#!/bin/sh

# This program is licensed under the GNU GPL version 2 or later.
# (c) Richard "RichiH" Hartmann <richih.mailinglist@gmail.com>, 2011-2013
# For details, see LICENSE. To submit patches, you have to agree to
# license your code under the GNU GPL version 2 or later.

# While the following is not legally binding, the author would like to
# explain the choice of GPLv2+ over GPLv3+.
# The author prefers GPLv3+ over GPLv2+ but feels it's better to maintain
# full compability with git. In case git ever changes its licensing terms,
# which is admittedly extremely unlikely to the point of being impossible,
# this software will most likely follow suit.

# This should always be the first line of code to facilitate debugging
[ -n "$VCSH_DEBUG" ] && set -vx

basename() {
	# Implemented in shell to avoid spawning another process
	local file
	file="${1##*/}"
	[ -z "$2" ] || file="${file%$2}"
	echo "$file"
}

SELF=$(basename $0)
VERSION='1.2'

fatal() {
	echo "$SELF: fatal: $1" >&2
	exit $2
}

# We need to run getops as soon as possible so we catch -d and other
# options that will modify our behaviour.
# Commands are handled at the end of this script.
while getopts "c:dv" flag; do
	if [ "$1" = '-d' ] || [ "$1" = '--debug' ]; then
		set -vx
		VCSH_DEBUG=1
		echo "$SELF $VERSION"
	elif [ "$1" = '-v' ];then
		VCSH_VERBOSE=1
		echo "$SELF $VERSION"
	elif [ "$1" = '-c' ];then
		VCSH_OPTION_CONFIG=$OPTARG
	fi
	shift 1
done

source_all() {
	# Source file even if it's in $PWD and does not have any slashes in it
	case "$1" in
		*/*) . "$1";;
		*)   . "$PWD/$1";;
	esac;
}


# Read configuration and set defaults if anything's not set
[ -n "$VCSH_DEBUG" ]                  && set -vx
[ -z "$XDG_CONFIG_HOME" ]             && XDG_CONFIG_HOME="$HOME/.config"

# Read configuration files if there are any
[ -r "/etc/vcsh/config" ]             && . "/etc/vcsh/config"
[ -r "$XDG_CONFIG_HOME/vcsh/config" ] && . "$XDG_CONFIG_HOME/vcsh/config"
if [ -n "$VCSH_OPTION_CONFIG" ]; then
	# Source $VCSH_OPTION_CONFIG if it can be read and is in $PWD of $PATH
	if [ -r "$VCSH_OPTION_CONFIG" ]; then
		source_all "$VCSH_OPTION_CONFIG"
	else
		fatal "Can not read configuration file '$VCSH_OPTION_CONFIG'" 1
	fi
fi
[ -n "$VCSH_DEBUG" ]                  && set -vx

# Read defaults
[ -z "$VCSH_REPO_D" ]                 && VCSH_REPO_D="$XDG_CONFIG_HOME/vcsh/repo.d"
[ -z "$VCSH_HOOK_D" ]                 && VCSH_HOOK_D="$XDG_CONFIG_HOME/vcsh/hooks-enabled"
[ -z "$VCSH_BASE" ]                   && VCSH_BASE="$HOME"
[ -z "$VCSH_GITIGNORE" ]              && VCSH_GITIGNORE='exact'


help() {
	echo "usage: $SELF <options> <command>

   options:
   -c <file>            Source file
   -d                   Enable debug mode
   -v                   Enable verbose mode

   commands:
   clone <remote> \\
         [<repo>]       Clone from an existing repository
   delete <repo>        Delete an existing repository
   enter <repo>         Enter repository; spawn new instance of \$SHELL
   help                 Display this help text
   init <repo>          Initialize a new repository
   list                 List all repositories
   list-tracked         List all files tracked by vcsh
   list-tracked-by \\
        <repo>          List files tracked by a repository
   rename <repo> \\
          <newname>     Rename repository
   run <repo> \\
       <command>        Use this repository
   upgrade <repo>       Upgrade repository to currently recommended settings
   version              Print version information
   which <substring>    Find substring in name of any tracked file
   write-gitignore \\
   <repo>               Write .gitignore.d/<repo> via git ls-files

   <repo> <git command> Shortcut to run git commands directly
   <repo>               Shortcut to enter repository" >&2
}

debug() {
	[ -n "$VCSH_DEBUG" ] && echo "$SELF: debug: $@"
}

verbose() {
	if [ -n "$VCSH_DEBUG" ] || [ -n "$VCSH_VERBOSE" ]; then echo "$SELF: verbose: $@"; fi
}

error() {
	echo "$SELF: error: $1" >&2
}

info() {
	echo "$SELF: info: $1"
}

clone() {
	init
	git remote add origin "$GIT_REMOTE"
	git config branch.master.remote origin
	git config branch.master.merge  refs/heads/master
	if [ $(git ls-remote origin master 2> /dev/null | wc -l ) -lt 1 ]; then
		info "remote is empty, not merging anything"
		exit
	fi
	git fetch
	for object in $(git ls-tree -r origin/master | awk '{print $4}'); do
		[ -e "$object" ] &&
			error "'$object' exists." &&
			VCSH_CONFLICT=1;
	done
	[ "$VCSH_CONFLICT" = '1' ] &&
		fatal "will stop after fetching and not try to merge!
  Once this situation has been resolved, run 'vcsh run $VCSH_REPO_NAME git pull' to finish cloning.\n" 17
	git merge origin/master
}

delete() {
	cd "$VCSH_BASE" || fatal "could not enter '$VCSH_BASE'" 11
	use
	info "This operation WILL DESTROY DATA!"
	files=$(git ls-files)
	echo "These files will be deleted:

$files

AGAIN, THIS WILL DELETE YOUR DATA!
To continue, type 'Yes, do as I say'"
	read answer
	[ "x$answer" = 'xYes, do as I say' ] || exit 16
	for file in $files; do
		rm -f $file || info "could not delete '$file', continuing with deletion"
	done
	rm -rf "$GIT_DIR" || error "could not delete '$GIT_DIR'"
}

enter() {
	hook pre-enter
	use
	$SHELL
	hook post-enter
}

git_dir_exists() {
	[ -d "$GIT_DIR" ] || fatal "no repository found for '$VCSH_REPO_NAME'" 12
}

hook() {
	for hook in $VCSH_HOOK_D/$1* $VCSH_HOOK_D/$VCSH_REPO_NAME.$1*; do
		[ -x "$hook" ] || continue
		verbose "executing '$hook'"
		"$hook"
	done
}

init() {
	[ ! -e "$GIT_DIR" ] || fatal "'$GIT_DIR' exists" 10
	export GIT_WORK_TREE="$VCSH_BASE"
	mkdir -p "$GIT_WORK_TREE" || fatal "could not create '$GIT_WORK_TREE'" 50
	cd "$GIT_WORK_TREE" || fatal "could not enter '$GIT_WORK_TREE'" 11
	git init
	upgrade
}

list() {
	for repo in "$VCSH_REPO_D"/*.git; do
		[ -d "$repo" ] && [ -r "$repo" ] && echo $(basename "$repo" .git)
	done
}

get_files() {
	export GIT_DIR="$VCSH_REPO_D/$VCSH_REPO_NAME.git"
	git ls-files
}

list_tracked() {
	for VCSH_REPO_NAME in $(list); do
		get_files
	done | sort -u
}

list_tracked_by() {
	use
	git ls-files | sort -u
}

rename() {
	git_dir_exists
	[ -d "$GIT_DIR_NEW" ] && fatal "'$GIT_DIR_NEW' exists" 54
	mv -f "$GIT_DIR" "$GIT_DIR_NEW" || fatal "Could not mv '$GIT_DIR' '$GIT_DIR_NEW'" 52

}

run() {
	hook pre-run
	use
	"$@"
	hook post-run
}

upgrade() {
	hook pre-upgrade
	use
	git config core.worktree     "$GIT_WORK_TREE"
	git config core.excludesfile ".gitignore.d/$VCSH_REPO_NAME"
	git config vcsh.vcsh         'true'
	[ -e "$VCSH_BASE/.gitignore.d/$VCSH_REPO_NAME" ] && git add -f "$VCSH_BASE/.gitignore.d/$VCSH_REPO_NAME"
	hook post-upgrade
}

use() {
	git_dir_exists
	export GIT_WORK_TREE="$(git config --get core.worktree)"
	export VCSH_DIRECTORY="$VCSH_REPO_NAME"
}

which() {
	for VCSH_REPO_NAME in $(list); do
		for VCSH_FILE in $(get_files); do
			echo $VCSH_FILE | grep -q "$VCSH_COMMAND_PARAMETER" && echo "$VCSH_REPO_NAME: $VCSH_FILE"
		done
	done | sort -u
}

write_gitignore() {
	use
	cd "$VCSH_BASE" || fatal "could not enter '$VCSH_BASE'" 11
	gitignores=$(for file in $(git ls-files); do
		while true; do
			echo $file; new="${file%/*}"
			[ "$file" = "$new" ] && break
			file="$new"
		done;
	done | sort -u)
	tempfile=$(mktemp) || fatal "could not create tempfile" 51
	echo '*' > "$tempfile" || fatal "could not write to '$tempfile'" 57
	for gitignore in $gitignores; do
		echo "$gitignore" | sed 's@^@!/@' >> "$tempfile" || fatal "could not write to '$tempfile'" 57
		if [ x$VCSH_GITIGNORE = x'recursive' ] && [ -d "$gitignore" ]; then
			{ echo "$gitignore/*" | sed 's@^@!/@' >> "$tempfile" || fatal "could not write to '$tempfile'" 57; }
		fi
	done
	if diff -N "$tempfile" "$VCSH_BASE/.gitignore.d/$VCSH_REPO_NAME" > /dev/null; then
		rm -f "$tempfile" || error "could not delete '$tempfile'"
		exit
	fi
	if [ -e "$VCSH_BASE/.gitignore.d/$VCSH_REPO_NAME" ]; then
		info "'$VCSH_BASE/.gitignore.d/$VCSH_REPO_NAME' differs from new data, moving it to '$VCSH_BASE/.gitignore.d/$VCSH_REPO_NAME.bak'"
		mv -f "$VCSH_BASE/.gitignore.d/$VCSH_REPO_NAME" "$VCSH_BASE/.gitignore.d/$VCSH_REPO_NAME.bak" ||
			fatal "could not move '$VCSH_BASE/.gitignore.d/$VCSH_REPO_NAME' to '$VCSH_BASE/.gitignore.d/$VCSH_REPO_NAME.bak'" 53
	fi
	mv -f "$tempfile" "$VCSH_BASE/.gitignore.d/$VCSH_REPO_NAME" ||
		fatal "could not move '$tempfile' to '$VCSH_BASE/.gitignore.d/$VCSH_REPO_NAME'" 53
}

if [ ! "x$VCSH_GITIGNORE" = 'xexact' ] && [ ! "x$VCSH_GITIGNORE" = 'xrecursive' ]; then
	fatal "'\$VCSH_GITIGNORE' must be either 'exact' or 'recursive'" 1
fi

if [ "$1" = 'clone' ]; then
	[ -z "$2" ] && fatal "$1: please specify a remote" 1
	export VCSH_COMMAND="$1"
	GIT_REMOTE="$2"
	[ -n "$3" ] && VCSH_REPO_NAME="$3" || VCSH_REPO_NAME=$(basename "$GIT_REMOTE" .git)
	export VCSH_REPO_NAME
	export GIT_DIR="$VCSH_REPO_D/$VCSH_REPO_NAME.git"
elif [ "$1" = 'version' ]; then
	echo "$SELF $VERSION"
	exit
elif [ "$1" = 'which' ]; then
	[ -z "$2" ] && fatal "$1: please specify a filename" 1
	[ -n "$3" ] && fatal "$1: too many parameters" 1
	export VCSH_COMMAND="$1"
	export VCSH_COMMAND_PARAMETER="$2"
elif [ "$1" = 'delete' ]           ||
     [ "$1" = 'enter' ]            ||
     [ "$1" = 'init' ]             ||
     [ "$1" = 'list-tracked-by' ]  ||
     [ "$1" = 'rename' ]           ||
     [ "$1" = 'run' ]              ||
     [ "$1" = 'upgrade' ]          ||
     [ "$1" = 'write-gitignore' ]; then
	[ -z $2 ]                      && fatal "$1: please specify repository to work on" 1
	[ "$1" = 'rename' -a -z "$3" ] && fatal "$1: please specify a target name" 1
	[ "$1" = 'run' -a -z "$3" ]    && fatal "$1: please specify a command" 1
	export VCSH_COMMAND="$1"
	export VCSH_REPO_NAME="$2"
	export GIT_DIR="$VCSH_REPO_D/$VCSH_REPO_NAME.git"
	[ "$VCSH_COMMAND" = 'rename' ]         && export GIT_DIR_NEW="$VCSH_REPO_D/$3.git"
	[ "$VCSH_COMMAND" = 'run' ] && shift 2
	[ "$VCSH_COMMAND" = 'write-gitignore' ]
elif [ "$1" = 'list' ] ||
     [ "$1" = 'list-tracked' ]; then
	export VCSH_COMMAND="$1"
elif [ -n "$2" ]; then
	export VCSH_COMMAND='run'
	export VCSH_REPO_NAME="$1"
	export GIT_DIR="$VCSH_REPO_D/$VCSH_REPO_NAME.git"
	[ -d $GIT_DIR ] || { help; exit 1; }
	shift 1
	set -- "git" "$@"
elif [ -n "$1" ]; then
	export VCSH_COMMAND='enter'
	export VCSH_REPO_NAME="$1"
	export GIT_DIR="$VCSH_REPO_D/$VCSH_REPO_NAME.git"
	[ -d $GIT_DIR ] || { help; exit 1; }
else
	# $1 is empty, or 'help'
	help && exit
fi

# Did we receive a directory instead of a name?
# Mangle the input to fit normal operation.
if echo $VCSH_REPO_NAME | grep -q '/'; then
	export GIT_DIR=$VCSH_REPO_NAME
	export VCSH_REPO_NAME=$(basename "$VCSH_REPO_NAME" .git)
fi


for check_directory in "$VCSH_REPO_D" "$VCSH_BASE/.gitignore.d"
do
	if [ ! -d "$check_directory" ]; then
		if [ -e "$check_directory" ]; then
			fatal "'$check_directory' exists but is not a directory" 13
		else
			info "attempting to create '$check_directory'"
			mkdir -p "$check_directory" || fatal "could not create '$check_directory'" 50
		fi
	fi
done

verbose "$VCSH_COMMAND begin"
export VCSH_COMMAND=$(echo $VCSH_COMMAND | sed 's/-/_/g')
hook pre-command
$VCSH_COMMAND "$@"
hook post-command
verbose "$VCSH_COMMAND end, exiting"