using System.Net.WebSockets;
using System.Text;
using System.Text.Json;
using System.Text.Json.Nodes;
using Microsoft.Extensions.Configuration;
using YY.Admin.Core.Services;

namespace YY.Admin.Services.Service.Print;

/// <summary>
/// PrintDot 本地桥接器 WebSocket 客户端。
/// URL 从 appsettings.json 的 PrintDot:Url 读取，可在运行时通过 <see cref="PrintDotSettings"/> 覆盖。
/// </summary>
public class PrintDotService : IPrintDotService
{
    private readonly IConfiguration _config;
    private static readonly JsonSerializerOptions JsonOpts = new() { PropertyNamingPolicy = JsonNamingPolicy.CamelCase };

    public PrintDotService(IConfiguration config)
    {
        _config = config;
    }

    private string ResolveWsUrl()
    {
        var url = PrintDotSettings.Current?.WsUrl
                  ?? _config.GetValue<string>("PrintDot:Url")
                  ?? "ws://127.0.0.1:1122/ws";
        return url.TrimEnd('/');
    }

    public async Task<IReadOnlyList<PrintDotPrinter>> GetPrintersAsync(CancellationToken ct = default)
    {
        var wsUrl = ResolveWsUrl();
        using var ws = new ClientWebSocket();
        await ws.ConnectAsync(new Uri(wsUrl), ct);

        // 连接后服务端立即推送 printer_list
        var json = await ReceiveTextAsync(ws, ct);
        var doc = JsonNode.Parse(json);
        if (doc?["type"]?.GetValue<string>() == "printer_list")
        {
            var arr = doc["data"]?.AsArray();
            if (arr != null)
            {
                return arr
                    .Where(n => n != null)
                    .Select(n => new PrintDotPrinter(
                        Name: n!["name"]?.GetValue<string>()?.Trim() ?? string.Empty,
                        IsDefault: n["isDefault"]?.GetValue<bool>() ?? false))
                    .Where(p => !string.IsNullOrWhiteSpace(p.Name))
                    .ToList();
            }
        }
        return [];
    }

    public async Task PrintAsync(string printerName, string pdfBase64, string jobName = "QH-MES", int copies = 1, CancellationToken ct = default)
    {
        // 去掉 data: 前缀
        var content = pdfBase64.Trim();
        var comma = content.IndexOf(',');
        if (content.StartsWith("data:", StringComparison.OrdinalIgnoreCase) && comma >= 0)
            content = content[(comma + 1)..];

        var payload = new
        {
            printer = printerName,
            content,
            job = new { name = jobName, copies = Math.Max(1, copies) }
        };

        var wsUrl = ResolveWsUrl();
        using var ws = new ClientWebSocket();
        await ws.ConnectAsync(new Uri(wsUrl), ct);

        // 先等服务端推送 printer_list 再发任务
        await ReceiveTextAsync(ws, ct);

        var msg = JsonSerializer.Serialize(payload, JsonOpts);
        await ws.SendAsync(Encoding.UTF8.GetBytes(msg), WebSocketMessageType.Text, true, ct);

        // 等待打印结果（最多 3 分钟）
        using var cts = CancellationTokenSource.CreateLinkedTokenSource(ct);
        cts.CancelAfter(TimeSpan.FromMinutes(3));
        while (ws.State == WebSocketState.Open)
        {
            var response = await ReceiveTextAsync(ws, cts.Token);
            var resDoc = JsonNode.Parse(response);
            var status = resDoc?["status"]?.GetValue<string>();
            if (status == null) continue;
            if (status == "success") return;
            var rawMsg = resDoc?["message"]?.GetValue<string>() ?? "PrintDot 打印失败";
            throw new InvalidOperationException(EnhanceErrorMessage(rawMsg));
        }
    }

    /// <summary>
    /// 将 PrintDot 返回的部分英文错误转换为带本地处理步骤的中文提示。
    /// 与 web 端 printDotBridge.ts::enhancePrintDotErrorMessage 行为一致，方便桌面端用户自助排查。
    /// </summary>
    private static string EnhanceErrorMessage(string raw)
    {
        var m = (raw ?? string.Empty).Trim();
        // 缺 SumatraPDF：是 PrintDot 客户端最常见的初始化错误
        if (System.Text.RegularExpressions.Regex.IsMatch(m, @"SumatraPDF\.exe not found", System.Text.RegularExpressions.RegexOptions.IgnoreCase)
            || System.Text.RegularExpressions.Regex.IsMatch(m, "SUMATRAPDF_PATH", System.Text.RegularExpressions.RegexOptions.IgnoreCase))
        {
            return m + "。\n本地处理：PrintDot 依赖 SumatraPDF 静默打印 PDF。请安装 SumatraPDF 后任选其一：\n" +
                   "① 将 SumatraPDF.exe 放在 PrintDot 客户端 exe 同目录；\n" +
                   "② 或将 SumatraPDF 安装目录加入系统 PATH；\n" +
                   "③ 或设置用户/系统环境变量 SUMATRAPDF_PATH 指向 SumatraPDF.exe 的完整路径；\n" +
                   "然后重启 PrintDot 桥接器即可。";
        }
        return m;
    }

    private static async Task<string> ReceiveTextAsync(ClientWebSocket ws, CancellationToken ct)
    {
        var buffer = new ArraySegment<byte>(new byte[64 * 1024]);
        using var ms = new System.IO.MemoryStream();
        WebSocketReceiveResult result;
        do
        {
            result = await ws.ReceiveAsync(buffer, ct);
            ms.Write(buffer.Array!, buffer.Offset, result.Count);
        } while (!result.EndOfMessage);
        return Encoding.UTF8.GetString(ms.ToArray());
    }
}