using System;
using System.IO;
using System.Text;
using System.Web;
using System.Web.Optimization;
using dotless.Core;
using dotless.Core.Abstractions;
using dotless.Core.Importers;
using dotless.Core.Input;
using dotless.Core.Loggers;
using dotless.Core.Parser;

public class LessMinify : IBundleTransform
{
    public void Process(BundleContext context, BundleResponse bundle)
    {
        if (bundle == null)
        {
            throw new ArgumentNullException("bundle");
        }

        context.HttpContext.Response.Cache.SetLastModifiedFromFileDependencies();

        var lessParser = new Parser();
        ILessEngine lessEngine = CreateLessEngine(lessParser);

        var content = new StringBuilder(bundle.Content.Length);

        foreach (FileInfo file in bundle.Files)
        {
            SetCurrentFilePath(lessParser, file.FullName);
            string source = File.ReadAllText(file.FullName);
            content.Append(lessEngine.TransformToCss(source, file.FullName));
            content.AppendLine();

            AddFileDependencies(lessParser);
        }

        bundle.ContentType = "text/css";
        bundle.Content = content.ToString();
    }

    /// <summary>
    /// Creates an instance of LESS engine.
    /// </summary>
    /// <param name="lessParser">The LESS parser.</param>
    private ILessEngine CreateLessEngine(Parser lessParser)
    {
        var logger = new AspNetTraceLogger(LogLevel.Debug, new Http());
        return new LessEngine(lessParser, logger, true, false);
    }

    /// <summary>
    /// Adds imported files to the collection of files on which the current response is dependent.
    /// </summary>
    /// <param name="lessParser">The LESS parser.</param>
    private void AddFileDependencies(Parser lessParser)
    {
        IPathResolver pathResolver = GetPathResolver(lessParser);

        foreach (string importedFilePath in lessParser.Importer.Imports)
        {
            string fullPath = pathResolver.GetFullPath(importedFilePath);
            HttpContext.Current.Response.AddFileDependency(fullPath);
        }

        lessParser.Importer.Imports.Clear();
    }

    /// <summary>
    /// Returns an <see cref="IPathResolver"/> instance used by the specified LESS lessParser.
    /// </summary>
    /// <param name="lessParser">The LESS prser.</param>
    private IPathResolver GetPathResolver(Parser lessParser)
    {
        var importer = lessParser.Importer as Importer;
        if (importer != null)
        {
            var fileReader = importer.FileReader as FileReader;
            if (fileReader != null)
            {
                return fileReader.PathResolver;
            }
        }

        return null;
    }

    /// <summary>
    /// Informs the LESS parser about the path to the currently processed file. 
    /// This is done by using custom <see cref="IPathResolver"/> implementation.
    /// </summary>
    /// <param name="lessParser">The LESS parser.</param>
    /// <param name="currentFilePath">The path to the currently processed file.</param>
    private void SetCurrentFilePath(Parser lessParser, string currentFilePath)
    {
        var importer = lessParser.Importer as Importer;
        if (importer != null)
        {
            var fileReader = importer.FileReader as FileReader;

            if (fileReader == null)
            {
                importer.FileReader = fileReader = new FileReader();
            }

            var pathResolver = fileReader.PathResolver as ImportedFilePathResolver;

            if (pathResolver != null)
            {
                pathResolver.CurrentFilePath = currentFilePath;
            }
            else
            {
                fileReader.PathResolver = new ImportedFilePathResolver(currentFilePath);
            }
        }
        else
        {
            throw new InvalidOperationException("Unexpected importer type on dotless parser");
        }
    }
}