# 設定編碼以防中文亂碼
[Console]::OutputEncoding = [System.Text.Encoding]::UTF8
Clear-Host

Write-Host "=========================================" -ForegroundColor Cyan
Write-Host "       端點網路狀態快速診斷工具          " -ForegroundColor Cyan
Write-Host "=========================================" -ForegroundColor Cyan
Write-Host ""

$failStage = $null
$ipInfo = ""

# 步驟 1: 檢查 IP 位址 (辨識是否為 169.254 APIPA 斷網狀態)
Write-Host "[*] 正在檢查本機 IP 設定..." -NoNewline
$ipConfig = Get-NetIPAddress -AddressFamily IPv4 -InterfaceIndex $(Get-NetConnectionProfile | Select-Object -ExpandProperty InterfaceIndex) -ErrorAction SilentlyContinue
$ipAddress = $ipConfig.IPAddress

if (-not $ipAddress) {
    $ipAddress = (Get-NetIPAddress -AddressFamily IPv4 -InterfaceIndex 12 -ErrorAction SilentlyContinue | Select-Object -ExpandProperty IPAddress)
}

if ($ipAddress) {
    Write-Host " [ 成功 ]" -ForegroundColor Green
    Write-Host "    -> 目前 IP: $ipAddress"
    
    # 檢查是否為 Windows 自動私人 IP (APIPA)
    if ($ipAddress -like "169.254.*") {
        $failStage = "IP_APIPA (DHCP 伺服器無回應，取得無效的 169.254 網段)"
    }
} else {
    Write-Host " [ 失敗 ]" -ForegroundColor Red
    $failStage = "IP_Missing (未取得任何 IPv4 位址)"
}

# 步驟 2: 檢查閘道器 (Gateway) 是否通
if (-not $failStage) {
    Write-Host "[*] 正在檢查區域網路閘道器 (Gateway)..." -NoNewline
    $gateway = (Get-NetRoute -DestinationPrefix "0.0.0.0/0" -ErrorAction SilentlyContinue | Select-Object -ExpandProperty NextHop | Select-Object -First 1)
    
    if ($gateway) {
        $pingGw = Test-Connection -ComputerName $gateway -Count 1 -Quiet
        if ($pingGw) {
            Write-Host " [ 成功 ] ($gateway)" -ForegroundColor Green
        } else {
            Write-Host " [ 失敗 ]" -ForegroundColor Red
            $failStage = "Gateway_Unreachable (有取得 IP 但無法連線至閘道器，實體線路或交換器異常)"
        }
    } else {
        Write-Host " [ 失敗 ]" -ForegroundColor Red
        $failStage = "Gateway_NotFound (找不到預設閘道器)"
    }
}

# 步驟 3: 檢查外網 IP (8.8.8.8) 是否通
if (-not $failStage) {
    Write-Host "[*] 正在檢查網際網路連線 (8.8.8.8)..." -NoNewline
    $pingExt = Test-Connection -ComputerName "8.8.8.8" -Count 1 -Quiet
    if ($pingExt) {
        Write-Host " [ 成功 ]" -ForegroundColor Green
    } else {
        Write-Host " [ 失敗 ]" -ForegroundColor Red
        $failStage = "External_Network_Fail (閘道器通，但無法連線至外網，可能路由器斷線或外線掉線)"
    }
}

# 步驟 4: 檢查 DNS 解析是否正常
if (-not $failStage) {
    Write-Host "[*] 正在檢查 DNS 解析 (google.com)..." -NoNewline
    try {
        $resolve = Resolve-DnsName -Name "google.com" -ErrorAction Stop
        Write-Host " [ 成功 ]" -ForegroundColor Green
    } catch {
        Write-Host " [ 失敗 ]" -ForegroundColor Red
        $failStage = "DNS_Fail (外網可通，但無法解析網域名稱，請檢查 DNS 設定)"
    }
}

Write-Host ""
Write-Host "=========================================" -ForegroundColor Cyan
if (-not $failStage) {
    Write-Host " 檢測結果：網路完全正常！ (OK)" -ForegroundColor Green
} else {
    Write-Host " 檢測結果：網路異常" -ForegroundColor Red
    Write-Host " 故障點：$failStage" -ForegroundColor Yellow
}
Write-Host "=========================================" -ForegroundColor Cyan
Write-Host ""

# 關鍵：強制畫面停留，等待人工按 Enter 才會關閉
Read-Host "請檢視上方結果，按下 Enter 鍵關閉視窗..."