#!/bin/bash

EMERGE_OPTS="-1av"
EBDIR="${HOME}/.ebuild-bisect"

determine_cpv() {
	echo $(portageq best_version / "${1}")
}

determine_ebuild() {
	local cpv="${1}"
	local result=""
	local c=""
	local p=""
	local v=""

	source /etc/make.conf

	if [ ! -z "${cpv}" ];
	then
		# TODO: Find ebuilds in overlays
		c=$(qatom ${cpv} | cut -d" " -f1)
		p=$(qatom ${cpv} | cut -d" " -f2)
		v=${cpv#"${c}/${p}-"}
		for i in "/usr/portage" ${PORTDIR_OVERLAY};
		do
			if ls "${i}/${c}/${p}/${p}-${v}.ebuild" 2>/dev/null;
			then
				result="${i}/${c}/${p}/${p}-${v}.ebuild"
			fi
		done
	fi
	echo ${result}
}

determine_ebuild_scm() {
	local ebuild="${1}"
	local scms="subversion git"
	local scm=""

	for i in ${scms};
	do
		if grep inherit ${ebuild} | grep -q ${i} ;
		then
			scm="${i}"
		fi
	done
	echo "${scm}"
}

display_help() {
	echo ""
	echo "Usage: ebuild-bisect <atom> start <good> <bad>"
	echo "       ebuild-bisect <atom> good|bad <good/bad>"
	echo "       ebuild-bisect <atom>"
	echo ""
	echo "Actions:"
	echo "  start        Initializes a bisection with two starting revisions"
	echo "  good/bad     Marks the last compiled revision as good or bad"
	echo "  none         Rebuilds the current revision"
}

build_current() {
	local cpv="${1}"
	local scm="${2}"
	
	local current=$(cat ${EBDIR}/${cpv}/current)
	scm_setrev "${scm}" "${current}"
	echo "* Running emerge ${EMERGE_OPTS} =${cpv}"
	emerge "${EMERGE_OPTS}" "=${cpv}"
}

scm_git_setrev() {
	export EGIT_COMMIT="${1}"
}

scm_git_bisect() {
	local good=${1}
	local bad=${2}
	gitdir=$(cat `portageq vdb_path`/${cpv}/environment.bz2 | bunzip2 > /tmp/ebuild-bisect-git-env; source /tmp/ebuild-bisect-git-env; echo ${EGIT_STORE_DIR}/${EGIT_PROJECT})
	if ! cd ${gitdir} ;
	then
		echo "! Git support requires the git ebuild to have been compiled successfully once."
		exit 1
	fi
	echo $(git rev-list --bisect ^${good} ${bad})
}

scm_subversion_setrev() {
	export ESVN_REVISION="${1}"
}

scm_subversion_bisect() {
	local good="${1}"
	local bad="${2}"
	echo $(((${good}+${bad})/2))
}

scm_setrev() {
	# Sets the environment up for ebuild a particular revision
	echo "* Setting ${1} revision at ${2}"
	scm_${1}_setrev "${2}"
}

scm_bisect() {
	# Bisect good/bad cpv
	# Returns middle revision
	echo $(scm_${1}_bisect "${2}" "${3}" "${4}")
}

### Main Program ###

if [ -z "${1}" ];
then
	echo "! Please provide at least an ebuild name"
	display_help
	exit 2
fi
cpv=$(determine_cpv "${1}")
ebuild=$(determine_ebuild "${cpv}")
if [ ! -z "${ebuild}" ];
then
	scm=$(determine_ebuild_scm ${ebuild})
else
	echo "! No ebuild found for ${1}"
	display_help
	exit 1
fi
if [ ! -z "${scm}" ];
then
	case "${2}" in
		start)
			if [ -z "${3}" -o -z "${4}" ];
			then
				echo "! Start requires a good and bad revision"
				display_help
				exit 1
			fi
			current=$(scm_bisect "${scm}" "${3}" "${4}" "${cpv}")
			if [ ! -z "${current}" ];
			then
				echo "* Creating ${EBDIR}/${cpv}"
				rm -fr "${EBDIR}/${cpv}"
				mkdir -p "${EBDIR}/${cpv}"
				echo "${3}" > "${EBDIR}/${cpv}/good"
				echo "${4}" > "${EBDIR}/${cpv}/bad"
				echo "* Setting current to ${current}"
				echo "${current}" > "${EBDIR}/${cpv}/current"
				build_current "${cpv}" "${scm}"
			else
				echo "! SCM bisection failed"
				display_help
				exit 1
			fi
		;;
		good|bad)
			echo "* Setting ${2} <= current"
			echo $(cat ${EBDIR}/${cpv}/current) > "${EBDIR}/${cpv}/${2}"
			good=$(cat ${EBDIR}/${cpv}/good)
			bad=$(cat ${EBDIR}/${cpv}/bad)
			current=$(scm_bisect "${scm}" "${good}" "${bad}" "${cpv}")
			if [ "${current}" == "${good}" -o "${current}" == "${bad}" ];
			then
				echo "All done!"
				echo "Good revision: ${good}"
				echo "Bad revision: ${bad}"
				exit 0
			fi
			echo "* Setting current <= ${current}"
			echo "${current}" > "${EBDIR}/${cpv}/current"
			build_current "${cpv}" "${scm}"
		;;
		help)
			display_help
		;;
		*)
			# Rebuild the current ebuild
			build_current ${cpv} ${scm}
		;;
	esac
else
	echo "! Ebuild ${ebuild} not using a supported scm"
	display_help
fi