# Example Application:
# Product: name, price, brand, slug, description, delete_flag, image_url
# Category: name,slug
# Product belongs to Category

# Use scopes instead of chained queries scattered all over your application

# Get all available apple products with price > 1000 and not older than 1 week
# BAD
products = Product.where(brand: "apple").where("price > ?", 1000).where(delete_flag: false).where("created_at > ?", 1.week.ago)

# GOOD
scope :price_bigger_than, -> { |min_price| where("price > ?", min_price) } # Yes you can pass parameter to scope
scope :for_brand, -> { |brand| where(brand: brand) }
default_scope :un_deleted, where(delete_flag: false)
scope :new, -> { |start_date = 1.week.ago| where("created_at > ?", start_date) } # Yes the scope parameter can have a default
default_scope :available, where(delete_flag: false)
default_scope :unavailable, where(delete_flag: true)

products = Product.for_brand("apple").price_bigger_than(1000).available.new

# What if we want to override the default scope?!
# Get all apple unavailable products 

products = Product.for_brand("apple") # Wont work, will get only the available
products = Product.for_brand("apple").unavailable # Wont work too, will get only the available

products = Product.unscoped.for_brand("apple").unavailable # works perfectly (Y)

# Now we want to get products updated today
# One can make
scope :most_updated, where("updated_at > ?", Date.today) # Watch Out!!!
# A scope is defined at initialisation, so what you start up your server, console, or in my case the DelayedJob worker, Date.today gets executed once and a scope is created called due that will return all the Books that are due on the day you start the process

# This must be me done using Lambda OR without scopes
scope :most_updated, -> { where("updated_at > ?", Date.today) }

# Note: -> AND lambda are equivalent

# You can define scope dynamically 
# Example for an api with api_keys
Status = {:normal => 0, :whitelisted => 1, :blacklisted => 2}
Status.each_pair do |k,v|
  scope "status_#{k}", where(:status => v)  # ApiKey.status_whitelisted,...

  define_singleton_method "status_#{k}?" do |st|  # ApiKey.status_whitelisted?(status),...
    v == st
  end

  define_method "status_#{k}?" do # api_key.status_whitelisted?,...
    self.status == v
  end
end