opal/opal

# frozen_string_literal: true

require 'opal/nodes/base'
require 'opal/ast/matcher'

module Opal
  module Nodes
    class IfNode < Base
      handle :if

      children :test, :true_body, :false_body

      def compile
        if should_compile_as_simple_expression?
          if true_body == s(:true)
            compile_with_binary_or
          elsif false_body == s(:false)
            compile_with_binary_and
          else
            compile_with_ternary
          end
        elsif could_become_switch?
          compile_with_switch
        else
          compile_with_if
        end
      end

      def compile_with_if
        push_closure if expects_expression?

        truthy = self.truthy
        falsy = self.falsy

        if falsy && !truthy
          # Let's optimize a little bit `unless` calls.
          push 'if (!', js_truthy(test), ') {'
          falsy, truthy = truthy, falsy
        else
          push 'if (', js_truthy(test), ') {'
        end

        # skip if-body if no truthy sexp
        indent { line stmt(truthy) } if truthy

        if falsy
          if falsy.type == :if
            line '} else ', stmt(falsy)
          else
            line '} else {'
            indent do
              line stmt(falsy)
            end

            line '}'
          end
        else
          line '}'

          # This resolution isn't finite. Let's ensure this block
          # always return something if we expect a return
          line 'return nil;' if expects_expression?
        end

        pop_closure if expects_expression?

        if expects_expression?
          return_kw = 'return ' if returning_if?

          if scope.await_encountered
            wrap "#{return_kw}(await (async function() {", '})())'
          else
            wrap "#{return_kw}(function() {", '})()'
          end
        end
      end

      def returning_if?
        @sexp.meta[:returning]
      end

      def truthy
        returnify(true_body)
      end

      def falsy
        returnify(false_body)
      end

      def returnify(body)
        if expects_expression? && body
          compiler.returns(body)
        else
          body
        end
      end

      def expects_expression?
        expr? || recv?
      end

      # There was a particular case in the past, that when we
      # expected an expression from if, we always had to closure
      # it. This produced an ugly code that was hard to minify.
      # This addition tries to make a few cases compiled with
      # a ternary operator instead and possibly a binary operator
      # even?
      def should_compile_as_simple_expression?
        expects_expression? && simple?(true_body) && simple?(false_body)
      end

      def compile_with_ternary
        truthy = true_body
        falsy = false_body

        push '('

        push js_truthy(test), ' ? '

        push '(', expr(truthy || s(:nil)), ') : '
        if !falsy || falsy.type == :if
          push expr(falsy || s(:nil))
        else
          push '(', expr(falsy || s(:nil)), ')'
        end

        push ')'
      end

      def compile_with_binary_and
        if sexp.meta[:do_js_truthy_on_true_body]
          truthy = js_truthy(true_body || s(:nil))
        else
          truthy = expr(true_body || s(:nil))
        end

        push '('
        push js_truthy(test), ' && '
        push '(', truthy, ')'
        push ')'
      end

      def compile_with_binary_or
        if sexp.meta[:do_js_truthy_on_false_body]
          falsy = js_truthy(false_body || s(:nil))
        else
          falsy = expr(false_body || s(:nil))
        end

        push '('
        push js_truthy(test), ' || '
        push '(', falsy, ')'
        push ')'
      end

      # Let's ensure there are no control flow statements inside.
      def simple?(body)
        case body
        when AST::Node
          case body.type
          when :return, :js_return, :break, :next, :redo, :retry
            false
          when :xstr
            XStringNode.single_line?(
              XStringNode.strip_empty_children(body.children)
            )
          else
            body.children.all? { |i| simple?(i) }
          end
        else
          true
        end
      end

      # NOTE: all following matcher will act on case/when statements in their rewitten form:
      #
      #   bin/opal --sexp -e'case some_value_or_expression; when 123; when 456, 789; end'
      #
      #   s(:top,
      #     s(:if,
      #       s(:send,
      #         s(:int, 123), :===,
      #         s(:lvasgn, "$ret_or_1",
      #           s(:send, nil, :some_value_or_expression))), nil,
      #       s(:if,
      #         s(:if,
      #           s(:send,
      #             s(:int, 456), :===,
      #             s(:js_tmp, "$ret_or_1")),
      #           s(:true),
      #           s(:send,
      #             s(:int, 789), :===,
      #             s(:js_tmp, "$ret_or_1"))), nil,
      #         s(:nil))))
      #

      # Matches: `case some_value_or_expression; when 123`
      # Captures: [s(:int, 123), "$ret_or_1", s(:send, nil, :some_value_or_expression))]
      SWITCH_TEST_MATCH = AST::Matcher.new do
        s(:send,
          cap(s(%i[float int sym str true false nil], :*)),
          :===,
          s(:lvasgn, cap(:*), cap(:*))
        )
      end

      # Matches: case some_value_or_expression; when 123, 456; end
      # Captures: [
      #   s(:int, 123),
      #   "$ret_or_1",
      #   s(:send, nil, :some_value_or_expression)),
      #   …here we delegate to either SWITCH_BRANCH_TEST_MATCH or SWITCH_BRANCH_TEST_MATCH_CONTINUED
      # ]
      SWITCH_TEST_MATCH_CONTINUED = AST::Matcher.new do
        s(:if,
          s(:send,
            cap(s(%i[float int sym str true false nil], :*)),
            :===,
            s(:lvasgn, cap(:*), cap(:*))
          ),
          s(:true),
          cap(:*)
        )
      end

      # Matches: `when 456` (from `case foo; when 123; when 456; end`)
      # Captures: [s(:int, 456), "$ret_or_1"]
      SWITCH_BRANCH_TEST_MATCH = AST::Matcher.new do
        s(:send,
          cap(s(%i[float int sym str true false nil], :*)),
          :===,
          s(:js_tmp, cap(:*))
        )
      end

      # Matches: `when 456`
      # Captures: [
      #   s(:int, 789),
      #   "$ret_or_1",
      #   …here we delegate to either SWITCH_BRANCH_TEST_MATCH or SWITCH_BRANCH_TEST_MATCH_CONTINUED
      # ]
      SWITCH_BRANCH_TEST_MATCH_CONTINUED = AST::Matcher.new do
        s(:if,
          s(:send,
            cap(s(%i[float int sym str true false nil], :*)),
            :===,
            s(:js_tmp, cap(:*))
          ),
          s(:true),
          cap(:*)
        )
      end

      def could_become_switch?
        return false if expects_expression?

        return true if sexp.meta[:switch_child]

        test_match = SWITCH_TEST_MATCH.match(test) || SWITCH_TEST_MATCH_CONTINUED.match(test)
        return false unless test_match
        @switch_test, @switch_variable, @switch_first_test, additional_rules = *test_match

        additional_rules = handle_additional_switch_rules(additional_rules)
        return false unless additional_rules # It's ok for them to be empty, but false denotes a mismatch
        @switch_additional_rules = additional_rules

        return false unless valid_switch_body?(true_body)

        could_become_switch_branch?(false_body)
      end

      def handle_additional_switch_rules(additional_rules)
        switch_additional_rules = []
        while additional_rules
          match = SWITCH_BRANCH_TEST_MATCH.match(additional_rules) || SWITCH_BRANCH_TEST_MATCH_CONTINUED.match(additional_rules)
          return false unless match

          switch_test, switch_variable, additional_rules = *match
          return false unless switch_variable == @switch_variable

          switch_additional_rules << switch_test
        end
        switch_additional_rules
      end

      def could_become_switch_branch?(body)
        if !body
          return true
        elsif body.type != :if
          if valid_switch_body?(body)
            body.meta[:switch_default] = true
            return true
          end
          return false
        end

        test, true_body, false_body = *body

        test_match = SWITCH_BRANCH_TEST_MATCH.match(test) || SWITCH_BRANCH_TEST_MATCH_CONTINUED.match(test)
        unless test_match
          if valid_switch_body?(body, true)
            body.meta[:switch_default] = true
            return true
          end
        end
        switch_test, switch_variable, additional_rules = *test_match

        switch_additional_rules = handle_additional_switch_rules(additional_rules)
        return false unless switch_additional_rules # It's ok for them to be empty, but false denotes a mismatch

        return false unless switch_variable == @switch_variable

        return false unless valid_switch_body?(true_body)
        return false unless could_become_switch_branch?(false_body)

        body.meta.merge!(switch_child: true,
                         switch_test: switch_test,
                         switch_variable: @switch_variable,
                         switch_additional_rules: switch_additional_rules
        )

        true
      end

      def valid_switch_body?(body, check_variable = false)
        case body
        when AST::Node
          case body.type
          when :break, :redo, :retry
            false
          when :iter, :while
            # Don't traverse the iters or whiles!
            true
          else
            body.children.all? { |i| valid_switch_body?(i, check_variable) }
          end
        when @switch_variable
          # Perhaps we ended abruptly and we lack a $ret_or variable... but sometimes
          # we can ignore this.
          !check_variable
        else
          true
        end
      end

      def compile_with_switch
        if sexp.meta[:switch_child]
          @switch_variable = sexp.meta[:switch_variable]
          @switch_additional_rules = sexp.meta[:switch_additional_rules]
          compile_switch_case(sexp.meta[:switch_test])
        else
          line "switch (", expr(@switch_first_test), ".valueOf()) {"
          indent do
            compile_switch_case(@switch_test)
          end
          line "}"
        end
      end

      def returning?(body)
        %i[return js_return next].include?(body.type) ||
          (body.type == :begin && %i[return js_return next].include?(body.children.last.type))
      end

      def compile_switch_case(test)
        line "case ", expr(test), ":"
        if @switch_additional_rules
          @switch_additional_rules.each do |rule|
            line "case ", expr(rule), ":"
          end
        end
        indent do
          line stmt(true_body)
          line "break;" if !true_body || !returning?(true_body)
        end
        if false_body
          if false_body.meta[:switch_default]
            compile_switch_default
          elsif false_body.meta[:switch_child]
            push stmt(false_body)
          end
        else
          push stmt(s(:nil))
        end
      end

      def compile_switch_default
        line "default:"
        indent do
          line stmt(false_body)
        end
      end
    end

    class BaseFlipFlop < Base
      children :start_condition, :end_condition

      def compile
        helper :truthy

        func_name = top_scope.new_temp
        flip_flop_state = "#{func_name}.$$ff"

        # Start function definition, checking and initializing it if necessary
        push "(#{func_name} = #{func_name} || function(_start_func, _end_func){"

        # If flip flop state is not defined, set it to false
        push "  var flip_flop = #{flip_flop_state} || false;"

        # If flip flop state is false, call the 'start_condition' function and store its truthy result into flip flop state
        push "  if (!flip_flop) #{flip_flop_state} = flip_flop = $truthy(_start_func());"

        # If flip flop state is true, call the 'end_condition' function and set flip flop state to false if 'end_condition' is truthy
        push "  #{excl}if (flip_flop && $truthy(_end_func())) #{flip_flop_state} = false;"

        # Return current state of flip flop
        push "  return flip_flop;"

        # End function definition
        push "})("

        # Call the function with 'start_condition' and 'end_condition' arguments wrapped in functions to ensure correct binding and delay evaluation
        push "  function() { ", stmt(compiler.returns(start_condition)), " },"
        push "  function() { ", stmt(compiler.returns(end_condition)), " }"
        push ")"
      end
    end

    class IFlipFlop < BaseFlipFlop
      handle :iflipflop

      # Inclusive flip flop, check 'end_condition' in the same iteration when 'start_condition' is truthy
      def excl
        ""
      end
    end

    class EFlipFlop < BaseFlipFlop
      handle :eflipflop

      # Exclusive flip flop, check 'end_condition' in the next iteration after 'start_condition' is truthy
      def excl
        "else "
      end
    end
  end
end