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BookCoverReader.cs
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BookCoverReader.cs
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#pragma warning disable // code analysis warnings have been temporarily disabled but need to be fixed in the future
using System;
using System.Collections.Generic;
using System.Linq;
using VersOne.Epub.Schema;
using VersOne.Epub.Utils;
namespace VersOne.Epub.Internal
{
internal static class BookCoverReader
{
public static EpubByteContentFileRef ReadBookCover(EpubSchema epubSchema, Dictionary<string, EpubByteContentFileRef> imageContentRefs)
{
List<EpubMetadataMeta> metaItems = epubSchema.Package.Metadata.MetaItems;
if (metaItems == null || !metaItems.Any())
{
return null;
}
EpubMetadataMeta coverMetaItem = metaItems.FirstOrDefault(metaItem => metaItem.Name.CompareOrdinalIgnoreCase("cover"));
if (coverMetaItem == null)
{
return null;
}
if (String.IsNullOrEmpty(coverMetaItem.Content))
{
throw new Exception("Incorrect EPUB metadata: cover item content is missing.");
}
EpubByteContentFileRef coverImageContentFileRef;
EpubManifestItem coverManifestItem = epubSchema.Package.Manifest.FirstOrDefault(manifestItem => manifestItem.Id.CompareOrdinalIgnoreCase(coverMetaItem.Content));
if (null != coverManifestItem?.Href && imageContentRefs.TryGetValue(coverManifestItem.Href, out coverImageContentFileRef))
{
return coverImageContentFileRef;
}
// For non-standard ebooks, we try several other ways...
if (null != coverManifestItem) // we have found the item but there was no corresponding image ...
{
// some ebooks seem to contain more than one item with Id="cover"
// thus we test if there is a second item, and whether that is an image....
coverManifestItem = epubSchema.Package.Manifest.Where(manifestItem => manifestItem.Id.CompareOrdinalIgnoreCase(coverMetaItem.Content)).Skip(1).FirstOrDefault();
if (null != coverManifestItem?.Href && imageContentRefs.TryGetValue(coverManifestItem.Href, out coverImageContentFileRef))
{
return coverImageContentFileRef;
}
}
// we have still not found the item
// 2019-08-20 Hotfix: if coverManifestItem is not found by its Id, then try it with its Href - some ebooks refer to the image directly!
coverManifestItem = epubSchema.Package.Manifest.FirstOrDefault(manifestItem => manifestItem.Href.CompareOrdinalIgnoreCase(coverMetaItem.Content));
if (null != coverManifestItem?.Href && imageContentRefs.TryGetValue(coverManifestItem.Href, out coverImageContentFileRef))
{
return coverImageContentFileRef;
}
// 2019-08-24 if it is still not found, then try to find an Id named cover
coverManifestItem = epubSchema.Package.Manifest.FirstOrDefault(manifestItem => manifestItem.Id.CompareOrdinalIgnoreCase(coverMetaItem.Name));
if (null != coverManifestItem?.Href && imageContentRefs.TryGetValue(coverManifestItem.Href, out coverImageContentFileRef))
{
return coverImageContentFileRef;
}
// 2019-08-24 if it is still not found, then try to find it in the guide
var guideItem = epubSchema.Package.Guide.FirstOrDefault(reference => reference.Title.CompareOrdinalIgnoreCase(coverMetaItem.Name));
if (null != guideItem?.Href && imageContentRefs.TryGetValue(guideItem.Href, out coverImageContentFileRef))
{
return coverImageContentFileRef;
}
throw new Exception($"Incorrect EPUB manifest: item with ID = \"{coverMetaItem.Content}\" is missing or no corresponding image was found.");
}
}
}