Kavita/API/Controllers/BookController.cs

using System.Collections.Generic;
using System.Linq;
using System.Threading.Tasks;
using API.DTOs;
using API.Extensions;
using API.Interfaces;
using API.Services;
using HtmlAgilityPack;
using Microsoft.AspNetCore.Mvc;
using Microsoft.Extensions.Logging;
using VersOne.Epub;

namespace API.Controllers
{
    public class BookController : BaseApiController
    {
        private readonly ILogger<BookController> _logger;
        private readonly IBookService _bookService;
        private readonly IUnitOfWork _unitOfWork;
        private static readonly string BookApiUrl = "book-resources?file=";


        public BookController(ILogger<BookController> logger, IBookService bookService, IUnitOfWork unitOfWork)
        {
            _logger = logger;
            _bookService = bookService;
            _unitOfWork = unitOfWork;
        }

        [HttpGet("{chapterId}/book-info")]
        public async Task<ActionResult<string>> GetBookInfo(int chapterId)
        {
            var chapter = await _unitOfWork.VolumeRepository.GetChapterAsync(chapterId);
            var book = await EpubReader.OpenBookAsync(chapter.Files.ElementAt(0).FilePath);

            return book.Title;
        }

        [HttpGet("{chapterId}/book-resources")]
        public async Task<ActionResult> GetBookPageResources(int chapterId, [FromQuery] string file)
        {
            var chapter = await _unitOfWork.VolumeRepository.GetChapterAsync(chapterId);
            var book = await EpubReader.OpenBookAsync(chapter.Files.ElementAt(0).FilePath);

            var key = BookService.CleanContentKeys(file);
            if (!book.Content.AllFiles.ContainsKey(key)) return BadRequest("File was not found in book");
            
            var bookFile = book.Content.AllFiles[key];
            var content = await bookFile.ReadContentAsBytesAsync();
            Response.AddCacheHeader(content);
            var contentType = BookService.GetContentType(bookFile.ContentType);
            return File(content, contentType, $"{chapterId}-{file}");
        }

        [HttpGet("{chapterId}/chapters")]
        public async Task<ActionResult<ICollection<BookChapterItem>>> GetBookChapters(int chapterId)
        {
            // This will return a list of mappings from ID -> pagenum. ID will be the xhtml key and pagenum will be the reading order
            // this is used to rewrite anchors in the book text so that we always load properly in FE
            var chapter = await _unitOfWork.VolumeRepository.GetChapterAsync(chapterId);
            var book = await EpubReader.OpenBookAsync(chapter.Files.ElementAt(0).FilePath);
            var mappings = await _bookService.CreateKeyToPageMappingAsync(book);
            
            var navItems = await book.GetNavigationAsync();
            var chaptersList = new List<BookChapterItem>();

            foreach (var navigationItem in navItems)
            {
                if (navigationItem.NestedItems.Count > 0)
                {
                    _logger.LogDebug("Header: {Header}", navigationItem.Title);
                    var nestedChapters = new List<BookChapterItem>();
                    
                    foreach (var nestedChapter in navigationItem.NestedItems)
                    {
                        if (nestedChapter.Link == null) continue;
                        var key = BookService.CleanContentKeys(nestedChapter.Link.ContentFileName);
                        if (mappings.ContainsKey(key))
                        {
                            nestedChapters.Add(new BookChapterItem()
                            {
                                Title = nestedChapter.Title,
                                Page = mappings[key],
                                Part = nestedChapter.Link.Anchor ?? string.Empty,
                                Children = new List<BookChapterItem>()
                            });
                        }
                    }

                    if (navigationItem.Link == null)
                    {
                        var item = new BookChapterItem()
                        {
                            Title = navigationItem.Title, 
                            Children = nestedChapters
                        };
                        if (nestedChapters.Count > 0)
                        {
                            item.Page = nestedChapters[0].Page;
                        }
                        chaptersList.Add(item);
                    }
                    else
                    {
                        var groupKey = BookService.CleanContentKeys(navigationItem.Link.ContentFileName);
                        if (mappings.ContainsKey(groupKey))
                        {
                            chaptersList.Add(new BookChapterItem()
                            {
                                Title = navigationItem.Title,
                                Page = mappings[groupKey], 
                                Children = nestedChapters
                            });
                        }
                    }
                }
            }

            if (chaptersList.Count == 0)
            {
                // Generate from TOC
                var tocPage = book.Content.Html.Keys.FirstOrDefault(k => k.ToUpper().Contains("TOC"));
                if (tocPage == null) return Ok(chaptersList);
                
                // Find all anchor tags, for each anchor we get inner text, to lower then titlecase on UI. Get href and generate page content
                var doc = new HtmlDocument();
                var content = await book.Content.Html[tocPage].ReadContentAsync();
                doc.LoadHtml(content);
                var anchors = doc.DocumentNode.SelectNodes("//a");
                if (anchors == null) return Ok(chaptersList);
                
                foreach (var anchor in anchors)
                {
                    if (anchor.Attributes.Contains("href"))
                    {
                        var key = BookService.CleanContentKeys(anchor.Attributes["href"].Value).Split("#")[0];
                        if (!mappings.ContainsKey(key))
                        {
                            // Fallback to searching for key (bad epub metadata)
                            var correctedKey = book.Content.Html.Keys.SingleOrDefault(s => s.EndsWith(key));
                            if (!string.IsNullOrEmpty(correctedKey))
                            {
                                key = correctedKey;
                            }
                        }
                        if (!string.IsNullOrEmpty(key) && mappings.ContainsKey(key))
                        {
                            var part = string.Empty;
                            if (anchor.Attributes["href"].Value.Contains("#"))
                            {
                                part = anchor.Attributes["href"].Value.Split("#")[1];
                            }
                            chaptersList.Add(new BookChapterItem()
                            {
                                Title = anchor.InnerText,
                                Page = mappings[key],
                                Part = part,
                                Children = new List<BookChapterItem>()
                            });
                        }
                    }
                }
                
            }
            return Ok(chaptersList);
        }
        
        [HttpGet("{chapterId}/book-page")]
        public async Task<ActionResult<string>> GetBookPage(int chapterId, [FromQuery] int page)
        {
            var chapter = await _unitOfWork.VolumeRepository.GetChapterAsync(chapterId);

            var book = await EpubReader.OpenBookAsync(chapter.Files.ElementAt(0).FilePath);
            var mappings = await _bookService.CreateKeyToPageMappingAsync(book);

            var counter = 0;
            var doc = new HtmlDocument();
            var baseUrl = Request.Scheme + "://" + Request.Host + Request.PathBase + "/api/";
            var apiBase = baseUrl + "book/" + chapterId + "/" + BookApiUrl;
            var bookPages = await book.GetReadingOrderAsync();
            foreach (var contentFileRef in bookPages)
            {
                if (page == counter)
                {
                    var content = await contentFileRef.ReadContentAsync();
                    if (contentFileRef.ContentType != EpubContentType.XHTML_1_1) return Ok(content);
                    
                    doc.LoadHtml(content);
                    var body = doc.DocumentNode.SelectSingleNode("/html/body");
                    
                    var inlineStyles = doc.DocumentNode.SelectNodes("//style");
                    if (inlineStyles != null)
                    {
                        foreach (var inlineStyle in inlineStyles)
                        {
                            var styleContent = await _bookService.ScopeStyles(inlineStyle.InnerHtml, apiBase);
                            body.PrependChild(HtmlNode.CreateNode($"<style>{styleContent}</style>"));
                        }
                    }
                    
                    var styleNodes = doc.DocumentNode.SelectNodes("/html/head/link");
                    if (styleNodes != null)
                    {
                        foreach (var styleLinks in styleNodes)
                        {
                            var key = BookService.CleanContentKeys(styleLinks.Attributes["href"].Value);
                            // Some epubs are malformed the key in content.opf might be: content/resources/filelist_0_0.xml but the actual html links to resources/filelist_0_0.xml
                            // In this case, we will do a search for the key that ends with
                            if (!book.Content.Css.ContainsKey(key))
                            {
                                var correctedKey = book.Content.Css.Keys.SingleOrDefault(s => s.EndsWith(key));
                                if (correctedKey == null)
                                {
                                    _logger.LogError("Epub is Malformed, key: {Key} is not matching OPF file", key);
                                    continue;
                                }

                                key = correctedKey;
                            }
                            var styleContent = await _bookService.ScopeStyles(await book.Content.Css[key].ReadContentAsync(), apiBase);
                            body.PrependChild(HtmlNode.CreateNode($"<style>{styleContent}</style>"));
                        }
                    }

                    var anchors = doc.DocumentNode.SelectNodes("//a");
                    if (anchors != null)
                    {
                        foreach (var anchor in anchors)
                        {
                            BookService.UpdateLinks(anchor, mappings, page);
                        }
                    }
                    
                    var images = doc.DocumentNode.SelectNodes("//img");
                    if (images != null)
                    {
                        foreach (var image in images)
                        {
                            if (image.Name != "img") continue;
                            
                            // Need to do for xlink:href
                            if (image.Attributes["src"] != null)
                            {
                                var imageFile = image.Attributes["src"].Value;
                                if (!book.Content.Images.ContainsKey(imageFile))
                                {
                                    var correctedKey = book.Content.Images.Keys.SingleOrDefault(s => s.EndsWith(imageFile));
                                    if (correctedKey != null)
                                    {
                                        imageFile = correctedKey;
                                    }
                                }
                                image.Attributes.Remove("src");
                                image.Attributes.Add("src", $"{apiBase}" + imageFile);
                            }
                        }
                    }
                    
                    images = doc.DocumentNode.SelectNodes("//image");
                    if (images != null)
                    {
                        foreach (var image in images)
                        {
                            if (image.Name != "image") continue;
                            
                            if (image.Attributes["xlink:href"] != null)
                            {
                                var imageFile = image.Attributes["xlink:href"].Value;
                                if (!book.Content.Images.ContainsKey(imageFile))
                                {
                                    var correctedKey = book.Content.Images.Keys.SingleOrDefault(s => s.EndsWith(imageFile));
                                    if (correctedKey != null)
                                    {
                                        imageFile = correctedKey;
                                    }
                                }
                                image.Attributes.Remove("xlink:href");
                                image.Attributes.Add("xlink:href", $"{apiBase}" + imageFile);
                            }
                        }
                    }
                    
                    
                    

                    return Ok(body.InnerHtml);
                }

                counter++;
            }

            return BadRequest("Could not find the appropriate html for that page");
        }
    }
}