# Yawpa

Yet Another Way to Parse Arguments is an argument-parsing library for Ruby.

## Features

- POSIX or non-POSIX mode (supports subcommands using POSIX mode)
- Options can require an arbitrary number of parameters
- Options can be defined with a range specifying the allowed number of parameters

## Example 1

```ruby
require "yawpa"

options = {
  version: {},
  verbose: {short: "v"},
  get: {nargs: 1},
  set: {nargs: 2},
}
opts, args = Yawpa.parse(ARGV, options)
opts.each_pair do |opt, val|
end
```

## Example 2

```ruby
require "yawpa"

options = {
  version: {},
  help: {short: "h"},
}
opts, args = Yawpa.parse(ARGV, options, posix_order: true)
if opts[:version]
  puts "my app, version 1.2.3"
end
if args[0] == "subcommand"
  subcommand_options = {
    "server": {nargs: (1..2), short: "s"},
    "dst": {nargs: 1, short: "d"},
  }
  opts, args = Yawpa.parse(args, subcommand_options)
end
```

## Using Yawpa.parse()

```ruby
opts, args = Yawpa.parse(params, options, flags = {})
```

Parse input parameters looking for options according to rules given in flags

- `params` is the list of program parameters to parse.
- `options` is a hash containing the long option names as keys, and hashes
  containing special flags for the options as values (example below).
- `flags` is optional. It supports the following keys:
  - `:posix_order`: Stop processing parameters when a non-option is seen.
    Set this to `true` if you want to implement subcommands.

An ArgumentParsingException will be raised if an unknown option is observed
or insufficient arguments are present for an option.

### Example `options`

```ruby
{
  version: {},
  verbose: {short: "v"},
  server: {nargs: (1..2)},
  username: {nargs: 1},
  password: {nargs: 1},
}
```

The keys of the `options` hash can be either strings or symbols.

Options that have no special flags should have an empty hash as the value.

Possible option flags:
- `:short`: specify a short option letter to associate with the long option
- `:nargs`: specify an exact number or range of possible numbers of
  arguments to the option

### Return values

The returned `opts` value will be a hash with the observed options as
keys and any option arguments as values.
The returned `args` will be an array of the unprocessed parameters (if
`:posix_order` was passed in `flags`, this array might contain further
options that were not processed after observing a non-option parameters).