using System;
using System.Collections.Generic;
using System.ComponentModel.Composition;
using System.Data.SQLite;
using System.Diagnostics;
using System.Diagnostics.Contracts;
using System.IO;
using System.Linq;
using System.Text;
using System.Threading;
using System.Threading.Tasks;
using Castle.ActiveRecord;
using Castle.ActiveRecord.Framework.Config;
using Pithos.Interfaces;
using Pithos.Network;
using log4net;

namespace Pithos.Core.Agents
{
    [Export(typeof(IStatusChecker)),Export(typeof(IStatusKeeper))]
    public class StatusAgent:IStatusChecker,IStatusKeeper
    {
        [System.ComponentModel.Composition.Import]
        public IPithosSettings Settings { get; set; }

        private Agent<Action> _persistenceAgent;


        private static readonly ILog Log = LogManager.GetLogger("StatusAgent");

        public StatusAgent()
        {            
            var appDataPath = Environment.GetFolderPath(Environment.SpecialFolder.LocalApplicationData);
            _pithosDataPath = Path.Combine(appDataPath , "Pithos");

            if (!Directory.Exists(_pithosDataPath))
                Directory.CreateDirectory(_pithosDataPath);
            var source = GetConfiguration(_pithosDataPath);
            ActiveRecordStarter.Initialize(source,typeof(FileState),typeof(FileTag));
            ActiveRecordStarter.UpdateSchema();
            

            if (!File.Exists(Path.Combine(_pithosDataPath ,"pithos.db")))
                ActiveRecordStarter.CreateSchema();

            CreateTrigger();
            
        }

        private void CreateTrigger()
        {
            using (var connection = GetConnection())
            using (var triggerCommand = connection.CreateCommand())
            {
                var cmdText = new StringBuilder()
                    .AppendLine("CREATE TRIGGER IF NOT EXISTS update_last_modified UPDATE ON FileState FOR EACH ROW")
                    .AppendLine("BEGIN")
                    .AppendLine("UPDATE FileState SET Modified=datetime('now')  WHERE Id=old.Id;")
                    .AppendLine("END;")
                    .AppendLine("CREATE TRIGGER IF NOT EXISTS insert_last_modified INSERT ON FileState FOR EACH ROW")
                    .AppendLine("BEGIN")
                    .AppendLine("UPDATE FileState SET Modified=datetime('now')  WHERE Id=new.Id;")
                    .AppendLine("END;")
                    .ToString();
                triggerCommand.CommandText = cmdText;                
                triggerCommand.ExecuteNonQuery();
            }
        }


        private static InPlaceConfigurationSource GetConfiguration(string pithosDbPath)
        {
            if (String.IsNullOrWhiteSpace(pithosDbPath))
                throw new ArgumentNullException("pithosDbPath");
            if (!Path.IsPathRooted(pithosDbPath))
                throw new ArgumentException("path must be a rooted path", "pithosDbPath");
            Contract.EndContractBlock();

            var properties = new Dictionary<string, string>
                                 {
                                     {"connection.driver_class", "NHibernate.Driver.SQLite20Driver"},
                                     {"dialect", "NHibernate.Dialect.SQLiteDialect"},
                                     {"connection.provider", "NHibernate.Connection.DriverConnectionProvider"},
                                     {
                                         "proxyfactory.factory_class",
                                         "NHibernate.ByteCode.Castle.ProxyFactoryFactory, NHibernate.ByteCode.Castle"
                                         },
                                 };

            var connectionString = String.Format(@"Data Source={0}\pithos.db;Version=3;Enlist=N", pithosDbPath);
            properties.Add("connection.connection_string", connectionString);

            var source = new InPlaceConfigurationSource();                        
            source.Add(typeof (ActiveRecordBase), properties);
            source.SetDebugFlag(false);            
            return source;
        }

        public void StartProcessing(CancellationToken token)
        {
            _persistenceAgent = Agent<Action>.Start(queue =>
            {
                Action loop = null;
                loop = () =>
                {
                    var job = queue.Receive();
                    job.ContinueWith(t =>
                    {
                        var action = job.Result;
                        try
                        {
                            action();
                        }
                        catch (SQLiteException ex)
                        {
                            Log.ErrorFormat("[ERROR] SQL \n{0}", ex);
                        }
                        catch (Exception ex)
                        {
                            Log.ErrorFormat("[ERROR] STATE \n{0}", ex);
                        }
// ReSharper disable AccessToModifiedClosure
                        queue.DoAsync(loop);
// ReSharper restore AccessToModifiedClosure
                    });
                };
                loop();
            });
            
        }

       

        public void Stop()
        {
            _persistenceAgent.Stop();            
        }
       

        public void ProcessExistingFiles(IEnumerable<FileInfo> existingFiles)
        {
            if(existingFiles  ==null)
                throw new ArgumentNullException("existingFiles");
            Contract.EndContractBlock();
            
            //Find new or matching files with a left join to the stored states
            var fileStates = FileState.Queryable;
            var currentFiles=from file in existingFiles
                      join state in fileStates on file.FullName.ToLower() equals state.FilePath.ToLower() into gs
                      from substate in gs.DefaultIfEmpty()
                               select new {File = file, State = substate};

            //To get the deleted files we must get the states that have no corresponding
            //files. 
            //We can't use the File.Exists method inside a query, so we get all file paths from the states
            var statePaths = (from state in fileStates
                             select new {state.Id, state.FilePath}).ToList();
            //and check each one
            var missingStates= (from path in statePaths
                                where !File.Exists(path.FilePath) && !Directory.Exists(path.FilePath)
                               select path.Id).ToList();
            //Finally, retrieve the states that correspond to the deleted files            
            var deletedFiles = from state in fileStates 
                        where missingStates.Contains(state.Id)
                        select new { File = default(FileInfo), State = state };

            var pairs = currentFiles.Union(deletedFiles);

            foreach(var pair in pairs)
            {
                var fileState = pair.State;
                var file = pair.File;
                if (fileState == null)
                {
                    //This is a new file
                    var fullPath = pair.File.FullName;
                    var createState = FileState.CreateForAsync(fullPath, BlockSize, BlockHash);
                    createState.ContinueWith(state => _persistenceAgent.Post(state.Result.Create));
                }                
                else if (file == null)
                {
                    //This file was deleted while we were down. We should mark it as deleted
                    //We have to go through UpdateStatus here because the state object we are using
                    //was created by a different ORM session.
                    _persistenceAgent.Post(()=> UpdateStatusDirect(fileState.Id, FileStatus.Deleted));                    
                }
                else
                {
                    //This file has a matching state. Need to check for possible changes
                    var hashString = file.CalculateHash(BlockSize,BlockHash);
                    //If the hashes don't match the file was changed
                    if (fileState.Checksum != hashString)
                    {
                        _persistenceAgent.Post(() => UpdateStatusDirect(fileState.Id, FileStatus.Modified));
                    }                    
                }
            };            
         
        }

        private int UpdateStatusDirect(Guid id, FileStatus status)
        {
            using (log4net.ThreadContext.Stacks["StatusAgent"].Push("UpdateStatusDirect"))
            {

                try
                {
                    
                    using (var connection = GetConnection())
                    using (
                        var command = new SQLiteCommand("update FileState set FileStatus= :fileStatus where Id = :id  ",
                                                        connection))
                    {                                                
                        command.Parameters.AddWithValue("fileStatus", status);

                        command.Parameters.AddWithValue("id", id);
                        
                        var affected = command.ExecuteNonQuery();
                        
                        return affected;
                    }

                }
                catch (Exception exc)
                {
                    Log.Error(exc.ToString());
                    throw;
                }
            }
        }
        
        private int UpdateStatusDirect(string path, FileStatus status)
        {
            using (log4net.ThreadContext.Stacks["StatusAgent"].Push("UpdateStatusDirect"))
            {

                try
                {

                    
                    using (var connection = GetConnection())
                    using (
                        var command =
                            new SQLiteCommand("update FileState set FileStatus= :fileStatus where FilePath = :path COLLATE NOCASE",
                                              connection))
                    {


                        command.Parameters.AddWithValue("fileStatus", status);

                        command.Parameters.AddWithValue("path", path);
                        
                        var affected = command.ExecuteNonQuery();
                        return affected;
                    }
                }
                catch (Exception exc)
                {
                    Log.Error(exc.ToString());
                    throw;
                }
            }
        }

        private int UpdateStatusDirect(string absolutePath, FileStatus fileStatus, FileOverlayStatus overlayStatus)
        {
            using (log4net.ThreadContext.Stacks["StatusAgent"].Push("UpdateStatusDirect"))
            {

                try
                {

                    
                    using (var connection = GetConnection())
                    using (
                        var command =
                            new SQLiteCommand(
                                "update FileState set OverlayStatus= :overlayStatus, FileStatus= :fileStatus where FilePath = :path COLLATE NOCASE ",
                                connection))
                    {

                        command.Parameters.AddWithValue("path", absolutePath);
                        command.Parameters.AddWithValue("fileStatus", fileStatus);
                        command.Parameters.AddWithValue("overlayStatus", overlayStatus);
                        
                        var affected = command.ExecuteNonQuery();
                        return affected;
                    }
                }
                catch (Exception exc)
                {
                    Log.Error(exc.ToString());
                    throw;
                }
            }
        }
        


        public string BlockHash { get; set; }

        public int BlockSize { get; set; }
        public void ChangeRoots(string oldPath, string newPath)
        {
            if (String.IsNullOrWhiteSpace(oldPath))
                throw new ArgumentNullException("oldPath");
            if (!Path.IsPathRooted(oldPath))
                throw new ArgumentException("oldPath must be an absolute path", "oldPath");
            if (string.IsNullOrWhiteSpace(newPath))
                throw new ArgumentNullException("newPath");
            if (!Path.IsPathRooted(newPath))
                throw new ArgumentException("newPath must be an absolute path", "newPath");
            Contract.EndContractBlock();

            FileState.ChangeRootPath(oldPath,newPath);

        }

        private PithosStatus _pithosStatus=PithosStatus.InSynch;       

        public void SetPithosStatus(PithosStatus status)
        {
            _pithosStatus = status;
        }

        public PithosStatus GetPithosStatus()
        {
            return _pithosStatus;
        }


        private readonly string _pithosDataPath;


        public FileState GetStateByFilePath(string path)
        {
            if (String.IsNullOrWhiteSpace(path))
                throw new ArgumentNullException("path");
            if (!Path.IsPathRooted(path))
                throw new ArgumentException("The path must be rooted", "path");
            Contract.EndContractBlock();

            try
            {
                
                using (var connection = GetConnection())
                using (var command = new SQLiteCommand("select Id, FilePath, OverlayStatus,FileStatus ,Checksum   ,Version    ,VersionTimeStamp,IsShared   ,SharedBy   ,ShareWrite  from FileState where FilePath=:path COLLATE NOCASE", connection))
                {
                    
                    command.Parameters.AddWithValue("path", path);
                    
                    using (var reader = command.ExecuteReader())
                    {
                        if (reader.Read())
                        {
                            //var values = new object[reader.FieldCount];
                            //reader.GetValues(values);
                            var state = new FileState
                                            {
                                                Id = reader.GetGuid(0),
                                                FilePath = reader.IsDBNull(1)?"":reader.GetString(1),
                                                OverlayStatus =reader.IsDBNull(2)?FileOverlayStatus.Unversioned: (FileOverlayStatus) reader.GetInt64(2),
                                                FileStatus = reader.IsDBNull(3)?FileStatus.Missing:(FileStatus) reader.GetInt64(3),
                                                Checksum = reader.IsDBNull(4)?"":reader.GetString(4),
                                                Version = reader.IsDBNull(5)?default(long):reader.GetInt64(5),
                                                VersionTimeStamp = reader.IsDBNull(6)?default(DateTime):reader.GetDateTime(6),
                                                IsShared = !reader.IsDBNull(7) && reader.GetBoolean(7),
                                                SharedBy = reader.IsDBNull(8)?"":reader.GetString(8),
                                                ShareWrite = !reader.IsDBNull(9) && reader.GetBoolean(9)
                                            };
/*
                            var state = new FileState
                                            {
                                                Id = (Guid) values[0],
                                                FilePath = (string) values[1],
                                                OverlayStatus = (FileOverlayStatus) (long)values[2],
                                                FileStatus = (FileStatus) (long)values[3],
                                                Checksum = (string) values[4],
                                                Version = (long?) values[5],
                                                VersionTimeStamp = (DateTime?) values[6],
                                                IsShared = (long)values[7] == 1,
                                                SharedBy = (string) values[8],
                                                ShareWrite = (long)values[9] == 1
                                            };
*/
                            return state;
                        }
                        else
                        {
                            return null;
                        }

                    }                    
                }
            }
            catch (Exception exc)
            {
                Log.ErrorFormat(exc.ToString());
                throw;
            }            
        }

        public FileOverlayStatus GetFileOverlayStatus(string path)
        {
            if (String.IsNullOrWhiteSpace(path))
                throw new ArgumentNullException("path");
            if (!Path.IsPathRooted(path))
                throw new ArgumentException("The path must be rooted", "path");
            Contract.EndContractBlock();

            try
            {
                
                using (var connection = GetConnection())
                using (var command = new SQLiteCommand("select OverlayStatus from FileState where FilePath=:path  COLLATE NOCASE", connection))
                {
                    
                    command.Parameters.AddWithValue("path", path);
                    
                    var s = command.ExecuteScalar();
                    return (FileOverlayStatus) Convert.ToInt32(s);
                }
            }
            catch (Exception exc)
            {
                Log.ErrorFormat(exc.ToString());
                return FileOverlayStatus.Unversioned;
            }
        }

        private string GetConnectionString()
        {
            var connectionString = String.Format(@"Data Source={0}\pithos.db;Version=3;Enlist=N;Pooling=True", _pithosDataPath);
            return connectionString;
        }

        private SQLiteConnection GetConnection()
        {
            var connectionString = GetConnectionString();
            var connection = new SQLiteConnection(connectionString);
            connection.Open();
            using(var cmd =connection.CreateCommand())
            {
                cmd.CommandText = "PRAGMA journal_mode=WAL";
                cmd.ExecuteNonQuery();
            }
            return connection;
        }

        public void SetFileOverlayStatus(string path, FileOverlayStatus overlayStatus)
        {
            if (String.IsNullOrWhiteSpace(path))
                throw new ArgumentNullException("path");
            if (!Path.IsPathRooted(path))
                throw new ArgumentException("The path must be rooted","path");
            Contract.EndContractBlock();

            _persistenceAgent.Post(() => FileState.StoreOverlayStatus(path,overlayStatus));
        }

       /* public void RenameFileOverlayStatus(string oldPath, string newPath)
        {
            if (String.IsNullOrWhiteSpace(oldPath))
                throw new ArgumentNullException("oldPath");
            if (!Path.IsPathRooted(oldPath))
                throw new ArgumentException("The oldPath must be rooted", "oldPath");
            if (String.IsNullOrWhiteSpace(newPath))
                throw new ArgumentNullException("newPath");
            if (!Path.IsPathRooted(newPath))
                throw new ArgumentException("The newPath must be rooted", "newPath");
            Contract.EndContractBlock();

            _persistenceAgent.Post(() =>FileState.RenameState(oldPath, newPath));
        }*/

        public void SetFileState(string path, FileStatus fileStatus, FileOverlayStatus overlayStatus)
        {
            if (String.IsNullOrWhiteSpace(path))
                throw new ArgumentNullException("path");
            if (!Path.IsPathRooted(path))
                throw new ArgumentException("The path must be rooted", "path");
            Contract.EndContractBlock();

            Debug.Assert(!path.Contains(FolderConstants.CacheFolder));
            Debug.Assert(!path.EndsWith(".ignore"));

            _persistenceAgent.Post(() => UpdateStatusDirect(path, fileStatus, overlayStatus));
        }

/*
        public void StoreInfo(string path,ObjectInfo objectInfo)
        {
            if (String.IsNullOrWhiteSpace(path))
                throw new ArgumentNullException("path");
            if (!Path.IsPathRooted(path))
                throw new ArgumentException("The path must be rooted", "path");            
            if (objectInfo == null)
                throw new ArgumentNullException("objectInfo", "objectInfo can't be empty");
            Contract.EndContractBlock();

            _persistenceAgent.Post(() =>
            {
                var filePath = path.ToLower();
                //Load the existing files state and set its properties in one session            
                using (new SessionScope())
                {
                    //Forgetting to use a sessionscope results in two sessions being created, one by 
                    //FirstOrDefault and one by Save()
                    var state =FileState.FindByFilePath(filePath);
                    
                    //Create a new empty state object if this is a new file
                    state = state ?? new FileState();

                    state.FilePath = filePath;
                    state.Checksum = objectInfo.Hash;
                    state.Version = objectInfo.Version;
                    state.VersionTimeStamp = objectInfo.VersionTimestamp;

                    state.FileStatus = FileStatus.Unchanged;
                    state.OverlayStatus = FileOverlayStatus.Normal;
                    
                  
                    //Do the save
                    state.Save();
                }
            });

        }
*/
        
        public void StoreInfo(string path, ObjectInfo objectInfo)
        {
            if (String.IsNullOrWhiteSpace(path))
                throw new ArgumentNullException("path");
            if (!Path.IsPathRooted(path))
                throw new ArgumentException("The path must be rooted", "path");
            if (objectInfo == null)
                throw new ArgumentNullException("objectInfo", "objectInfo can't be empty");
            Contract.EndContractBlock();

            _persistenceAgent.Post(() => StoreInfoDirect(path, objectInfo));

        }

        private void StoreInfoDirect(string path, ObjectInfo objectInfo)
        {
            try
            {
                
                using (var connection = GetConnection())
                using (var command = new SQLiteCommand(connection))
                {
                    if (StateExists(path, connection))
                        command.CommandText =
                            "update FileState set FileStatus= :fileStatus where FilePath = :path  COLLATE NOCASE ";
                    else
                    {
                        command.CommandText =
                            "INSERT INTO FileState (Id,FilePath,Checksum,Version,VersionTimeStamp,FileStatus,OverlayStatus) VALUES (:id,:path,:checksum,:version,:versionTimeStamp,:fileStatus,:overlayStatus)";
                        command.Parameters.AddWithValue("id", Guid.NewGuid());
                    }

                    command.Parameters.AddWithValue("path", path);
                    command.Parameters.AddWithValue("checksum", objectInfo.Hash);
                    command.Parameters.AddWithValue("version", objectInfo.Version);
                    command.Parameters.AddWithValue("versionTimeStamp",
                                                    objectInfo.VersionTimestamp);
                    command.Parameters.AddWithValue("fileStatus", FileStatus.Unchanged);
                    command.Parameters.AddWithValue("overlayStatus",
                                                    FileOverlayStatus.Normal);

                    var affected = command.ExecuteNonQuery();
                    return;
                }
            }
            catch (Exception exc)
            {
                Log.Error(exc.ToString());
                throw;
            }
        }

        private bool StateExists(string filePath,SQLiteConnection connection)
        {
            using (var command = new SQLiteCommand("Select count(*) from FileState where FilePath=:path  COLLATE NOCASE", connection))
            {
                command.Parameters.AddWithValue("path", filePath);
                var result = command.ExecuteScalar();
                return ((long)result >= 1);
            }

        }

        public void SetFileStatus(string path, FileStatus status)
        {
            if (String.IsNullOrWhiteSpace(path))
                throw new ArgumentNullException("path");
            if (!Path.IsPathRooted(path))
                throw new ArgumentException("The path must be rooted", "path");
            Contract.EndContractBlock();
            
            _persistenceAgent.Post(() => UpdateStatusDirect(path, status));
        }

        public FileStatus GetFileStatus(string path)
        {
            if (String.IsNullOrWhiteSpace(path))
                throw new ArgumentNullException("path");
            if (!Path.IsPathRooted(path))
                throw new ArgumentException("The path must be rooted", "path");
            Contract.EndContractBlock();

            
            using (var connection = GetConnection())
            {
                var command = new SQLiteCommand("select FileStatus from FileState where FilePath=:path  COLLATE NOCASE", connection);
                command.Parameters.AddWithValue("path", path);
                
                var statusValue = command.ExecuteScalar();
                if (statusValue==null)
                    return FileStatus.Missing;
                return (FileStatus)Convert.ToInt32(statusValue);
            }
        }

        /// <summary>
        /// Deletes the status of the specified file
        /// </summary>
        /// <param name="path"></param>
        public void ClearFileStatus(string path)
        {
            if (String.IsNullOrWhiteSpace(path))
                throw new ArgumentNullException("path");
            if (!Path.IsPathRooted(path))
                throw new ArgumentException("The path must be rooted", "path");
            Contract.EndContractBlock();

            _persistenceAgent.Post(() => DeleteDirect(path));   
        }

        /// <summary>
        /// Deletes the status of the specified folder and all its contents
        /// </summary>
        /// <param name="path"></param>
        public void ClearFolderStatus(string path)
        {
            if (String.IsNullOrWhiteSpace(path))
                throw new ArgumentNullException("path");
            if (!Path.IsPathRooted(path))
                throw new ArgumentException("The path must be rooted", "path");
            Contract.EndContractBlock();

            _persistenceAgent.Post(() => DeleteFolderDirect(path));   
        }

        public IEnumerable<FileState> GetChildren(FileState fileState)
        {
            if (fileState == null)
                throw new ArgumentNullException("fileState");
            Contract.EndContractBlock();

            var children = from state in FileState.Queryable
                           where state.FilePath.StartsWith(fileState.FilePath + "\\")
                           select state;
            return children;
        }

        private int DeleteDirect(string filePath)
        {
            using (log4net.ThreadContext.Stacks["StatusAgent"].Push("DeleteDirect"))
            {

                try
                {

                    
                    using (var connection = GetConnection())
                    {
                        var command = new SQLiteCommand("delete from FileState where FilePath = :path  COLLATE NOCASE",
                                                        connection);

                        command.Parameters.AddWithValue("path", filePath);
                        
                        var affected = command.ExecuteNonQuery();
                        return affected;
                    }
                }
                catch (Exception exc)
                {
                    Log.Error(exc.ToString());
                    throw;
                }
            }
        }

        private int DeleteFolderDirect(string filePath)
        {
            using (log4net.ThreadContext.Stacks["StatusAgent"].Push("DeleteDirect"))
            {

                try
                {

                    
                    using (var connection = GetConnection())
                    {
                        var command = new SQLiteCommand("delete from FileState where FilePath = :path or FilePath like :path + '/%'  COLLATE NOCASE",
                                                        connection);

                        command.Parameters.AddWithValue("path", filePath);
                        
                        var affected = command.ExecuteNonQuery();
                        return affected;
                    }
                }
                catch (Exception exc)
                {
                    Log.Error(exc.ToString());
                    throw;
                }
            }
        }

        public void UpdateFileChecksum(string path, string checksum)
        {
            if (String.IsNullOrWhiteSpace(path))
                throw new ArgumentNullException("path");
            if (!Path.IsPathRooted(path))
                throw new ArgumentException("The path must be rooted", "path");            
            Contract.EndContractBlock();

            _persistenceAgent.Post(() => FileState.UpdateChecksum(path, checksum));
        }

    }

   
}