HTML Comparison

using System;
using System.Collections.Generic;
using System.IO;
using System.Linq;
using System.Threading.Tasks;
using Aspose.App.Models;
using Aspose.Html;
using Tools.Foundation.Models;

namespace Aspose.App.Controllers
{
    internal class AsposeHtmlComparisonController : ApiControllerBase
    {
        public async Task<Response> Compare(string fileName1, string fileName2, string folderName)
        {
            Aspose.App.Models.License.SetAsposeHtmlLicense();
            var comparedDocument = string.Format("{0}_compare_to_{1}.html",
                Path.GetFileNameWithoutExtension(fileName1), Path.GetFileNameWithoutExtension(fileName2));

            return await Process(this.GetType().Name, comparedDocument, folderName, ".html", false, false,
        AsposeHTML + ComparisonApp, ProductFamilyNameKeysEnum.html, "Compare",
                (inFilePath, outPath, zipOutFolder) =>
                {
                    var tc1 = GetTextContent(AppSettings.WorkingDirectory + folderName + "/" + fileName1);
                    var tc2 = GetTextContent(AppSettings.WorkingDirectory + folderName + "/" + fileName2);
                    var count = Math.Min(tc1.Count, tc2.Count);
                    var result = new Aspose.Html.HTMLDocument();
                    for (int i = 0; i < count; i++)
                    {
                        var originalStr = tc1[i].Trim();
                        var modifiedStr = tc2[i].Trim();
                        var changes = Levenshtein3(originalStr, modifiedStr);
                        var modifications = new System.Collections.Generic.List<Modification>();
                        int pos1 = 0, pos2 = 0;
                        var current = new Modification
                        {
                            Status = changes.route[0]
                        };
                        for (int ii = 0; ii < changes.route.Length; ii++)
                        {
                            var status = changes.route[ii];
                            char symbol = ' ';
                            if (changes.route[ii] == '=')
                            {
                                symbol = originalStr[pos1++];
                                pos2++;
                            }
                            if (changes.route[ii] == 'I')
                            {
                                symbol = modifiedStr[pos2++];
                            }
                            if (changes.route[ii] == 'D')
                            {
                                symbol = originalStr[pos1++];
                                pos2++;
                            }
                            if (changes.route[ii] == 'R')
                            {
                                symbol = modifiedStr[pos2++];
                                pos1++;
                            }
                            if (current.Status == status)
                            {
                                current.Value += symbol;
                            }
                            else
                            {
                                modifications.Add(current);
                                current = new Modification
                                {
                                    Status = status,
                                    Value = symbol.ToString()
                                };
                            }
                        }
                        modifications.Add(current);
                        var sb = new System.Text.StringBuilder();
                        foreach (var item in modifications)
                        {
                            switch (item.Status)
                            {
                                case '=':
                                    sb.AppendFormat("<span>{0}</span>", item.Value);
                                    break;
                                case 'I':
                                    sb.AppendFormat("<ins>{0}</ins>", item.Value);
                                    break;
                                case 'R':
                                    sb.AppendFormat("<mark>{0}</mark>", item.Value);
                                    break;
                                case 'D':
                                    sb.AppendFormat("<del>{0}</del>", item.Value);
                                    break;
                                default:
                                    break;
                            }
                        }
                        result.Body.InnerHTML += sb.ToString();
                    }
                    result.Save(outPath);
                });
        }
        private static List<string> GetTextContent(string fileName)
        {
            var document = new HTMLDocument(System.IO.File.ReadAllText(fileName), string.Empty);

            var scriptsElements = document.GetElementsByTagName("script");
            foreach (var element in scriptsElements)
            {
                element.TextContent = string.Empty;
            }
            var styleElements = document.GetElementsByTagName("style");
            foreach (var element in styleElements)
            {
                element.TextContent = string.Empty;
            }

            var textFragments = new List<string>();

            foreach (var element in document.Children)
            {
                textFragments.Add(element.TextContent);
            }
            return textFragments;
        }
        private static Prescription Levenshtein3(string S1, string S2)
        {
            int m = S1.Length, n = S2.Length;
            int h = (int)Math.Sqrt(m + 1);
            int[,] D = new int[h + 1, n + 1];
            char[,] P = new char[h + 1, n + 1];

            int d = 0;
            var route = new System.Text.StringBuilder();
            int iPos = m, jPos = n;
            do
            {
                for (int i = 0; i <= jPos; i++)
                {
                    D[0, i] = i;
                    P[0, i] = 'I';
                }
                int index = 1;
                for (int i = 1; i <= iPos; i++)
                {
                    for (int j = 0; j <= jPos; j++)
                    {
                        if (j == 0) D[index, j] = i;
                        else
                        {
                            int cost = (S1[i - 1] != S2[j - 1]) ? 1 : 0;
                            if (D[index, j - 1] < D[index - 1, j] && D[index, j - 1] < D[index - 1, j - 1] + cost)
                            {
                                //Insert
                                D[index, j] = D[index, j - 1] + 1;
                                P[index, j] = 'I';
                            }
                            else if (D[index - 1, j] < D[index - 1, j - 1] + cost)
                            {
                                //Remove
                                D[index, j] = D[index - 1, j] + 1;
                                P[index, j] = 'D';
                            }
                            else
                            {
                                //Replace or no ops
                                D[index, j] = D[index - 1, j - 1] + cost;
                                P[index, j] = (cost == 1) ? 'R' : '=';
                            }
                        }
                    }
                    if (i % h == 0)
                    {
                        //Allocate of memory for new lines and copying the last from the previous band to the first line of the new
                        int[] vRow = new int[n + 1];
                        char[] cRow = new char[n + 1];
                        for (int j = 0; j <= n; j++)
                        {
                            vRow[j] = D[index, j];
                            cRow[j] = P[index, j];
                        }
                        D = new int[h + 1, n + 1];
                        P = new char[h + 1, n + 1];
                        for (int j = 0; j <= n; j++)
                        {
                            D[0, j] = vRow[j];
                            P[0, j] = cRow[j];
                        }
                        index = 0;
                    }
                    index++;
                }
                if (iPos == m && jPos == n) d = D[index - 1, n];
                //Restore prescriptions in the last _i - 1 lines
                while (index > 0 && iPos != 0 && jPos != 0)
                {
                    char c = P[index - 1, jPos];
                    route.Append(c);
                    if (c == 'R' || c == '=')
                    {
                        iPos--;
                        jPos--;
                        index--;
                    }
                    else if (c == 'D')
                    {
                        iPos--;
                        index--;
                    }
                    else
                    {
                        jPos--;
                    }
                }
            } while ((iPos != 0) && (jPos != 0));
            return new Prescription(d, string.Join(string.Empty, route.ToString().ToCharArray().Reverse()));
        }

    }

    internal class Prescription
    {
        public string route;
        public int distance;

        public Prescription(int distance, string route)
        {
            this.distance = distance;
            this.route = route;
        }
    }
    internal class Modification
    {
        public char Status;
        public string Value;
    }

}