shopt -s extglob

_hg_commands()
{
    local commands
    commands="$("$hg" debugcomplete "$cur" 2>/dev/null)" || commands=""
    COMPREPLY=(${COMPREPLY[@]:-} $(compgen -W '$commands' -- "$cur"))
}

_hg_paths()
{
    local paths="$("$hg" paths 2>/dev/null | sed -e 's/ = .*$//')"
    COMPREPLY=(${COMPREPLY[@]:-} $(compgen -W '$paths' -- "$cur"))
}

_hg_repos()
{
    local i
    for i in $(compgen -d -- "$cur"); do
	test ! -d "$i"/.hg || COMPREPLY=(${COMPREPLY[@]:-} "$i")
    done
}

_hg_status()
{
    local files="$("$hg" status -n$1 . 2>/dev/null)"
    COMPREPLY=(${COMPREPLY[@]:-} $(compgen -W '$files' -- "$cur"))
}

_hg_tags()
{
    local tags="$("$hg" tags -q 2>/dev/null)"
    local IFS=$'\n'
    COMPREPLY=(${COMPREPLY[@]:-} $(compgen -W '$tags' -- "$cur"))
}

# this is "kind of" ugly...
_hg_count_non_option()
{
    local i count=0
    local filters="$1"

    for ((i=1; $i<=$COMP_CWORD; i++)); do
	if [[ "${COMP_WORDS[i]}" != -* ]]; then
	    if [[ ${COMP_WORDS[i-1]} == @($filters|$global_args) ]]; then
		continue
	    fi
	    count=$(($count + 1))
	fi
    done

    echo $(($count - 1))
}

_hg()
{
    local cur prev cmd opts i
    # global options that receive an argument
    local global_args='--cwd|-R|--repository'
    local hg="$1"

    COMPREPLY=()
    cur="$2"
    prev="$3"

    # searching for the command
    # (first non-option argument that doesn't follow a global option that
    #  receives an argument)
    for ((i=1; $i<=$COMP_CWORD; i++)); do
	if [[ ${COMP_WORDS[i]} != -* ]]; then
	    if [[ ${COMP_WORDS[i-1]} != @($global_args) ]]; then
		cmd="${COMP_WORDS[i]}"
		break
	    fi
	fi
    done

    if [[ "$cur" == -* ]]; then
	opts=$("$hg" debugcomplete --options "$cmd" 2>/dev/null)

	COMPREPLY=(${COMPREPLY[@]:-} $(compgen -W '$opts' -- "$cur"))
	return
    fi

    # global options
    case "$prev" in
	-R|--repository)
	    _hg_repos
	    return
	;;
	--cwd)
	    # Stick with default bash completion
	    return
	;;
    esac

    if [ -z "$cmd" ] || [ $COMP_CWORD -eq $i ]; then
	_hg_commands
	return
    fi

    # try to generate completion candidates for whatever command the user typed
    local help
    local canonical=0
    if _hg_command_specific; then
	return
    fi

    # canonicalize the command name and try again
    help=$("$hg" help "$cmd" 2>/dev/null)
    if [ $? -ne 0 ]; then
	# Probably either the command doesn't exist or it's ambiguous
	return
    fi
    cmd=${help#hg }
    cmd=${cmd%%[$' \n']*}
    canonical=1
    _hg_command_specific
}

_hg_command_specific()
{
    if [ "$cmd" != status ] && [ "$prev" = -r ] || [ "$prev" == --rev ]; then
	if [ $canonical = 1 ]; then
	    _hg_tags
	    return 0
	elif [[ status != "$cmd"* ]]; then
	    _hg_tags
	    return 0
	else
	    return 1
	fi
    fi

    case "$cmd" in
	help)
	    _hg_commands
	;;
	export|manifest|update)
	    _hg_tags
	;;
	pull|push|outgoing|incoming)
	    _hg_paths
	    _hg_repos
	;;
	paths)
	    _hg_paths
	;;
	add)
	    _hg_status "u"
	;;
	commit)
	    _hg_status "mar"
	;;
	remove)
	    _hg_status "d"
	;;
	forget)
	    _hg_status "a"
	;;
	diff)
	    _hg_status "mar"
	;;
	revert)
	    _hg_status "mard"
	;;
	clone)
	    local count=$(_hg_count_non_option)
	    if [ $count = 1 ]; then
		_hg_paths
	    fi
	    _hg_repos
	;;
	debugindex|debugindexdot)
	    COMPREPLY=(${COMPREPLY[@]:-} $(compgen -f -X "!*.i" -- "$cur"))
	;;
	debugdata)
	    COMPREPLY=(${COMPREPLY[@]:-} $(compgen -f -X "!*.d" -- "$cur"))
	;;
	*)
	    return 1
	;;
    esac

    return 0
}

complete -o bashdefault -o default -F _hg hg 2>/dev/null \
    || complete -o default -F _hg hg