module Dry::Initializer::Builders
  # @private
  class Attribute
    def self.[](definition)
      new(definition).call
    end

    def call
      lines.compact
    end

    private

    # rubocop: disable Metrics/MethodLength
    def initialize(definition)
      @definition = definition
      @option     = definition.option
      @type       = definition.type
      @optional   = definition.optional
      @default    = definition.default
      @source     = definition.source
      @ivar       = definition.ivar
      @null       = definition.null ? "Dry::Initializer::UNDEFINED" : "nil"
      @opts       = "__dry_initializer_options__"
      @congif     = "__dry_initializer_config__"
      @item       = "__dry_initializer_definition__"
      @val        = @option ? "__dry_initializer_value__" : @source
    end
    # rubocop: enable Metrics/MethodLength

    def lines
      [
        "",
        definition_line,
        reader_line,
        default_line,
        coercion_line,
        assignment_line
      ]
    end

    def reader_line
      return unless @option
      @optional ? optional_reader : required_reader
    end

    def optional_reader
      "#{@val} = #{@opts}.fetch(:'#{@source}', #{@null})"
    end

    def required_reader
      "#{@val} = #{@opts}.fetch(:'#{@source}')" \
      " { raise KeyError, \"\#{self.class}: #{@definition} is required\" }"
    end

    def definition_line
      return unless @type || @default
      "#{@item} = __dry_initializer_config__.definitions[:'#{@source}']"
    end

    def default_line
      return unless @default
      "#{@val} = instance_exec(&#{@item}.default) if #{@null} == #{@val}"
    end

    def coercion_line
      return unless @type
      arity = @type.is_a?(Proc) ? @type.arity : @type.method(:call).arity
      if arity.abs == 1
        "#{@val} = #{@item}.type.call(#{@val}) unless #{@null} == #{@val}"
      else
        "#{@val} = #{@item}.type.call(#{@val}, self) unless #{@null} == #{@val}"
      end
    end

    def assignment_line
      "#{@ivar} = #{@val}" \
      " unless #{@null} == #{@val} && instance_variable_defined?(:#{@ivar})"
    end
  end
end