From a2208a8f5f49734d3436b31c09dcb116643baa00 Mon Sep 17 00:00:00 2001
From: Jeremy Kaplan <jdkaplan@metagram.net>
Date: Wed, 11 Dec 2019 21:43:08 -0800
Subject: [PATCH] 2019: Day 11 Part 1

---
 2019/day11/intcode.rb | 243 ++++++++++++++++++++++++++++++++++++++++++
 2019/day11/part1.rb   | 127 ++++++++++++++++++++++
 2 files changed, 370 insertions(+)
 create mode 100644 2019/day11/intcode.rb
 create mode 100644 2019/day11/part1.rb

diff --git a/2019/day11/intcode.rb b/2019/day11/intcode.rb
new file mode 100644
index 0000000..e29ac62
--- /dev/null
+++ b/2019/day11/intcode.rb
@@ -0,0 +1,243 @@
+# frozen_string_literal: true
+
+require 'forwardable'
+
+module Intcode
+  def self.read(filename)
+    parse File.read(filename)
+  end
+
+  def self.parse(input)
+    parsed = input
+             .gsub(/^#.*$/, '')
+             .gsub('\s', '')
+             .split(',')
+             .map(&:to_i)
+    Program.new parsed
+  end
+
+  class Program
+    def initialize(mem)
+      @initial_state = mem
+    end
+
+    def as_memory
+      Memory.new(@initial_state.clone)
+    end
+
+    def run(&user_input)
+      Computer.new(as_memory).run(&user_input)
+    end
+  end
+
+  class Memory
+    extend Forwardable
+
+    def_delegator :@cells, :[]
+    def_delegator :@cells, :[]=
+
+    attr_accessor :relative_base
+
+    def initialize(cells)
+      @cells = cells
+      @relative_base = 0
+    end
+
+    def to_s
+      batch_size = 10
+      s = String.new
+      @cells.each_slice(batch_size).each_with_index do |batch, idx|
+        prefix = idx * batch_size
+        s << "#{prefix}: #{batch.join(' ')}\n"
+      end
+      s
+    end
+
+    def read(addr, mode)
+      # raise ArgumentError, "address out of range: #{addr}" if addr.negative? || addr >= @cells.length
+      return 0 if addr.negative? || addr >= @cells.length
+
+      case mode
+      when INDIRECT_MODE
+        read(@cells[addr], IMMEDIATE_MODE)
+      when IMMEDIATE_MODE
+        @cells[addr]
+      when RELATIVE_MODE
+        read(@cells[addr] + relative_base, IMMEDIATE_MODE)
+      else
+        raise ArgumentError, "unexpected mode: #{mode}"
+      end
+    end
+
+    def write(addr, mode, val)
+      raise ArgumentError, "address out of range: #{addr}" if addr.negative? || addr >= @cells.length
+
+      case mode
+      when INDIRECT_MODE
+        r = @cells[addr]
+        @cells[r] = val
+      when IMMEDIATE_MODE
+        raise ArgumentError, 'writes are not allowed in immediate mode'
+        @cells[addr]
+      when RELATIVE_MODE
+        r = @cells[addr] + relative_base
+        @cells[r] = val
+      else
+        raise ArgumentError, "unexpected mode: #{mode}"
+      end
+    end
+  end
+
+  INDIRECT_MODE = 0
+  IMMEDIATE_MODE = 1
+  RELATIVE_MODE = 2
+
+  class Computer
+    def initialize(mem, &block)
+      @mem = mem
+      @ip = 0
+      @input_block = block
+    end
+
+    def on_output(&block)
+      @output_block = block
+    end
+
+    def run
+      loop do
+        return if tick == :done_executing
+      end
+    end
+
+    def tick
+      opcode = operation(@mem[@ip])
+      case opcode
+      when 1
+        add!
+        nil
+      when 2
+        mul!
+        nil
+      when 3
+        input!(&@input_block)
+        nil
+      when 4
+        output!(&@output_block)
+      when 5
+        branch_if_not_zero!
+        nil
+      when 6
+        branch_if_zero!
+        nil
+      when 7
+        less_than!
+        nil
+      when 8
+        equal!
+        nil
+      when 9
+        move_relative_base!
+      when 99
+        :done_executing
+      else
+        raise StandardError, "unexpected opcode: #{opcode}"
+      end
+    end
+
+    private
+
+    def add!
+      mode = modes(@mem[@ip])
+      a = @mem.read(@ip + 1, mode[0])
+      b = @mem.read(@ip + 2, mode[1])
+      @mem.write(@ip + 3, mode[2], a + b)
+      @ip += 4
+    end
+
+    def mul!
+      mode = modes(@mem[@ip])
+      a = @mem.read(@ip + 1, mode[0])
+      b = @mem.read(@ip + 2, mode[1])
+      @mem.write(@ip + 3, mode[2], a * b)
+      @ip += 4
+    end
+
+    def input!(&user_input)
+      mode = modes(@mem[@ip])
+      inp = input(&user_input)
+      @mem.write(@ip + 1, mode[0], inp)
+      @ip += 2
+    end
+
+    def output!(&user_output)
+      mode = modes(@mem[@ip])
+      output = @mem.read(@ip + 1, mode[0])
+      user_output.call output if block_given?
+      @ip += 2
+      output
+    end
+
+    def branch_if_not_zero!
+      mode = modes(@mem[@ip])
+      a = @mem.read(@ip + 1, mode[0])
+      b = @mem.read(@ip + 2, mode[1])
+      @ip = a.zero? ? @ip + 3 : b
+    end
+
+    def branch_if_zero!
+      mode = modes(@mem[@ip])
+      a = @mem.read(@ip + 1, mode[0])
+      b = @mem.read(@ip + 2, mode[1])
+      @ip = a.zero? ? b : @ip + 3
+    end
+
+    def less_than!
+      mode = modes(@mem[@ip])
+      a = @mem.read(@ip + 1, mode[0])
+      b = @mem.read(@ip + 2, mode[1])
+      val = a < b ? 1 : 0
+      @mem.write(@ip + 3, mode[2], val)
+      @ip += 4
+    end
+
+    def equal!
+      mode = modes(@mem[@ip])
+      a = @mem.read(@ip + 1, mode[0])
+      b = @mem.read(@ip + 2, mode[1])
+      val = a == b ? 1 : 0
+      @mem.write(@ip + 3, mode[2], val)
+      @ip += 4
+    end
+
+    def move_relative_base!
+      mode = modes(@mem[@ip])
+      delta = @mem.read(@ip + 1, mode[0])
+      @mem.relative_base += delta
+      @ip += 2
+    end
+
+    def input
+      if block_given?
+        inp = yield
+        raise "Invalid input: #{inp.inspect}" unless inp.is_a?(Numeric)
+
+        return inp
+      end
+
+      print 'input> '
+      gets.to_i
+    end
+
+    def operation(cell)
+      (cell % 100)
+    end
+
+    def modes(cell)
+      m = Hash.new(0)
+      (cell / 100).truncate.digits.each_with_index do |d, i|
+        m[i] = d
+      end
+      m
+    end
+  end
+end
diff --git a/2019/day11/part1.rb b/2019/day11/part1.rb
new file mode 100644
index 0000000..fb907a0
--- /dev/null
+++ b/2019/day11/part1.rb
@@ -0,0 +1,127 @@
+# frozen_string_literal: true
+
+require 'set'
+require_relative 'intcode'
+
+Point = Struct.new(:x, :y) do
+  def to_s
+    "(#{x}, #{y})"
+  end
+end
+
+class Hull
+  def initialize
+    @panels = Hash.new { |hash, key| hash[key] = :black }
+    @painted = Set.new
+  end
+
+  def color_at(point)
+    @panels[point]
+  end
+
+  def paint(point, color)
+    @painted << point
+    @panels[point] = color
+  end
+
+  def painted
+    @painted.count
+  end
+end
+
+class DoneExecuting < StandardError; end
+
+class Robot
+  def initialize(program, hull)
+    @computer = Intcode::Computer.new(program.as_memory) { on_input }
+    @hull = hull
+    @facing = :up
+    @position = Point.new(0, 0)
+  end
+
+  def step
+    color_output = nil
+    direction_output = nil
+
+    color_output = tick until color_output
+    direction_output = tick until direction_output
+
+    @hull.paint(@position, color(color_output))
+    @facing = turn(@facing, direction_output)
+    @position = move(@position, @facing)
+  end
+
+  def tick
+    ret = @computer.tick
+    raise DoneExecuting if ret == :done_executing
+
+    ret
+  end
+
+  def on_input
+    color = @hull.color_at(@position)
+    case color
+    when :black
+      0
+    when :white
+      1
+    else
+      raise ArgumentError, "unexpected color: #{color}"
+    end
+  end
+
+  def color(code)
+    case code
+    when 0
+      :black
+    when 1
+      :white
+    else
+      raise ArgumentError, "unexpected color code: #{code}"
+    end
+  end
+
+  DIRECTIONS = %i[up right down left].freeze
+
+  def turn(facing, direction_code)
+    idx = DIRECTIONS.index(facing)
+    case direction_code
+    when 0
+      # left 90 degrees (ccw)
+      next_idx = (idx - 1) % DIRECTIONS.length
+    when 1
+      # right 90 degrees (cw)
+      next_idx = (idx + 1) % DIRECTIONS.length
+    else
+      raise ArgumentError, "unexpected direction code: #{direction_code}"
+    end
+    DIRECTIONS.fetch(next_idx)
+  end
+
+  def move(pos, direction)
+    case direction
+    when :up
+      Point.new(pos.x, pos.y - 1)
+    when :down
+      Point.new(pos.x, pos.y + 1)
+    when :left
+      Point.new(pos.x - 1, pos.y)
+    when :right
+      Point.new(pos.x + 1, pos.y)
+    else
+      raise ArgumentError, "unexpected direction: #{direction}"
+    end
+  end
+end
+
+program = Intcode.read(File.join(__dir__, 'input'))
+hull = Hull.new
+robot = Robot.new(program, hull)
+
+loop do
+  robot.step
+rescue DoneExecuting
+  break
+end
+
+puts hull.painted