feat(print): Windows print agent — the cloud↔LAN bridge (Phase 3)

A standalone net10.0-windows console app (agent/Meezi.PrintAgent) installed on the
café cash PC. It pairs with a one-time code (POST /print-agent/claim), stores the
token in %APPDATA%, holds a SignalR connection to /hubs/print-agent (retries
forever, re-reports on reconnect), discovers installed printers via WMI (USB +
network, classified), and prints jobs it receives by writing raw ESC/POS bytes —
winspool RAW passthrough for installed printers, raw TCP for ip:port devices —
acking each job back. Not in the API solution or CI (own net10.0-windows build);
see agent/README.md for build/publish/pair. Builds clean; startup + pairing flow
smoke-tested.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

agent/Meezi.PrintAgent/AgentConfig.cs

@@ -0,0 +1,40 @@
+using System.Text.Json;
+
+namespace Meezi.PrintAgent;
+
+/// <summary>Persisted agent identity — written to %APPDATA%\MeeziPrintAgent\config.json.</summary>
+public class AgentConfig
+{
+    /// <summary>Origin of the Meezi API, e.g. https://app.meezi.ir.</summary>
+    public string? ApiBaseUrl { get; set; }
+    public string? Token { get; set; }
+    public string? CafeId { get; set; }
+    public string? AgentId { get; set; }
+    public string? Name { get; set; }
+
+    private static string Dir =>
+        Path.Combine(Environment.GetFolderPath(Environment.SpecialFolder.ApplicationData), "MeeziPrintAgent");
+    private static string FilePath => Path.Combine(Dir, "config.json");
+
+    public bool IsPaired => !string.IsNullOrWhiteSpace(Token) && !string.IsNullOrWhiteSpace(ApiBaseUrl);
+
+    public static AgentConfig Load()
+    {
+        try
+        {
+            if (File.Exists(FilePath))
+                return JsonSerializer.Deserialize<AgentConfig>(File.ReadAllText(FilePath)) ?? new AgentConfig();
+        }
+        catch
+        {
+            // corrupt/unreadable config → start fresh
+        }
+        return new AgentConfig();
+    }
+
+    public void Save()
+    {
+        Directory.CreateDirectory(Dir);
+        File.WriteAllText(FilePath, JsonSerializer.Serialize(this, new JsonSerializerOptions { WriteIndented = true }));
+    }
+}

agent/Meezi.PrintAgent/Meezi.PrintAgent.csproj

@@ -0,0 +1,23 @@
+<Project Sdk="Microsoft.NET.Sdk">
+
+  <PropertyGroup>
+    <OutputType>Exe</OutputType>
+    <!-- Windows-only: uses winspool (raw printing) + WMI (printer discovery).
+         Overrides the repo-wide net10.0 / central package management on purpose so
+         this app stays independent of the API build (CI never compiles it). -->
+    <TargetFramework>net10.0-windows</TargetFramework>
+    <ManagePackageVersionsCentrally>false</ManagePackageVersionsCentrally>
+    <Nullable>enable</Nullable>
+    <ImplicitUsings>enable</ImplicitUsings>
+    <RootNamespace>Meezi.PrintAgent</RootNamespace>
+    <AssemblyName>MeeziPrintAgent</AssemblyName>
+    <Version>0.1.0</Version>
+    <InvariantGlobalization>true</InvariantGlobalization>
+  </PropertyGroup>
+
+  <ItemGroup>
+    <PackageReference Include="Microsoft.AspNetCore.SignalR.Client" Version="10.0.0" />
+    <PackageReference Include="System.Management" Version="10.0.0" />
+  </ItemGroup>
+
+</Project>

agent/Meezi.PrintAgent/Pairing.cs

@@ -0,0 +1,43 @@
+using System.Net.Http.Json;
+
+namespace Meezi.PrintAgent;
+
+/// <summary>Redeems a one-time pairing code for a long-lived agent token.</summary>
+public static class Pairing
+{
+    private record ClaimReq(string code, string? name, string? machineName);
+    private record ApiEnvelope<T>(bool success, T? data);
+    private record ClaimData(string agentId, string token, string cafeId, string agentName);
+
+    public static async Task<AgentConfig?> ClaimAsync(string apiBaseUrl, string code, string name)
+    {
+        using var http = new HttpClient { BaseAddress = new Uri(apiBaseUrl), Timeout = TimeSpan.FromSeconds(20) };
+        HttpResponseMessage resp;
+        try
+        {
+            resp = await http.PostAsJsonAsync("/api/print-agent/claim",
+                new ClaimReq(code, name, Environment.MachineName));
+        }
+        catch (Exception ex)
+        {
+            Console.WriteLine($"  network error: {ex.Message}");
+            return null;
+        }
+
+        if (!resp.IsSuccessStatusCode)
+            return null;
+
+        var env = await resp.Content.ReadFromJsonAsync<ApiEnvelope<ClaimData>>();
+        if (env?.success != true || env.data is null)
+            return null;
+
+        return new AgentConfig
+        {
+            ApiBaseUrl = apiBaseUrl.TrimEnd('/'),
+            Token = env.data.token,
+            CafeId = env.data.cafeId,
+            AgentId = env.data.agentId,
+            Name = env.data.agentName,
+        };
+    }
+}

agent/Meezi.PrintAgent/PrinterDiscovery.cs

@@ -0,0 +1,45 @@
+using System.Management;
+using System.Runtime.Versioning;
+
+namespace Meezi.PrintAgent;
+
+/// <summary>One printer the agent can reach. SystemName is what it prints to (the
+/// Windows printer name, or "ip:port" for a raw network device).</summary>
+public record DiscoveredPrinter(string SystemName, string DisplayName, string Kind);
+
+[SupportedOSPlatform("windows")]
+public static class PrinterDiscovery
+{
+    /// <summary>Every printer installed on this PC (USB and network-with-driver alike).</summary>
+    public static List<DiscoveredPrinter> Discover()
+    {
+        var list = new List<DiscoveredPrinter>();
+        try
+        {
+            using var searcher = new ManagementObjectSearcher(
+                "SELECT Name, PortName, Network FROM Win32_Printer");
+            foreach (var o in searcher.Get())
+            {
+                using var p = (ManagementObject)o;
+                var name = p["Name"]?.ToString();
+                if (string.IsNullOrWhiteSpace(name)) continue;
+                var port = p["PortName"]?.ToString() ?? "";
+                var network = p["Network"] as bool? ?? false;
+                list.Add(new DiscoveredPrinter(name!, name!, ClassifyKind(port, network)));
+            }
+        }
+        catch
+        {
+            // WMI unavailable — report nothing rather than crash.
+        }
+        return list;
+    }
+
+    private static string ClassifyKind(string port, bool network)
+    {
+        var up = port.ToUpperInvariant();
+        if (up.StartsWith("USB") || up.StartsWith("DOT4")) return "usb";
+        if (network || up.StartsWith("IP_") || up.StartsWith("WSD") || up.Contains(':')) return "network";
+        return "other";
+    }
+}

agent/Meezi.PrintAgent/Program.cs

@@ -0,0 +1,143 @@
+using Meezi.PrintAgent;
+using Microsoft.AspNetCore.SignalR.Client;
+
+Console.OutputEncoding = System.Text.Encoding.UTF8;
+Console.WriteLine("=== Meezi Print Agent (پرینت‌سرور میزی) ===");
+
+var config = AgentConfig.Load();
+var wantsPair = args.Length > 0 && args[0].Equals("pair", StringComparison.OrdinalIgnoreCase);
+
+if (!config.IsPaired || wantsPair)
+{
+    var paired = await PairInteractiveAsync(config);
+    if (paired is null)
+    {
+        Console.WriteLine("Pairing cancelled or failed.");
+        return 1;
+    }
+    paired.Save();
+    config = paired;
+    Console.WriteLine($"✓ Paired as '{config.Name}'. Configuration saved.");
+}
+
+await RunAsync(config);
+return 0;
+
+static async Task<AgentConfig?> PairInteractiveAsync(AgentConfig existing)
+{
+    var defaultUrl = existing.ApiBaseUrl ?? "https://app.meezi.ir";
+    Console.Write($"Meezi API URL [{defaultUrl}]: ");
+    var url = Console.ReadLine();
+    if (string.IsNullOrWhiteSpace(url)) url = defaultUrl;
+
+    Console.Write("Pairing code (from Dashboard → Settings → Printers): ");
+    var code = Console.ReadLine()?.Trim();
+    if (string.IsNullOrWhiteSpace(code)) return null;
+
+    Console.Write($"Name for this PC [{Environment.MachineName}]: ");
+    var name = Console.ReadLine();
+    if (string.IsNullOrWhiteSpace(name)) name = Environment.MachineName;
+
+    Console.WriteLine("Pairing…");
+    var cfg = await Pairing.ClaimAsync(url!, code!, name!);
+    if (cfg is null) Console.WriteLine("  Invalid/expired code, or the URL is wrong.");
+    return cfg;
+}
+
+static async Task RunAsync(AgentConfig config)
+{
+    var hubUrl = $"{config.ApiBaseUrl!.TrimEnd('/')}/hubs/print-agent" +
+                 $"?access_token={Uri.EscapeDataString(config.Token!)}";
+
+    var connection = new HubConnectionBuilder()
+        .WithUrl(hubUrl)
+        .WithAutomaticReconnect(new ForeverRetry())
+        .Build();
+
+    connection.On<string, string, string>("PrintJob", async (jobId, printerSystemName, base64) =>
+    {
+        var ok = false;
+        string? err = null;
+        try
+        {
+            var data = Convert.FromBase64String(base64);
+            await RawPrinter.PrintAsync(printerSystemName, data, CancellationToken.None);
+            ok = true;
+            Console.WriteLine($"[print] {data.Length} bytes → {printerSystemName}  ✓");
+        }
+        catch (Exception ex)
+        {
+            err = ex.Message;
+            Console.WriteLine($"[print] {printerSystemName}  ✗ {ex.Message}");
+        }
+        try { await connection.InvokeAsync("JobResult", jobId, ok, err); } catch { /* ack best-effort */ }
+    });
+
+    connection.Reconnected += async _ =>
+    {
+        Console.WriteLine("[hub] reconnected");
+        await SafeReportAsync(connection);
+    };
+    connection.Closed += _ =>
+    {
+        Console.WriteLine("[hub] connection closed");
+        return Task.CompletedTask;
+    };
+
+    await ConnectWithRetryAsync(connection);
+    Console.WriteLine("[hub] connected");
+    await SafeReportAsync(connection);
+
+    // Heartbeat + re-report every 2 minutes (printers added/removed get picked up).
+    _ = Task.Run(async () =>
+    {
+        using var timer = new PeriodicTimer(TimeSpan.FromMinutes(2));
+        while (await timer.WaitForNextTickAsync())
+        {
+            try
+            {
+                await connection.InvokeAsync("Heartbeat");
+                await SafeReportAsync(connection);
+            }
+            catch { /* will recover on reconnect */ }
+        }
+    });
+
+    Console.WriteLine("Agent running. Leave this window open. Press Ctrl+C to quit.");
+    await Task.Delay(Timeout.Infinite);
+}
+
+static async Task SafeReportAsync(HubConnection connection)
+{
+    try
+    {
+        var printers = PrinterDiscovery.Discover();
+        await connection.InvokeAsync("ReportPrinters", printers);
+        Console.WriteLine($"[printers] reported {printers.Count}: " +
+                          string.Join(", ", printers.Select(p => $"{p.DisplayName} ({p.Kind})")));
+    }
+    catch (Exception ex)
+    {
+        Console.WriteLine($"[printers] report failed: {ex.Message}");
+    }
+}
+
+static async Task ConnectWithRetryAsync(HubConnection connection)
+{
+    while (true)
+    {
+        try { await connection.StartAsync(); return; }
+        catch (Exception ex)
+        {
+            Console.WriteLine($"[hub] connect failed: {ex.Message}; retrying in 5s");
+            await Task.Delay(5000);
+        }
+    }
+}
+
+/// <summary>Retry reconnecting forever with capped exponential backoff.</summary>
+sealed class ForeverRetry : IRetryPolicy
+{
+    public TimeSpan? NextRetryDelay(RetryContext ctx) =>
+        TimeSpan.FromSeconds(Math.Min(30, Math.Pow(2, Math.Min(ctx.PreviousRetryCount, 5))));
+}

agent/Meezi.PrintAgent/RawPrinter.cs

@@ -0,0 +1,95 @@
+using System.Net.Sockets;
+using System.Runtime.InteropServices;
+using System.Runtime.Versioning;
+
+namespace Meezi.PrintAgent;
+
+/// <summary>Writes raw ESC/POS bytes to a printer — by Windows name (winspool RAW
+/// passthrough) or to an "ip:port" endpoint (raw TCP).</summary>
+[SupportedOSPlatform("windows")]
+public static class RawPrinter
+{
+    public static async Task PrintAsync(string systemName, byte[] data, CancellationToken ct)
+    {
+        if (TryParseEndpoint(systemName, out var ip, out var port))
+        {
+            await PrintTcpAsync(ip, port, data, ct);
+            return;
+        }
+        if (!SendBytesToPrinter(systemName, data))
+            throw new Exception($"winspool write failed (last error {Marshal.GetLastWin32Error()})");
+    }
+
+    private static bool TryParseEndpoint(string s, out string ip, out int port)
+    {
+        ip = "";
+        port = 9100;
+        var idx = s.LastIndexOf(':');
+        if (idx <= 0) return false;
+        var host = s[..idx];
+        if (!host.Contains('.')) return false; // not an IPv4-ish host → treat as printer name
+        if (int.TryParse(s[(idx + 1)..], out var p)) port = p;
+        ip = host;
+        return true;
+    }
+
+    private static async Task PrintTcpAsync(string ip, int port, byte[] data, CancellationToken ct)
+    {
+        using var client = new TcpClient();
+        using var cts = CancellationTokenSource.CreateLinkedTokenSource(ct);
+        cts.CancelAfter(TimeSpan.FromSeconds(8));
+        await client.ConnectAsync(ip, port, cts.Token);
+        await using var stream = client.GetStream();
+        await stream.WriteAsync(data, cts.Token);
+        await stream.FlushAsync(cts.Token);
+    }
+
+    // ── winspool raw printing ────────────────────────────────────────────────
+    [StructLayout(LayoutKind.Sequential, CharSet = CharSet.Unicode)]
+    private struct DOCINFOW
+    {
+        [MarshalAs(UnmanagedType.LPWStr)] public string pDocName;
+        [MarshalAs(UnmanagedType.LPWStr)] public string? pOutputFile;
+        [MarshalAs(UnmanagedType.LPWStr)] public string pDataType;
+    }
+
+    [DllImport("winspool.drv", CharSet = CharSet.Unicode, SetLastError = true)]
+    private static extern bool OpenPrinter(string src, out IntPtr hPrinter, IntPtr pd);
+    [DllImport("winspool.drv", SetLastError = true)]
+    private static extern bool ClosePrinter(IntPtr hPrinter);
+    [DllImport("winspool.drv", CharSet = CharSet.Unicode, SetLastError = true)]
+    private static extern bool StartDocPrinter(IntPtr hPrinter, int level, ref DOCINFOW di);
+    [DllImport("winspool.drv", SetLastError = true)]
+    private static extern bool EndDocPrinter(IntPtr hPrinter);
+    [DllImport("winspool.drv", SetLastError = true)]
+    private static extern bool StartPagePrinter(IntPtr hPrinter);
+    [DllImport("winspool.drv", SetLastError = true)]
+    private static extern bool EndPagePrinter(IntPtr hPrinter);
+    [DllImport("winspool.drv", SetLastError = true)]
+    private static extern bool WritePrinter(IntPtr hPrinter, IntPtr pBytes, int dwCount, out int dwWritten);
+
+    private static bool SendBytesToPrinter(string printerName, byte[] bytes)
+    {
+        if (!OpenPrinter(printerName, out var hPrinter, IntPtr.Zero)) return false;
+        try
+        {
+            var di = new DOCINFOW { pDocName = "Meezi Receipt", pDataType = "RAW" };
+            if (!StartDocPrinter(hPrinter, 1, ref di)) return false;
+            try
+            {
+                if (!StartPagePrinter(hPrinter)) return false;
+                var ptr = Marshal.AllocHGlobal(bytes.Length);
+                try
+                {
+                    Marshal.Copy(bytes, 0, ptr, bytes.Length);
+                    if (!WritePrinter(hPrinter, ptr, bytes.Length, out _)) return false;
+                }
+                finally { Marshal.FreeHGlobal(ptr); }
+                EndPagePrinter(hPrinter);
+            }
+            finally { EndDocPrinter(hPrinter); }
+        }
+        finally { ClosePrinter(hPrinter); }
+        return true;
+    }
+}