//
// Copyright (c) Microsoft. All rights reserved.
// Licensed under the MIT license. See LICENSE file in the project root for full license information.
//

using System;
using System.Collections.Generic;
using System.IO;
using System.Text;
using System.Text.RegularExpressions;
using System.Linq;
using Microsoft.SqlTools.EditorServices.Utility;
using Microsoft.SqlTools.ServiceLayer.WorkspaceServices.Contracts;

namespace Microsoft.SqlTools.ServiceLayer.WorkspaceServices
{
    /// <summary>
    /// Manages a "workspace" of script files that are open for a particular
    /// editing session.  Also helps to navigate references between ScriptFiles.
    /// </summary>
    public class Workspace : IDisposable
    {
        #region Private Fields

        private Dictionary<string, ScriptFile> workspaceFiles = new Dictionary<string, ScriptFile>();

        #endregion

        #region Properties

        /// <summary>
        /// Gets or sets the root path of the workspace.
        /// </summary>
        public string WorkspacePath { get; set; }

        #endregion

        #region Constructors

        /// <summary>
        /// Creates a new instance of the Workspace class.
        /// </summary>
        public Workspace()
        {
        }

        #endregion

        #region Public Methods

        /// <summary>
        /// Gets an open file in the workspace.  If the file isn't open but
        /// exists on the filesystem, load and return it.
        /// </summary>
        /// <param name="filePath">The file path at which the script resides.</param>
        /// <exception cref="FileNotFoundException">
        /// <paramref name="filePath"/> is not found.
        /// </exception>
        /// <exception cref="ArgumentException">
        /// <paramref name="filePath"/> contains a null or empty string.
        /// </exception>
        public ScriptFile GetFile(string filePath)
        {
            Validate.IsNotNullOrEmptyString("filePath", filePath);

            // Resolve the full file path 
            string resolvedFilePath = this.ResolveFilePath(filePath);
            string keyName = resolvedFilePath.ToLower();

            // Make sure the file isn't already loaded into the workspace
            ScriptFile scriptFile = null;
            if (!this.workspaceFiles.TryGetValue(keyName, out scriptFile))
            {
                // This method allows FileNotFoundException to bubble up 
                // if the file isn't found.
                using (FileStream fileStream = new FileStream(resolvedFilePath, FileMode.Open, FileAccess.Read))
                using (StreamReader streamReader = new StreamReader(fileStream, Encoding.UTF8))
                {
                    scriptFile = new ScriptFile(resolvedFilePath, filePath,streamReader);

                    this.workspaceFiles.Add(keyName, scriptFile);
                }

                Logger.Write(LogLevel.Verbose, "Opened file on disk: " + resolvedFilePath);
            }

            return scriptFile;
        }
        
        private string ResolveFilePath(string filePath)
        {
            if (!IsPathInMemory(filePath))
            {
                if (filePath.StartsWith(@"file://"))
                {
                    // Client sent the path in URI format, extract the local path and trim
                    // any extraneous slashes
                    Uri fileUri = new Uri(filePath);
                    filePath = fileUri.LocalPath.TrimStart('/');
                }

                // Some clients send paths with UNIX-style slashes, replace those if necessary
                filePath = filePath.Replace('/', '\\');

                // Clients could specify paths with escaped space, [ and ] characters which .NET APIs
                // will not handle.  These paths will get appropriately escaped just before being passed
                // into the SqlTools engine.
                filePath = UnescapePath(filePath);

                // Get the absolute file path
                filePath = Path.GetFullPath(filePath);
            }

            Logger.Write(LogLevel.Verbose, "Resolved path: " + filePath);

            return filePath;
        }

        internal static bool IsPathInMemory(string filePath)
        {
            // When viewing SqlTools files in the Git diff viewer, VS Code
            // sends the contents of the file at HEAD with a URI that starts
            // with 'inmemory'.  Untitled files which have been marked of
            // type SqlTools have a path starting with 'untitled'.
            return
                filePath.StartsWith("inmemory") ||
                filePath.StartsWith("untitled");
        }

        /// <summary>
        /// Unescapes any escaped [, ] or space characters. Typically use this before calling a
        /// .NET API that doesn't understand PowerShell escaped chars.
        /// </summary>
        /// <param name="path">The path to unescape.</param>
        /// <returns>The path with the ` character before [, ] and spaces removed.</returns>
        public static string UnescapePath(string path)
        {
            if (!path.Contains("`"))
            {
                return path;
            }

            return Regex.Replace(path, @"`(?=[ \[\]])", "");
        }

         /// <summary>
        /// Gets a new ScriptFile instance which is identified by the given file
        /// path and initially contains the given buffer contents.
        /// </summary>
        /// <param name="filePath"></param>
        /// <param name="initialBuffer"></param>
        /// <returns></returns>
        public ScriptFile GetFileBuffer(string filePath, string initialBuffer)
        {
            Validate.IsNotNullOrEmptyString("filePath", filePath);

            // Resolve the full file path 
            string resolvedFilePath = this.ResolveFilePath(filePath);
            string keyName = resolvedFilePath.ToLower();

            // Make sure the file isn't already loaded into the workspace
            ScriptFile scriptFile = null;
            if (!this.workspaceFiles.TryGetValue(keyName, out scriptFile))
            {
                scriptFile = new ScriptFile(resolvedFilePath, filePath, initialBuffer);

                this.workspaceFiles.Add(keyName, scriptFile);

                Logger.Write(LogLevel.Verbose, "Opened file as in-memory buffer: " + resolvedFilePath);
            }

            return scriptFile;
        }

        /// <summary>
        /// Gets an array of all opened ScriptFiles in the workspace.
        /// </summary>
        /// <returns>An array of all opened ScriptFiles in the workspace.</returns>
        public ScriptFile[] GetOpenedFiles()
        {
            return workspaceFiles.Values.ToArray();
        }

        /// <summary>
        /// Closes a currently open script file with the given file path.
        /// </summary>
        /// <param name="scriptFile">The file path at which the script resides.</param>
        public void CloseFile(ScriptFile scriptFile)
        {
            Validate.IsNotNull("scriptFile", scriptFile);

            this.workspaceFiles.Remove(scriptFile.Id);
        }

        private string GetBaseFilePath(string filePath)
        {
            if (IsPathInMemory(filePath))
            {
                // If the file is in memory, use the workspace path
                return this.WorkspacePath;
            }

            if (!Path.IsPathRooted(filePath))
            {
                // TODO: Assert instead?
                throw new InvalidOperationException(
                    string.Format(
                        "Must provide a full path for originalScriptPath: {0}", 
                        filePath));
            }

            // Get the directory of the file path
            return Path.GetDirectoryName(filePath); 
        }

        private string ResolveRelativeScriptPath(string baseFilePath, string relativePath)
        {
            if (Path.IsPathRooted(relativePath))
            {
                return relativePath;
            }

            // Get the directory of the original script file, combine it
            // with the given path and then resolve the absolute file path.
            string combinedPath =
                Path.GetFullPath(
                    Path.Combine(
                        baseFilePath,
                        relativePath));

            return combinedPath;
        }

        #endregion  

        #region IDisposable Implementation

        /// <summary>
        /// Disposes of any Runspaces that were created for the
        /// services used in this session.
        /// </summary>
        public void Dispose()
        {
        }

        #endregion
    }
}