require "./parser.cr"

module Parcom
  # `Exactly` 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 number of successes is less than
  # OR greater than the specified number, the parser fails.
  class Exactly(T, V) < Parser(T, Array(V))
    @p : Sequence(T, V)

    # Accepts the number of parsing attempts, and the parser to use.
    # If a negative int is given, it is treated as if it were `0`.
    def initialize(i : Int, p : Parser(T, V))
      i = i.negative? ? 0 : i
      # put `i` copies of `p` into an array
      ps = ([p] of Parser(T, V)) * i
      @p = Sequence.new(ps)
    end

    # Tries to parse the given number of times.
    def parse(tokens : Tokens(T)) : Result(T, Array(V))
      @p.parse(tokens)
    rescue ex : ParserFail
      raise ParserFail.new("Exactly: #{ex.message}")
    end
  end
end