module SCSSLint
  # Check for allowed units
  class Linter::PropertyUnits < Linter
    include LinterRegistry

    NUMBER_WITH_UNITS_REGEX = /
      (?:
       (["']).+?\1 # [0: quote mark] quoted string, e.g. "hi there"
       |           # or
       (?:^|\s)    # beginning of value or whitespace
       (?:
        \d+        # any number of digits, e.g. 123
        |          # or
        \d*\.?\d+  # any number of digits with decimal, e.g. 1.23 or .123
       )
       ([a-z%]+)   # [1: units] letters or percent sign, e.g. px or %
      )
    /ix.freeze

    def visit_root(_node)
      @globally_allowed_units = config['global'].to_set
      @allowed_units_for_property = config['properties']

      yield # Continue linting children
    end

    def visit_prop(node)
      property = node.name.join

      # Handle nested properties by ensuring the full name is extracted
      if @nested_under
        property = "#{@nested_under}-#{property}"
      end

      if node.value.first.respond_to?(:value)
        node.value.first.value.to_s.scan(NUMBER_WITH_UNITS_REGEX).each do |matches|
          is_quoted_value = !matches[0].nil?
          next if is_quoted_value
          units = matches[1]
          check_units(node, property, units)
        end
      end

      @nested_under = property
      yield # Continue linting nested properties
      @nested_under = nil
    end

  private

    # Checks if a property value's units are allowed.
    #
    # @param node [Sass::Tree::Node]
    # @param property [String]
    # @param units [String]
    def check_units(node, property, units)
      allowed_units = allowed_units_for_property(property)
      return if allowed_units.include?(units)

      add_lint(node,
               "#{units} units not allowed on `#{property}`; must be one of " \
               "(#{allowed_units.to_a.sort.join(', ')})")
    end

    # Return the list of allowed units for a property.
    #
    # @param property [String]
    # @return Array<String>
    def allowed_units_for_property(property)
      if @allowed_units_for_property.key?(property)
        @allowed_units_for_property[property]
      else
        @globally_allowed_units
      end
    end
  end
end