zle widgets coolness: pipe command template

[Max Mikhanosha <max@xxxxxxxxxxxx>]

Wrote my first zle widget, thought I'll share:

# define-pipe-widget <widget-name> "template1" "template2" ....
#
# Defines "pipe widget" templates. Its hard to describe the best way
# is through an example:
#
# define-pipe-widget insert_grep  "grep \"@@@\"" "grep -i \"@@@\"" "grep @@@" 
# define-pipe-widget insert_head "head" "head\n"
#
# bindkey "\M-g" insert_grep
# bindkey "\M-h" insert_head
#
# Now pressing Alt-G will insert (| represents cursor position)
#
# On empty command line: grep "|"
#
# On non-empty command line: <old cmdline> | grep "|"
#
# Pressing Alt-G one more time cycles through choices
# ie:
#  ... |  grep "|"
#  ... | grep -i "|"
#  ... | grep
#  
# If template has \n in the end, then it will be auto-accepted:
# 
#      Alt-H does: ... | head <cursor here>
#  2nd Alt-H does  ... | head<Enter>
#
declare -gA pipe_widgets
function define-pipe-widget () {
    local var=$1 
    local templates=_${var}_templates
    declare -ga $templates
    shift
    set -A $templates $@
    zle -N $var insert-pipe-command
}

insert-pipe-command () {
    emulate -L zsh
    local var=$WIDGET
    local templates=_${var}_templates
    local before after auto_accept same patnum

    set nomatch
    # see if command line is same as in our last invocation
    if [[ $CURSOR == ${pipe_widgets[cursor_$var]} 
                && $HISTNO == $pipe_widgets[histno_$var] 
                && $BUFFER == $pipe_widgets[buffer_$var] ]] ; then
        (( patnum = ++pipe_widgets[patnum_$var] ))
        # wrap around
        if [[ $patnum -gt ${#${(P)templates}}  ]] ; then
            (( patnum = pipe_widgets[patnum_$var] = 1 ))
        fi
        BUFFER=$pipe_widgets[buffer_before_$var]
        CURSOR=$pipe_widgets[cursor_before_$var]
    else
       # start from scratch
       (( patnum = pipe_widgets[patnum_$var] = 1 ))
       pipe_widgets[buffer_before_$var]=$BUFFER
       pipe_widgets[cursor_before_$var]=$CURSOR
    fi
    local tmp=${${(P)templates}[$patnum]}
    if [[ $tmp == *\\n ]] ; then
        auto_accept=1
        tmp=$tmp[1,-3]
    fi
    # cursor in the end if not specified
    if [[ $tmp != *@@@* ]] ; then
        tmp="${tmp}@@@"
    fi
    before=${tmp%@@@*}
    after=${tmp#*@@@}
    if [[ -n ${LBUFFER## *} ]] ; then
        RBUFFER+=" | "
    else
        if [[ $after == '' && $before[-1] != " " ]] ; then
            before+=" "
        fi
        auto_accept=
    fi
    RBUFFER+=$before$after
    CURSOR=$(( $#BUFFER - $#after))
    # incase we were in vi mode
    builtin zle vi-insert 
    if [[ $auto_accept == 1 ]] ; then
        builtin zle accept-line
    fi
    pipe_widgets[histno_$var]=$HISTNO
    pipe_widgets[buffer_$var]=$BUFFER
    pipe_widgets[cursor_$var]=$CURSOR
}