require 'csv_row_model/import/file/callbacks'
require 'csv_row_model/import/file/validations'

module CsvRowModel
  module Import
    # Represents a csv file and handles parsing to return `Import` or `Mapper`
    class File
      include Callbacks
      include Validations

      # @return [Csv]
      attr_reader :csv
      # @return [Input,Mapper] model class returned for importing
      attr_reader :row_model_class

      # Current index of the row model
      # @return [Integer] returns -1 = start of file, 0 to infinity = index of row_model, nil = end of file, no row_model
      attr_reader :index
      # @return [Input, Mapper] the current row model set by {#next}
      attr_reader :current_row_model
      # @return [Input, Mapper] the previous row model set by {#next}
      attr_reader :previous_row_model

      delegate :header, :size, :skipped_rows, to: :csv

      # @param [String] file_path path of csv file
      # @param [Import, Mapper] row_model_class model class returned for importing
      def initialize(file_path, row_model_class)
        @csv, @row_model_class = Csv.new(file_path), row_model_class
        reset
      end

      # Resets the file back to the top
      def reset
        csv.reset
        @index = -1
        @current_row_model = nil
      end

      # Gets the next row model based on the context
      #
      # @param context [Hash] context passed to the {Import}
      def next(context={})
        if is_single_model?
          return set_end_of_file if end_of_file?
          set_single_model(context)
        else
          next_collection_model(context)
        end
      end

      # @return [Boolean] returns true, if the object is at the end of file
      def end_of_file?
        csv.end_of_file?
      end

      # Iterates through the entire csv file and provides the `current_row_model` in a block, while handing aborts and skips
      # via. calling {Model#abort?} and {Model#skip?}
      #
      # @param context [Hash] context passed to the {Import}
      def each(context={})
        return to_enum(__callee__, context) unless block_given?
        return false if _abort?

        while self.next(context)
          return false if _abort?
          next if _skip?

          run_callbacks :yield do
            yield current_row_model
          end
        end
      end

      protected

      # @return [boolean] if type of model is collection_model
      def is_single_model?
        @is_single_model ||= begin
          row_model_class.respond_to?(:type) ? (row_model_class.type == :single_model) : false
        end
      end

      def set_current_collection_model(context)
        @current_row_model = row_model_class.new(csv.current_row, index: csv.index, context: context, source_header: header, previous: previous_row_model)
        @index += 1
      end

      def set_single_model(context={})
        source_row = Array.new(row_model_class.header_matchers.size)
        while !end_of_file?
          csv.read_row
          update_source_row(source_row)
        end
        @current_row_model = row_model_class.new(source_row, context: context)
      end

      def update_source_row(source_row)
        current_row = csv.current_row
        return unless current_row
        current_row.each_with_index do |cell, position|
          next if cell.blank?
          index = row_model_class.index_header_match(cell)
          next unless index
          source_row[index] = current_row[position + 1]
          break
        end
      end

      def next_collection_model(context)
        csv.skip_header

        next_row_is_parent = true
        loop do
          @previous_row_model = current_row_model if next_row_is_parent

          csv.read_row
          return set_end_of_file if csv.end_of_file?

          set_current_collection_model(context) if next_row_is_parent

          next_row_is_parent = !current_row_model.append_child(csv.next_row)
          return current_row_model if next_row_is_parent
        end
      end

      def set_end_of_file
        # please return nil
        @current_row_model = @index = nil
      end
    end
  end
end