Extract Executor class

2019/day5/intcode.rb

@@ -1,5 +1,7 @@
 # frozen_string_literal: true
 
+require 'forwardable'
+
 module Intcode
   def self.read(filename)
     parse File.read(filename)
@@ -14,7 +16,24 @@ module Intcode
     Program.new parsed
   end
 
+  class Program
+    def initialize(mem)
+      @input = nil
+      @initial_state = mem
+    end
+
+    def run(&user_input)
+      mem = Memory.new(@initial_state.clone)
+      Executor.new(mem).run(&user_input)
+    end
+  end
+
   class Memory
+    extend Forwardable
+
+    def_delegator :@cells, :[]
+    def_delegator :@cells, :[]=
+
     def initialize(cells)
       @cells = cells
     end
@@ -28,109 +47,105 @@ module Intcode
       end
       output
     end
-
-    def [](addr)
-      @cells[addr]
   end
 
-    def []=(addr, val)
+  class DoneExecuting < StandardError; end
-      @cells[addr] = val
-    end
-  end
 
-  class Program
+  class Executor
-    attr_accessor :mem
     def initialize(mem)
-      @input = nil
+      @mem = mem
-      @initial_state = mem
+      @ip = 0
     end
 
     def run(&user_input)
-      @mem = Memory.new(@initial_state.clone)
-      ip = 0
       loop do
-        opcode = operation(mem[ip])
+        tick(&user_input)
-        mode = modes(mem[ip])
+      rescue DoneExecuting
+        # TODO: Stop using exceptions for control flow
+        return
+      end
+    end
+
+    def tick(&user_input)
+      opcode = operation(@mem[@ip])
+      mode = modes(@mem[@ip])
       case opcode
       when 1
-          r1 = mem[ip + 1]
+        r1, r2, r3 = @mem[@ip + 1, 3]
-          r2 = mem[ip + 2]
-          r3 = mem[ip + 3]
         a = param(r1, mode[0])
         b = param(r2, mode[1])
         raise StandardError, "unexpected mode: #{mode[2]}" if mode[2] != 0
 
-          mem[r3] = a + b
+        @mem[r3] = a + b
-          ip += 4
+        @ip += 4
       when 2
-          r1 = mem[ip + 1]
+        r1 = @mem[@ip + 1]
-          r2 = mem[ip + 2]
+        r2 = @mem[@ip + 2]
-          r3 = mem[ip + 3]
+        r3 = @mem[@ip + 3]
         a = param(r1, mode[0])
         b = param(r2, mode[1])
         raise StandardError, "unexpected mode: #{mode[2]}" if mode[2] != 0
 
-          mem[r3] = a * b
+        @mem[r3] = a * b
-          ip += 4
+        @ip += 4
       when 3
-          r1 = mem[ip + 1]
+        r1 = @mem[@ip + 1]
         raise StandardError, "unexpected mode: #{mode[0]}" if mode[0] != 0
 
-          mem[r1] = user_input.nil? ? input : user_input.call
+        @mem[r1] = user_input.nil? ? input : user_input.call
-          ip += 2
+        @ip += 2
       when 4
-          r1 = mem[ip + 1]
+        r1 = @mem[@ip + 1]
         output = param(r1, mode[0])
         puts "output: #{output}"
 
-          ip += 2
+        @ip += 2
       when 5
-          r1 = mem[ip + 1]
+        r1 = @mem[@ip + 1]
-          r2 = mem[ip + 2]
+        r2 = @mem[@ip + 2]
         a = param(r1, mode[0])
         b = param(r2, mode[1])
         if !a.zero?
-            ip = b
+          @ip = b
         else
-            ip += 3
+          @ip += 3
         end
       when 6
-          r1 = mem[ip + 1]
+        r1 = @mem[@ip + 1]
-          r2 = mem[ip + 2]
+        r2 = @mem[@ip + 2]
         a = param(r1, mode[0])
         b = param(r2, mode[1])
         if a.zero?
-            ip = b
+          @ip = b
         else
-            ip += 3
+          @ip += 3
         end
       when 7
-          r1 = mem[ip + 1]
+        r1 = @mem[@ip + 1]
-          r2 = mem[ip + 2]
+        r2 = @mem[@ip + 2]
-          r3 = mem[ip + 3]
+        r3 = @mem[@ip + 3]
         a = param(r1, mode[0])
         b = param(r2, mode[1])
         raise StandardError, "unexpected mode: #{mode[2]}" if mode[2] != 0
 
-          mem[r3] = a < b ? 1 : 0
+        @mem[r3] = a < b ? 1 : 0
-          ip += 4
+        @ip += 4
       when 8
-          r1 = mem[ip + 1]
+        r1 = @mem[@ip + 1]
-          r2 = mem[ip + 2]
+        r2 = @mem[@ip + 2]
-          r3 = mem[ip + 3]
+        r3 = @mem[@ip + 3]
         a = param(r1, mode[0])
         b = param(r2, mode[1])
         raise StandardError, "unexpected mode: #{mode[2]}" if mode[2] != 0
 
-          mem[r3] = a == b ? 1 : 0
+        @mem[r3] = a == b ? 1 : 0
-          ip += 4
+        @ip += 4
       when 99
-          return mem[0]
+        raise DoneExecuting
       else
         raise StandardError, "unexpected opcode: #{opcode}"
       end
     end
-    end
 
     private
 
@@ -162,12 +177,16 @@ module Intcode
     def param(val, mode)
       case mode
       when 0
-        mem[val]
+        @mem[val]
       when 1
         val
       else
         raise StandardError, "unexpected mode: #{mode}"
       end
     end
+
+    # Operators
+
+    def add; end
   end
 end