Class: Csvtool::Infrastructure::CSV::CsvStatsScanner

Inherits:
Object
  • Object
show all
Defined in:
lib/csvtool/infrastructure/csv/csv_stats_scanner.rb

Instance Method Summary collapse

Constructor Details

#initialize(csv: ::CSV) ⇒ CsvStatsScanner

Returns a new instance of CsvStatsScanner.



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# File 'lib/csvtool/infrastructure/csv/csv_stats_scanner.rb', line 9

def initialize(csv: ::CSV)
  @csv = csv
end

Instance Method Details

#call(file_path:, col_sep:, headers_present:) ⇒ Object 



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# File 'lib/csvtool/infrastructure/csv/csv_stats_scanner.rb', line 13

def call(file_path:, col_sep:, headers_present:)
  data_row_count = 0
  headers = nil
  column_count = 0
  column_stats = []

  # Streaming scan: memory grows with per-column metrics, not row count.
  @csv.foreach(file_path, headers: headers_present, col_sep: col_sep) do |row|
    if headers_present
      headers ||= row.headers
      column_count = headers.length
      if column_stats.empty?
        column_stats = headers.map { |name| { name: name, blank_count: 0, non_blank_count: 0 } }
      end
      fields = row.fields
      fields.fill(nil, fields.length...column_count)
      fields.each_with_index { |value, index| apply_value(column_stats[index], value) }
      data_row_count += 1
    else
      fields = row.is_a?(::CSV::Row) ? row.fields : row
      column_count = [column_count, fields.length].max
      while column_stats.length < column_count
        column_stats << {
          name: "column_#{column_stats.length + 1}",
          blank_count: 0,
          non_blank_count: 0
        }
      end
      fields.fill(nil, fields.length...column_count)
      fields.each_with_index { |value, index| apply_value(column_stats[index], value) }
      data_row_count += 1
    end
  end

  {
    row_count: data_row_count,
    column_count: column_count,
    headers: headers,
    column_stats: column_stats
  }
end