libppub/src/lib/Builder.vala

using Invercargill;
using Gee;

namespace Ppub {

    public class Builder {

        private Series<BuilderAsset> assets = new Series<BuilderAsset>();

        private uint64 position = 0;

        public void add_metadata(Metadata metadata) {
            var data = (uint8[])metadata.to_string().to_utf8();
            var mis = new MemoryInputStream.from_data(data);
            var compress = new CompressionInfo(mis);
            mis.seek(0, SeekType.SET);
            add_asset("metadata", "application/x-ppub-metadata", mis, empty<string>(), compress);
        }

        public void add_asset(string name, string mimetype, InputStream stream, Enumerable<string> flags, CompressionInfo compression) {

            lock(assets) {
                var asset = new BuilderAsset();
                asset.name = name;
                asset.start_location = position;
                asset.end_location = position + compression.size_in_ppub;
                asset.mimetype = mimetype;
                asset.stream = stream;

                // Exclude any gzip flags, as we will add that later if we are compressing the content
                asset.flags = flags.where(f => f != "gzip").to_vector();

                if(compression.compress) {
                    asset.flags.add("gzip");
                }
    
                position += compression.size_in_ppub;
                assets.add(asset);
            }

        }

        public void write(OutputStream stream) throws IOError {

            var index_entries = assets.to_string(a => a.to_string());

            print(index_entries);
            var index_data = (uint8[])index_entries.to_utf8();
            var header_data = (uint8[])(@"$(Publication.MAGIC)\n$(index_data.length)\n".to_utf8());

            stream.write(header_data);
            stream.write(index_data);

            foreach (var asset in assets) {
                if(asset.flags.any(f => f == "gzip")) {
                    var compressor = new ZlibCompressor(ZlibCompressorFormat.GZIP, 9);
                    var conv_stream = new ConverterInputStream(asset.stream, compressor);
                    stream.splice(conv_stream, OutputStreamSpliceFlags.CLOSE_SOURCE);
                }
                else {
                    stream.splice(asset.stream, OutputStreamSpliceFlags.CLOSE_SOURCE);
                }
            }

        }

    }

    public class BuilderAsset : Asset {
        
        public InputStream stream {get; set;}

    }

    public class CompressionInfo {

        public bool compress {get; private set;}
        public uint64 uncompressed_size {get; private set;}
        public uint64 compressed_size {get; private set;}

        public CompressionInfo.uncompressed(uint64 size) {
            compress = false;
            uncompressed_size = size;
        }

        public CompressionInfo(InputStream stream, CompressionPolicy policy = CompressionPolicy.AUTO) throws IOError {
            var uncompressed_counter = new InputStreamMonitor(stream);
            var compressor = new ZlibCompressor(ZlibCompressorFormat.GZIP, 9);
            var conv_stream = new ConverterInputStream(uncompressed_counter, compressor);
            var compressed_counter = new InputStreamMonitor(conv_stream);
            
            compressed_counter.count_to_end();

            uncompressed_size = uncompressed_counter.bytes_read;
            compressed_size = compressed_counter.bytes_read;

            switch (policy) {
                case CompressionPolicy.AUTO:
                    compress = uncompressed_size > compressed_size;
                    break;
                case CompressionPolicy.ALWAYS_COMPRESS:
                    compress = true;
                    break;
                case CompressionPolicy.NEVER_COMPRESS:
                    compress = false;
                    break;
            }
        }

        public uint64 size_in_ppub {
            get {
                return compress ? compressed_size : uncompressed_size;
            }
        }

    }

    public enum CompressionPolicy {
        AUTO,
        ALWAYS_COMPRESS,
        NEVER_COMPRESS
    }

    public static string guess_mimetype(string name, uint8[] sample) {
        if(name == "metadata") {
            return "application/x-ppub-metadata";
        }
        if(name.has_suffix(".ppvm")) {
            return "application/x-ppvm";
        }

        bool result_uncertain;
        var content_type = ContentType.guess(name, sample, out result_uncertain);
        var mime = ContentType.get_mime_type(content_type);

        return mime ?? "application/octet-stream";
    }

}