= Cri =

link:http://rubygems.org/gems/cri[image:http://img.shields.io/gem/v/cri.svg[]]
link:https://travis-ci.org/ddfreyne/cri[image:http://img.shields.io/travis/ddfreyne/cri.svg[]]
link:https://coveralls.io/r/ddfreyne/cri[image:http://img.shields.io/coveralls/ddfreyne/cri.svg[]]
link:https://codeclimate.com/github/ddfreyne/cri[image:http://img.shields.io/codeclimate/github/ddfreyne/cri.svg[]]
link:http://inch-ci.org/github/ddfreyne/cri/[image:http://inch-ci.org/github/ddfreyne/cri.svg[]]

Cri is a library for building easy-to-use command-line tools with support for
nested commands.

== Requirements ==

Cri requires Ruby 2.1 or newer.

== Usage ==

The central concept in Cri is the _command_, which has option definitions as
well as code for actually executing itself. In Cri, the command-line tool
itself is a command as well.

Here’s a sample command definition:

[source,ruby]
--------------------------------------------------------------------------------
command = Cri::Command.define do
  name        'dostuff'
  usage       'dostuff [options]'
  aliases     :ds, :stuff
  summary     'does stuff'
  description 'This command does a lot of stuff. I really mean a lot.'

  flag   :h,  :help,  'show help for this command' do |value, cmd|
    puts cmd.help
    exit 0
  end
  flag   nil, :more,  'do even more stuff'
  option :s,  :stuff, 'specify stuff to do', argument: :required

  run do |opts, args, cmd|
    stuff = opts.fetch(:stuff, 'generic stuff')
    puts "Doing #{stuff}!"

    if opts[:more]
      puts 'Doing it even more!'
    end
  end
end
--------------------------------------------------------------------------------

To run this command, invoke the `#run` method with the raw arguments. For
example, for a root command (the command-line tool itself), the command could
be called like this:

[source,ruby]
--------------------------------------------------------------------------------
command.run(ARGV)
--------------------------------------------------------------------------------

Each command has automatically generated help. This help can be printed using
`Cri::Command#help`; something like this will be shown:

--------------------------------------------------------------------------------
usage: dostuff [options]

does stuff

    This command does a lot of stuff. I really mean a lot.

options:

    -h --help      show help for this command
       --more      do even more stuff
    -s --stuff     specify stuff to do
--------------------------------------------------------------------------------

=== General command metadata ===

Let’s disect the command definition and start with the first five lines:

[source,ruby]
--------------------------------------------------------------------------------
name        'dostuff'
usage       'dostuff [options]'
aliases     :ds, :stuff
summary     'does stuff'
description 'This command does a lot of stuff. I really mean a lot.'
--------------------------------------------------------------------------------

These lines of the command definition specify the name of the command (or the
command-line tool, if the command is the root command), the usage, a list of
aliases that can be used to call this command, a one-line summary and a (long)
description. The usage should not include a “usage:” prefix nor the name of
the supercommand, because the latter will be automatically prepended.

Aliases don’t make sense for root commands, but for subcommands they do.

=== Command-line options ===

The next few lines contain the command’s option definitions:

[source,ruby]
--------------------------------------------------------------------------------
flag   :h,  :help,  'show help for this command' do |value, cmd|
  puts cmd.help
  exit 0
end
flag   nil, :more,  'do even more stuff'
option :s,  :stuff, 'specify stuff to do', argument: :required
--------------------------------------------------------------------------------

Options can be defined using the following methods:

* `Cri::CommandDSL#option` or `Cri::CommandDSL#opt`
* `Cri::CommandDSL#flag` (implies no arguments passed to option)
* `Cri::CommandDSL#required` (implies required argument)
* `Cri::CommandDSL#optional` (implies optional argument)

All these methods take these arguments:

1. a short option
2. a long option
3. a description
4. optional extra parameters

Either the short or the long form can be nil, but not both (because that
would not make any sense). In the example above, the `--more` option has no
short form.

Each of the above methods also take a block, which will be executed when the
option is found. The argument to the block are the option value (`true` in
case the option does not have an argument) and the command.

==== Options with default values ====

The `:default` parameter sets the option value that will be used if no explicit value is provided:

[source,ruby]
--------------------------------------------------------------------------------
optional :a, :animal, 'add animal', default: 'giraffe'
--------------------------------------------------------------------------------

In the example above, the value for the `--animal` option will be the string
`"giraffe"`, unless otherwise specified:

--------------------------------------------------------------------------------
OPTIONS
    -a --animal[=<value>]      add animal (default: giraffe)
--------------------------------------------------------------------------------

==== Multivalued options ====

Each of these four methods take a `:multiple` parameter. When set to true, multiple
option valus are accepted, and the option values will be stored in an array.

For example, to parse the command line options string `-o foo.txt -o bar.txt`
into an array, so that `options[:output]` contains `[ 'foo.txt', 'bar.txt' ]`,
you can use an option definition like this:

[source,ruby]
--------------------------------------------------------------------------------
option :o, :output, 'specify output paths', argument: :required, multiple: true
--------------------------------------------------------------------------------

This can also be used for flags (options without arguments). In this case, the
length of the options array is relevant.

For example, you can allow setting the verbosity level using `-v -v -v`. The
value of `options[:verbose].size` would then be the verbosity level (three in
this example). The option definition would then look like this:

[source,ruby]
--------------------------------------------------------------------------------
flag :v, :verbose, 'be verbose (use up to three times)', multiple: true
--------------------------------------------------------------------------------

=== The run block ===

The last part of the command defines the execution itself:

[source,ruby]
--------------------------------------------------------------------------------
run do |opts, args, cmd|
  stuff = opts.fetch(:stuff, 'generic stuff')
  puts "Doing #{stuff}!"

  if opts[:more]
    puts 'Doing it even more!'
  end
end
--------------------------------------------------------------------------------

The +Cri::CommandDSL#run+ method takes a block with the actual code to
execute. This block takes three arguments: the options, any arguments passed
to the command, and the command itself.

Instead of defining a run block, it is possible to declare a class, the
_command runner_ class (`Cri::CommandRunner`) that will perform the actual
execution of the command. This makes it easier to break up large run blocks
into manageable pieces.

=== Subcommands ===

Commands can have subcommands. For example, the `git` command-line tool would be
represented by a command that has subcommands named `commit`, `add`, and so on.
Commands with subcommands do not use a run block; execution will always be
dispatched to a subcommand (or none, if no subcommand is found).

To add a command as a subcommand to another command, use the
`Cri::Command#add_command` method, like this:

[source,ruby]
--------------------------------------------------------------------------------
root_cmd.add_command(cmd_add)
root_cmd.add_command(cmd_commit)
root.cmd.add_command(cmd_init)
--------------------------------------------------------------------------------

You can specify a default subcommand. This subcommand will be executed when the
command has subcommands, and no subcommands are otherwise explicitly specified:

[source,ruby]
--------------------------------------------------------------------------------
default_subcommand 'compile'
--------------------------------------------------------------------------------

== Contributors ==

* Toon Willems
* Ken Coar

Thanks for Lee “injekt” Jarvis for link:https://github.com/injekt/slop[Slop],
which has inspired the design of Cri 2.0.