#region Copyright © 2001-2003 Jean-Claude Manoli [jc@manoli.net]
/*
 * This software is provided 'as-is', without any express or implied warranty.
 * In no event will the author(s) be held liable for any damages arising from
 * the use of this software.
 * 
 * Permission is granted to anyone to use this software for any purpose,
 * including commercial applications, and to alter it and redistribute it
 * freely, subject to the following restrictions:
 * 
 *   1. The origin of this software must not be misrepresented; you must not
 *      claim that you wrote the original software. If you use this software
 *      in a product, an acknowledgment in the product documentation would be
 *      appreciated but is not required.
 * 
 *   2. Altered source versions must be plainly marked as such, and must not
 *      be misrepresented as being the original software.
 * 
 *   3. This notice may not be removed or altered from any source distribution.
 */
#endregion

using System.Reflection;
using System.Text;
using System.Text.RegularExpressions;
using Nop.Core;

namespace Nop.Services.Html.CodeFormatter;

/// <summary>
///    Provides a base implementation for all code formatters.
/// </summary>
/// <remarks>
/// <para>
/// To display the formatted code on your web site, the web page must 
/// refer to a stylesheet that defines the formatting for the different 
/// CSS classes generated by CSharpFormat:
/// .csharpcode, pre, .rem, .kwrd, .str, .op, .preproc, .alt, .lnum.
/// </para>
/// <para>
/// Note that if you have multi-line comments in your source code
/// (like /* ... */), the "line numbers" or "alternate line background" 
/// options will generate code that is not strictly HTML 4.01 compliant. 
/// The code will still look good with IE5+ or Mozilla 0.8+. 
/// </para>
/// </remarks>
public abstract partial class SourceFormat
{
    /// <summary/>
    protected SourceFormat()
    {
        TabSpaces = 4;
        LineNumbers = false;
        Alternate = false;
        EmbedStyleSheet = false;
    }

    /// <summary>
    /// Gets the CSS stylesheet as a stream.
    /// </summary>
    /// <returns>A text <see cref="Stream"/> of the CSS definitions.</returns>
    public static Stream GetCssStream()
    {
        return Assembly.GetExecutingAssembly().GetManifestResourceStream(
            "Manoli.Utils.CSharpFormat.csharp.css");
    }

    /// <summary>
    /// Gets the CSS stylesheet as a string.
    /// </summary>
    /// <returns>A string containing the CSS definitions.</returns>
    public static string GetCssString()
    {
        using var reader = new StreamReader(GetCssStream());
        return reader.ReadToEnd();
    }

    /// <summary>
    /// Gets or sets the tabs width.
    /// </summary>
    /// <value>The number of space characters to substitute for tab 
    /// characters. The default is <b>4</b>, unless overridden is a 
    /// derived class.</value>
    public byte TabSpaces { get; set; }

    /// <summary>
    /// Enables or disables line numbers in output.
    /// </summary>
    /// <value>When <b>true</b>, line numbers are generated. 
    /// The default is <b>false</b>.</value>
    public bool LineNumbers { get; set; }

    /// <summary>
    /// Enables or disables alternating line background.
    /// </summary>
    /// <value>When <b>true</b>, lines background is alternated. 
    /// The default is <b>false</b>.</value>
    public bool Alternate { get; set; }

    /// <summary>
    /// Enables or disables the embedded CSS style sheet.
    /// </summary>
    /// <value>When <b>true</b>, the CSS &lt;style&gt; element is included 
    /// in the HTML output. The default is <b>false</b>.</value>
    public bool EmbedStyleSheet { get; set; }

    /// <overloads>Transform source code to HTML 4.01.</overloads>
    /// 
    /// <summary>
    /// Transforms a source code stream to HTML 4.01.
    /// </summary>
    /// <param name="source">Source code stream.</param>
    /// <returns>A string containing the HTML formatted code.</returns>
    public string FormatCode(Stream source)
    {
        using var reader = new StreamReader(source);
        var s = reader.ReadToEnd();
        return FormatCode(s, LineNumbers, Alternate, EmbedStyleSheet, false);
    }

    /// <summary>
    /// Transforms a source code string to HTML 4.01.
    /// </summary>
    /// <returns>A string containing the HTML formatted code.</returns>
    public string FormatCode(string source)
    {
        return FormatCode(source, LineNumbers, Alternate, EmbedStyleSheet, false);
    }

    /// <summary>
    /// Allows formatting a part of the code in a different language,
    /// for example a JavaScript block inside an HTML file.
    /// </summary>
    public string FormatSubCode(string source)
    {
        return FormatCode(source, false, false, false, true);
    }

    /// <summary>
    /// The regular expression used to capture language tokens.
    /// </summary>
    protected Regex CodeRegex { get; set; }

    /// <summary>
    /// Called to evaluate the HTML fragment corresponding to each 
    /// matching token in the code.
    /// </summary>
    /// <param name="match">The <see cref="Match"/> resulting from a 
    /// single regular expression match.</param>
    /// <returns>A string containing the HTML code fragment.</returns>
    protected abstract string MatchEval(Match match);

    //does the formatting job
    protected string FormatCode(string source, bool lineNumbers, 
        bool alternate, bool embedStyleSheet, bool subCode)
    {
        //replace special characters
        var sb = new StringBuilder(source);

        if (!subCode)
        {
            sb.Replace("&", "&amp;");
            sb.Replace("<", "&lt;");
            sb.Replace(">", "&gt;");
            sb.Replace("\t", string.Empty.PadRight(TabSpaces));
        }

        //color the code
        source = CodeRegex.Replace(sb.ToString(), MatchEval);

        sb = new StringBuilder();

        if (embedStyleSheet)
        {
            sb.AppendFormat("<style type=\"{0}\">\n", MimeTypes.TextCss);
            sb.Append(GetCssString());
            sb.Append("</style>\n");
        }

        if (lineNumbers || alternate) //we have to process the code line by line
        {
            if (!subCode)
                sb.Append("<div class=\"csharpcode\">\n");

            var reader = new StringReader(source);
            var i = 0;
            const string spaces = "    ";
            string line;
            while ((line = reader.ReadLine()) != null)
            {
                i++;
                if (alternate && i % 2 == 1)
                {
                    sb.Append("<pre class=\"alt\">");
                }
                else
                {
                    sb.Append("<pre>");
                }

                if (lineNumbers)
                {
                    var order = (int)Math.Log10(i);
                    sb.Append("<span class=\"lnum\">"
                              + spaces[0..(3 - order)] + i
                              + ":  </span>");
                }

                sb.Append(line.Length == 0 ? "&nbsp;" : line);
                sb.Append("</pre>\n");
            }

            reader.Close();

            if (!subCode)
                sb.Append("</div>");
        }
        else
        {
            //have to use a <pre> because IE below ver 6 does not understand 
            //the "white-space: pre" CSS value
            if (!subCode)
                sb.Append("<pre class=\"csharpcode\">\n");

            sb.Append(source);
            if (!subCode)
                sb.Append("</pre>");
        }

        return sb.ToString();
    }
}