# Encoding: UTF-8

# A (too) simple Gorilla-style shooter for two players.
# Shows how Gosu and RMagick can be used together to generate a map, implement
# a dynamic landscape and generally look great.
# Also shows a very minimal, yet effective way of designing a game's object system.

# Doesn't make use of Gosu's Z-ordering. Not many different things to draw, it's
# easy to get the order right without it.

# Known issues:
# * Collision detection of the missiles is lazy, allows shooting through thin walls.
# * The look of dead soldiers is, err, by accident. Soldier.png needs to be
#   designed in a less obfuscated way :)

require 'rubygems'
require 'gosu'
require 'rmagick'

WIDTH, HEIGHT = 640, 480

NULL_PIXEL = Magick::Pixel.from_color('none')

# The class for this game's map.
# Design:
# * Dynamic map creation at startup, holding it as RMagick Image in @image
# * Testing for solidity by testing @image's pixel values
# * Drawing from a Gosu::Image instance
# * Blasting holes into the map is implemented by drawing and erasing portions
#   of @image, then recreating the corresponding area in the Gosu::Image

class Map
  def initialize
    # Let's start with something simple and load the sky via RMagick.
    # Loading SVG files isn't possible with Gosu, so say wow!
    # (Seems to take a while though)
    sky = Magick::Image.read("media/landscape.svg").first
    @sky = Gosu::Image.new(sky, :tileable => true)
      
    # Create the map an stores the RMagick image in @image
    create_rmagick_map
    
    # Copy the RMagick Image to a Gosu Image (still unchanged)
    @gosu_image = Gosu::Image.new(@image, :tileable => true)
  end
  
  def solid? x, y
    # Map is open at the top.
    return false if y < 0
    # Map is closed on all other sides.
    return true if x < 0 or x >= WIDTH or y >= HEIGHT
    # Inside of the map, determine solidity from the map image.
    @image.pixel_color(x, y) != NULL_PIXEL
  end
  
  def draw
    # Sky background.
    @sky.draw 0, 0, 0
    # The landscape.
    @gosu_image.draw 0, 0, 0
  end

  # Radius of a crater.
  RADIUS = 25
  # Radius of a crater, Shadow included.
  SH_RADIUS = 45
  
  # Create the crater image (basically a circle shape that is used to erase
  # parts of the map) and the crater shadow image.
  CRATER_IMAGE = begin
    crater = Magick::Image.new(2 * RADIUS, 2 * RADIUS) { self.background_color = 'none' }
    gc = Magick::Draw.new
    gc.fill('black').circle(RADIUS, RADIUS, RADIUS, 0)
    gc.draw crater
    crater
  end
  CRATER_SHADOW = CRATER_IMAGE.shadow(0, 0, (SH_RADIUS - RADIUS) / 2, 1)
  
  def blast x, y
    # Draw the shadow (twice for more intensity), then erase a circle from the map.
    @image.composite! CRATER_SHADOW, x - SH_RADIUS, y - SH_RADIUS, Magick::AtopCompositeOp
    @image.composite! CRATER_SHADOW, x - SH_RADIUS, y - SH_RADIUS, Magick::AtopCompositeOp
    @image.composite! CRATER_IMAGE,  x - RADIUS,    y - RADIUS,    Magick::DstOutCompositeOp
    
    # Isolate the affected portion of the RMagick image.
    dirty_portion = @image.crop(x - SH_RADIUS, y - SH_RADIUS, SH_RADIUS * 2, SH_RADIUS * 2)
    # Overwrite this part of the Gosu image. If the crater begins outside of the map, still
    # just update the inner part.
    @gosu_image.insert dirty_portion, [x - SH_RADIUS, 0].max, [y - SH_RADIUS, 0].max
  end
  
  private
  
  def create_rmagick_map
    # This is the one large RMagick image that represents the map.
    @image = Magick::Image.new(WIDTH, HEIGHT) { self.background_color = 'none' }
    
    # Set up a Draw object that fills with an earth texture.
    earth = Magick::Image.read('media/earth.png').first.resize(1.5)
    gc = Magick::Draw.new
    gc.pattern('earth', 0, 0, earth.columns, earth.rows) { gc.composite(0, 0, 0, 0, earth) }    
    gc.fill('earth')
    gc.stroke('#603000').stroke_width(1.5)
    # Draw a smooth bezier island onto the map!
    polypoints = [0, HEIGHT]
    0.upto(8) do |x|
      polypoints += [x * 100, HEIGHT * 0.2 + rand(HEIGHT * 0.8)]
    end
    polypoints += [WIDTH, HEIGHT]
    gc.bezier(*polypoints)
    gc.draw(@image)
    
    # Create a bright-dark gradient fill, an image from it and change the map's
    # brightness with it.
    fill = Magick::GradientFill.new(0, HEIGHT * 0.4, WIDTH, HEIGHT * 0.4, '#fff', '#666')
    gradient = Magick::Image.new(WIDTH, HEIGHT, fill)
    gradient = @image.composite(gradient, 0, 0, Magick::InCompositeOp)
    @image.composite!(gradient, 0, 0, Magick::MultiplyCompositeOp)

    # Finally, place the star in the middle of the map, just onto the ground.
    star = Magick::Image.read('media/large_star.png').first
    star_y = 0
    star_y += 20 until solid?(WIDTH / 2, star_y)
    @image.composite!(star, (WIDTH - star.columns) / 2, star_y - star.rows * 0.85,
      Magick::DstOverCompositeOp)
  end
end

# Player class.
# Note that applies to the whole game:
# All objects implement an informal interface.
# draw: Draws the object (obviously)
# update: Moves the object etc., returns false if the object is to be deleted
# hit_by?(missile): Returns true if an object is hit by the missile, causing
#                   it to explode on this object. 

class Player
  # Magic numbers considered harmful! This is the height of the
  # player as used for collision detection.
  HEIGHT = 14
  
  attr_reader :x, :y, :dead
  
  def initialize(window, x, y, color)
    # Only load the images once for all instances of this class.
    @@images ||= Gosu::Image.load_tiles("media/soldier.png", 40, 50)
    
    @window, @x, @y, @color = window, x, y, color
    @vy = 0
    
    # -1: left, +1: right
    @dir = -1

    # Aiming angle.
    @angle = 90
  end
  
  def draw
    if dead
      # Poor, broken soldier.
      @@images[0].draw_rot(x, y, 0, 290 * @dir, 0.5, 0.65, @dir * 0.5, 0.5, @color)
      @@images[2].draw_rot(x, y, 0, 160 * @dir, 0.95, 0.5, 0.5, @dir * 0.5, @color)
    else
      # Was moved last frame?
      if @show_walk_anim
        # Yes: Display walking animation.
        frame = Gosu.milliseconds / 200 % 2
      else
        # No: Stand around (boring).
        frame = 0
      end
      
      # Draw feet, then chest.
      @@images[frame].draw(x - 10 * @dir, y - 20, 0, @dir * 0.5, 0.5, @color)
      angle = @angle
      angle = 180 - angle if @dir == -1
      @@images[2].draw_rot(x, y - 5, 0, angle, 1, 0.5, 0.5, @dir * 0.5, @color)
    end
  end
  
  def update
    # First, assume that no walking happened this frame.
    @show_walk_anim = false
    
    # Gravity.
    @vy += 1
    
    if @vy > 1
      # Move upwards until hitting something.
      @vy.times do
        if @window.map.solid?(x, y + 1)
          @vy = 0
          break
        else
          @y += 1
        end
      end
    else
      # Move downwards until hitting something.
      (-@vy).times do
        if @window.map.solid?(x, y - HEIGHT - 1)
          @vy = 0
          break
        else
          @y -= 1
        end
      end
    end
    
    # Soldiers are never deleted (they may die, but that is a different thing).
    true
  end
  
  def aim_up
    @angle -= 2 unless @angle < 10
  end
  
  def aim_down
    @angle += 2 unless @angle > 170
  end
  
  def try_walk(dir)
    @show_walk_anim = true
    @dir = dir
    # First, magically move up (so soldiers can run up hills)
    2.times { @y -= 1 unless @window.map.solid?(x, y - HEIGHT - 1) }
    # Now move into the desired direction.
    @x += dir unless @window.map.solid?(x + dir, y) or
                     @window.map.solid?(x + dir, y - HEIGHT) 
    # To make up for unnecessary movement upwards, sink downward again.
    2.times { @y += 1 unless @window.map.solid?(x, y + 1) }
  end
  
  def try_jump
    @vy = -12 if @window.map.solid?(x, y + 1)
  end
  
  def shoot
    @window.objects << Missile.new(@window, x + 10 * @dir, y - 10, @angle * @dir)
  end
  
  def hit_by? missile
    if Gosu.distance(missile.x, missile.y, x, y) < 30
      # Was hit :(
      @dead = true
      return true
    else
      return false
    end    
  end
end

# Implements the same interface as Player, except it's a missile!

class Missile
  attr_reader :x, :y, :vx, :vy

  # All missile instances use the same sound.
  EXPLOSION = Gosu::Sample.new("media/explosion.wav")
  
  def initialize(window, x, y, angle)
    # Horizontal/vertical velocity.
    @vx, @vy = Gosu.offset_x(angle, 20).to_i, Gosu.offset_y(angle, 20).to_i
    
    @window, @x, @y = window, x + @vx, y + @vy
  end
  
  def update
    # Movement, gravity
    @x += @vx
    @y += @vy
    @vy += 1
    # Hit anything?
    if @window.map.solid?(x, y) or @window.objects.any? { |o| o.hit_by?(self) }
      # Create great particles.
      5.times { @window.objects << Particle.new(@window, x - 25 + rand(51), y - 25 + rand(51)) }
      @window.map.blast(x, y)
      # Weeee, stereo sound!
      EXPLOSION.play_pan((1.0 * @x / WIDTH) * 2 - 1)
      return false
    else
      return true
    end
  end
  
  def draw
    # Just draw a small rectangle.
    Gosu.draw_rect x-2, y-2, 4, 4, 0xff_800000
  end
  
  def hit_by?(missile)
    # Missiles can't be hit by other missiles!
    false
  end
end

# Very minimal object that just draws a fading particle.

class Particle
  def initialize(window, x, y)
    # All Particle instances use the same image
    @@image ||= Gosu::Image.new('media/smoke.png')
    
    @x, @y = x, y
    @color = Gosu::Color.new(255, 255, 255, 255)
  end
  
  def update
    @y -= 5
    @x = @x - 1 + rand(3)
    @color.alpha -= 5
    
    # Remove if faded completely.
    @color.alpha > 0
  end
  
  def draw
    @@image.draw(@x - 25, @y - 25, 0, 1, 1, @color)
  end
  
  def hit_by?(missile)
    # Smoke can't be hit!
    false
  end
end

# Finally, the class that ties it all together.
# Very straightforward implementation.

class RMagickIntegration < (Example rescue Gosu::Window)
  attr_reader :map, :objects
  
  def initialize
    super WIDTH, HEIGHT
    
    self.caption = "RMagick Integration Demo"

    # Texts to display in the appropriate situations.
    @player_instructions = []
    @player_won_messages = []
    2.times do |plr|
      @player_instructions << Gosu::Image.from_text(
        "It is the #{ plr == 0 ? 'green' : 'red' } toy soldier's turn.\n" +
        "(Arrow keys to walk and aim, Return to jump, Space to shoot)",
        30, :width => width, :align => :center)
      @player_won_messages << Gosu::Image.from_text(
        "The #{ plr == 0 ? 'green' : 'red' } toy soldier has won!",
        30, :width => width, :align => :center)
    end

    # Create everything!
    @map = Map.new
    @players = [Player.new(self, 100, 40, 0xff_308000), Player.new(self, WIDTH - 100, 40, 0xff_803000)]
    @objects = @players.dup
    
    # Let any player start.
    @current_player = rand(2)
    # Currently not waiting for a missile to hit something.
    @waiting = false
  end
  
  def draw
    # Draw the main game.
    @map.draw
    @objects.each { |o| o.draw }
    
    # If any text should be displayed, draw it - and add a nice black border around it
    # by drawing it four times, with a little offset in each direction.
    
    cur_text = @player_instructions[@current_player] if not @waiting
    cur_text = @player_won_messages[1 - @current_player] if @players[@current_player].dead
    
    if cur_text
      x, y = 0, 30
      cur_text.draw(x - 1, y, 0, 1, 1, 0xff_000000)
      cur_text.draw(x + 1, y, 0, 1, 1, 0xff_000000)
      cur_text.draw(x, y - 1, 0, 1, 1, 0xff_000000)
      cur_text.draw(x, y + 1, 0, 1, 1, 0xff_000000)
      cur_text.draw(x,     y, 0, 1, 1, 0xff_ffffff)
    end
  end
  
  def update
    # if waiting for the next player's turn, continue to do so until the missile has
    # hit something.
    @waiting &&= !@objects.grep(Missile).empty?
     
    # Remove all objects whose update method returns false. 
    @objects.reject! { |o| o.update == false }

    # If it's a player's turn, forward controls.
    if not @waiting and not @players[@current_player].dead
      player = @players[@current_player]
      player.aim_up       if Gosu.button_down? Gosu::KB_UP
      player.aim_down     if Gosu.button_down? Gosu::KB_DOWN
      player.try_walk(-1) if Gosu.button_down? Gosu::KB_LEFT
      player.try_walk(+1) if Gosu.button_down? Gosu::KB_RIGHT
      player.try_jump     if Gosu.button_down? Gosu::KB_RETURN
    end
  end
  
  def button_down(id)
    if id == Gosu::KB_SPACE and not @waiting and not @players[@current_player].dead
      # Shoot! This is handled in button_down because holding space shouldn't auto-fire.
      @players[@current_player].shoot
      @current_player = 1 - @current_player
      @waiting = true
    else
      super
    end
  end
end

# So far we have only defined how everything *should* work - now set it up and run it!
RMagickIntegration.new.show if __FILE__ == $0