#!/bin/bash
# 2010-07-19 <pille+dotVC@struction.de>
# inspired by "setup" from mnemonikk (http://mnemonikk.org/2009/03/23/finally-putting-my-personal-configuration-files-under-version-control)
#
# documentation, source & howto: http://struction.de/projects/dotVC
#
# DEPEND dirname find grep sed sort uniq basename pwd ln mv cat
# 
# $Id: dotVC,v 28:5be6849e75a6 2011-06-08 14:35 +0200 pille $



# patterns of version controll directories to ignore (space seperated, including trailing slash)
VC_PATTERNS=".hg/ .git/"

# base for version control repositories (location of this script)
VC_DIR=`dirname $0`
cd "${VC_DIR}"
VC_REPOS=`find . -maxdepth 1 -type d |grep "^\./" |sort`
SELF=`basename $0`
VC_CONFIG=".${SELF}"


# set InputFieldSeperator to \n
function setIFSnewline {
    IFS='
'
}


# set InputFieldSeperator to blank
function setIFSblank {
    IFS=' '
}

# backup the file in first parameter, if it exists by moving the original out of way
function backupIfExists() {
    filename="$1"
    if [ -e "${filename}" ]; then
	echo "target exists. backing up ${filename} to ${filename}.vc_backup first."
	mv "${filename}" "${filename}.vc_backup"
    fi
}


# create parent directory of file, if it doesn't exist already
function createParent() {
    parent_dir="$(dirname $1)"
    if [ ! -d "${parent_dir}" ]; then
	echo "creating parent directory first (${parent_dir})"
	mkdir -p "${parent_dir}"
    fi
}

# prepend appropriate amount of "../" to fix keep relative symlinks correct
function correctRelativeSymlink {
    filename="$1"
    
    c=0
    while [ ${#filename} -gt 1 ]; do
	c=$(($c+1))
	filename="$(dirname ${filename})"
    done
    
    # prepend appropriate amount of "../" to fix keep relative symlinks correct
    rel_dir_prefix=""
    for i in `seq 1 $((c-1))`; do
	rel_dir_prefix="${rel_dir_prefix}../"
    done
    
    echo ${rel_dir_prefix}
}


# try to figure out the absolute path of your .vc dirctory by keeping the shortest match and cd into
# this is hardcoded, since it cannot be determined on the fly during bootstrap.
# symlink it inside $VC_DIR
function bootstrap {
    # get absolute path to this script
    ABS_SELF="$(pwd)/${SELF}"

    # change to .vc dir
    cd `pwd |sed 's_/.vc/.*$_/.vc/_'`

    # strip absolute .vc path from absolute path of this script
    REL_SELF=`echo "${ABS_SELF}" |sed "s_$(pwd)/__"`

    echo "symlinking ${REL_SELF} to $(pwd)/${SELF}"
    backupIfExists "${SELF}"
    ln -s "${REL_SELF}" "${SELF}"

    # try to find a config file in one of the repositories.
    echo "looking for an existing .${SELF} file inside repositories."
    CONF=`find $(pwd) -type f -name ".${SELF}" |sed "s_$(pwd)/__"`
    case `echo "${CONF}" |wc -l` in
	1)	if [ "${CONF}" == "" ]; then
		    echo "WARNING: no config file could be found."
		    echo
		    echo "generate a template config using '${SELF} -t >.${SELF}' and edit it."
		    echo "place it at the same directory as your symlinked ${SELF} ($(pwd)) or"
		    echo "take advantage of checking it into ONE repository and symlinking from there."
		    echo "afterwards this step is done automatically during bootstrap on new systems."
		    echo "it's best practise to check it in as '.vc/.${SELF}', so it becomes self-contained."
		else
		    echo "found ${CONF} and symlinking it to $(pwd)/.${SELF}"
		    ln -s "${CONF}"
		fi
		;;
	*)	echo "WARNING: more than one config file was found."
		echo
		echo "you have to decide which one to symlink to $(pwd)/"
		echo "candidates are:"
		echo "${CONF}"
    esac
}


# generate config from all files found in repositories.
function generateConfigFromRepos {
    echo "# in this file you can define the mappings which file to take from which repository."
    echo "# lines starting with a hashmark (#) are ignored."
    echo "#"
    echo "# for each file there is a mapping in the following form:"
    echo "# relative/path/to/file"
    echo "# repository"
    echo "#"
    echo "# which means that the file \"relative/path/to/file\" is symlinked from the repository \"repository\""
    echo "# to the parent directory."
    echo "# if more than one repository is specified, the corresponding file is generated by concatenating"
    echo "# a combined version from all repositories in the order given."
    echo "#"
    echo "# a newline seperates single file definitions."
    echo "#"
    echo "# this file was generated to include all files from all repositories found."
    echo "# all repositories are commented out by default, so you just need to uncomment from which one to pick a file."
    echo "#"
    echo "# place this file (${VC_CONFIG}) in your $(basename $(pwd)) directory (the same as this script)"
    echo
    
    VC_FILES=`find . -mindepth 2 -type f |grep '^\./' |sed 's_^\./[^/]*/__' |sort |uniq`
    setIFSnewline
    for vc_file in ${VC_FILES}; do
	# skip files starting with VC_PATTERNS
	setIFSblank
	for vc_pattern in ${VC_PATTERNS}; do
	    vc_pattern_length=${#vc_pattern}
	    if [ "${vc_file:0:${vc_pattern_length}}" = "${vc_pattern}" ]; then continue 2; fi
	done
	
	echo "${vc_file}"
	
	# print repositories $vc_file is in
	setIFSnewline
	for vc_repo in ${VC_REPOS}; do
	    if [ -f "${vc_repo}/${vc_file}" ]; then 
		echo "#${vc_repo:2}"
	    fi
	done
	
	echo
    done
    echo "# TO AVOID PARSING ERRORS, MAKE SURE THE LAST LINE IS A COMMENT! THANKS FOR BUYING QUALITY SOFTWARE!"
}


# parse config and do symlinking/concanating based on the rules found
function generateFiles {
    if [ ! -f "${VC_CONFIG}" ]; then
	echo "ERROR: ${SELF} config file not found (${VC_CONFIG})" >&2
	echo "You can generate a template running '${SELF} generateTemplate'." >&2
	exit 2
    fi

    STATE=LookingForFile
    cat "${VC_CONFIG}" | \
	while read cfgline; do
    	    # ignore comment lines
    	    if [ "${cfgline:0:1}" = "#" ]; then continue; fi

    	    if [ "${#cfgline}" != "0" ]; then
    		if [ "${STATE}" = "LookingForFile" ]; then
    		    FILE="${cfgline}"
    		    STATE=LookingForRepository
    		    continue
    		fi

    		if [ "${STATE}" = "LookingForRepository" ]; then
		    REPOSITORY[${#REPOSITORY[@]}]=${cfgline}
		    continue
		fi
	    elif [ "${STATE}" = "LookingForRepository" ]; then
		case "${#REPOSITORY[@]}" in
		    0) 	echo "WARNING: file ${FILE} is listed in config file (${VC_CONFIG}), but without any repository." >&2
			;;
		    1)	echo "symlinking ${REPOSITORY}/${FILE} to ../${FILE}"
			if [ -e "${REPOSITORY}/${FILE}" ]; then
			    backupIfExists "../${FILE}"
			    createParent "../${FILE}"
			    
			    ln -s "$(correctRelativeSymlink ${FILE})$(basename $(pwd))/${REPOSITORY}/${FILE}" "../${FILE}"
			else 
			    echo "WARNING: ${FILE} is referenced by config from repository ${REPOSITORY} but does not exist (${REPOSITORY}/${FILE}). skipping." >&2
			    #continue
			fi
			;;
		    *)	backupIfExists "../${FILE}"
    			createParent "../${FILE}"
    			echo "concatenating files "
			setIFSnewline
    			for vc_repo in "${REPOSITORY[@]}"; do
    			    if [ -e "${vc_repo}/${FILE}" ]; then
    				echo "  ${vc_repo}/${FILE}"
    				cat "${vc_repo}/${FILE}" >> "../${FILE}"
    			    else
    				echo "WARNING: ${FILE} is referenced by config from repository ${vc_repo} but does not exist (${vc_repo}/${FILE}). skipping." >&2
				#continue
    			    fi
    			done
    			echo "to ../${FILE}"
    		esac
    	    
    		# reset parsed information for next item
    		unset FILE
    		unset REPOSITORY
    		STATE=LookingForFile
    	    fi
	done
}

case "$1" in
	"bootstrap"|"-b")		bootstrap
					;;
        "generateTemplate"|"-t")	generateConfigFromRepos
    					;;
    	"generateFiles"|"-f")		generateFiles
    					;;
        *)				echo "${SELF} <ACTION>"
    					echo "    ACTION:"
    					echo "        bootstrap (-b)           - bootstrap this script by symlinking it from the repository it's inside."
    					echo "        generateTemplate (-t)    - generate a config file template from all files found in repositories. output goes to STDOUT."
    					echo "        generateFiles    (-f)    - generate symlinks or concanate files based on the rules of config file (${VC_CONFIG})."
    					exit 1
esac