#!/bin/bash
set -e
LOADED_APT_DOWNLOAD="yes"

function check-and-download() {
	remote_file=$1
	local_file=$2
	wget -q --spider ${remote_file}
	if [ $? -eq 0 ]; then
		echo "downloading ${remote_file}"
		wget -q -N -O ${local_file} ${remote_file}
		return
	fi
	return 0
}


function apt-download-binary() {
	base_url=$1
	dist=$2
	repo=$3
	arch=$4
	dest_base_dir=$5
	
	dest_dir="${dest_base_dir}/dists/${dist}"
	[ ! -d "$dest_dir" ] && mkdir -p "$dest_dir"
	check-and-download "${base_url}/dists/${dist}/Contents-${arch}.gz" "${dest_dir}/Contents-${arch}.gz" || true
	check-and-download "${base_url}/dists/${dist}/InRelease"  "${dest_dir}/InRelease" || true
	check-and-download "${base_url}/dists/${dist}/Release" "${dest_dir}/Release"
	check-and-download "${base_url}/dists/${dist}/Release.gpg" "${dest_dir}/Release.gpg" || true

	dest_dir="${dest_base_dir}/dists/${dist}/${repo}/binary-${arch}"
	[ ! -d "$dest_dir" ] && mkdir -p "$dest_dir"

	pkgidxes=('Packages' 'Packages.gz' 'Packages.bz2' 'Packages.xz')
	pkgidx_content=""
	for pkgidx in ${pkgidxes[@]}; do
		pkgidx_file="${dest_dir}/${pkgidx}"
		pkglist_url="${base_url}/dists/${dist}/${repo}/binary-${arch}/${pkgidx}"
		check-and-download "${pkglist_url}" ${pkgidx_file} || true
		if [ -z "${pkgidx_content}" -a -f ${pkgidx_file} ]; then
			echo "getting packages index content"
			case $pkgidx in
				"*.bz2")
					pkgidx_content=`bunzip2 -c ${pkgidx_file}`
					;;
				"*.gz")
					pkgidx_content=`gunzip -c ${pkgidx_file}`
					;;
				*)
					pkgidx_content=`cat ${pkgidx_file}`
					;;
			esac
		fi
	done

	if [ -z "${pkgidx_content}" ]; then
		echo "index is empty, failed"
		return 1
	fi
	
	(echo -e "${pkgidx_content}" | grep -e '^Filename' -e '^Size' -e '^MD5sum' | cut -d' ' -f 2) | \
	while read pkg_filename; read pkg_size; read pkg_md5; do
		dest_filename="${dest_base_dir}/${pkg_filename}"
		dest_dir=`dirname ${dest_filename}`
		[ ! -d "$dest_dir" ] && mkdir -p "$dest_dir"
		pkg_url="${base_url}/${pkg_filename}"
		let downloaded="false"
		if [ -f ${dest_filename} ]; then
			rsize=`stat -c "%s" ${dest_filename}`
			if [ ${rsize} -eq ${pkg_size} ]; then
				downloaded="true"
				echo "Skipping ${pkg_filename}, size ${pkg_size}"
			fi
		fi
		while [ $downloaded != "true" ]; do
			echo "downloading ${pkg_url}"
			wget -q -O ${dest_filename} ${pkg_url} && {
				echo "${pkg_md5}  ${dest_filename}" | md5sum -c - && downloaded=true # two space for md5sum check format
			}
		done
	done

}