epub.sh

#!/opt/homebrew/bin/bash -

shopt -s nullglob
shopt -s extglob
shopt -s globstar

cd "$(dirname "$0")"
if [ ! -f rsa.key ]; then
    exit 1
fi

mkdir -p books
cd books

for bookzip in *.zip; do
    book="$(basename "$bookzip" .zip)"

    if [ ! -d "$book" ]; then
        mkdir -p "$book"
        unzip "$bookzip" -d "$book"
        rm "$bookzip"
    fi

    if [ ! -f "$book"/META-INF/encryption.xml ]; then
        continue
    fi
    pushd "$book"

    [ -d moo_extra/ ] && rm -r moo_extra/

    ek="$(base64 -d -i ../"$book".key | openssl pkeyutl -decrypt -inkey "$(dirname "$0")"/rsa.key | xxd -p -c 256)"
    opf="$(xmllint --xpath 'string(//*[name()="rootfile"]/@full-path)' META-INF/container.xml)"

    bookid="$(xmllint --xpath 'string(//*[name()="dc:identifier"][@id="'"$(xmllint --xpath 'string(/*[name()="package"]/@unique-identifier)' "$opf")"'"])' "$opf")"
    title="$(xmllint --xpath 'string(//*[name()="dc:title"])' "$opf")"

    i=0
    while true; do
        i=$((i + 1))
        xml="$(xmllint --xpath '//*[name()="EncryptedData"]['"$i"']' META-INF/encryption.xml 2>/dev/null)"
        [ "$xml" ] || break

        file="$(xmllint --xpath 'string(//*[name()="CipherReference"]/@URI)' - <<<"$xml")"
        file="$(printf '%b' "${file//%/\\x}")"
        [ ! -f "$file" ] && continue
        echo ... "$file"

        algorithm="$(xmllint --xpath 'string(//*[name()="EncryptionMethod"]/@Algorithm)' - <<<"$xml")"
        if [ "$algorithm" = 'http://www.idpf.org/2008/embedding' ]; then
            "$(dirname "$0")"/embedding.py "$file" "$bookid" >"$file".plain
            mv "$file".plain "$file"

        else
            method="$(xmllint --xpath 'string(//*[name()="Compression"]/@Method)' - <<<"$xml")"
            length="$(xmllint --xpath 'string(//*[name()="Compression"]/@OriginalLength)' - <<<"$xml")"

            iv="$(head -c16 "$file" | xxd -p)"
            tail -c+17 "$file" | openssl enc -aes256 -d -K "$ek" -iv "$iv" -nopad -out "$file".plain
            if [ "$method" -eq 8 ]; then
                cat <(printf "\x1f\x8b\x08\x00\x00\x00\x00\x00\x00\x00") "$file".plain | gzip -dc >"$file" 2>/dev/null
                size="$(stat -c %s "$file")"
                if [ "$size" != "$length" ]; then
                    echo "$size" != "$length"
                    exit 1
                fi
            else
                head -n"$length" "$file".plain >"$file"
            fi
            rm "$file".plain
        fi
    done

    sed -E -i -e 's/ class="moofs([0-9]+|NaN) moolh([0-9]+|NaN)( non-moofont)?"//g' **/*.xhtml
    sed -E -i -e 's/ class="(([^"]+) )?moofs([0-9]+|NaN) moolh([0-9]+|NaN)( non-moofont)?"/ class="\2"/g' **/*.xhtml
    sed -E -i -e 's/<meta name="moo_white_margins" content="[^"]+"\/>//g' **/*.xhtml
    sed -E -i -e 's/<meta content="Bisheng [0-9.]+" name="moo[^"]+"\/>//' "$opf"
    if [ -d moo_extra ]; then
        sed -E -i -e 's/<item href="\.\.\/moo_extra\/[^>]+\/>//g' "$opf"
        rm -r moo_extra
    fi

    rm META-INF/encryption.xml
    rm ../"$book".key

    zip -9 -X -r ../"$book"\ "${title//\//_}".epub mimetype !(mimetype)
    popd
    rm -r "$book"
done