#!/usr/bin/env ruby

require 'rmagick'
require 'yaml'
require 'erb'

data = YAML.load(File.read('spritesheet.yml'))

class Sprite
  def initialize(image:, sx:, sy:, width:, height:)
    @image = image
    @sx = sx
    @sy = sy
    @width = width
    @height = height
  end

  def pixel_data
    @height.times.each_with_object([]) do |y, obj|
      obj << @width.times.map do |x|
        color = @image.pixel_color(x + @sx, y + @sy)

        colormap.find_index { |c| c == color }
      end
    end
  end

  private

  def colormap
    @colormap ||= @image.colors.times.map do |i|
      Magick::Pixel.from_color(@image.colormap(i))
    end
  end
end

MovBytePtr = Data.define(:offset, :data)

ASM_TEMPLATE = <<~ASM
  <% sprites.each do |sprite| %>
  PUBLIC <%= sprite.exported_name %><% end %>

  .386
  .model flat,c

  .CODE

  <% sprites.each do |sprite| %>
  <%= sprite.exported_name %>:
    push ebp
    mov ebp, esp
    push ebx

    mov eax, [ebp + 8]

    <% sprite.bytes.each do |byte| %>
    mov BYTE PTR [eax + <%= byte.offset %>], <%= byte.data %><% end %>

    pop ebx
    pop ebp
    ret

  <% end %>
  end
ASM

C_TEMPLATE = <<~C
  <% sprites.each do |sprite| %>
  extern void <%= sprite.function_name %>(byte *);
  #pragma aux (__cdecl) <%= sprite.function_name %> "<%= sprite.exported_name %>"
  <% end %>
C

class AssemblerSprite
  def initialize(
    name:,
    pixel_data:,
    screen_width:,
    transparent_color:,
    offset_x:,
    offset_y:,
    prefix:
  )
    @name = name
    @pixel_data = pixel_data
    @screen_width = screen_width
    @transparent_color = transparent_color
    @offset_x = offset_x
    @offset_y = offset_y
    @prefix = prefix
  end

  def exported_name
    "#{function_name}_"
  end

  def function_name
    "#{@prefix}_#{@name}"
  end

  def bytes
    return @bytes if defined?(@bytes)

    bytes = []

    @pixel_data.each_with_index do |row, y|
      row.each_with_index do |column, x|
        next if @pixel_data[y][x] == @transparent_color

        bytes << MovBytePtr.new(
          data: @pixel_data[y][x],
          offset: x - @offset_x + (y - @offset_y) * @screen_width
        )
      end
    end

    bytes
  end
end

Screen = Data.define(:width, :transparent_color)
SpriteData = Data.define(:image, :name, :position, :dimensions, :offset, :prefix)

screen = Screen.new(
  width: data["screen"]["width"],
  transparent_color: data["screen"]["transparentColor"]
)

sprite_data = []

data["files"].each do |spritesheet|
  image = Magick::Image.read(spritesheet["file"]).first

  spritesheet["sprites"].each do |name, details|
    sprite_data << SpriteData.new(
      image:,
      name:,
      prefix: spritesheet["prefix"],
      position: details["position"],
      dimensions: details["dimensions"],
      offset: details["offset"]
    )
  end
end

sprites = sprite_data.map do |sd|
  sprite = Sprite.new(
    image: sd.image,
    sx: sd.position[0],
    sy: sd.position[1],
    width: sd.dimensions[0],
    height: sd.dimensions[1],
  )

  AssemblerSprite.new(
    name: sd.name,
    prefix: sd.prefix,
    pixel_data: sprite.pixel_data,
    screen_width: screen.width,
    transparent_color: screen.transparent_color,
    offset_x: sd.offset[0],
    offset_y: sd.offset[1],
  )
end

File.open('sprites.asm', 'w') do |fh|
  fh.puts ERB.new(ASM_TEMPLATE).result_with_hash(sprites:)
end

File.open('sprites.h', 'w') do |fh|
  fh.puts ERB.new(C_TEMPLATE).result_with_hash(sprites:)
end

puts "sprites.{asm,h} written"