Module: FixpointDiff

Defined in:
lib/fixpoint_diff.rb

Overview

Helper module which implements diff-ing for fixpoints

Constant Summary collapse

DELETED_KEY = 
'++DELETED++'
IGNORE_ATTRIBUTES = 
['updated_at']

Class Method Summary collapse

Class Method Details

.apply_changes(parent_records_in_tables, changes_in_tables) ⇒ Object 



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# File 'lib/fixpoint_diff.rb', line 7

def apply_changes(parent_records_in_tables, changes_in_tables)
  tables = (parent_records_in_tables.keys + changes_in_tables.keys).uniq

  tables.each_with_object({}) do |table, records|
    records[table] = apply_records_changes(parent_records_in_tables[table], changes_in_tables[table])
  end
end

.apply_records_changes(parent_records, changes) ⇒ Object 



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# File 'lib/fixpoint_diff.rb', line 27

def apply_records_changes(parent_records, changes)
  return parent_records if changes.blank?

  parent_records ||= [] # the table was not part of an earlier fixpoint
  changes.zip(parent_records).collect do |change, parent_record| # we can rely on the fact that changes has always more entries than parent_records
    next change if parent_record.nil? # we do have a new record
    next nil if change[DELETED_KEY]

    parent_record.merge(change)
  end.compact
end

.extract_changes(parent_records_in_tables, records_in_tables) ⇒ Object 



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# File 'lib/fixpoint_diff.rb', line 15

def extract_changes(parent_records_in_tables, records_in_tables)
  tables = (parent_records_in_tables.keys + records_in_tables.keys).uniq

  tables.each_with_object({}) do |table, changes_in_tables|
    changes_in_tables[table] = extract_records_changes(parent_records_in_tables[table], records_in_tables[table])
  end
end

.extract_records_changes(parent_records, records) ⇒ Object 



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# File 'lib/fixpoint_diff.rb', line 39

def extract_records_changes(parent_records, records)
  return records if parent_records.blank?
  records ||= []

  # we pad parent_records with nil values so we can zip them together
  parent_records = parent_records + [nil] * (records.count - parent_records.count) if parent_records.count < records.count
  
  parent_records.zip(records).collect do |parent, record|
    next { DELETED_KEY => true } if record.nil?
    next record if parent.nil? # newly added record

    parent.each_with_object({}) do |(parent_key, parent_value), changes| # we can rely on the fact that both hashes have the same attributes
      record_value = record[parent_key]
      changes[parent_key] = record_value unless record_value == parent_value || IGNORE_ATTRIBUTES.include?(parent_key)
    end
  end
end