#!/bin/bash

if [ -z "$1" -o ! -d "$1" ]; then
    echo "Usage: $0 <top-directory> [<days ago>]" 1>&2
    exit 1
fi

top="${1}"
shift

source "${top}/etc/settings.sh"
tmp="$(mktemp -d)"
cd "${tmp}"

browser="Mozilla/4.76 [de] (X11; U; Linux 2.2.18 i586)"
newn="${day}.png"

wget ${wget_args} -U "$browser" http://www.xkcd.com -O index.html

url=$(grep -A 1 "Image URL" index.html | sed 'N;s/.*\(http.*png\)<\?.*/\1/')
imgname=$(echo "$url" | tr '/' '\n' | tail -1)

# get additional information
img_tag=$(grep -A2 "src=\"${url}" index.html | sed 'N;N;s/.*\(<img [^>]\+>\).*/\1/')
title=$(sed 's/.*title="\([^"]*\)".*/\1/'<<< $img_tag)
alt=$(sed 's/.*alt="\([^"]*\)".*/\1/'<<< $img_tag)

if [ ! -s "${image_dir}/$newn" ]; then
    # no image availalable for current date

    if ! grep -q "${url}" "${state_file}" >/dev/null; then
        # new image
        echo $url > "${state_file}"

        wget ${wget_args} -U "$browser" -O "${tmp}/${newn}" \
            --header="Referer: http://www.xkcd.com/" "$url"

        if [ -s "${tmp}/${newn}" ]; then
            # save
            mv "${tmp}/${newn}" "${image_dir}/$newn"
            echo "$title" > "${image_dir}/${day}.title"
            echo "$alt" > "${image_dir}/${day}.alt"

            # update symlinks
            rm -f "${comic_dir}/latest.png" "${comic_dir}/latest.title" "${comic_dir}/latest.alt"
            ln -s "${image_offset}/$newn" "${comic_dir}/latest.png"
            ln -s "${image_offset}/${day}.title" "${comic_dir}/latest.title"
            ln -s "${image_offset}/${day}.alt" "${comic_dir}/latest.alt"
        fi
    fi
fi

rm -rf ${tmp}