#!/bin/bash
set -e

if [[ $# -ne 2 || "$1" == '-h' || "$1" == '--help' ]]
then
	echo 'Lists all relevant files in a Debian-style repository' >&2
	echo >&2
	echo 'Usage: deb-repo-ls ARCHIVEROOT DISTRIBUTION' >&2
	exit 1
fi

archiveRoot="$1"
distribution="$2"

while [[ "${archiveRoot}" == */ ]]; do archiveRoot="${archiveRoot%/}"; done  # Strip trailing slashes since they're added again manually below
if [[ "${distribution}" == */ || "${distribution}" == /* ]]; then echo "Invalid distribution" >&2; exit 1; fi

declare -i fetchedSize
declare -i totalSize=0

pipe=$(mktemp -u); mkfifo "${pipe}"; exec 3<>"${pipe}"; rm "${pipe}"; unset pipe  # For fetch size

function maybe_decompress {
	url="$1"
	if [[ "${url}" == *'.gz' ]]
	then
		gunzip
	elif [[ "${url}" == *'.bz2' ]]
	then
		bunzip2
	elif [[ "${url}" == *'.xz' ]]
	then
		unxz
	else
		# Peek at the data to see if it's compressed
		beginning="$(head -c 10 | xxd -p)"
		{
			xxd -p -r <<<"${beginning}"
			cat
		} | {
			if [[ "${beginning}" == '1f8b'* ]]
			then
				gunzip
			elif [[ "${beginning}" == '425a68'??'314159265359'* ]]
			then
				bunzip2
			elif [[ "${beginning}" == 'fd377a585a00'* ]]
			then
				unxz
			else
				cat
			fi
		}
	fi
}

function fetch_and_print {
	url="$1"
	# Fetch url, print it to stdout; as side effects, the HTTP body is stored in fetchedBody and its size is added to totalSize
	# If the url ends with .gz, it's gunzipped; if it ends in .bz2, it gets bunzip2'd. The totalSize reflects the compressed size.
	echo "Fetching ${url}" >&2
	fetchedBody="$(curl -A 'Debian APT-HTTP/1.3 (1.8.2)' -s "${url}" | tee >(wc -c >&3) | maybe_decompress "${url}")"
	echo "${url}"
	#totalSize+=$(LANG=C; LC_ALL=C; echo ${#fetchedBody})
	totalSize+=$(head -1 <&3)
}

function head_and_print {
	url="$1"
	# Issue a HEAD request on url, print it to stdout, and add its content length to totalSize
	echo "Heading ${url}" >&2
	declare -i contentLength="$(curl -A 'Debian APT-HTTP/1.3 (1.8.2)' -s --head "${url}" | grep -i '^Content-Length: ' | awk '{print $2}' | tr -d '\r')"
	echo "${url}"
	totalSize+=${contentLength}
}

# Retrieve Release and accompanying files, parse it and extract the next level
fetch_and_print "${archiveRoot}/dists/${distribution}/Release"
inHashSection=
declare -A files  # filename -> size
while IFS='' read -r line
do
	if [[ "${line}" == 'MD5Sum:' || "${line}" == 'SHA1:' || "${line}" == 'SHA256:' || "${line}" == 'SHA512:' ]]
	then
		inHashSection=1
		continue
	fi
	if [[ "${line}" != ' '* ]]
	then
		inHashSection=
		continue
	fi
	if [[ "${inHashSection}" ]]
	then
		files["$(awk '{print $3}' <<<"${line}")"]="$(awk '{print $2}' <<<"${line}")"
	fi
done <<<"${fetchedBody}"

head_and_print "${archiveRoot}/dists/${distribution}/Release.gpg"
head_and_print "${archiveRoot}/dists/${distribution}/InRelease"

# Process files
filename=
declare -i size=-1
declare -A debfiles  # filename -> size
for fn in "${!files[@]}"
do
	# Legacy releases
	if [[ "${fn}" =~ /Release$ ]]
	then
		echo "${archiveRoot}/dists/${distribution}/${fn}"
		totalSize+="${files[$fn]}"

	# Package indices
	elif [[ "${fn}" =~ /Packages(\.[^/]*)?$ ]]
	then
		echo "Processing package: ${fn}" >&2
		fetch_and_print "${archiveRoot}/dists/${distribution}/${fn}"
		filename=
		size=-1
		while IFS= read -r line
		do
			if [[ "${line}" == '' ]]
			then
				filename=
				size=-1
			elif [[ "${line}" == 'Filename: '* ]]
			then
				filename="${line:10}"
			elif [[ "${line}" == 'Size: '* ]]
			then
				size="${line:6}"
			fi
			if [[ "${filename}" && ${size} -ge 0 ]]
			then
				debfiles["${archiveRoot}/${filename}"]=${size}
				filename=
				size=-1
			fi
		done <<<"${fetchedBody}"

	# Contents indices
	elif [[ "${fn}" =~ /Contents-[^/]*$ ]]
	then
		# Nothing really to do here but take note of its existence
		echo "${archiveRoot}/dists/${distribution}/${fn}"
		totalSize+="${files[$fn]}"

	# Anything else
	else
		echo "${archiveRoot}/dists/${distribution}/${fn}"
		totalSize+="${files[$fn]}"
		echo "Skipping unknown file: ${fn}" >&2
	fi
done

# Print the debfiles and add them to the total size
for debfile in "${!debfiles[@]}"
do
	echo "${debfile}"
	totalSize+="${debfiles[$debfile]}"
done

# Report total size to stderr
echo "Total size: ${totalSize} bytes" >&2