class Eco::API::UseCases::Default::Utils::SortCsv < Eco::API::Custom::UseCase
  name 'sort-csv'
  type :other

  require_relative 'cli/sort_csv_cli'

  def main(*_args)
    if simulate?
      count = Eco::CSV.count(input_file)
      log(:info) { "CSV '#{input_file}' has #{count} rows." }
    else
      group_input_rows
      generate_file
    end
  end

  private

  attr_reader :headers, :headers_rest

  def group_input_rows
    idx   = 0
    first = true

    Eco::CSV.foreach(input_file, headers: true, skip_blanks: true) do |row|
      idx += 1

      if first
        first           = false
        @output_headers = row.headers
        require_sort_field!(row, file: input_file)
      end

      pivot_value = row[sort_field]
      (row_groups[pivot_value] ||= []) << row

      if (idx % 500).zero?
        print "... Tracked #{idx} rows          \r"
        $stdout.flush
      end
    end
  ensure
    log(:info) { "Tracked #{idx} rows"}
  end

  def generate_file
    idx = 0

    CSV.open(output_filename, 'wb') do |csv|
      csv << @output_headers

      row_groups.keys.sort.each do |key|
        row_groups[key].each do |row|
          csv << row.values_at(*@output_headers)

          idx += 1
          if (idx % 500).zero?
            print "... Sorted #{idx} rows          \r"
            $stdout.flush
          end
        end
      end
    end
  ensure
    msg = "Generated file '#{output_filename}' with #{idx} rows."
    log(:info) { msg } unless simulate?
  end

  def row_groups
    @row_groups ||= {}
  end

  def output_filename
    return nil unless input_name

    File.join(input_dir, "#{input_name}_sorted#{input_ext}")
  end

  def input_name
    @input_name ||= File.basename(input_basename, input_ext)
  end

  def input_ext
    @input_ext ||= input_basename.split('.')[1..].join('.').then do |name|
      ".#{name}"
    end
  end

  def input_basename
    @input_basename ||= File.basename(input_full_filename)
  end

  def input_dir
    @input_dir = File.dirname(input_full_filename)
  end

  def input_full_filename
    @input_full_filename ||= File.expand_path(input_file)
  end

  def input_file
    options.dig(:input, :file)
  end

  def require_sort_field!(row, file:)
    return true if row.key?(sort_field)

    msg = "Sort field '#{sort_field}' missing in header of file '#{file}'"
    log(:error) { msg }
    raise msg
  end

  def sort_field
    @sort_field ||= opts_sort_by.tap do |pivot|
      next if pivot

      msg = "The pivot field should be specified with -by option"

      log(:error) { msg }
      raise msg
    end
  end

  def opts_sort_by
    options.dig(:input, :sort_by)
  end
end