:PROPERTIES:
:ID:       bf63b6c5-f32f-462e-82ad-8d4a15f7ba48
:END:
#+DATE: 2026-04-10
#+filetags: :powershell:scripts:ess:esp:microlise:
#+STARTUP: showall
#+title: ESP — PowerShell Script Architecture

* Overview
:PROPERTIES:
:RELATED: [[id:a6c345df-8db9-4538-b87e-0e72e2414905][ESP Deployment Pipeline — Index]] 
:END:

The deployment scripts are structured in *three tiers*, loosely analogous to a presentation/domain/data layered architecture in software. This separation exists to:

- Keep ESP-specific knowledge isolated to higher tiers
- Allow Tier 3 functions to be tested in isolation
- Allow the scripts to run independently of AzDO
- Make incremental automation easier (replace manual prompts one function at a time)

* Entry Point — How to Call the Scripts

#+BEGIN_SRC powershell
Invoke-Deployment.ps1 -Customer ROMAC -Environment DEV -Stages PREDEPLOY,DEPLOY,POSTDEPLOY
#+END_SRC

You can pass any combination of stages. For example, to only validate:

#+BEGIN_SRC powershell
Invoke-Deployment.ps1 -Customer ROMAC -Environment DEV -Stages VALIDATE
#+END_SRC

* Tier 1 — Entry Point (Presentation Layer)

** Responsibility
- The *single entry point* to the whole deployment system
- Loads and validates the manifest (see [[id:9bf19a8b-5581-4be8-9892-913c51df0128][ESP — The Manifest]])
- Loads all required PowerShell modules (Tier 2, Tier 3, helpers)
- Calls the appropriate Tier 2 functions for the requested stages
- Passes the manifest object through to Tier 2

** Key Characteristics
- One script: ~Invoke-Deployment.ps1~
- Does NOT contain deployment logic itself
- Acts as a wiring layer only

** Pseudocode
#+BEGIN_SRC powershell
param(
    [string]$Customer,
    [string]$Environment,
    [string[]]$Stages
)

$manifest = Load-Manifest -Customer $Customer -Environment $Environment
Assert-ManifestValid -Manifest $manifest

Import-Module ./Tier2/PreDeployment.psm1
Import-Module ./Tier2/Deployment.psm1
Import-Module ./Tier2/PostDeployment.psm1
Import-Module ./Helpers/Logging.psm1

foreach ($stage in $Stages) {
    switch ($stage) {
        "PREDEPLOY"   { Invoke-PreDeployment  -Manifest $manifest }
        "DEPLOY"      { Invoke-Deployment     -Manifest $manifest }
        "POSTDEPLOY"  { Invoke-PostDeployment -Manifest $manifest }
    }
}
#+END_SRC

* Tier 2 — Orchestration Layer (Domain Layer)

** Responsibility
- One script per deployment stage (e.g. ~PreDeployment.psm1~, ~Deployment.psm1~)
- Contains the *logic and sequencing* of what needs to happen
- Decides *which* Tier 3 functions to call and in what order
- Reacts to return values from Tier 3 (e.g. if a function fails, abort or retry)

** Key Constraints
- *Does NOT* pass the manifest to Tier 3 — all required data is extracted and passed as explicit parameters
- *Does NOT* directly perform any action itself — delegates entirely to Tier 3
- *Does* have knowledge of ESP and what a deployment involves

** Why "Does Not Pass Manifest to Tier 3"?
Tier 3 functions are designed to be generic and reusable. If they accepted a manifest object, they'd need to know about its structure — breaking isolation. Instead, Tier 2 extracts what Tier 3 needs:

#+BEGIN_SRC powershell
# BAD — passes the whole manifest (couples Tier 3 to manifest structure)
Stop-WindowsService -Manifest $manifest

# GOOD — extracts what's needed and passes explicitly
Stop-WindowsService -ServiceName $manifest.Services.DLService.Name `
                    -ServerName  $manifest.Servers.AppServer
#+END_SRC

** Scripts in This Tier
| Script                | Stage it covers     |
|-----------------------+---------------------|
| ~Validation.psm1~     | VALIDATE stage      |
| ~Prerequisites.psm1~  | PREREQUISITES stage |
| ~PreDeployment.psm1~  | PREDEPLOY stage     |
| ~Deployment.psm1~     | DEPLOY stage        |
| ~PostDeployment.psm1~ | POSTDEPLOY stage    |

* Tier 3 — Functional Layer (Workers)

** Responsibility
- Small, *single-purpose* functions
- No knowledge of ESP, the manifest, or deployment context
- Accept all required data as *explicit parameters*
- Can be tested in isolation with mock data

** Key Characteristics
- Examples: ~Stop-WindowsService~, ~Invoke-SqlScript~, ~Copy-Files~, ~Get-RemoteSession~, ~Send-CitrixNotification~
- Initially implemented as *manual prompt wrappers* — the function prints instructions to a human and waits for confirmation
- Will be replaced with real automation incrementally

** The Manual Prompt Pattern (Current State)
#+BEGIN_SRC powershell
function Stop-WindowsService {
    param([string]$ServiceName, [string]$ServerName)

    # Current implementation — prompts a human
    $response = Invoke-ManualPrompt -Message "Please stop service '$ServiceName' on '$ServerName', then press Enter."
    return $response
}
#+END_SRC

** Target Implementation (Automated)
#+BEGIN_SRC powershell
function Stop-WindowsService {
    param([string]$ServiceName, [string]$ServerName)

    $session = Get-RemoteSession -ServerName $ServerName
    Invoke-Command -Session $session -ScriptBlock {
        Stop-Service -Name $using:ServiceName -Force
        (Get-Service -Name $using:ServiceName).WaitForStatus('Stopped', '00:01:00')
    }
}
#+END_SRC

** Exceptions — Functions That Cannot Be Manual Prompts
A small number of Tier 3 functions *must* be implemented for real from the start because they return data the scripts need to function:

| Function            | Why it can't be a manual prompt                       |
|---------------------+-------------------------------------------------------|
| ~Load-Manifest~     | Returns the manifest object — must actually read file |
| ~Get-RemoteSession~ | Returns a PS session — must actually connect          |
| ~Read-File~         | Returns file contents — must actually read            |

* Helper Modules

In addition to the three tiers, *general-purpose helper modules* exist that can be called from anywhere (Tier 1, 2, or 3):

| Module         | Purpose                                    |
|----------------+--------------------------------------------|
| ~Logging.psm1~ | Write structured log output                |
| ~Prompt.psm1~  | The manual prompt mechanism used by Tier 3 |
|                |                                            |

Helpers follow the same rule as Tier 3: *the manifest is never passed to them*.

* Testing Strategy

Because Tier 3 functions are isolated, they can be unit tested without any connection to a real ESP environment:

#+BEGIN_SRC powershell
# Example Pester test for Stop-WindowsService
Describe "Stop-WindowsService" {
    It "calls Invoke-Command with correct service name" {
        Mock Invoke-Command {}
        Mock Get-RemoteSession { return [PSCustomObject]@{ Session = "MockSession" } }

        Stop-WindowsService -ServiceName "DLService" -ServerName "SERVER01"

        Assert-MockCalled Invoke-Command -Times 1
    }
}
#+END_SRC

* Incremental Automation Plan

The architecture is designed so that automation can be added *one function at a time*, without restructuring anything:

1. Deploy with all Tier 3 functions as manual prompts (guided checklist)
2. Identify the lowest-risk, simplest functions to automate first
3. Replace manual prompts with real implementations one by one
4. Each replacement can be independently tested before deployment

Suggested automation order (rough):
1. ~Stop-WindowsService~ / ~Start-WindowsService~ — well-understood, low risk
2. ~Copy-Files~ — straightforward file operations
3. ~Invoke-SqlScript~ — once databases are in dacpac-ready state
4. Citrix-related functions — last, most complex

* Architecture Diagram (Text)

#+BEGIN_SRC
AzDO Pipeline (YAML)
│
└─► Invoke-Deployment.ps1         [TIER 1]
        │  Loads manifest
        │  Loads all modules
        │
        ├─► PreDeployment.psm1    [TIER 2]
        │       ├─► Copy-Files    [TIER 3]
        │       └─► ...
        │
        ├─► Deployment.psm1       [TIER 2]
        │       ├─► Stop-WindowsService    [TIER 3]
        │       ├─► Invoke-SqlScript       [TIER 3]
        │       ├─► Start-WindowsService   [TIER 3]
        │       └─► ...
        │
        └─► PostDeployment.psm1   [TIER 2]
                ├─► Get-ServiceStatus      [TIER 3]
                └─► ...

        [Helpers: Logging, Prompt — available at any tier]
#+END_SRC

** Mermaid Diagram (Text)
#+BEGIN_SRC mermaid
graph TD

    %% Tier 1
    subgraph "Tier 1 - Entry Point"
        A[Invoke-Deployment.ps1]
    end

    %% Tier 2
    subgraph "Tier 2 - Deployment Phases"
        B[PreDeployment.psm1]
        C[Deployment.psm1]
        D[PostDeployment.psm1]
    end

    %% Tier 3
    subgraph "Tier 3 - Actions"
        E[Copy-Files]
        F[Stop-WindowsService]
        G[Invoke-SqlScript]
        H[Start-WindowsService]
        I[Get-ServiceStatus]
    end

    %% Helpers
    subgraph "Helpers (All Tiers)"
        J[Logging Helper]
        K[Prompt Helper]
    end

    %% Relationships
    A --> B
    A --> C
    A --> D

    B --> E

    C --> F
    C --> G
    C --> H

    D --> I

    A --> J
    A --> K
#+END_SRC
