class Pyrosoma
  class Pattern
    def initialize(source)
      @source = source
      @rx = Regexp.new compile
    end

    def compile
      @fields = {}
      field_count = 1
      r = '\A'
      @source.scan(/((?:\*\*|\*|%|\$|\{.*?\})(?::(\w+))?|:\w+|.)/m) { |token, name|
        r << case token
             when /^\*\*/
               '(.*?)'
             when /^\*/
               '([^/]*?)'
             when /^%/
               '(\d+)'
             when /^\$/
               '([A-Fa-f0-9]+)'
             when /^\{(.*)\}/
               "(" + $1.split(',').map { |x| Regexp.quote x }.join("|") + ")"

             when /^:/
               @fields[$'.downcase.intern] = field_count
               '([^/]*?)'

             else
               field_count -= 1      # oops, no field
               Regexp.quote(token)
             end

        @fields[name.downcase.intern] = field_count  if name
        field_count += 1
      }

      r << '\z'
    end

    def match(uri)
      if uri =~ @rx
        matches = {}
        $~.captures.each_with_index { |v, k|
          matches[k+1] = v
        }
        @fields.each { |k, v|
          matches[k] = matches[v]
        }
        matches
      else
        nil
      end
    end

    alias =~ match

    def generality
      [@fields.size,
       @source.index("**") || 0,
       @rx.source.index('(') || 0,
       @rx.source.size]
    end
  end
end