class PgSearch::Features::TSearch

def conditions
  ["(#{tsdocument}) @@ (#{tsquery})", interpolations]
end

def dictionary
  options[:dictionary] || :simple
end

def initialize(*args)
  super
  if options[:prefix] && model.connection.send(:postgresql_version) < 80400
    raise PgSearch::NotSupportedForPostgresqlVersion.new(<<-MESSAGE.gsub /^\s*/, '')
      Sorry, {:using => {:tsearch => {:prefix => true}}} only works in PostgreSQL 8.4 and above.")
    MESSAGE
  end
end

def interpolations
  {:query => query.to_s, :dictionary => dictionary.to_s}
end

def normalization
  options[:normalization] || 0
end

def rank
  tsearch_rank
end

def tsdocument
  if options[:tsvector_column]
    column_name = connection.quote_column_name(options[:tsvector_column])
    "#{quoted_table_name}.#{column_name}"
  else
    columns.map do |search_column|
      tsvector = "to_tsvector(:dictionary, #{normalize(search_column.to_sql)})"
      if search_column.weight.nil?
        tsvector
      else
        "setweight(#{tsvector}, #{connection.quote(search_column.weight)})"
      end
    end.join(" || ")
  end
end

def tsearch_rank
  ["ts_rank((#{tsdocument}), (#{tsquery}), #{normalization})", interpolations]
end

def tsquery
  return "''" if query.blank?
  query_terms = query.split(" ").compact
  tsquery_terms = query_terms.map { |term| tsquery_for_term(term) }
  tsquery_terms.join(options[:any_word] ? ' || ' : ' && ')
end

def tsquery_for_term(term)
  sanitized_term = term.gsub(DISALLOWED_TSQUERY_CHARACTERS, " ")
  term_sql = normalize(connection.quote(sanitized_term))
  # After this, the SQL expression evaluates to a string containing the term surrounded by single-quotes.
  # If :prefix is true, then the term will also have :* appended to the end.
  tsquery_sql = [
    connection.quote("' "),
    term_sql,
    connection.quote(" '"),
    (connection.quote(':*') if options[:prefix])
  ].compact.join(" || ")
  "to_tsquery(:dictionary, #{tsquery_sql})"
end