<#
.SYNOPSIS
    Bootstrap script to deploy and start the Autopilot Monitor agent.

.DESCRIPTION
    Designed to be deployed via Intune as a PowerShell Script during Autopilot.
    Runs very early in the enrollment process (first Intune action) and:
      1. Runs five pre-flight guards to skip productive devices and ghost re-installs
      2. Downloads the monitoring agent ZIP from Azure Blob Storage
      3. Verifies integrity via SHA-256 hash from the version manifest
         (legacy fallback: Content-MD5 header from the blob response)
      4. Extracts the agent into %ProgramData%\AutopilotMonitor\Agent
      5. Runs the agent in --install mode (registers Scheduled Task, spawns the runtime)
      6. Verifies the runtime process actually launched
    Agent self-destructs when enrollment completes.

.PARAMETER AgentDownloadUrl
    URL to download the agent ZIP from. Defaults to the production blob; override only
    for parallel lab/dev assignments that point at a separate pre-release ZIP.

.PARAMETER VersionJsonName
    Filename of the integrity manifest in the same blob container as the agent ZIP.
    Defaults to "version.json"; override only for parallel lab/dev manifests.

.PARAMETER MaxBootstrapWindowHours
    Maximum device uptime (hours) within which the bootstrap is still considered
    valid. Devices booted more than this many hours ago are skipped because we no
    longer trust their OOBE state. Default: 12.

.NOTES
    - Agent is temporary and auto-removes after enrollment.
    - All files live under C:\ProgramData\AutopilotMonitor (easy cleanup).
    - One registry key remains after removal: HKLM\SOFTWARE\AutopilotMonitor\Deployed
      (prevents ghost re-installs on re-Autopilot of the same device).
    - Scheduled Task survives reboots during enrollment.
    - This script MUST remain pure ASCII (no Unicode/UTF-8 special chars).
      PowerShell 5.1 (IME) reads scripts without BOM as ANSI, corrupting multi-byte chars.

.CHANGELOG
    2026-05-09  v2.0  Generic bootstrap: agent owns its own defaults (e.g. 600 s
                      TenantId-wait), so the script only calls `--install` plain.
                      Hardened post-install with a 10 s runtime-process verify.
    2026-04-09  v1.1  Introduced explicit script version, logged on startup.
    2026-03-31        Replaced OS age + MDM pre-flight checks with multi-signal guard
                      (registry deployment marker, WMI/filesystem user profile, last
                      logged-on user, 12 h bootstrap window).
    2026-03-30        Fixed non-ASCII characters that broke parsing under PowerShell 5.1.
    2026-03-29        Hardened integrity check: SHA-256 verification via version.json.
    2026-02-13        Simplified bootstrapper, introduced --install parameter for agent.
    2026-02-12        Robust download with integrity check (Content-MD5), boot time support,
                      pre-flight check to skip if agent already installed.
    2026-02-05        Initial version.
#>

[CmdletBinding()]
param(
    [Parameter(Mandatory = $false)]
    [string]$AgentDownloadUrl = "https://autopilotmonitor.blob.core.windows.net/agent/AutopilotMonitor-Agent.zip",

    [Parameter(Mandatory = $false)]
    [string]$VersionJsonName = "version.json",

    [Parameter(Mandatory = $false)]
    [int]$MaxBootstrapWindowHours = 12
)

# Script version (bump on meaningful changes; see .CHANGELOG above)
$ScriptVersion = "2.0"

# Configuration - Everything in ProgramData for easy cleanup
$AgentBasePath = "$env:ProgramData\AutopilotMonitor"
$AgentBinPath = "$AgentBasePath\Agent"
$AgentLogPath = "$AgentBasePath\Logs"
$LogFile = "$AgentLogPath\bootstrap_agent.log"

New-Item -Path $AgentBasePath -ItemType Directory -Force -ErrorAction SilentlyContinue | Out-Null
New-Item -Path $AgentBinPath -ItemType Directory -Force -ErrorAction SilentlyContinue | Out-Null
New-Item -Path $AgentLogPath -ItemType Directory -Force -ErrorAction SilentlyContinue | Out-Null

function Write-Log {
    param([string]$Message)
    $timestamp = Get-Date -Format "yyyy-MM-dd HH:mm:ss"
    $logMessage = "[$timestamp] $Message"
    Write-Output $logMessage
    Add-Content -Path $LogFile -Value $logMessage -ErrorAction SilentlyContinue
}

function Get-FileMd5Base64 {
    param(
        [Parameter(Mandatory = $true)]
        [string]$Path
    )

    $md5 = [System.Security.Cryptography.MD5]::Create()
    try {
        $stream = [System.IO.File]::OpenRead($Path)
        try {
            $hashBytes = $md5.ComputeHash($stream)
        }
        finally {
            $stream.Dispose()
        }

        return [Convert]::ToBase64String($hashBytes)
    }
    finally {
        $md5.Dispose()
    }
}

try {
    Write-Log "===== Autopilot Monitor Bootstrap Started ====="
    Write-Log "Bootstrap script version: v$ScriptVersion"

    # Guard 1: Agent was already deployed on this device (registry marker survives self-destruct)
    $deployed = (Get-ItemProperty -Path 'HKLM:\SOFTWARE\AutopilotMonitor' -Name 'Deployed' -ErrorAction SilentlyContinue).Deployed
    if ($deployed) {
        Write-Log "SKIP: Agent was previously deployed at $deployed."
        exit 0
    }

    # Guard 2: No real user profile should exist yet (primary productive-device guard).
    # Combines WMI (Win32_UserProfile.Special flag) and filesystem for maximum reliability.
    $excludePattern = '^(defaultuser\d*|Public|Default( User)?|All Users)$'

    $profileNames = @(
        try {
            Get-CimInstance Win32_UserProfile -ErrorAction Stop |
                Where-Object { -not $_.Special -and $_.LocalPath -like 'C:\Users\*' } |
                ForEach-Object { Split-Path $_.LocalPath -Leaf }
        } catch { Write-Log "INFO: WMI profile query failed, continuing with filesystem check." }

        (Get-ChildItem 'C:\Users' -Directory -ErrorAction SilentlyContinue).Name
    ) | Where-Object { $_ -and $_ -notmatch $excludePattern } |
        Select-Object -Unique

    if ($profileNames) {
        $names = ($profileNames | Select-Object -First 3) -join ', '
        Write-Log "SKIP: Real user profile(s) found ($names). Device appears productive."
        exit 0
    }

    # Guard 3: LastLoggedOnUser - during Device ESP no real user has logged on yet.
    $lastLoggedOnUser = (Get-ItemProperty -Path 'HKLM:\SOFTWARE\Microsoft\Windows\CurrentVersion\Authentication\LogonUI' -Name 'LastLoggedOnUser' -EA SilentlyContinue).LastLoggedOnUser
    if ($lastLoggedOnUser -and $lastLoggedOnUser -notmatch 'defaultuser\d*') {
        Write-Log "SKIP: LastLoggedOnUser found ($lastLoggedOnUser). Device appears productive."
        exit 0
    }

    # Guard 4: Bootstrap window check - device uptime must be within accepted OOBE window.
    # Sleep/standby does not reset uptime, only real boot/restart does.
    $lastBoot = (Get-CimInstance Win32_OperatingSystem).LastBootUpTime
    $uptimeHours = ((Get-Date) - $lastBoot).TotalHours
    Write-Log "Device uptime: $([int]$uptimeHours)h (last boot: $lastBoot)"
    if ($uptimeHours -gt $MaxBootstrapWindowHours) {
        Write-Log "SKIP: Device uptime is $([int]$uptimeHours)h. OOBE state is older than accepted bootstrap window of ${MaxBootstrapWindowHours}h."
        exit 0
    }

    # Guard 5: Is the agent already installed? (leftover from previous run)
    if (Test-Path $AgentBinPath) {
        $existingAgent = Get-ChildItem -Path $AgentBinPath -Filter "AutopilotMonitor.Agent.exe" -ErrorAction SilentlyContinue
        if ($existingAgent) {
            Write-Log "SKIP: Agent already installed at $($existingAgent.FullName)."
            exit 0
        }
    }

    Write-Log "Pre-flight checks passed -- no prior deployment, no real user profiles, no logged-on user, within bootstrap window"

    # Download and extract agent binaries
    $agentExePath = Join-Path $AgentBinPath "AutopilotMonitor.Agent.exe"

    if (Test-Path $agentExePath) {
        Write-Log "Agent already installed at $agentExePath"
    }
    else {
        Write-Log "Downloading agent from $AgentDownloadUrl..."

        try {
            # Derive manifest URL from the agent download URL (same blob container)
            $versionJsonUrl = $AgentDownloadUrl -replace '[^/]+$', $VersionJsonName
            $expectedSha256 = $null

            try {
                Write-Log "Fetching $VersionJsonName from $versionJsonUrl for integrity verification..."
                $versionJsonResponse = Invoke-RestMethod -Uri $versionJsonUrl -UseBasicParsing -TimeoutSec 5 -ErrorAction Stop
                if ($versionJsonResponse.sha256) {
                    $expectedSha256 = $versionJsonResponse.sha256.ToLowerInvariant()
                    Write-Log "SHA-256 hash from manifest: $expectedSha256 (version: $($versionJsonResponse.version))"
                } else {
                    Write-Log "Manifest has no sha256 field - falling back to legacy MD5 check (older build)"
                }
            }
            catch {
                Write-Log "WARNING: Could not fetch manifest - falling back to legacy MD5 check: $($_.Exception.Message)"
            }

            $zipPath = Join-Path $env:TEMP "AutopilotMonitor-Agent.zip"
            $maxDownloadAttempts = 3
            $downloadAttempt = 0
            $downloadResponse = $null

            do {
                $downloadAttempt++
                try {
                    Write-Log "Download attempt ${downloadAttempt}/${maxDownloadAttempts}"
                    $downloadResponse = Invoke-WebRequest `
                        -Uri $AgentDownloadUrl `
                        -OutFile $zipPath `
                        -UseBasicParsing `
                        -TimeoutSec 30 `
                        -ErrorAction Stop `
                        -PassThru
                    Write-Log "Downloaded agent to $zipPath"
                    break
                }
                catch {
                    if ($downloadAttempt -ge $maxDownloadAttempts) {
                        throw
                    }

                    $retryDelaysInSeconds = @(2, 4, 8)
                    $retryDelaySeconds = $retryDelaysInSeconds[$downloadAttempt - 1]
                    Write-Log "Download failed (attempt $downloadAttempt): $($_.Exception.Message). Retrying in ${retryDelaySeconds}s..."
                    Start-Sleep -Seconds $retryDelaySeconds
                }
            } while ($downloadAttempt -lt $maxDownloadAttempts)

            if ($expectedSha256) {
                $actualSha256 = (Get-FileHash $zipPath -Algorithm SHA256).Hash.ToLowerInvariant()
                Write-Log "Validating SHA-256 hash against manifest"
                if ($actualSha256 -ne $expectedSha256) {
                    throw "SHA-256 integrity check FAILED. Expected='$expectedSha256', Actual='$actualSha256'. Download may be tampered or corrupted."
                }
                Write-Log "SHA-256 integrity check passed"
            }
            else {
                $expectedMd5Header = $downloadResponse.Headers["Content-MD5"]
                $expectedMd5 = if ($expectedMd5Header -is [System.Array]) { "$($expectedMd5Header[0])".Trim() } else { "$expectedMd5Header".Trim() }
                if ($expectedMd5 -notmatch '\S') {
                    Write-Log "WARNING: No SHA-256 and no Content-MD5 header - skipping integrity validation"
                }
                else {
                    $actualMd5 = Get-FileMd5Base64 -Path $zipPath
                    Write-Log "Validating Content-MD5 header against downloaded ZIP"
                    if ($actualMd5 -ne $expectedMd5) {
                        throw "MD5 integrity check failed. Expected (Content-MD5)='$expectedMd5', Actual='$actualMd5'"
                    }
                    Write-Log "MD5 integrity check passed"
                }
            }

            Expand-Archive -Path $zipPath -DestinationPath $AgentBinPath -Force
            Write-Log "Extracted agent to $AgentBinPath"

            Remove-Item $zipPath -Force -ErrorAction SilentlyContinue
            Write-Log "Cleaned up temporary files"

            if (-not (Test-Path $agentExePath)) {
                throw "Agent executable not found after extraction at $agentExePath"
            }

            Write-Log "Agent installation completed successfully"
        }
        catch {
            Write-Log "ERROR downloading/extracting agent: $($_.Exception.Message)"
            throw
        }
    }

    Write-Log "Calling agent install mode (--install)..."
    & $agentExePath --install
    $installExitCode = $LASTEXITCODE
    if ($installExitCode -ne 0) {
        throw "Agent install failed with exit code $installExitCode"
    }
    Write-Log "Agent install mode completed successfully"

    $runtimeProcessName = 'AutopilotMonitor.Agent'
    $verifyTimeoutSec = 10
    $verifyDeadline = (Get-Date).AddSeconds($verifyTimeoutSec)
    $runtimeProc = $null
    while ((Get-Date) -lt $verifyDeadline) {
        $runtimeProc = Get-Process -Name $runtimeProcessName -ErrorAction SilentlyContinue | Select-Object -First 1
        if ($null -ne $runtimeProc) { break }
        Start-Sleep -Milliseconds 500
    }
    if ($null -ne $runtimeProc) {
        $startedUtc = 'unavailable'
        try { $startedUtc = $runtimeProc.StartTime.ToUniversalTime().ToString('o') } catch { }
        Write-Log ("Runtime process verified: name={0}.exe pid={1} startedUtc={2}" -f $runtimeProcessName, $runtimeProc.Id, $startedUtc)
    } else {
        Write-Log ("WARNING: Runtime process verification FAILED. Agent --install reported success but no '{0}.exe' process appeared within {1}s. Likely silent block (AV/EDR, AppLocker/WDAC) of the runtime launch. Agent should still come up at next boot via the BootTrigger task. Check Event Viewer > Microsoft > Windows > TaskScheduler/Operational and AV/EDR logs for '{0}.exe'." -f $runtimeProcessName, $verifyTimeoutSec)
    }

    Write-Log "===== Bootstrap Completed Successfully ====="

    exit 0
}
catch {
    Write-Log "===== Bootstrap FAILED ====="
    Write-Log "ERROR: $($_.Exception.Message)"
    Write-Log "Stack trace: $($_.ScriptStackTrace)"
    Write-Log "Please check log file: $LogFile"

    $errMsg = "AutopilotMonitor bootstrap failed: $($_.Exception.Message)"
    if ($errMsg.Length -gt 2048) { $errMsg = $errMsg.Substring(0, 1045) + '...' }
    [Console]::Error.WriteLine($errMsg)

    exit 1
}