require "./parser.cr"
require "./map.cr"
require "./exactly.cr"
require "./optional.cr"

module Parcom
  # `AtMost` is a `Parser` that tries to parse with another parser a specific
  # number of times. The results of each successful parse are returned in an
  # array. If the specific number of parses succeed, the parsing stops, even
  # if it is possible to keep parsing. If the parser is never successful, it
  # succeeds with an empty array.
  class AtMost(T, V) < Parser(T, Array(V))
    @p : Map(T, Array(V?), Array(V))

    # Accepts the number of parsing attempts, and the parser to use.
    def initialize(i : Int, p : Parser(T, V))
      @p = Exactly.new(i, Optional.new(p)).map(&.compact)
    end

    # Tries to parse up to the given number of times.
    # If the parser never succeeds, returns an empty array.
    def parse(tokens : Tokens(T)) : Result(T, Array(V))
      @p.parse(tokens)
    rescue ex : ParserFail
      raise ParserFail.new("AtMost: #{ex.message}")
    end
  end
end