayName -HomePage $activeDirectoryApplicationHomePage -OutVariable app

if ($app -eq $null) {
    Write-Output "Call to New-AzADApplication returned null."
    exit
}
else {
    Write-Output "Got application from New-AzADApplication..."
    Write-Output $app
}

$servicePrincipalClientId = $app.AppId

Write-Output "Calling New-AzADAppCredential..."
New-AzADAppCredential -ApplicationId $app.AppId -StartDate $credentialStartTime -EndDate $credentialEndTime -OutVariable generatedCredential

if ($generatedCredential -eq $null) {
    Write-Output "Call to New-AzADAppCredential returned null."
    exit
}
else {
    Write-Output "Got generated credential from New-AzADAppCredential..."
    Write-Output $generatedCredential
}

$generatedSecretText = $generatedCredential.SecretText

Write-Output "SecretText: $generatedSecretText"

Write-Output "Calling New-AzADServicePrincipal..."
New-AzADServicePrincipal -ApplicationId $app.AppId -OutVariable servicePrincipal

if ($servicePrincipal -eq $null) {
    Write-Output "Call to New-AzADServicePrincipal returned null."
    exit
}
else {
    Write-Output "Got service principal from New-AzADServicePrincipal..."
    Write-Output $servicePrincipal
}

Write-Output $servicePrincipal

Write-Output "Pausing for a bit to let New-AzureRmADServicePrincipal catch up before adding role assignment..."
Start-Sleep -s 10

Write-Output "Calling New-AzRoleAssignment..."
New-AzRoleAssignment -RoleDefinitionName Contributor -ServicePrincipalName $app.AppId -OutVariable roleAssignment

if ($roleAssignment -eq $null) {
    Write-Output "Call to New-AzRoleAssignment returned null."
    exit
}
else {
    Write-Output "Got role assignment from New-AzRoleAssignment..."
    Write-Output $roleAssignment
}

Write-Output $roleAssignment

Write-Output "Reloading what we just created..."

Get-AzADApplication -DisplayNameStartWith $activeDirectoryApplicationDisplayName -OutVariable reloadedApp
Get-AzADServicePrincipal -ServicePrincipalName $reloadedApp.AppId -OutVariable SPN

Write-Output "Here's the SPN..."
Write-Output $SPN

$nowTicks = [DateTime]::Now.Ticks;

$keyValueFilename = "service-principal-info-$nowTicks.txt"

# create an instance of StringBuilder
$sb = New-Object System.Text.StringBuilder

[void]$sb.AppendLine()
[void]$sb.AppendLine("******************************")
[void]$sb.AppendLine()
[void]$sb.AppendLine("Here's all the info you need.")
[void]$sb.AppendLine()
[void]$sb.AppendLine("Subscription Id:")
[void]$sb.AppendLine("$subscriptionId")
[void]$sb.AppendLine()
[void]$sb.AppendLine("Subscription Name:")
[void]$sb.AppendLine("$subscriptionName")
[void]$sb.AppendLine()
[void]$sb.AppendLine("Service Principal Client Id:")
[void]$sb.AppendLine("$servicePrincipalClientId")
[void]$sb.AppendLine()
[void]$sb.AppendLine("Service Principal Key:")
[void]$sb.AppendLine("$generatedSecretText")
[void]$sb.AppendLine()
[void]$sb.AppendLine("Tenant Id:")
[void]$sb.AppendLine("$tenantId")
[void]$sb.AppendLine()
[void]$sb.AppendLine("******************************")
[void]$sb.AppendLine("Script created by Benjamin Day")
[void]$sb.AppendLine("Benjamin Day Consulting, Inc.")
[void]$sb.AppendLine("https://www.benday.com")
[void]$sb.AppendLine("info@benday.com")
[void]$sb.AppendLine("******************************")
[void]$sb.AppendLine()

$sb.ToString() | Out-File .\$keyValueFilename 

Write-Output $sb.ToString()
Write-Output "This info is also written to $keyValueFilename"

Write-Output "Done."