#399 Autocomplete Search Terms pro

rails g resource search_suggestion term popularity:integer
rake db:migrate
rake search_suggestions:index
brew install redis

class SearchSuggestions
  def initialize(app)
    @app = app
  end
  
  def call(env)
    if env["PATH_INFO"] == "/search_suggestions"
      request = Rack::Request.new(env)
      terms = SearchSuggestion.terms_for(request.params["term"])
      [200, {"Content-Type" => "appication/json"}, [terms.to_json]]
    else
      @app.call(env)
    end
  end
end

config.middleware.insert_before 0, "SearchSuggestions"

class SearchSuggestion < ActiveRecord::Base
  attr_accessible :popularity, :term
  
  def self.terms_for(prefix)
    Rails.cache.fetch(["search-terms", prefix]) do
      suggestions = where("term like ?", "#{prefix}_%")
      suggestions.order("popularity desc").limit(10).pluck(:term)
    end
  end
  
  def self.index_products
    Product.find_each do |product|
      index_term(product.name)
      index_term(product.category)
      product.name.split.each { |t| index_term(t) }
    end
  end
  
  def self.index_term(term)
    where(term: term.downcase).first_or_initialize.tap do |suggestion|
      suggestion.increment! :popularity
    end
  end
end

namespace :search_suggestions do
  desc "Generate search suggestions from products"
  task :index => :environment do
    SearchSuggestion.index_products
  end
end

gem 'rack-mini-profiler'

gem 'redis'

$redis = Redis.new

class SearchSuggestion
  def self.terms_for(prefix)
    $redis.zrevrange "search-suggestions:#{prefix.downcase}", 0, 9
  end
  
  def self.index_products
    Product.find_each do |product|
      index_term(product.name)
      index_term(product.category)
      product.name.split.each { |t| index_term(t) }
    end
  end
  
  def self.index_term(term)
    1.upto(term.length-1) do |n|
      prefix = term[0, n]
      $redis.zincrby "search-suggestions:#{prefix.downcase}", 1, term.downcase
    end
  end
end