Add new 'menu' sub-command

New command allows to define flexible menus in INI files.

Single INI root now contains all menu definitons.  Each menu consists of
item generator, selector and consumer, which are checked and chained
together.

Alternatively to specifying a generator, items can be listed right in
the INI section.

mkit/config.ini

     src/libexec/saturnin-iam                = saturnin-iam
     src/libexec/saturnin-kb                 = saturnin-kb
     src/libexec/saturnin-ln                 = saturnin-ln
+    src/libexec/saturnin-menu               = saturnin-menu
     src/libexec/saturnin-www                = saturnin-www
 
 [files:share]

src/libexec/saturnin-menu

+#!/bin/bash
+
+. $(ffoom path)
+
+ffoo import inigrep
+ffoo import pretty
+
+usage() {
+    mkusage "[name]"
+}
+
+SATURNIN_MENU_MNAME=""
+SATURNIN_MENU_GENERATOR=""
+SATURNIN_MENU_SELECTOR=""
+SATURNIN_MENU_SELECT_ARGS=""
+SATURNIN_MENU_CONSUMER=""
+
+load_parts() {
+    #
+    # Load mandatory parts
+    #
+    local mname
+    mname=$(get_mname) || usage
+    inigrep -s menu.$mname | grep -q . \
+     || die "no such menu: $mname"
+    SATURNIN_MENU_GENERATOR="$(get_generator)"  \
+     || die "cannot find generator for menu: $mname"
+    SATURNIN_MENU_SELECTOR="$(get_selector)" \
+     || die "cannot find selector for menu: $mname"
+    SATURNIN_MENU_SELECT_ARGS="$(get_select_args)"
+    SATURNIN_MENU_CONSUMER="$(get_consumer)" \
+     || die "cannot find consumer for menu: $mname"
+}
+
+get_mname() {
+    #
+    # If not set, take from global INI default
+    #
+    test -n "$SATURNIN_MENU_MNAME" && {
+        printf '%s' "$SATURNIN_MENU_MNAME"
+        return 0
+    }
+    inigrep -1 -p menu._default_.name | grep .
+}
+
+get_generator() {
+    #
+    # Obtain and echo generator for menu $mname
+    #
+    # First, look for 'generator' key in menu definition,
+    # then for items as 'item' keys at the same place,
+    # finally default 'generator'.
+    #
+    inigrep -1 -p menu.$mname.generator | grep . \
+     && return 0
+    inigrep -p menu.$mname.item | grep -m 1 -q . \
+     && printf "inigrep -p menu.$mname.item" \
+     && return 0
+    inigrep -1 -p menu._default_.generator | grep . \
+     && return 0
+    return 1
+}
+
+get_selector() {
+    #
+    # Obtain and echo selector for menu $mname
+    #
+    # First, look for 'selector' key in menu definition,
+    # then a default 'selector'.
+    #
+    inigrep -1 -p menu.$mname.selector | grep . \
+     && return 0
+    inigrep -1 -p menu._default_.selector | grep .
+}
+
+get_select_args() {
+    #
+    # Obtain and echo selector args for menu $mname
+    #
+    # First, look for 'select_args' key in menu definition,
+    # then a default 'select_args'.
+    #
+    inigrep -1 -p menu.$mname.select_args | grep . \
+     && return 0
+    inigrep -1 -p menu._default_.select_args
+}
+
+get_consumer() {
+    #
+    # Obtain and echo consumer args for menu $mname
+    #
+    # First, look for 'consumer' key in menu definition,
+    # then a default 'consumer'.
+    #
+    inigrep -1 -p menu.$mname.consumer | grep . \
+     && return 0
+    inigrep -1 -p menu._default_.consumer | grep .
+}
+
+do_generate() {
+    #
+    # Generate menu items
+    #
+    bash -n <<<"$SATURNIN_MENU_GENERATOR" \
+     || die "syntax errors in generator: $SATURNIN_MENU_GENERATOR"
+    eval "$SATURNIN_MENU_GENERATOR"
+}
+
+do_select() {
+    #
+    # Bring up selection UI
+    #
+    bash -n <<<"$SATURNIN_MENU_SELECTOR" \
+     || die "syntax errors in selector: $SATURNIN_MENU_SELECTOR"
+    eval "$SATURNIN_MENU_SELECTOR $SATURNIN_MENU_SELECT_ARGS"
+}
+
+
+do_consume() {
+    #
+    # Process the selected item(s)
+    #
+    bash -n <<<"$SATURNIN_MENU_CONSUMER" \
+     || die "syntax errors in consumer: $SATURNIN_MENU_CONSUMER"
+    eval "$SATURNIN_MENU_CONSUMER"
+}
+
+SATURNIN_MENU_MNAME="$1"
+
+load_parts
+
+debug -v SATURNIN_MENU_MNAME \
+         SATURNIN_MENU_GENERATOR \
+         SATURNIN_MENU_SELECTOR \
+         SATURNIN_MENU_SELECT_ARGS \
+         SATURNIN_MENU_CONSUMER
+
+do_generate | do_select | do_consume