#!/bin/bash

abort() {
	echo $1
	exit 1
}

cmd="$1"
shift

USAGE="usage: zit COMMAND FILE [ARGS...]"

zit_help() {
	cmd="$1"
	shift
	case $cmd in
		git)
		git help "$@"
		;;
		*)
		echo $USAGE
		echo ""
		echo "Set up a git repository under .zit.FILE to track changes for FILE."
		echo "File must be a regular file and in the current directory."
		echo ""
		echo "Zit commands:"
		echo "   init		Synonym for track"
		echo "   list		Synonym for tracked"
		echo "   track	Start tracking changes to FILE"
		echo "   tracked	List tracked files in current directory"
		echo ""
		echo "See 'zit help git' or 'git help' for git commands."
		;;
	esac
}

ZIT_DIR=.zit

zit_setup() {
	ZIT_FILE="$1"
	test $ZIT_FILE || abort "Please specify a file"
	test -f $ZIT_FILE || abort "No such file $ZIT_FILE"
	test $ZIT_FILE = "`basename $ZIT_FILE`" || abort "Sorry, Zit only works on files in the current directory"

	export GIT_WORK_TREE="`pwd`"

	# first, check if a repo exists already, looking for
	# .zit/file.git or .file.git, in that order
	# if neither is found, and .zit exists, set the repo dir
	# to .zit/file.git, otherwise set it to .file.git
	GIT_DIR="$ZIT_DIR/$ZIT_FILE.git"
	if ! test -d "$GIT_DIR"; then
		GIT_DIR=".$ZIT_FILE.git"
		if ! test -d "$GIT_DIR"; then
			test -d "$ZIT_DIR" && GIT_DIR="$ZIT_DIR/$ZIT_FILE.git"
		fi
	fi
	export GIT_DIR
}

zit_init() {
	if test "$1"; then
		zit_setup $1
		test -e $GIT_DIR && abort "$GIT_DIR exists, is $ZIT_FILE tracked already?"
		mkdir $GIT_DIR && echo "Initializing Zit repository in $GIT_DIR"
		test -d $GIT_DIR || abort "Failed to create $GIT_DIR"
		git init || abort "Failed to initialize Git repository in $GIT_DIR" 
		rm -rf $GIT_DIR/{hooks,info,branches,refs/tags,objects/pack,description}
		ZIT_IGNORE="$HOME/.zitignore"
		if ! test -f "$ZIT_IGNORE"; then
			touch "$ZIT_IGNORE" || abort "Cannot create $ZIT_IGNORE file"
			echo "# Ignore patterns used by Zit repositories" > "$ZIT_IGNORE"
			echo "# By default it's the single '*' glob, since we want to ignore all" >> $ZIT_IGNORE
			echo "# non-tracked files in the work-tree" >> $ZIT_IGNORE
			echo "*" >> $ZIT_IGNORE
		fi
		git config core.excludesfile "$ZIT_IGNORE"
		git add -f $ZIT_FILE || abort "Failed to add $ZIT_FILE"
		git commit "$@" || abort "Failed to make first commit for $ZIT_FILE"
	else
		if test -d "$ZIT_DIR"; then
			echo "$ZIT_DIR exists already"
			exit
		fi
		test -e $ZIT_DIR && abort "$ZIT_DIR exists but it's not a directory, cannot continue"
		mkdir $ZIT_DIR
	fi
}

zit_list() {
	export GIT_WORK_TREE="`pwd`"
	GIT_DIR=""
	for file in "$ZIT_DIR"/*.git .*.git; do
		if ! test -e $file; then
			continue
		fi
		export GIT_DIR="$file"
		file="${file#.}"
		file="${file#zit/}"
		file="${file%.git}"
		# TODO show actual file status
		git ls-files -t $file
	done;
	# if $GIT_DIR is empty, no files were found
	test "$GIT_DIR" || echo "(no files tracked by zit)"
}

case $cmd in
	"")
	echo $USAGE
	;;
	help)
	zit_help "$@"
	;;
	init|track)
	zit_init $1
	;;
	list|tracked)
	zit_list
	;;
	# Most commands will work with the generic catch-all mechanism used
	# below, but some of them require a more thorough analysis of the
	# parameters to decide whether $ZIT_FILE should be put back into the
	# parameter list or not. For example,
	# $ zit commit somefile
	# wouldn't do what one expects it to do, unless 'add' is run first,
	# (except that
	# $ zit add somefile
	# wouldn't work either), however
	# $ zit commit somefile -a
	# would work correctly. So we handle some commands separately (for the
	# moment just add and commit)
	add|commit)
	zit_setup $1
	shift
	git $cmd "$@" "$ZIT_FILE"
	;;
	# the raw<command> method can be used to not replicate $ZIT_FILE in the
	# parameter list
	raw*)
	zit_setup $1
	shift
	git ${cmd#raw} "$@"
	;;
	*)
	zit_setup $1
	shift
	git $cmd "$@"
	;;
esac