using System;
using System.Globalization;
using System.IO;
using System.Text;
using System.Text.RegularExpressions;
using Lskj.CommandKernel;
using Newtonsoft.Json;

namespace Lskj.AgentBridge
{
    public sealed class JsonLineCommandAuditSink :
        ICommandAuditSink,
        IBridgeOperationalAuditSink,
        IDisposable
    {
        public const long DefaultMaximumFileBytes = 64L * 1024L * 1024L;
        public const long DefaultMaximumDirectoryBytes = 512L * 1024L * 1024L;
        public const int DefaultMaximumInstanceFiles = 256;
        public const int MaximumRecordBytes = 64 * 1024;
        private static readonly Regex SafeEventName = new Regex(
            "^[a-z][a-z0-9_]{0,63}$",
            RegexOptions.Compiled | RegexOptions.CultureInvariant);
        private static readonly Regex SafeProtocolName = new Regex(
            "^[A-Za-z0-9_.:-]{1,128}$",
            RegexOptions.Compiled | RegexOptions.CultureInvariant);
        private static readonly Regex SafeOutcomeCode = new Regex(
            "^[a-z0-9_.-]{1,128}$",
            RegexOptions.Compiled | RegexOptions.CultureInvariant);
        private readonly object _syncRoot = new object();
        private readonly string _path;
        private readonly long _maximumFileBytes;
        private FileStream _stream;

        public JsonLineCommandAuditSink(string path)
            : this(path, DefaultMaximumFileBytes, false)
        {
        }

        public JsonLineCommandAuditSink(string path, long maximumFileBytes)
            : this(path, maximumFileBytes, false)
        {
        }

        private JsonLineCommandAuditSink(
            string path,
            long maximumFileBytes,
            bool createNew)
        {
            if (string.IsNullOrWhiteSpace(path))
                throw new ArgumentException("审计日志路径不能为空。", "path");
            if (maximumFileBytes < 4096L || maximumFileBytes > 1024L * 1024L * 1024L)
                throw new ArgumentOutOfRangeException(
                    "maximumFileBytes",
                    "单个审计日志容量必须在 4 KB 到 1 GB 之间。");
            _path = Path.GetFullPath(path);
            _maximumFileBytes = maximumFileBytes;
            string directory = Path.GetDirectoryName(_path);
            if (!string.IsNullOrWhiteSpace(directory)) Directory.CreateDirectory(directory);
            try
            {
                _stream = Open(createNew ? FileMode.CreateNew : FileMode.OpenOrCreate);
                EnsureWritableState(_stream);
                _stream.Flush();
            }
            catch (IOException)
            {
                if (_stream != null) _stream.Dispose();
                _stream = null;
                if (createNew && File.Exists(_path))
                    throw Error(
                        "audit_log_instance_exists",
                        "当前 ERP 启动实例的审计文件已经存在，禁止复用或覆盖。");
                throw;
            }
            catch
            {
                if (_stream != null) _stream.Dispose();
                _stream = null;
                throw;
            }
        }

        public static JsonLineCommandAuditSink CreateProcessBound(
            string directory,
            int processId,
            DateTime processStartedAtUtc)
        {
            return CreateProcessBound(
                directory,
                processId,
                processStartedAtUtc,
                DefaultMaximumFileBytes,
                DefaultMaximumDirectoryBytes,
                DefaultMaximumInstanceFiles);
        }

        public static JsonLineCommandAuditSink CreateProcessBound(
            string directory,
            int processId,
            DateTime processStartedAtUtc,
            long maximumFileBytes,
            long maximumDirectoryBytes,
            int maximumInstanceFiles)
        {
            if (maximumDirectoryBytes < maximumFileBytes
                || maximumDirectoryBytes > 8L * 1024L * 1024L * 1024L)
                throw new ArgumentOutOfRangeException(
                    "maximumDirectoryBytes",
                    "审计目录容量必须覆盖一个日志文件且不能超过 8 GB。");
            if (maximumInstanceFiles < 1 || maximumInstanceFiles > 4096)
                throw new ArgumentOutOfRangeException(
                    "maximumInstanceFiles",
                    "审计实例文件数量上限必须在 1-4096 之间。");
            string path = BuildProcessBoundPath(directory, processId, processStartedAtUtc);
            string fullDirectory = Path.GetDirectoryName(path);
            Directory.CreateDirectory(fullDirectory);
            string[] existing = Directory.GetFiles(
                fullDirectory,
                "audit-p*-s*.jsonl",
                SearchOption.TopDirectoryOnly);
            long existingBytes = 0L;
            foreach (string item in existing)
            {
                long length = new FileInfo(item).Length;
                if (length > maximumDirectoryBytes - existingBytes)
                    throw Error(
                        "audit_archive_required",
                        "AgentBridge 审计目录已达到留存上限，请先按客户策略归档后再启用桥。");
                existingBytes += length;
            }
            if (existing.Length >= maximumInstanceFiles
                || existingBytes > maximumDirectoryBytes - maximumFileBytes)
            {
                throw Error(
                    "audit_archive_required",
                    "AgentBridge 审计目录已达到留存上限，请先按客户策略归档后再启用桥。");
            }
            return new JsonLineCommandAuditSink(path, maximumFileBytes, true);
        }

        public static string BuildProcessBoundPath(
            string directory,
            int processId,
            DateTime processStartedAtUtc)
        {
            if (string.IsNullOrWhiteSpace(directory))
                throw new ArgumentException("审计日志目录不能为空。", "directory");
            if (processId < 1)
                throw new ArgumentOutOfRangeException("processId", "ERP 进程 ID 必须为正数。");
            DateTime started = processStartedAtUtc.Kind == DateTimeKind.Utc
                ? processStartedAtUtc
                : processStartedAtUtc.ToUniversalTime();
            if (started == DateTime.MinValue || started == DateTime.MaxValue)
                throw new ArgumentOutOfRangeException(
                    "processStartedAtUtc",
                    "ERP 进程启动时间无效。");
            string fileName = string.Format(
                CultureInfo.InvariantCulture,
                "audit-p{0}-s{1}.jsonl",
                processId,
                started.Ticks);
            return Path.Combine(Path.GetFullPath(directory), fileName);
        }

        public void Planned(CommandDescriptor descriptor, CommandPlan plan, CommandExecutionContext context)
        {
            Write("planned", descriptor, plan, context, null, null);
        }

        public void Completed(
            CommandDescriptor descriptor,
            CommandPlan plan,
            CommandResult result,
            CommandExecutionContext context)
        {
            Write("completed", descriptor, plan, context, result, null);
        }

        public void Failed(
            CommandDescriptor descriptor,
            CommandPlan plan,
            Exception exception,
            CommandExecutionContext context)
        {
            Write("failed", descriptor, plan, context, null, exception);
        }

        public void RecordOperationalEvent(
            string eventName,
            string method,
            string commandName,
            string stage,
            string outcomeCode,
            CommandExecutionContext context)
        {
            if (!SafeEventName.IsMatch(eventName ?? string.Empty)
                || !SafeProtocolName.IsMatch(method ?? string.Empty)
                || (!string.IsNullOrWhiteSpace(commandName)
                    && !SafeProtocolName.IsMatch(commandName))
                || (stage != "request"
                    && stage != "plan"
                    && stage != "execute")
                || !SafeOutcomeCode.IsMatch(outcomeCode ?? string.Empty))
            {
                throw Error(
                    "audit_operational_event_invalid",
                    "AgentBridge 运维审计事件格式无效。");
            }
            Append(new
            {
                occurredAtUtc = DateTime.UtcNow,
                eventName = eventName,
                correlationId = context == null ? null : context.CorrelationId,
                clientSessionId = context == null ? null : context.ClientSessionId,
                userId = context == null ? null : context.UserId,
                accountBook = context == null ? null : context.AccountBook,
                subSystemId = context == null ? null : context.SubSystemId,
                uatAuthorizationIdSha256 = context == null
                    ? null : context.UatAuthorizationIdSha256,
                uatCaseCode = context == null ? null : context.UatCaseCode,
                method = method,
                command = string.IsNullOrWhiteSpace(commandName)
                    ? null : commandName,
                stage = stage,
                outcomeCode = outcomeCode
            });
        }

        private void Write(
            string eventName,
            CommandDescriptor descriptor,
            CommandPlan plan,
            CommandExecutionContext context,
            CommandResult result,
            Exception exception)
        {
            CommandKernelException known = exception as CommandKernelException;
            object record = new
            {
                occurredAtUtc = DateTime.UtcNow,
                eventName = eventName,
                correlationId = context == null ? null : context.CorrelationId,
                clientSessionId = context == null ? null : context.ClientSessionId,
                userId = context == null ? null : context.UserId,
                accountBook = context == null ? null : context.AccountBook,
                subSystemId = context == null ? null : context.SubSystemId,
                uatAuthorizationIdSha256 = context == null
                    ? null : context.UatAuthorizationIdSha256,
                uatCaseCode = context == null ? null : context.UatCaseCode,
                command = descriptor == null ? null : descriptor.Name,
                commandVersion = descriptor == null ? null : descriptor.Version,
                risk = descriptor == null ? null : descriptor.Risk.ToString().ToLowerInvariant(),
                planId = plan == null ? null : plan.PlanId,
                inputFingerprint = plan == null ? null : plan.InputFingerprint,
                moduleCode = plan == null ? null : plan.ModuleCode,
                success = result == null ? (bool?)null : result.Success,
                resultCode = result == null ? null : result.Code,
                recordId = result == null ? null : result.RecordId,
                replayed = result == null ? (bool?)null : result.Replayed,
                transactionEvidenceId = result == null ? null : result.TransactionEvidenceId,
                businessAuditId = result == null ? null : result.BusinessAuditId,
                errorCode = known == null ? null : known.Code,
                exceptionType = exception == null ? null : exception.GetType().FullName
            };

            Append(record);
        }

        private void Append(object record)
        {
            string directory = Path.GetDirectoryName(_path);
            if (!string.IsNullOrWhiteSpace(directory)) Directory.CreateDirectory(directory);
            string line = JsonConvert.SerializeObject(record, Formatting.None) + Environment.NewLine;
            byte[] bytes = new UTF8Encoding(false, true).GetBytes(line);
            if (bytes.Length > MaximumRecordBytes)
                throw Error(
                    "audit_record_too_large",
                    "AgentBridge 审计记录超过安全上限，已拒绝写入。");
            lock (_syncRoot)
            {
                if (_stream == null)
                    throw Error("audit_log_unavailable", "AgentBridge 审计日志已经关闭。");
                EnsureWritableState(_stream);
                if (bytes.LongLength > _maximumFileBytes - _stream.Length)
                    throw Error(
                        "audit_log_capacity_exceeded",
                        "当前 ERP 启动实例的审计日志已满，请归档后重启受控桥会话。");
                _stream.Position = _stream.Length;
                _stream.Write(bytes, 0, bytes.Length);
                _stream.Flush();
            }
        }

        public void Dispose()
        {
            lock (_syncRoot)
            {
                if (_stream == null) return;
                try { _stream.Flush(); }
                finally
                {
                    _stream.Dispose();
                    _stream = null;
                }
            }
        }

        private FileStream Open(FileMode mode)
        {
            return new FileStream(
                _path,
                mode,
                FileAccess.ReadWrite,
                FileShare.Read,
                4096,
                FileOptions.WriteThrough);
        }

        private void EnsureWritableState(FileStream stream)
        {
            if (stream == null) throw new ArgumentNullException("stream");
            if (stream.Length > _maximumFileBytes)
                throw Error(
                    "audit_log_capacity_exceeded",
                    "当前 ERP 启动实例的审计日志已超过安全上限。");
            if (stream.Length == 0) return;
            stream.Position = stream.Length - 1L;
            if (stream.ReadByte() != (byte)'\n')
                throw Error(
                    "audit_log_corrupt",
                    "AgentBridge 审计日志尾部不完整，禁止继续追加。");
        }

        private static CommandKernelException Error(string code, string message)
        {
            return new CommandKernelException(code, message, 6);
        }
    }
}