Download all the books from a talebook website. The https://curl.se/ and https://stedolan.github.io/jq/ are required for using this script.

download_talebook.sh

#!/usr/bin/env bash

# Download metadata, modify these as your needs.
## The directory to save the downloaded files.
download_directory="/volume1/Download/EPUB"
## The website you want to visit.
calibre_site="http://soulseeker.myds.me:25788"
## The formats you want to download. We only download the first present format.
## All the formats should be upper case.
allow_formats=( EPUB MOBI AZW3 )

################################################################
#
#  Don't modify the scripts below.
#
################################################################

## Clean up the user provided variables.
download_directory=${download_directory%/}
calibre_site=${calibre_site%/}

## Variables when execute the script.
minimal_size=10240
index_file="$download_directory/startIndex"
cookie_file="$download_directory/cookie.txt"
start=0
end=0

register_account() {
    echo "Start register account on site <$calibre_site>"

    read -p "Enter the username: " username

    times=0
    while [ $times -eq 0 ] || [ "$password" != "$repassword" ];
    do
        if [ $times -gt 0 ]; then
            echo "The two password didn't match. Please try again"
        fi
        read -sp "Enter the password: " password
        echo ""
        read -sp "Enter the password (again): " repassword
        echo ""

        times=$((times + 1))
    done

    read -p "Enter the nickname: " nickname
    read -p "Enter the email: " email

    ## Register account
    curl -X POST -d "username=$username" -d "password=$password" -d "nickname=$nickname" -d "email=$email" $calibre_site/api/user/sign_up

    ## Jump to account login.
    echo "Successful registered account, jump to login."
    login_account
}

login_account() {
    touch $cookie_file

    read -p "Enter your username, please: " username
    read -sp "Enter your password, please: " password
    echo ""

    curl -c - --silent --output /dev/null -X POST -d "username=$username" -d "password=$password" "$calibre_site/api/user/sign_in" > $cookie_file
    echo "Get cookie from $calibre_site:"
    echo ""
    echo "`cat $cookie_file`"
    echo ""
    echo ""
}

loading_cookie() {
    while true; do
        read -p "Do you have account for <${calibre_site}>? [Y/n] " have_account
        have_account=${have_account:-y}

        case $have_account in
            [Yy]* ) login_account; break;;
            [Nn]* ) register_account; break;;
            * ) echo "Please answer y or n.";;
        esac
    done
}

query_start_index() {
    if [ ! -f "$index_file" ]; then
        touch $index_file
        echo 1 > $index_file
    fi

    start=$(cat $index_file)
    echo "Start to download from $start"
}

query_maximum_index() {
    end=`curl -b $cookie_file -c $cookie_file "$calibre_site/api/recent" | jq '.books[0].id'`
    echo "The last book id is $end"
}

download_file() {
    ## Receive arguments.
    file_id=$1
    file_format=$2

    ## Generate file path and download link.
    file_path=$download_directory/$file_id.$(echo "$file_format" | awk '{print tolower($0)}')
    file_url=$calibre_site/api/book/$file_id.$file_format

    ## Download file.
    echo "Start downloading $file_url"
    curl -b $cookie_file -c $cookie_file "$file_url" --output "$file_path"
    echo "Finish download $file_url"

    ## Remove the file which could be too small (in lower condition).
    file_size=`ls -l $file_path | awk '{print  $5}'`
    if [ $file_size -lt $minimal_size ]; then
        echo "$file_path is a blank file, remove it."
        rm -rf $file_path
    fi
}

try_download_file() {
    echo "Try to query file info from <$calibre_site>"

    file_id=$1
    file_info=`curl -b $cookie_file -c $cookie_file "$calibre_site/api/book/$file_id"`
    exists=`jq -r '.err' <<< "$file_info"`

    if [ "$exists" == "ok" ]; then
        ## Find the available format one by one.
        for format in "${allow_formats[@]}"
        do
            echo "Try to find $format format for book $file_id."

            format_info=`jq -r ".book.files[] | select(.format | contains(\"$format\"))" <<< "$file_info"`
            if [ -z "$format_info" ]; then
                echo "Couldn't find $format format for book $file_id"
            else
                download_file $file_id $format
                break
            fi
        done
    else
        echo "Error in query file formats, message: $exists"
    fi
}

# The beginning of the script logic.

## Check the required command line tools.
command -v curl >/dev/null 2>&1 || { echo >&2 "Require curl but it's not installed. Aborting."; exit 1; }
command -v jq >/dev/null 2>&1 || { echo >&2 "Require https://stedolan.github.io/jq/ but it's not installed. Aborting."; exit 1; }

## Load the cookie.
loading_cookie

## Query the start index from cache.
query_start_index

## Query the stop index from website.
query_maximum_index

for((i=$start;i<=$end;i++));
do
    ## Try to download file from allowed formats.
    try_download_file $i

    ## Record file id to index file.
    echo $i > $index_file
done