using System.IO.Compression;
using System.Xml;

namespace Content
{
    public class ODF
    {
        public  string ReadText(string filePath)
        {
            string textContent = "";

            using (ZipArchive zipArchive = ZipFile.OpenRead(filePath))
            {
                foreach (var entry in zipArchive.Entries)
                    {
                        if (entry.FullName.EndsWith(".xml", StringComparison.OrdinalIgnoreCase))
                        {
                            using StreamReader reader = new StreamReader(entry.Open());
                            string xmlContent = reader.ReadToEnd();
                          textContent += ExtractTextFromXml(xmlContent);  
                        }
                    }
            }

            return textContent; // output : text content 
        }

        public string ExtractTextFromXml(string xmlContent)
        {
            string textContent = "";

            XmlDocument xmlDoc = new XmlDocument();
            xmlDoc.LoadXml(xmlContent);

            // add required namespace for different types of documents
            XmlNamespaceManager nsManager = new XmlNamespaceManager(xmlDoc.NameTable);
            nsManager.AddNamespace("text", "urn:oasis:names:tc:opendocument:xmlns:text:1.0"); // for doc files with extension .odt   
            nsManager.AddNamespace("office", "urn:oasis:names:tc:opendocument:xmlns:office:1.0"); // comman for all ODF files  

            foreach (XmlNode node in xmlDoc.SelectNodes("//text:p | //text:h", nsManager))
            {
                textContent += node.InnerText + Environment.NewLine;
            }

            return textContent;
        }
    }
}