using System;
using System.IO;
using System.Text;
using NLog;
using NLog.Config;
using NLog.Targets;

namespace TeamAAS.Logging
{
    /// <summary>
    /// NLog 统一接入点：全应用只此一份 NLog 配置，挂两个文件目标——
    ///   公共日志（Common）：路径由 CommonPattern 解析（年/日期滚动），AppLogger 与插件 1/2 级日志共用；
    ///   任务日志（Task）：路径由 TaskPattern 解析，流程名/任务名由每条日志的事件属性带入。
    /// 单文件大小归档（ArchiveAboveSize）与保留天数自动删除（MaxArchiveDays）均由 NLog 原生完成。
    /// 行格式由调用侧拼好后以 ${message} 原样写入。
    /// </summary>
    internal static class NLogHub
    {
        /// <summary>公共日志器名（AppLogger + 插件 1/2 级共用）。</summary>
        public const string CommonLoggerName = "TeamAAS.Common";

        /// <summary>任务日志器名（插件 3/4 级用）。</summary>
        public const string TaskLoggerName = "TeamAAS.Task";

        /// <summary>流程名事件属性名（TaskPattern 中的 {flow}）。</summary>
        public const string FlowPropertyName = "flow";

        /// <summary>任务名事件属性名（TaskPattern 中的 {task}）。</summary>
        public const string TaskPropertyName = "task";

        private static readonly object Gate = new object();
        private static PluginLogConfig _config;
        private static string _appliedSignature;

        /// <summary>下发日志配置（启动加载/保存系统配置时调用），配置变化时重建 NLog 目标。</summary>
        public static void Configure(PluginLogConfig config)
        {
            lock (Gate)
            {
                _config = config ?? new PluginLogConfig();
                _appliedSignature = null;   // 强制下次 Apply 重建
            }
            Apply();
        }

        /// <summary>确保 NLog 配置已就绪（未下发时用默认配置）；配置未变则幂等返回。</summary>
        public static void Apply()
        {
            lock (Gate)
            {
                var cfg = _config ?? (_config = new PluginLogConfig());
                var signature = BuildSignature(cfg);
                if (signature == _appliedSignature && LogManager.Configuration != null)
                    return;

                var rootDir = ResolveRoot(cfg.RootPath);
                var commonFileName = Path.Combine(rootDir, ToLayout(cfg.CommonPattern, @"{year}\{time}.log"));
                var taskFileName = Path.Combine(rootDir, ToLayout(cfg.TaskPattern, @"{flow}\{task}\{year}\{time}.log"));

                long maxBytes = cfg.MaxFileMB > 0 ? (long)cfg.MaxFileMB * 1024 * 1024 : 0;
                int maxDays = cfg.RetentionDays > 0 ? cfg.RetentionDays : 0;

                var nlogCfg = new LoggingConfiguration();
                var commonTarget = MakeTarget("common", commonFileName, maxBytes, maxDays);
                var taskTarget = MakeTarget("task", taskFileName, maxBytes, maxDays);
                nlogCfg.AddRule(NLog.LogLevel.Trace, NLog.LogLevel.Fatal, commonTarget, CommonLoggerName);
                nlogCfg.AddRule(NLog.LogLevel.Trace, NLog.LogLevel.Fatal, taskTarget, TaskLoggerName);

                LogManager.Configuration = nlogCfg;
                _appliedSignature = signature;
            }
        }

        /// <summary>构造一个文件目标：日期滚动 + 超大小归档 + 超保留天数自动删除。</summary>
        private static FileTarget MakeTarget(string name, string fileName, long maxBytes, int maxDays)
            => new FileTarget(name)
            {
                FileName = fileName,
                Layout = "${message}",
                Encoding = Encoding.UTF8,
                KeepFileOpen = false,
                ConcurrentWrites = true,
                ArchiveAboveSize = maxBytes,                       // 0=不按大小归档
                ArchiveNumbering = ArchiveNumberingMode.Rolling,
                MaxArchiveFiles = 0,                               // 不按份数限制
                MaxArchiveDays = maxDays                           // 0=不按天数删除
            };

        /// <summary>公共日志器（AppLogger + 插件 1/2 级）。</summary>
        public static Logger Common => LogManager.GetLogger(CommonLoggerName);

        /// <summary>任务日志器（插件 3/4 级）。</summary>
        public static Logger Task => LogManager.GetLogger(TaskLoggerName);

        /// <summary>解析日志根目录：绝对路径直接用，相对路径拼到程序目录下。</summary>
        private static string ResolveRoot(string root)
            => Path.IsPathRooted(root ?? "")
                ? root
                : Path.Combine(TeamAAS.PathHelper.Root, string.IsNullOrWhiteSpace(root) ? "Logs" : root);

        /// <summary>把路径公式里的占位符转为 NLog 布局渲染器（日期/事件属性），交由 NLog 自行滚动与归档。</summary>
        private static string ToLayout(string pattern, string fallback)
        {
            if (string.IsNullOrWhiteSpace(pattern)) pattern = fallback;
            return pattern
                .Replace("{year}", "${date:format=yyyy}")
                .Replace("{month}", "${date:format=MM}")
                .Replace("{day}", "${date:format=dd}")
                .Replace("{time}", "${date:format=yyyy-MM-dd}")
                .Replace("{timestamp}", "${date:format=yyyyMMdd_HHmmss}")
                .Replace("{flow}", "${event-properties:item=" + FlowPropertyName + ":whenEmpty=_}")
                .Replace("{task}", "${event-properties:item=" + TaskPropertyName + ":whenEmpty=_}");
        }

        /// <summary>配置指纹：任一关键字段变化则重建 NLog 配置。</summary>
        private static string BuildSignature(PluginLogConfig c)
            => string.Join("|", c.RootPath, c.CommonPattern, c.TaskPattern, c.MaxFileMB, c.RetentionDays);
    }
}