<#
.SYNOPSIS
    注册 / 移除 BakNRet 的每日备份计划任务。

.DESCRIPTION
    任务直接调用 Backup-Data.ps1。脚本自身会写日志并按失败数返回退出码，
    因此「上次运行结果」在任务计划程序里是可读的，不需要额外包装。

    注册计划任务需要管理员权限（本脚本不自己提权，请从管理员终端运行）。

.EXAMPLE
    # 先看将要注册什么（只读，不需要管理员）
    .\tools\Register-BackupTask.ps1 -At '21:30' -DryRun

.EXAMPLE
    .\tools\Register-BackupTask.ps1 -At '21:30'

.EXAMPLE
    .\tools\Register-BackupTask.ps1 -Remove
#>

[CmdletBinding(SupportsShouldProcess = $true)]
param(
    [string]$TaskName = 'BakNRet Backup',

    # 每日触发时间，HH:mm
    [ValidatePattern('^\d{1,2}:\d{2}$')]
    [string]$At = '21:30',

    # 额外传给 Backup-Data.ps1 的参数，例如 @('-Snapshot')
    [string[]]$BackupArgument = @(),

    [ValidateSet('S4U', 'Interactive')]
    [string]$LogonType = 'S4U',

    # 用哪个 PowerShell 宿主执行（默认优先 pwsh.exe）
    [string]$PowerShellPath,

    [switch]$Remove,
    [switch]$DryRun
)

$ErrorActionPreference = 'Stop'

$projectRoot = Split-Path -Parent $PSScriptRoot
$backupScript = Join-Path $projectRoot 'Backup-Data.ps1'

if (-not (Test-Path -LiteralPath $backupScript)) {
    Write-Error "找不到 Backup-Data.ps1：$backupScript"
    exit 1
}

if (-not $PowerShellPath) {
    $pwsh = Get-Command pwsh.exe -ErrorAction SilentlyContinue | Select-Object -First 1 -ExpandProperty Source
    $PowerShellPath = if ($pwsh) { $pwsh } else { (Get-Command powershell.exe -ErrorAction Stop).Source }
}

$argumentParts = @('-NoProfile', '-ExecutionPolicy', 'Bypass', '-File', "`"$backupScript`"") + $BackupArgument
$argument = ($argumentParts -join ' ')

Write-Host ''
Write-Host "任务名   : $TaskName"
Write-Host "执行程序 : $PowerShellPath"
Write-Host "参数     : $argument"
Write-Host "触发     : 每天 $At"
Write-Host "登录类型 : $LogonType（S4U = 未登录也运行，但访问不到网络资源）"
Write-Host ''

if ($Remove) {
    if ($DryRun) {
        Write-Host '[试运行] 将移除计划任务' -ForegroundColor Yellow
        exit 0
    }
    if (-not (Get-Command Unregister-ScheduledTask -ErrorAction SilentlyContinue)) {
        Write-Error '当前环境没有计划任务 cmdlet。'
        exit 1
    }
    try {
        Unregister-ScheduledTask -TaskName $TaskName -Confirm:$false -ErrorAction Stop
        Write-Host "已移除计划任务：$TaskName" -ForegroundColor Green
    }
    catch {
        Write-Error "移除失败（多半是权限不足，请用管理员终端）：$_"
        exit 1
    }
    exit 0
}

if ($DryRun) {
    Write-Host '[试运行] 未实际注册。去掉 -DryRun 并确保在管理员终端里执行即可注册。' -ForegroundColor Yellow
    exit 0
}

foreach ($cmdlet in 'Register-ScheduledTask', 'New-ScheduledTaskTrigger', 'New-ScheduledTaskAction', 'New-ScheduledTaskSettingsSet', 'New-ScheduledTaskPrincipal') {
    if (-not (Get-Command $cmdlet -ErrorAction SilentlyContinue)) {
        Write-Error "当前环境缺少 $cmdlet，无法注册计划任务。"
        exit 1
    }
}

$action = New-ScheduledTaskAction -Execute $PowerShellPath -Argument $argument -WorkingDirectory $projectRoot
$trigger = New-ScheduledTaskTrigger -Daily -At $At

$settings = New-ScheduledTaskSettingsSet `
    -StartWhenAvailable `
    -MultipleInstances IgnoreNew `
    -AllowStartIfOnBatteries `
    -DontStopIfGoingOnBatteries `
    -ExecutionTimeLimit (New-TimeSpan -Hours 6)

$identity = [System.Security.Principal.WindowsIdentity]::GetCurrent().Name
$principal = New-ScheduledTaskPrincipal -UserId $identity -LogonType $LogonType -RunLevel Highest

try {
    Register-ScheduledTask -TaskName $TaskName -Action $action -Trigger $trigger `
        -Settings $settings -Principal $principal -Force -ErrorAction Stop | Out-Null
    Write-Host "已注册计划任务：$TaskName（每天 $At）" -ForegroundColor Green
    Write-Host "查看上次运行结果：Get-ScheduledTaskInfo -TaskName '$TaskName'" -ForegroundColor DarkGray
    Write-Host "手动跑一次验证  ：Start-ScheduledTask -TaskName '$TaskName'" -ForegroundColor DarkGray
}
catch {
    Write-Error "注册失败（多半是权限不足，请用管理员终端）：$_"
    exit 1
}

exit 0