module DynamicQuery

# File lib/dynamic_query.rb, line 52
def all_columns_in(*models)
  models.map { |m| m.columns.map { |col| "#{m.table_name}.#{col.name}" } }.flatten.join ', '
end

# File lib/dynamic_query.rb, line 65
def conditioned_count(dq, query, model)
  conditions = dq.conditions query, model.table_name
  statement = Querier.statement conditions
  model.where(statement).count
end

# File lib/dynamic_query.rb, line 12
def dynamic_query(*models, opt)
  models.flatten!
  DynamicQueryInstance.new(*models, opt)
end

# File lib/dynamic_query.rb, line 56
def estimate_total(dq, query)
  models = dq.models
  et = models.map { |m| { :table => m.table_name, :total => m.count, :conditioned => conditioned_count(dq, query, m) } }
  major = et.max_by { |i| i[:total] }
  et.delete major
  estimate = major[:conditioned] * et.map { |i| i[:conditioned].to_f / i[:total] }.reduce(:*)
  estimate = estimate.to_i
end

# File lib/dynamic_query.rb, line 17
def tables_joined_by(from, *to_tables)
  sql = ''
  from_table = from.table_name
  to_tables_count = Hash.new(0)
  to_tables.each do |to|
    to_table = to.first.table_name
    if to_tables_count[to_table] == 0
      sql << "INNER JOIN `#{to_table}` ON "
      mappings = []
      to.drop(1).each do |mapping|
        if mapping.kind_of? Array
          mappings << "`#{from_table}`.`#{mapping.first}` = `#{to_table}`.`#{mapping.last}`"
        else
          mappings << "`#{from_table}`.`#{mapping}` = `#{to_table}`.`#{mapping}`"
        end
      end
      sql << "(#{mappings.join(' AND ')})"
      to_tables_count[to_table] += 1
    else
      sql << "INNER JOIN `#{to_table}` `#{to_table}_#{to_tables_count[to_table]}` ON "
      mappings = []
      to.drop(1).each do |mapping|
        if mapping.kind_of? Array
          mappings << "`#{from_table}`.`#{mapping.first}` = `#{to_table}_#{to_tables_count[to_table]}`.`#{mapping.last}`"
        else
          mappings << "`#{from_table}`.`#{mapping}` = `#{to_table}_#{to_tables_count[to_table]}`.`#{mapping}`"
        end
      end
      sql << "(#{mappings.join(' AND ')})"
      to_tables_count[to_table] += 1
    end
  end
  sql
end