require "ca_postal_code/version"

module CAPostalCode
  REGIONS = {
    NL: ?A,
    NS: ?B,
    PE: ?C,
    NB: ?E,
    QC: [?G, ?H, ?J],
    ON: [?K, ?L, ?M, ?N, ?P],
    MB: ?R,
    SK: ?S,
    AB: ?T,
    BC: ?V,
    NU: /^X0[A-C]/,
    NT: [/^X0[EG]/, /^X1A/],
    YT: ?Y,
  }

  def self.guess_region(string)
    entry = patterns.detect do |pattern, region|
      pattern.match?(string)
    end

    entry[1] if entry
  end

  # Lists the patterns the library will use. It is made public only to
  # make the implementation visible.
  def self.patterns
    @@patterns
  end

  private

  def self.add_pattern(pattern, region)
    unless pattern.is_a?(Regexp)
      pattern = Regexp.new("^" + pattern)
    end

    @@patterns[pattern] = region.to_s
  end

  @@patterns = {}

  REGIONS.each do |region, patterns|
    unless patterns.is_a?(Array)
      patterns = [patterns]
    end

    patterns.each do |pattern|
      add_pattern(pattern, region)
    end
  end
end