using System;
using System.Configuration;
using System.Diagnostics;
using System.IO;
using System.Reflection;
using FileInterface.Scheduler;
using com.itac.mes.imsapi.client.dotnet;
using com.itac.mes.imsapi.domain.container;

namespace FileinterfaceCronScheduler.IMSApi
{
    /// <summary>
    /// Initializes IMSApiDotNet, logs in once and exposes customFunction to the scheduler.
    /// Configuration is read from App.config.
    /// </summary>
    public sealed class ImsApiClient : ICustomFunctionInvoker, IDisposable
    {
        private readonly object _sync = new object();
        private readonly object _callSync = new object();
        private IIMSApiDotNet _imsapi;
        private IMSApiSessionContextStruct _sessionContext;
        private bool _initialized;
        private bool _disposed;
        private readonly bool _serializeCalls = String.Equals(ConfigurationManager.AppSettings["IMS.SerializeCalls"], "true", StringComparison.OrdinalIgnoreCase);

        public bool IsInitialized { get { lock (_sync) return _initialized; } }
        public bool IsLoggedIn { get { lock (_sync) return _sessionContext != null; } }
        public long SessionId { get { lock (_sync) return _sessionContext == null ? 0L : _sessionContext.sessionId; } }

        public void Connect()
        {
            lock (_sync)
            {
                ThrowIfDisposed();
                EnsureInitializedNoLock();
                EnsureLoggedInNoLock();
            }
        }

        private void EnsureInitializedNoLock()
        {
            if (_initialized && _imsapi != null)
                return;

            string appId = Required("IMS.AppID", "AppID");
            string serverUrl = Required("IMS.ServerUrl", "Server_URL");
            string baseDir = AppDomain.CurrentDomain.BaseDirectory;
            string propDir = Get("IMS.PropertyDirectory", baseDir);
            if (!Path.IsPathRooted(propDir))
                propDir = Path.Combine(baseDir, propDir);

            Directory.CreateDirectory(propDir);
            string ihas = Path.Combine(propDir, "ihas.properties");
            if (!File.Exists(ihas))
                File.WriteAllText(ihas, String.Empty);

            Trace.TraceInformation("Initializing IMSApiDotNet. AppID={0}, Server={1}, PropDir={2}", appId, serverUrl, propDir);

            IMSApiDotNet.setProperty("itac.appid", appId);
            IMSApiDotNet.setProperty("itac.artes.clusternodes", serverUrl);
            IMSApiDotNet.setProperty("itac.propdir", propDir);

            _imsapi = IMSApiDotNet.loadLibrary();
            if (_imsapi == null)
                throw new InvalidOperationException("IMSApiDotNet.loadLibrary() returned null.");

            string version;
            int versionResult = _imsapi.imsapiGetLibraryVersion(out version);
            if (versionResult == IMSApiDotNetConstants.RES_OK)
                Trace.TraceInformation("IMSApiDotNet library version: " + version);
            else
                Trace.TraceWarning("imsapiGetLibraryVersion returned " + versionResult);

            int initResult = _imsapi.imsapiInit();
            if (initResult != IMSApiDotNetConstants.RES_OK)
                throw new InvalidOperationException("imsapiInit failed. Result=" + initResult);

            _initialized = true;
            Trace.TraceInformation("IMSApiDotNet initialized successfully.");
        }

        private void EnsureLoggedInNoLock()
        {
            if (_sessionContext != null)
                return;

            string station = Required("IMS.StationNumber", "StationNr");
            // Original FileInterface contains the historic typo 'CleintNO'. Both names are supported.
            string client = FirstNonEmpty(
                ConfigurationManager.AppSettings["IMS.ClientNumber"],
                ConfigurationManager.AppSettings["ClientNO"],
                ConfigurationManager.AppSettings["CleintNO"]);
            if (String.IsNullOrWhiteSpace(client))
                throw new ConfigurationErrorsException("Missing IMS client number. Configure IMS.ClientNumber (or legacy CleintNO).");

            string registrationType = Get("IMS.RegistrationType", "S");
            var validation = new IMSApiSessionValidationStruct
            {
                stationNumber = station,
                client = client,
                registrationType = registrationType
            };

            Trace.TraceInformation("Calling regLogin(). Station={0}, Client={1}, RegistrationType={2}", station, client, registrationType);

            IMSApiSessionContextStruct newSessionContext;
            int loginResult = _imsapi.regLogin(validation, out newSessionContext);
            if (loginResult != IMSApiDotNetConstants.RES_OK || newSessionContext == null)
                throw new InvalidOperationException("IMS regLogin failed. Result=" + loginResult);

            _sessionContext = newSessionContext;
            Trace.TraceInformation("IMS login successful. SessionId=" + _sessionContext.sessionId);
        }

        public CustomFunctionCallResult Invoke(string customFunctionName, string[] inArgs)
        {
            if (String.IsNullOrWhiteSpace(customFunctionName))
                return CustomFunctionCallResult.Fail("CustomFunction is empty.");

            try
            {
                IIMSApiDotNet api;
                IMSApiSessionContextStruct session;

                // Only connection/login state is protected. The actual CustomFunction call
                // can run concurrently for independent cron jobs.
                lock (_sync)
                {
                    ThrowIfDisposed();
                    EnsureInitializedNoLock();
                    EnsureLoggedInNoLock();
                    api = _imsapi;
                    session = _sessionContext;
                }

                if (_serializeCalls)
                {
                    lock (_callSync)
                        return InvokeCore(api, session, customFunctionName, inArgs);
                }

                return InvokeCore(api, session, customFunctionName, inArgs);
            }
            catch (Exception ex)
            {
                Trace.TraceError("IMS customFunction failed: " + ex);
                return CustomFunctionCallResult.Fail(ex.ToString());
            }
        }

        private static CustomFunctionCallResult InvokeCore(
            IIMSApiDotNet api,
            IMSApiSessionContextStruct session,
            string customFunctionName,
            string[] inArgs)
        {
            string[] outArgs;
            string customErrorString;
            int result = api.customFunction(
                session,
                customFunctionName,
                inArgs ?? new string[0],
                out outArgs,
                out customErrorString);

            string outText = outArgs == null || outArgs.Length == 0
                ? String.Empty
                : String.Join(" | ", outArgs);

            if (result != IMSApiDotNetConstants.RES_OK)
            {
                return CustomFunctionCallResult.Fail(
                    "IMS result=" + result +
                    (String.IsNullOrWhiteSpace(customErrorString) ? String.Empty : "; Error=" + customErrorString) +
                    (String.IsNullOrWhiteSpace(outText) ? String.Empty : "; OutArgs=" + outText));
            }

            return CustomFunctionCallResult.Ok(
                "IMS result=0" +
                (String.IsNullOrWhiteSpace(customErrorString) ? String.Empty : "; Info=" + customErrorString) +
                (String.IsNullOrWhiteSpace(outText) ? String.Empty : "; OutArgs=" + outText));
        }

        public void Dispose()
        {
            lock (_sync)
            {
                if (_disposed) return;
                _disposed = true;

                // The FileInterface source currently has no regLogout/imsapiFinish call.
                // We therefore release managed references here. If the deployed IMSAPI
                // version exposes an explicit logout method, it can safely be added here.
                _sessionContext = null;
                _imsapi = null;
                _initialized = false;
            }
        }

        private static string Get(string key, string fallback)
        {
            string value = ConfigurationManager.AppSettings[key];
            return String.IsNullOrWhiteSpace(value) ? fallback : value.Trim();
        }

        private static string Required(string preferredKey, string legacyKey)
        {
            string value = FirstNonEmpty(
                ConfigurationManager.AppSettings[preferredKey],
                ConfigurationManager.AppSettings[legacyKey]);
            if (String.IsNullOrWhiteSpace(value))
                throw new ConfigurationErrorsException("Missing setting '" + preferredKey + "' (legacy: '" + legacyKey + "').");
            return value.Trim();
        }

        private static string FirstNonEmpty(params string[] values)
        {
            if (values == null) return null;
            foreach (string value in values)
                if (!String.IsNullOrWhiteSpace(value)) return value.Trim();
            return null;
        }

        private void ThrowIfDisposed()
        {
            if (_disposed) throw new ObjectDisposedException(GetType().FullName);
        }
    }
}