class Scopable

# File lib/scopable.rb, line 87
def self.model(model = nil)
  @model ||= model
end

# File lib/scopable.rb, line 7
def initialize(model = nil, scopes = nil)
  @model = model || self.class.model
  @scopes = scopes || self.class.scopes
end

# File lib/scopable.rb, line 83
def self.resolve(params = {})
  new.resolve(params)
end

# File lib/scopable.rb, line 95
def self.scope(name, options = {}, &block)
  scopes.store name, options.merge(block: block)
end

# File lib/scopable.rb, line 91
def self.scopes
  @scopes ||= {}
end

# File lib/scopable.rb, line 12
def delegator(relation, value, params)
  SimpleDelegator.new(relation).tap do |delegator|
    delegator.define_singleton_method(:value) do
      value
    end
    delegator.define_singleton_method(:params) do
      params
    end
  end
end

# File lib/scopable.rb, line 23
def resolve(params = {})
  params = params.with_indifferent_access

  scopes.reduce(model.all) do |relation, scope|
    name, options = *scope

    # Resolve param name.
    param = options[:param] || name

    # Resolve a value for the scope.
    value = options[:value] || params[param] || options[:default]

    # When value is empty treat it as nil.
    value = nil if value.respond_to?(:empty?) && value.empty?

    # When a nil value was given either skip the scope or bail with #none (if the required options was used).
    if value.nil?
      if options[:required]
        break relation.none
      else
        next relation
      end
    end

    # Cast boolean-like strings.
    case value.to_s
    when /\A(false|no|off)\z/
      value = false
    when /\A(true|yes|on)\z/
      value = true
    end

    # Enforce 'if' option.
    if options[:if]
      unless delegator(relation, value, params).instance_exec(&options[:if])
        next relation
      end
    end

    # Enforce 'unless' option.
    if options[:unless]
      if delegator(relation, value, params).instance_exec(&options[:unless])
        next relation
      end
    end

    # Bail if the value is false or nil.
    next relation unless value

    # When a block is present, use that, otherwise call the scope method.
    if options[:block].present?
      delegator(relation, value, params).instance_exec(&options[:block])
    elsif value == true
      relation.send(name)
    else
      relation.send(name, value)
    end
  end
end