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# optparse.coffee

#

A simple OptionParser class to parse option flags from the command-line. Use it like so:

    parser  = new OptionParser switches, helpBanner
    options = parser.parse process.argv

The first non-option is considered to be the start of the file (and file option) list, and all subsequent arguments are left unparsed.

    exports.OptionParser = class OptionParser

#

Initialize with a list of valid options, in the form:

    [short-flag, long-flag, description]

Along with an an optional banner for the usage help.

      constructor: (rules, banner) ->
        @banner = banner
        @rules  = buildRules rules

#

Parse the list of arguments, populating an `options` object with all of the specified options, and returning it. `options.arguments` will be an array containing the remaning non-option arguments. This is a simpler API than many option parsers that allow you to attach callback actions for every flag. Instead, you're responsible for interpreting the options object.

      parse: (args) ->
        options = arguments: []
        args    = normalizeArguments args
        for arg, i in args
          isOption = !!(arg.match(LONG_FLAG) or arg.match(SHORT_FLAG))
          matchedRule = no
          for rule in @rules
            if rule.shortFlag is arg or rule.longFlag is arg
              value = if rule.hasArgument then args[i += 1] else true
              options[rule.name] = if rule.isList then (options[rule.name] or []).concat value else value
              matchedRule = yes
              break
          throw new Error "unrecognized option: #{arg}" if isOption and not matchedRule
          if not isOption
            options.arguments = args[i...args.length]
            break
        options

#

Return the help text for this OptionParser, listing and describing all of the valid options, for `--help` and such.

      help: ->
        lines = ['Available options:']
        lines.unshift "#{@banner}\n" if @banner
        for rule in @rules
          spaces  = 15 - rule.longFlag.length
          spaces  = if spaces > 0 then (' ' for i in [0..spaces]).join('') else ''
          letPart = if rule.shortFlag then rule.shortFlag + ', ' else '    '
          lines.push '  ' + letPart + rule.longFlag + spaces + rule.description
        "\n#{ lines.join('\n') }\n"

#

## Helpers

#

Regex matchers for option flags.

    LONG_FLAG  = /^(--\w[\w\-]+)/
    SHORT_FLAG = /^(-\w)/
    MULTI_FLAG = /^-(\w{2,})/
    OPTIONAL   = /\[(\w+(\*?))\]/

#

Build and return the list of option rules. If the optional short-flag is unspecified, leave it out by padding with `null`.

    buildRules = (rules) ->
      for tuple in rules
        tuple.unshift null if tuple.length < 3
        buildRule tuple...

#

Build a rule from a `-o` short flag, a `--output [DIR]` long flag, and the description of what the option does.

    buildRule = (shortFlag, longFlag, description, options) ->
      match     = longFlag.match(OPTIONAL)
      longFlag  = longFlag.match(LONG_FLAG)[1]
      options or= {}
      {
        name:         longFlag.substr 2
        shortFlag:    shortFlag
        longFlag:     longFlag
        description:  description
        hasArgument:  !!(match and match[1])
        isList:       !!(match and match[2])
      }

#

Normalize arguments by expanding merged flags into multiple flags. This allows you to have `-wl` be the same as `--watch --lint`.

    normalizeArguments = (args) ->
      args = args.slice 0
      result = []
      for arg in args
        if match = arg.match MULTI_FLAG
          result.push '-' + l for l in match[1].split ''
        else
          result.push arg
      result