module Archetype::SassExtensions::UI::Scopes

  #
  # registers a breakpoint
  #
  # *Parameters*:
  # - <tt>$key</tt> {String} the key to register it under
  # - <tt>$value</tt> {*} the value to register
  # - <tt>$force</tt> {Boolean} if true, forces any new value into the registry
  # *Returns*:
  # - {Boolean} whether or not the value was registered
  #
  def register_breakpoint(key, value, force = nil)
    # we need a dup as the Hash is frozen
    breakpoints = registered_breakpoints.dup
    force = force.nil? ? false : force.value
    not_registered = breakpoints[key].nil? || helpers.is_null(breakpoints[key])
    # if there's no key registered...
    if force || not_registered
      # just register the value
      breakpoints[key] = value
    # otherwise, if the current value is different...
    elsif breakpoints[key] != value
      # throw a warning
      helpers.warn("[#{Archetype.name}:breakpoint] a breakpoint for `#{key}` is already set to `#{breakpoints[key]}`, ignoring `#{value}`")
      return bool(false)
    end
    environment.global_env.set_var('CONFIG_BREAKPOINTS', Sass::Script::Value::Map.new(breakpoints))
    return bool(true)
  end
  Sass::Script::Functions.declare :register_breakpoint, [:key, :value]
  Sass::Script::Functions.declare :register_breakpoint, [:key, :value, :force]

  #
  # retrieves a breakpoint
  #
  # *Parameters*:
  # - <tt>$key</tt> {String} the key to lookup
  # *Returns*:
  # - {*} the registered breakpoint
  #
  def get_breakpoint(key)
    return registered_breakpoints[key] || null
  end
  Sass::Script::Functions.declare :get_breakpoint, [:key]

  #
  # convert a modifier/element context to a BEM style selector
  #
  # *Parameters*:
  # - <tt>$context</tt> {String} the root selector to scope to
  # - <tt>$element</tt> {String} the element name
  # - <tt>$modifier</tt> {String} the modifier
  # *Returns*:
  # - {String} the BEM formatted selector
  #
  def bem_selector(context = nil, element = nil, modifier = nil)
    element_separator = environment.var('CONFIG_BEM_ELEMENT_SEPARATOR')
    element_separator = element_separator.nil? ? '__' : element_separator.value

    modifier_separator = environment.var('CONFIG_BEM_MODIFIER_SEPARATOR')
    modifier_separator = modifier_separator.nil? ? '--' : modifier_separator.value

    context  = helpers.is_null(context) ? ''  : context.value
    element  = helpers.is_null(element) ? nil : element.value
    modifier = helpers.is_null(modifier) ? nil : modifier.value

    selector = context

    warning = "[#{Archetype.name}:bem] the current context may produce a non-standard BEM selector for";

    unless element.nil?
      helpers.warn("#{warning} element `#{element}`: #{context}") if (context.include?(element_separator) || context.include?(modifier_separator))
      selector = "#{selector}#{element_separator}#{element}"
    end

    unless modifier.nil?
      helpers.warn("#{warning} modifier `#{modifier}`: #{context}") if context.include?(modifier_separator)
      selector = "#{selector}#{modifier_separator}#{modifier}"
    end

    return identifier(selector)
  end
  Sass::Script::Functions.declare :bem_selector, [:context]
  Sass::Script::Functions.declare :bem_selector, [:context, :element]
  Sass::Script::Functions.declare :bem_selector, [:context, :modifier]
  Sass::Script::Functions.declare :bem_selector, [:context, :element, :modifier]

private

  def registered_breakpoints
    breakpoints = environment.var('CONFIG_BREAKPOINTS')
    breakpoints.respond_to?(:to_h) ? breakpoints.to_h : {}
  end

end