module ActiveRecord
  module Sanitization
    extend ActiveSupport::Concern

    module ClassMethods
      private

        # Accepts an array or string of SQL conditions and sanitizes
        # them into a valid SQL fragment for a WHERE clause.
        #
        #   sanitize_sql_for_conditions(["name=? and group_id=?", "foo'bar", 4])
        #   # => "name='foo''bar' and group_id=4"
        #
        #   sanitize_sql_for_conditions(["name=:name and group_id=:group_id", name: "foo'bar", group_id: 4])
        #   # => "name='foo''bar' and group_id='4'"
        #
        #   sanitize_sql_for_conditions(["name='%s' and group_id='%s'", "foo'bar", 4])
        #   # => "name='foo''bar' and group_id='4'"
        #
        #   sanitize_sql_for_conditions("name='foo''bar' and group_id='4'")
        #   # => "name='foo''bar' and group_id='4'"
        def sanitize_sql_for_conditions(condition) # :doc:
          return nil if condition.blank?

          case condition
          when Array; sanitize_sql_array(condition)
          else        condition
          end
        end
        alias :sanitize_sql :sanitize_sql_for_conditions
        alias :sanitize_conditions :sanitize_sql
        deprecate sanitize_conditions: :sanitize_sql

        # Accepts an array, hash, or string of SQL conditions and sanitizes
        # them into a valid SQL fragment for a SET clause.
        #
        #   sanitize_sql_for_assignment(["name=? and group_id=?", nil, 4])
        #   # => "name=NULL and group_id=4"
        #
        #   sanitize_sql_for_assignment(["name=:name and group_id=:group_id", name: nil, group_id: 4])
        #   # => "name=NULL and group_id=4"
        #
        #   Post.send(:sanitize_sql_for_assignment, { name: nil, group_id: 4 })
        #   # => "`posts`.`name` = NULL, `posts`.`group_id` = 4"
        #
        #   sanitize_sql_for_assignment("name=NULL and group_id='4'")
        #   # => "name=NULL and group_id='4'"
        def sanitize_sql_for_assignment(assignments, default_table_name = self.table_name) # :doc:
          case assignments
          when Array; sanitize_sql_array(assignments)
          when Hash;  sanitize_sql_hash_for_assignment(assignments, default_table_name)
          else        assignments
          end
        end

        # Accepts an array, or string of SQL conditions and sanitizes
        # them into a valid SQL fragment for an ORDER clause.
        #
        #   sanitize_sql_for_order(["field(id, ?)", [1,3,2]])
        #   # => "field(id, 1,3,2)"
        #
        #   sanitize_sql_for_order("id ASC")
        #   # => "id ASC"
        def sanitize_sql_for_order(condition) # :doc:
          if condition.is_a?(Array) && condition.first.to_s.include?("?")
            sanitize_sql_array(condition)
          else
            condition
          end
        end

        # Accepts a hash of SQL conditions and replaces those attributes
        # that correspond to a {#composed_of}[rdoc-ref:Aggregations::ClassMethods#composed_of]
        # relationship with their expanded aggregate attribute values.
        #
        # Given:
        #
        #   class Person < ActiveRecord::Base
        #     composed_of :address, class_name: "Address",
        #       mapping: [%w(address_street street), %w(address_city city)]
        #   end
        #
        # Then:
        #
        #   { address: Address.new("813 abc st.", "chicago") }
        #   # => { address_street: "813 abc st.", address_city: "chicago" }
        def expand_hash_conditions_for_aggregates(attrs) # :doc:
          expanded_attrs = {}
          attrs.each do |attr, value|
            if aggregation = reflect_on_aggregation(attr.to_sym)
              mapping = aggregation.mapping
              mapping.each do |field_attr, aggregate_attr|
                if mapping.size == 1 && !value.respond_to?(aggregate_attr)
                  expanded_attrs[field_attr] = value
                else
                  expanded_attrs[field_attr] = value.send(aggregate_attr)
                end
              end
            else
              expanded_attrs[attr] = value
            end
          end
          expanded_attrs
        end

        # Sanitizes a hash of attribute/value pairs into SQL conditions for a SET clause.
        #
        #   sanitize_sql_hash_for_assignment({ status: nil, group_id: 1 }, "posts")
        #   # => "`posts`.`status` = NULL, `posts`.`group_id` = 1"
        def sanitize_sql_hash_for_assignment(attrs, table) # :doc:
          c = connection
          attrs.map do |attr, value|
            value = type_for_attribute(attr.to_s).serialize(value)
            "#{c.quote_table_name_for_assignment(table, attr)} = #{c.quote(value)}"
          end.join(", ")
        end

        # Sanitizes a +string+ so that it is safe to use within an SQL
        # LIKE statement. This method uses +escape_character+ to escape all occurrences of "\", "_" and "%".
        #
        #   sanitize_sql_like("100%")
        #   # => "100\\%"
        #
        #   sanitize_sql_like("snake_cased_string")
        #   # => "snake\\_cased\\_string"
        #
        #   sanitize_sql_like("100%", "!")
        #   # => "100!%"
        #
        #   sanitize_sql_like("snake_cased_string", "!")
        #   # => "snake!_cased!_string"
        def sanitize_sql_like(string, escape_character = "\\") # :doc:
          pattern = Regexp.union(escape_character, "%", "_")
          string.gsub(pattern) { |x| [escape_character, x].join }
        end

        # Accepts an array of conditions. The array has each value
        # sanitized and interpolated into the SQL statement.
        #
        #   sanitize_sql_array(["name=? and group_id=?", "foo'bar", 4])
        #   # => "name='foo''bar' and group_id=4"
        #
        #   sanitize_sql_array(["name=:name and group_id=:group_id", name: "foo'bar", group_id: 4])
        #   # => "name='foo''bar' and group_id=4"
        #
        #   sanitize_sql_array(["name='%s' and group_id='%s'", "foo'bar", 4])
        #   # => "name='foo''bar' and group_id='4'"
        def sanitize_sql_array(ary) # :doc:
          statement, *values = ary
          if values.first.is_a?(Hash) && /:\w+/.match?(statement)
            replace_named_bind_variables(statement, values.first)
          elsif statement.include?("?")
            replace_bind_variables(statement, values)
          elsif statement.blank?
            statement
          else
            statement % values.collect { |value| connection.quote_string(value.to_s) }
          end
        end

        def replace_bind_variables(statement, values)
          raise_if_bind_arity_mismatch(statement, statement.count("?"), values.size)
          bound = values.dup
          c = connection
          statement.gsub(/\?/) do
            replace_bind_variable(bound.shift, c)
          end
        end

        def replace_bind_variable(value, c = connection)
          if ActiveRecord::Relation === value
            value.to_sql
          else
            quote_bound_value(value, c)
          end
        end

        def replace_named_bind_variables(statement, bind_vars)
          statement.gsub(/(:?):([a-zA-Z]\w*)/) do |match|
            if $1 == ":" # skip postgresql casts
              match # return the whole match
            elsif bind_vars.include?(match = $2.to_sym)
              replace_bind_variable(bind_vars[match])
            else
              raise PreparedStatementInvalid, "missing value for :#{match} in #{statement}"
            end
          end
        end

        def quote_bound_value(value, c = connection)
          if value.respond_to?(:map) && !value.acts_like?(:string)
            if value.respond_to?(:empty?) && value.empty?
              c.quote(nil)
            else
              value.map { |v| c.quote(v) }.join(",")
            end
          else
            c.quote(value)
          end
        end

        def raise_if_bind_arity_mismatch(statement, expected, provided)
          unless expected == provided
            raise PreparedStatementInvalid, "wrong number of bind variables (#{provided} for #{expected}) in: #{statement}"
          end
        end
    end

    # TODO: Deprecate this
    def quoted_id # :nodoc:
      self.class.connection.quote(@attributes[self.class.primary_key].value_for_database)
    end
  end
end