Keyword Search

Description

Generic library to parse GMail-style search strings for keyword/value pairs; supports definition of valid keywords and handling of quoted values.

Requirements

None.

Features

The library features a very simple, easy-to-use API.

• Define handlers for supported keywords with blocks
• Define the default keyword (values not part of a keyword/value pair)
• Handle negation

Please see the example provided below.

Synopsis

Here's an example using ActiveRecord (though the library is generic, and can be used for any Ruby project). The library isn't limited to search terms, as shown in this example; how you use it is up to you.

First, let's build up some variables we'll be populating for a SQL query.

clauses = []
arguments = []

Now let's set an example string to parse. Presumably you'd get this from a form (ie, params[:terms]) or some other form of input.

terms = 'account has:attachment since:2006-12-03 -description:crazy'

Now let's do the search, defining the handlers to deal with each keyword.

KeywordSearch.search(terms) do |with|

  # This sets the keyword handler for bare words in the string,
  # ie "account" in our example search terms
  with.default_keyword :title

  # Here's what we do when we encounter a "title" keyword
  with.keyword :title do |values|
    clauses << "title like ?"
    arguments << "%#{values.join(' ')}%"
  end

  # For "has," we check the value provided (and only support "attachment")
  with.keyword :has do |values|
    clauses << 'has_attachment = true' if values.include?('attachment')
  end

  # Here we do some date parsing
  with.keyword :since do |values|
    date = Date.parse(values.first) # only support one
    clauses << 'created_on >= ?'
    arguments << date.to_s
  end

  # If a second parameter is defined for a block, you can handle negation.
  # In this example, we don't want results whose description includes
  # the word "crazy"
  with.keyword :description do |values, positive|
    clauses << "description #{'not' unless positive} like ?"
    arguments << "%#{values.join(' ')}%"
  end

end

Immediately after the block is defined, the string is parsed and handlers fire. Due to the magic of closures, we now have populated variables we can use to build a real SQL query.

query = clauses.map { |c| "(#{c})" }.join(' AND ')
conditions = [query, *arguments]
results = Message.all(:conditions => conditions)

Installation

gem install keyword_search

License

See LICENSE.

Legal Notes

GMail is copyright Google, Inc.