#!/bin/bash
#
#   vcsget - downloader agent that generates tarballs from VCS repos
#   @configure_input@
#
#   Copyright (c) 2012 Luke Shumaker <lukeshu@sbcglobal.net>
#
#   This program is free software; you can redistribute it and/or modify
#   it under the terms of the GNU General Public License as published by
#   the Free Software Foundation; either version 2 of the License, or
#   (at your option) any later version.
#
#   This program is distributed in the hope that it will be useful,
#   but WITHOUT ANY WARRANTY; without even the implied warranty of
#   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
#   GNU General Public License for more details.
#
#   You should have received a copy of the GNU General Public License
#   along with this program.  If not, see <http://www.gnu.org/licenses/>.
#

# gettext initialization
export TEXTDOMAIN='pacman-scripts'
export TEXTDOMAINDIR='@localedir@'

unset CDPATH

m4_include(library/output_format.sh)

##
#  usage : in_array( $needle, $haystack )
# return : 0 - found
#          1 - not found
##
in_array() {
	local needle=$1; shift
	local item
	for item in "$@"; do
		[[ $item = "$needle" ]] && return 0 # Found
	done
	return 1 # Not Found
}

usage() {
	echo "Usage: $0 <URL> <OUTPUT_TARBALL>"
	echo ""
	echo "Talks with multiple version control systems (VCSs) to create a"
	echo "tarball of a specific commit."
	echo ""
	echo "<OUTPUT_TARBALL> is a plain, uncompressed tarball. Given the same"
	echo "commit, the tarball will always have the same checksum."
	echo ""
	echo "<URL> is the repository, and possibly commit to download and tar."
	echo "The following schemes are recognized:"
	echo "  * cvs://"
	echo "  * git://"
	echo "  * git+PROTO://"
	echo "  * svn+PROTO://"
	echo "  * bzr://"
	echo "  * hg+PROTO://"
	echo ""
	echo "URLs to be consumed by $0 are not always in the format of the"
	echo "relevent VCS program, but normalized to proper URLs. Simply, this"
	echo "means:"
	echo ""
	echo "    scheme://[authinfo@]host[:port]/path[#fragment]"
	echo ""
	echo "Where <authinfo> is in the format \"username[:password]\" and"
	echo "<fragment> is the commit ID, branch, or tag to be returned."
}

##
# Get the column "$2" from the space-delimited string "$1".
# This has the advantage over `set -- $1` and `arr=($1)` that it separates on
# a single space, instead of '\s+', which allows it to have empty columns.
##
get_field() {
	local str=$1
	local i=$2
	echo "$str"|cut -d' ' -f $i
}

##
# Parse a URL into parts, according to RFC 3986, "URI Generic Syntax".
# Sets the variables `scheme`, `authority`, `path`, `query` and `fragment`.
##
parse_url() {
	local url=$1

	# This regex is copied from RFC 3986
	local regex='^(([^:/?#]+):)?(//([^/?#]*))?([^?#]*)(\?([^#]*))?(#(.*))?'
	local parts=$(echo "$url"|sed -r "s@$regex@\2 \4 \5 \7 \9@")

	scheme=$(   get_field "$parts" 1)
	authority=$(get_field "$parts" 2)
	path=$(     get_field "$parts" 3)
	query=$(    get_field "$parts" 4)
	fragment=$( get_field "$parts" 5)
}

##
# Parse an authority from a URL.
# Sets the variables `user`, `pass`, `sock`, `host` and `port`.
# `sock` is socket, which is defined as `hostport` in the RFC.
##
parse_authority() {
	local authority=$1

	local regex='^(([^:]*)(:([^@]*))?@)?(([^:]+)(:([0-9]*))?)'
	#             12      3 4           56      7 8
	# 1 = userinfo@
	# 2 = user
	# 3 = :pass
	# 4 = pass
	# 5 = hostport
	# 6 = host
	# 7 = :port
	# 8 = port
	local parts=$(echo "$authority"|sed -r "s%$regex%\2 \4 \5 \6 \8%")
	user=$(get_field "$parts" 1)
	pass=$(get_field "$parts" 2)
	sock=$(get_field "$parts" 3)
	host=$(get_field "$parts" 4)
	port=$(get_field "$parts" 5)
}

download_cvs() {
	# TODO
	error "$(gettext 'CVS not implemented')"
	exit 1
}

download_git() {
	msg "$(gettext 'Getting source from git')"
	: ${fragment:=master} # default to 'master' if not set
	send_url="${scheme#git+}://${authority}${path}"

	# Where to checkout the code to
	dir="$basedir/git/$send_url"
	if [[ "${dir##*.}" != git ]]; then
		dir="${dir}/.git"
	fi

	# Download
	if [ ! -d "$dir" ]; then
		msg2 "$(gettext 'doing initial clone')"
		mkdir -p "$dir"
		git clone --bare "$send_url" "$dir"
	fi

	cd "$dir"
	refs=($(git show-ref|sed 's@.*/@@'|sort -u))
	if in_array "$fragment" "${refs[@]}"; then
		# The ref is symbolic, so it may have changed upstream
		msg2 "$(gettext 'fetching updates')"
		git fetch --all
	fi

	# Generate tarball
	archive=(git archive --format=tar --prefix="$base/"
		"$fragment" -o "$tarball")
	msg2 "$(gettext 'trying to generate tarball')"
	if "${archive[@]}" 2>/dev/null; then
		# success
		msg2 "$(gettext 'success')"
		exit 0
	else
		# the relevent commit is probably newer than we have
		msg2 "$(gettext 'failure, forcing an update')"
		git fetch --all
		msg2 "$(gettext 'generating tarball')"
		"${archive[@]}"
		local s=$?
		exit $?
	fi
}

download_svn() {
	msg "$(gettext 'Getting source from Subversion')"
	parse_authority "$authority"
	send_url="${scheme#svn+}://${sock}${path}"
	args=('--config-dir' "$basedir/svn/.config")
	if [ -n "$user" ]; then
		args+=('--username' "$user")
	fi
	if [ -n "$pass" ]; then
		args+=('--password' "$pass")
	fi
	if [ -n "$fragment" ]; then
		args+=('-r' "$fragment")
	fi

	# Where to checkout the code to
	dir="$basedir/svn/$send_url#$fragment"

	# Download
	if [ ! -d "$dir" ]; then
		mkdir -p "$dir"
		svn co "${args[@]}" "$send_url" "$dir"
	else
		cd "$dir"
		svn up "${args[@]}"
	fi

	# Generate tarball
	mkdir "$dir.tmp$$"
	cp -r "$dir" "$dir.tmp$$/$base"
	find "$dir.tmp$$/$base" -name .svn -exec rm -rf '{}' +
	cd "$dir.tmp$$"
	bsdtar cf "$tarball" "$base"
	rm -rf "$dir.tmp$$"
}

download_bzr() {
	# TODO finish bzr support
	error "$(gettext 'Bazaar not implemented')"
	exit 1

	send_url="${url%%#*}"
	if [ "$scheme" != 'bzr+ssh' ]; then
		send_url="${send_url#bzr+}"
	fi

	dir="$basedir/bzr/$send_url"

	# Download
	if [ ! -d "$dir" ]; then
		msg2 "$(gettext 'doing initial checkout')"
		mkdir -p "$dir"
		bzr checkout "$send_url" "$dir"
	fi

	cd "$dir"
	bzr update

	# Generate tarball
}

download_hg() {
	msg "$(gettext 'Getting source from Mercurial')"
	send_url="${url#hg+}"
	hg clone -U "$send_url"
	dir="$basedir/hg/${send_url%%#*}"

	# Download
	if [ ! -d "$dir" ]; then
		mkdir -p "$dir"
		hg clone "$send_url" "$dir"
	else
		cd "$dir"
		hg update -r "$fragment"
	fi

	# Generate tarball
	mkdir "$dir.tmp$$"
	cp -r "$dir" "$dir.tmp$$/$base"
	rm -rf "$dir.tmp$$/$base/.hg"
	cd "$dir.tmp$$"
	bsdtar cf "$tarball" "$base"
	rm -rf "$dir.tmp$$"
}

main() {
	url=$1
	tarball=$(readlink -m "$2")

	base="${tarball##*/}"
	base="${base%%.*}"
	basedir="${tarball%/*}/vcs-cache"

	if ( in_array '-h' "$@" || in_array '--help' "$@" ); then
		usage
		exit 0
	fi
	if [ "$#" -ne 2 ]; then
		usage
		exit 1
	fi

	msg "$(printf "$(gettext "Saving '%s' to '%s'")" "$url" "$tarball")"

	parse_url "$url"
	case "$scheme" in
		cvs) download_cvs;;
		git+*|git) download_git;;
		svn+*) download_svn;;
		bzr) download_bzr;;
		hg+*) download_hg;;
		*)
			error "$(gettext 'Unable to match a VCS with scheme'): $scheme"
			exit 1;;
	esac
}

main "$@"