module CalculateAll

# File lib/calculate-all.rb, line 7
def calculate_all(*function_aliases, **functions, &block)

  # If only one function_alias is given, the result can be just a single value
  # So return [{ cash: 3 }] instead of [{ cash: { count: 3 }}]
  if function_aliases.size == 1 && functions == {}
    return_plain_values = true
  end

  # Convert the function_aliases to actual SQL
  functions.merge!(
    CalculateAll::Helpers.decode_function_aliases(function_aliases)
  )

  # Check if any functions are given
  if functions == {}
    raise ArgumentError, 'provide at least one function to calculate'
  end

  # If function is called without a group, the pluck method will still return
  # an array but it is an array with the final results instead of each group
  # The plain_rows boolean states how the results should be used
  if functions.size == 1 && group_values.size == 0
    plain_rows = true
  end

  # Final output hash
  results = {}

  # Fetch all the requested calculations from the database
  # Note the map(&:to_s). It is required since groupdate returns a
  # Groupdate::OrderHack instead of a string for the group_values which is not
  # accepted by ActiveRecord's pluck method.
  sql_snippets = group_values.map(&:to_s) + functions.values
  # Fix DEPRECATION WARNING:
  # Dangerous query method, will be disallowed in Rails 6.0
  # using Arel.sql() to silence the warning
  # https://github.com/rails/rails/commit/310c3a8f2d043f3d00d3f703052a1e160430a2c2
  pluck(*sql_snippets.map { |sql| Arel.sql(sql) }).each do |row|

    # If no grouping, make sure it is still a results array
    row = [row] if plain_rows

    # If only one value, return a single value, else return a hash
    if return_plain_values
      value = row.last
    else
      value = functions.keys.zip(row.last(functions.size)).to_h
    end

    # Call the block for each group
    value = block.call(value) if block

    # Return unwrapped hash directly for scope without any .group()
    return value if group_values.empty?

    # If only one group is provided, the resulting key is just the group name
    # if multiple group methods are provided, the key will be an array.
    if group_values.size == 1
      key = row.first
    else
      key = row.first(group_values.size)
    end

    # Set the value in the output array
    results[key] = value
  end

  # Return the output array
  results
end