# frozen_string_literal: true

module Arel # :nodoc: all
  module Visitors
    class UnsupportedVisitError < StandardError
      def initialize(object)
        super "Unsupported argument type: #{object.class.name}. Construct an Arel node instead."
      end
    end

    class ToSql < Arel::Visitors::Visitor
      ##
      # This is some roflscale crazy stuff.  I'm roflscaling this because
      # building SQL queries is a hotspot.  I will explain the roflscale so that
      # others will not rm this code.
      #
      # In YARV, string literals in a method body will get duped when the byte
      # code is executed.  Let's take a look:
      #
      # > puts RubyVM::InstructionSequence.new('def foo; "bar"; end').disasm
      #
      #   == disasm: <RubyVM::InstructionSequence:foo@<compiled>>=====
      #    0000 trace            8
      #    0002 trace            1
      #    0004 putstring        "bar"
      #    0006 trace            16
      #    0008 leave
      #
      # The `putstring` bytecode will dup the string and push it on the stack.
      # In many cases in our SQL visitor, that string is never mutated, so there
      # is no need to dup the literal.
      #
      # If we change to a constant lookup, the string will not be duped, and we
      # can reduce the objects in our system:
      #
      # > puts RubyVM::InstructionSequence.new('BAR = "bar"; def foo; BAR; end').disasm
      #
      #  == disasm: <RubyVM::InstructionSequence:foo@<compiled>>========
      #  0000 trace            8
      #  0002 trace            1
      #  0004 getinlinecache   11, <ic:0>
      #  0007 getconstant      :BAR
      #  0009 setinlinecache   <ic:0>
      #  0011 trace            16
      #  0013 leave
      #
      # `getconstant` should be a hash lookup, and no object is duped when the
      # value of the constant is pushed on the stack.  Hence the crazy
      # constants below.
      #
      # `matches` and `doesNotMatch` operate case-insensitively via Visitor subclasses
      # specialized for specific databases when necessary.
      #

      WHERE    = " WHERE "    # :nodoc:
      SPACE    = " "          # :nodoc:
      COMMA    = ", "         # :nodoc:
      GROUP_BY = " GROUP BY " # :nodoc:
      ORDER_BY = " ORDER BY " # :nodoc:
      WINDOW   = " WINDOW "   # :nodoc:
      AND      = " AND "      # :nodoc:

      DISTINCT = "DISTINCT"   # :nodoc:

      def initialize(connection)
        super()
        @connection = connection
      end

      def compile(node, collector = Arel::Collectors::SQLString.new)
        accept(node, collector).value
      end

      private

        def visit_Arel_Nodes_DeleteStatement(o, collector)
          o = prepare_delete_statement(o)

          collector << "DELETE FROM "
          collector = visit o.relation, collector

          collect_where_for(o, collector)
        end

        def visit_Arel_Nodes_UpdateStatement(o, collector)
          o = prepare_update_statement(o)

          collector << "UPDATE "
          collector = visit o.relation, collector
          unless o.values.empty?
            collector << " SET "
            collector = inject_join o.values, collector, ", "
          end

          collect_where_for(o, collector)
        end

        def visit_Arel_Nodes_InsertStatement(o, collector)
          collector << "INSERT INTO "
          collector = visit o.relation, collector
          if o.columns.any?
            collector << " (#{o.columns.map { |x|
              quote_column_name x.name
            }.join ', '})"
          end

          if o.values
            maybe_visit o.values, collector
          elsif o.select
            maybe_visit o.select, collector
          else
            collector
          end
        end

        def visit_Arel_Nodes_Exists(o, collector)
          collector << "EXISTS ("
          collector = visit(o.expressions, collector) << ")"
          if o.alias
            collector << " AS "
            visit o.alias, collector
          else
            collector
          end
        end

        def visit_Arel_Nodes_Casted(o, collector)
          collector << quoted(o.val, o.attribute).to_s
        end

        def visit_Arel_Nodes_Quoted(o, collector)
          collector << quoted(o.expr, nil).to_s
        end

        def visit_Arel_Nodes_True(o, collector)
          collector << "TRUE"
        end

        def visit_Arel_Nodes_False(o, collector)
          collector << "FALSE"
        end

        def visit_Arel_Nodes_ValuesList(o, collector)
          collector << "VALUES "

          len = o.rows.length - 1
          o.rows.each_with_index { |row, i|
            collector << "("
            row_len = row.length - 1
            row.each_with_index do |value, k|
              case value
              when Nodes::SqlLiteral, Nodes::BindParam
                collector = visit(value, collector)
              else
                collector << quote(value)
              end
              collector << COMMA unless k == row_len
            end
            collector << ")"
            collector << COMMA unless i == len
          }
          collector
        end

        def visit_Arel_Nodes_Values(o, collector)
          collector << "VALUES ("

          len = o.expressions.length - 1
          o.expressions.each_with_index { |value, i|
            case value
            when Nodes::SqlLiteral, Nodes::BindParam
              collector = visit value, collector
            else
              collector << quote(value).to_s
            end
            unless i == len
              collector << COMMA
            end
          }

          collector << ")"
        end

        def visit_Arel_Nodes_SelectStatement(o, collector)
          if o.with
            collector = visit o.with, collector
            collector << SPACE
          end

          collector = o.cores.inject(collector) { |c, x|
            visit_Arel_Nodes_SelectCore(x, c)
          }

          unless o.orders.empty?
            collector << ORDER_BY
            len = o.orders.length - 1
            o.orders.each_with_index { |x, i|
              collector = visit(x, collector)
              collector << COMMA unless len == i
            }
          end

          visit_Arel_Nodes_SelectOptions(o, collector)

          collector
        end

        def visit_Arel_Nodes_SelectOptions(o, collector)
          collector = maybe_visit o.limit, collector
          collector = maybe_visit o.offset, collector
          collector = maybe_visit o.lock, collector
        end

        def visit_Arel_Nodes_SelectCore(o, collector)
          collector << "SELECT"

          collector = maybe_visit o.set_quantifier, collector

          collect_nodes_for o.projections, collector, SPACE

          if o.source && !o.source.empty?
            collector << " FROM "
            collector = visit o.source, collector
          end

          collect_nodes_for o.wheres, collector, WHERE, AND
          collect_nodes_for o.groups, collector, GROUP_BY
          unless o.havings.empty?
            collector << " HAVING "
            inject_join o.havings, collector, AND
          end
          collect_nodes_for o.windows, collector, WINDOW

          collector
        end

        def collect_nodes_for(nodes, collector, spacer, connector = COMMA)
          unless nodes.empty?
            collector << spacer
            len = nodes.length - 1
            nodes.each_with_index do |x, i|
              collector = visit(x, collector)
              collector << connector unless len == i
            end
          end
        end

        def visit_Arel_Nodes_Bin(o, collector)
          visit o.expr, collector
        end

        def visit_Arel_Nodes_Distinct(o, collector)
          collector << DISTINCT
        end

        def visit_Arel_Nodes_DistinctOn(o, collector)
          raise NotImplementedError, "DISTINCT ON not implemented for this db"
        end

        def visit_Arel_Nodes_With(o, collector)
          collector << "WITH "
          inject_join o.children, collector, COMMA
        end

        def visit_Arel_Nodes_WithRecursive(o, collector)
          collector << "WITH RECURSIVE "
          inject_join o.children, collector, COMMA
        end

        def visit_Arel_Nodes_Union(o, collector)
          collector << "( "
          infix_value(o, collector, " UNION ") << " )"
        end

        def visit_Arel_Nodes_UnionAll(o, collector)
          collector << "( "
          infix_value(o, collector, " UNION ALL ") << " )"
        end

        def visit_Arel_Nodes_Intersect(o, collector)
          collector << "( "
          infix_value(o, collector, " INTERSECT ") << " )"
        end

        def visit_Arel_Nodes_Except(o, collector)
          collector << "( "
          infix_value(o, collector, " EXCEPT ") << " )"
        end

        def visit_Arel_Nodes_NamedWindow(o, collector)
          collector << quote_column_name(o.name)
          collector << " AS "
          visit_Arel_Nodes_Window o, collector
        end

        def visit_Arel_Nodes_Window(o, collector)
          collector << "("

          if o.partitions.any?
            collector << "PARTITION BY "
            collector = inject_join o.partitions, collector, ", "
          end

          if o.orders.any?
            collector << SPACE if o.partitions.any?
            collector << "ORDER BY "
            collector = inject_join o.orders, collector, ", "
          end

          if o.framing
            collector << SPACE if o.partitions.any? || o.orders.any?
            collector = visit o.framing, collector
          end

          collector << ")"
        end

        def visit_Arel_Nodes_Rows(o, collector)
          if o.expr
            collector << "ROWS "
            visit o.expr, collector
          else
            collector << "ROWS"
          end
        end

        def visit_Arel_Nodes_Range(o, collector)
          if o.expr
            collector << "RANGE "
            visit o.expr, collector
          else
            collector << "RANGE"
          end
        end

        def visit_Arel_Nodes_Preceding(o, collector)
          collector = if o.expr
            visit o.expr, collector
          else
            collector << "UNBOUNDED"
          end

          collector << " PRECEDING"
        end

        def visit_Arel_Nodes_Following(o, collector)
          collector = if o.expr
            visit o.expr, collector
          else
            collector << "UNBOUNDED"
          end

          collector << " FOLLOWING"
        end

        def visit_Arel_Nodes_CurrentRow(o, collector)
          collector << "CURRENT ROW"
        end

        def visit_Arel_Nodes_Over(o, collector)
          case o.right
          when nil
            visit(o.left, collector) << " OVER ()"
          when Arel::Nodes::SqlLiteral
            infix_value o, collector, " OVER "
          when String, Symbol
            visit(o.left, collector) << " OVER #{quote_column_name o.right.to_s}"
          else
            infix_value o, collector, " OVER "
          end
        end

        def visit_Arel_Nodes_Offset(o, collector)
          collector << "OFFSET "
          visit o.expr, collector
        end

        def visit_Arel_Nodes_Limit(o, collector)
          collector << "LIMIT "
          visit o.expr, collector
        end

        def visit_Arel_Nodes_Lock(o, collector)
          visit o.expr, collector
        end

        def visit_Arel_Nodes_Grouping(o, collector)
          if o.expr.is_a? Nodes::Grouping
            visit(o.expr, collector)
          else
            collector << "("
            visit(o.expr, collector) << ")"
          end
        end

        def visit_Arel_SelectManager(o, collector)
          collector << "("
          visit(o.ast, collector) << ")"
        end

        def visit_Arel_Nodes_Ascending(o, collector)
          visit(o.expr, collector) << " ASC"
        end

        def visit_Arel_Nodes_Descending(o, collector)
          visit(o.expr, collector) << " DESC"
        end

        def visit_Arel_Nodes_Group(o, collector)
          visit o.expr, collector
        end

        def visit_Arel_Nodes_NamedFunction(o, collector)
          collector << o.name
          collector << "("
          collector << "DISTINCT " if o.distinct
          collector = inject_join(o.expressions, collector, ", ") << ")"
          if o.alias
            collector << " AS "
            visit o.alias, collector
          else
            collector
          end
        end

        def visit_Arel_Nodes_Extract(o, collector)
          collector << "EXTRACT(#{o.field.to_s.upcase} FROM "
          visit(o.expr, collector) << ")"
        end

        def visit_Arel_Nodes_Count(o, collector)
          aggregate "COUNT", o, collector
        end

        def visit_Arel_Nodes_Sum(o, collector)
          aggregate "SUM", o, collector
        end

        def visit_Arel_Nodes_Max(o, collector)
          aggregate "MAX", o, collector
        end

        def visit_Arel_Nodes_Min(o, collector)
          aggregate "MIN", o, collector
        end

        def visit_Arel_Nodes_Avg(o, collector)
          aggregate "AVG", o, collector
        end

        def visit_Arel_Nodes_TableAlias(o, collector)
          collector = visit o.relation, collector
          collector << " "
          collector << quote_table_name(o.name)
        end

        def visit_Arel_Nodes_Between(o, collector)
          collector = visit o.left, collector
          collector << " BETWEEN "
          visit o.right, collector
        end

        def visit_Arel_Nodes_GreaterThanOrEqual(o, collector)
          collector = visit o.left, collector
          collector << " >= "
          visit o.right, collector
        end

        def visit_Arel_Nodes_GreaterThan(o, collector)
          collector = visit o.left, collector
          collector << " > "
          visit o.right, collector
        end

        def visit_Arel_Nodes_LessThanOrEqual(o, collector)
          collector = visit o.left, collector
          collector << " <= "
          visit o.right, collector
        end

        def visit_Arel_Nodes_LessThan(o, collector)
          collector = visit o.left, collector
          collector << " < "
          visit o.right, collector
        end

        def visit_Arel_Nodes_Matches(o, collector)
          collector = visit o.left, collector
          collector << " LIKE "
          collector = visit o.right, collector
          if o.escape
            collector << " ESCAPE "
            visit o.escape, collector
          else
            collector
          end
        end

        def visit_Arel_Nodes_DoesNotMatch(o, collector)
          collector = visit o.left, collector
          collector << " NOT LIKE "
          collector = visit o.right, collector
          if o.escape
            collector << " ESCAPE "
            visit o.escape, collector
          else
            collector
          end
        end

        def visit_Arel_Nodes_JoinSource(o, collector)
          if o.left
            collector = visit o.left, collector
          end
          if o.right.any?
            collector << SPACE if o.left
            collector = inject_join o.right, collector, SPACE
          end
          collector
        end

        def visit_Arel_Nodes_Regexp(o, collector)
          raise NotImplementedError, "~ not implemented for this db"
        end

        def visit_Arel_Nodes_NotRegexp(o, collector)
          raise NotImplementedError, "!~ not implemented for this db"
        end

        def visit_Arel_Nodes_StringJoin(o, collector)
          visit o.left, collector
        end

        def visit_Arel_Nodes_FullOuterJoin(o, collector)
          collector << "FULL OUTER JOIN "
          collector = visit o.left, collector
          collector << SPACE
          visit o.right, collector
        end

        def visit_Arel_Nodes_OuterJoin(o, collector)
          collector << "LEFT OUTER JOIN "
          collector = visit o.left, collector
          collector << " "
          visit o.right, collector
        end

        def visit_Arel_Nodes_RightOuterJoin(o, collector)
          collector << "RIGHT OUTER JOIN "
          collector = visit o.left, collector
          collector << SPACE
          visit o.right, collector
        end

        def visit_Arel_Nodes_InnerJoin(o, collector)
          collector << "INNER JOIN "
          collector = visit o.left, collector
          if o.right
            collector << SPACE
            visit(o.right, collector)
          else
            collector
          end
        end

        def visit_Arel_Nodes_On(o, collector)
          collector << "ON "
          visit o.expr, collector
        end

        def visit_Arel_Nodes_Not(o, collector)
          collector << "NOT ("
          visit(o.expr, collector) << ")"
        end

        def visit_Arel_Table(o, collector)
          if o.table_alias
            collector << "#{quote_table_name o.name} #{quote_table_name o.table_alias}"
          else
            collector << quote_table_name(o.name)
          end
        end

        def visit_Arel_Nodes_In(o, collector)
          if Array === o.right && o.right.empty?
            collector << "1=0"
          else
            collector = visit o.left, collector
            collector << " IN ("
            visit(o.right, collector) << ")"
          end
        end

        def visit_Arel_Nodes_NotIn(o, collector)
          if Array === o.right && o.right.empty?
            collector << "1=1"
          else
            collector = visit o.left, collector
            collector << " NOT IN ("
            collector = visit o.right, collector
            collector << ")"
          end
        end

        def visit_Arel_Nodes_And(o, collector)
          inject_join o.children, collector, " AND "
        end

        def visit_Arel_Nodes_Or(o, collector)
          collector = visit o.left, collector
          collector << " OR "
          visit o.right, collector
        end

        def visit_Arel_Nodes_Assignment(o, collector)
          case o.right
          when Arel::Nodes::Node, Arel::Attributes::Attribute
            collector = visit o.left, collector
            collector << " = "
            visit o.right, collector
          else
            collector = visit o.left, collector
            collector << " = "
            collector << quote(o.right).to_s
          end
        end

        def visit_Arel_Nodes_Equality(o, collector)
          right = o.right

          collector = visit o.left, collector

          if right.nil?
            collector << " IS NULL"
          else
            collector << " = "
            visit right, collector
          end
        end

        def visit_Arel_Nodes_NotEqual(o, collector)
          right = o.right

          collector = visit o.left, collector

          if right.nil?
            collector << " IS NOT NULL"
          else
            collector << " != "
            visit right, collector
          end
        end

        def visit_Arel_Nodes_As(o, collector)
          collector = visit o.left, collector
          collector << " AS "
          visit o.right, collector
        end

        def visit_Arel_Nodes_Case(o, collector)
          collector << "CASE "
          if o.case
            visit o.case, collector
            collector << " "
          end
          o.conditions.each do |condition|
            visit condition, collector
            collector << " "
          end
          if o.default
            visit o.default, collector
            collector << " "
          end
          collector << "END"
        end

        def visit_Arel_Nodes_When(o, collector)
          collector << "WHEN "
          visit o.left, collector
          collector << " THEN "
          visit o.right, collector
        end

        def visit_Arel_Nodes_Else(o, collector)
          collector << "ELSE "
          visit o.expr, collector
        end

        def visit_Arel_Nodes_UnqualifiedColumn(o, collector)
          collector << "#{quote_column_name o.name}"
          collector
        end

        def visit_Arel_Attributes_Attribute(o, collector)
          join_name = o.relation.table_alias || o.relation.name
          collector << "#{quote_table_name join_name}.#{quote_column_name o.name}"
        end
        alias :visit_Arel_Attributes_Integer :visit_Arel_Attributes_Attribute
        alias :visit_Arel_Attributes_Float :visit_Arel_Attributes_Attribute
        alias :visit_Arel_Attributes_Decimal :visit_Arel_Attributes_Attribute
        alias :visit_Arel_Attributes_String :visit_Arel_Attributes_Attribute
        alias :visit_Arel_Attributes_Time :visit_Arel_Attributes_Attribute
        alias :visit_Arel_Attributes_Boolean :visit_Arel_Attributes_Attribute

        def literal(o, collector); collector << o.to_s; end

        def visit_Arel_Nodes_BindParam(o, collector)
          collector.add_bind(o.value) { "?" }
        end

        alias :visit_Arel_Nodes_SqlLiteral :literal
        alias :visit_Integer               :literal

        def quoted(o, a)
          if a && a.able_to_type_cast?
            quote(a.type_cast_for_database(o))
          else
            quote(o)
          end
        end

        def unsupported(o, collector)
          raise UnsupportedVisitError.new(o)
        end

        alias :visit_ActiveSupport_Multibyte_Chars :unsupported
        alias :visit_ActiveSupport_StringInquirer  :unsupported
        alias :visit_BigDecimal                    :unsupported
        alias :visit_Class                         :unsupported
        alias :visit_Date                          :unsupported
        alias :visit_DateTime                      :unsupported
        alias :visit_FalseClass                    :unsupported
        alias :visit_Float                         :unsupported
        alias :visit_Hash                          :unsupported
        alias :visit_NilClass                      :unsupported
        alias :visit_String                        :unsupported
        alias :visit_Symbol                        :unsupported
        alias :visit_Time                          :unsupported
        alias :visit_TrueClass                     :unsupported

        def visit_Arel_Nodes_InfixOperation(o, collector)
          collector = visit o.left, collector
          collector << " #{o.operator} "
          visit o.right, collector
        end

        alias :visit_Arel_Nodes_Addition       :visit_Arel_Nodes_InfixOperation
        alias :visit_Arel_Nodes_Subtraction    :visit_Arel_Nodes_InfixOperation
        alias :visit_Arel_Nodes_Multiplication :visit_Arel_Nodes_InfixOperation
        alias :visit_Arel_Nodes_Division       :visit_Arel_Nodes_InfixOperation

        def visit_Arel_Nodes_UnaryOperation(o, collector)
          collector << " #{o.operator} "
          visit o.expr, collector
        end

        def visit_Array(o, collector)
          inject_join o, collector, ", "
        end
        alias :visit_Set :visit_Array

        def quote(value)
          return value if Arel::Nodes::SqlLiteral === value
          @connection.quote value
        end

        def quote_table_name(name)
          return name if Arel::Nodes::SqlLiteral === name
          @connection.quote_table_name(name)
        end

        def quote_column_name(name)
          return name if Arel::Nodes::SqlLiteral === name
          @connection.quote_column_name(name)
        end

        def maybe_visit(thing, collector)
          return collector unless thing
          collector << " "
          visit thing, collector
        end

        def inject_join(list, collector, join_str)
          len = list.length - 1
          list.each_with_index.inject(collector) { |c, (x, i)|
            if i == len
              visit x, c
            else
              visit(x, c) << join_str
            end
          }
        end

        def has_join_sources?(o)
          o.relation.is_a?(Nodes::JoinSource) && !o.relation.right.empty?
        end

        def has_limit_or_offset_or_orders?(o)
          o.limit || o.offset || !o.orders.empty?
        end

        # The default strategy for an UPDATE with joins is to use a subquery. This doesn't work
        # on MySQL (even when aliasing the tables), but MySQL allows using JOIN directly in
        # an UPDATE statement, so in the MySQL visitor we redefine this to do that.
        def prepare_update_statement(o)
          if o.key && (has_limit_or_offset_or_orders?(o) || has_join_sources?(o))
            stmt = o.clone
            stmt.limit = nil
            stmt.offset = nil
            stmt.orders = []
            stmt.wheres = [Nodes::In.new(o.key, [build_subselect(o.key, o)])]
            stmt.relation = o.relation.left if has_join_sources?(o)
            stmt
          else
            o
          end
        end
        alias :prepare_delete_statement :prepare_update_statement

        # FIXME: we should probably have a 2-pass visitor for this
        def build_subselect(key, o)
          stmt             = Nodes::SelectStatement.new
          core             = stmt.cores.first
          core.froms       = o.relation
          core.wheres      = o.wheres
          core.projections = [key]
          stmt.limit       = o.limit
          stmt.offset      = o.offset
          stmt.orders      = o.orders
          stmt
        end

        def collect_where_for(o, collector)
          unless o.wheres.empty?
            collector << " WHERE "
            collector = inject_join o.wheres, collector, " AND "
          end

          unless o.orders.empty?
            collector << " ORDER BY "
            collector = inject_join o.orders, collector, ", "
          end

          maybe_visit o.limit, collector
        end

        def infix_value(o, collector, value)
          collector = visit o.left, collector
          collector << value
          visit o.right, collector
        end

        def aggregate(name, o, collector)
          collector << "#{name}("
          if o.distinct
            collector << "DISTINCT "
          end
          collector = inject_join(o.expressions, collector, ", ") << ")"
          if o.alias
            collector << " AS "
            visit o.alias, collector
          else
            collector
          end
        end
    end
  end
end
