Nexus.Reader/src/NexusReader.Infrastructure/Services/EpubExtractor.cs

using System.Text.RegularExpressions;
using FluentResults;
using Microsoft.Extensions.Logging;
using NexusReader.Application.Abstractions.Services;
using VersOne.Epub;

namespace NexusReader.Infrastructure.Services;

public class EpubExtractor : IEpubExtractor
{
    private readonly ILogger<EpubExtractor> _logger;

    public EpubExtractor(ILogger<EpubExtractor> logger)
    {
        _logger = logger;
    }

    public async Task<Result<List<string>>> ExtractChaptersTextAsync(string relativePath, CancellationToken cancellationToken = default)
    {
        try
        {
            var fullPath = ResolvePath(relativePath);
            if (string.IsNullOrEmpty(fullPath) || !File.Exists(fullPath))
            {
                _logger.LogError("[EpubExtractor] EPUB file not found at path: {FilePath}", relativePath);
                return Result.Fail<List<string>>($"Plik EPUB nie został znaleziony na dysku: {relativePath}");
            }

            using var bookRef = await EpubReader.OpenBookAsync(fullPath);
            var readingOrder = bookRef.GetReadingOrder();

            if (readingOrder == null || !readingOrder.Any())
            {
                return Result.Fail<List<string>>("EPUB nie zawiera czytelnych rozdziałów.");
            }

            var chapters = new List<string>();
            foreach (var chapterRef in readingOrder)
            {
                if (cancellationToken.IsCancellationRequested)
                {
                    break;
                }

                var rawContent = await chapterRef.ReadContentAsTextAsync();
                var cleanText = StripHtml(rawContent);
                chapters.Add(cleanText);
            }

            return Result.Ok(chapters);
        }
        catch (Exception ex)
        {
            _logger.LogError(ex, "[EpubExtractor] Error extracting chapters from EPUB: {FilePath}", relativePath);
            return Result.Fail<List<string>>(new Error("Failed to parse and extract text from EPUB").CausedBy(ex));
        }
    }

    private static string? ResolvePath(string relativePath)
    {
        var normalized = relativePath.Replace('/', Path.DirectorySeparatorChar);
        var currentDir = new DirectoryInfo(AppDomain.CurrentDomain.BaseDirectory);
        while (currentDir != null)
        {
            var candidate = Path.Combine(currentDir.FullName, "wwwroot", normalized);
            if (File.Exists(candidate)) return candidate;

            var devCandidate = Path.Combine(currentDir.FullName, "src", "NexusReader.Web", "wwwroot", normalized);
            if (File.Exists(devCandidate)) return devCandidate;

            currentDir = currentDir.Parent;
        }
        return null;
    }

    private static string StripHtml(string html)
    {
        if (string.IsNullOrEmpty(html)) return string.Empty;
        var clean = Regex.Replace(html, @"<(style|script)\b[^>]*>.*?</\1>", "", RegexOptions.IgnoreCase | RegexOptions.Singleline);
        clean = Regex.Replace(clean, @"<[^>]*>", " ");
        clean = System.Net.WebUtility.HtmlDecode(clean);
        clean = Regex.Replace(clean, @"\s+", " ").Trim();
        return clean;
    }
}