path_prepend "i686-elf-gcc/bin"

configure do
  rscons "i686-elf-gcc.rb", "-b", "#{build_dir}/i686-elf-gcc"
  check_c_compiler "i686-elf-gcc"
  check_program "genext2fs"
  check_program "grub-mkstandalone"
  check_program "mformat", on_fail: "Install the mtools package"
  check_program "xorriso"
  check_cfg package: "freetype2", on_fail: "Install libfreetype-dev", use: "freetype"
end

require "tmpdir"

# EFI (w/ GRUB) partition size (MiB)
EFI_PART_SIZE = 8
# HOS partition size (MiB)
HOS_PART_SIZE = 4
# Kernel default font size
KFONT_SIZE = 15

class BiosImage < Builder
  def run(options)
    unless @cache.up_to_date?(@target, nil, @sources, @env)
      print_run_message("Generating BIOS boot image #{@target}", nil)
      Dir.mktmpdir do |tmpdir|
        # Create iso directory.
        FileUtils.mkdir_p("#{tmpdir}/iso/boot/grub")
        File.open("#{tmpdir}/iso/boot/grub/grub.cfg", "wb") do |fh|
          fh.write(<<EOF)
set default="0"
set timeout=1
menuentry "HOS" {
insmod multiboot2
multiboot2 /hos.elf
}
EOF
        end
        @sources.each do |source|
          FileUtils.cp(source, "#{tmpdir}/iso")
        end
        # Build bootable GRUB image.
        system(*%W[grub-mkrescue -o #{@target} #{tmpdir}/iso], err: "#{@env.build_root}/grub-mkrescue.log")
      end
      @cache.register_build(@target, nil, @sources, @env)
    end
    true
  end
end

class EfiImage < Builder
  def run(options)
    unless @cache.up_to_date?(@target, nil, @sources, @env)
      print_run_message("Generating EFI boot image #{@target}", nil)
      Dir.mktmpdir do |tmpdir|
        # Build a standalone GRUB.
        File.open("#{tmpdir}/grub.cfg", "wb") do |fh|
          fh.write(<<EOF)
insmod part_gpt
configfile (hd0,gpt2)/grub.cfg
EOF
        end
        system(*%W[grub-mkstandalone -O x86_64-efi -o #{tmpdir}/BOOTX64.EFI boot/grub/grub.cfg=#{tmpdir}/grub.cfg])
        # Create EFI partition.
        system(*%W[dd if=/dev/zero of=#{tmpdir}/efi.part bs=1M count=#{EFI_PART_SIZE}], err: "/dev/null")
        system(*%W[mformat -i #{tmpdir}/efi.part ::])
        system(*%W[mmd -i #{tmpdir}/efi.part ::/EFI])
        system(*%W[mmd -i #{tmpdir}/efi.part ::/EFI/BOOT])
        system(*%W[mcopy -i #{tmpdir}/efi.part #{tmpdir}/BOOTX64.EFI ::/EFI/BOOT])
        # Create ext2 HOS partition.
        FileUtils.mkdir_p("#{tmpdir}/ext2")
        @sources.each do |source|
          FileUtils.cp(source, "#{tmpdir}/ext2")
        end
        File.open("#{tmpdir}/ext2/grub.cfg", "wb") do |fh|
          fh.write(<<EOF)
set default="0"
set timeout=1
menuentry "HOS" {
insmod part_gpt
insmod multiboot2
set root=(hd0,gpt2)
multiboot2 /hos.elf
}
EOF
        end
        system(*%W[genext2fs -b #{HOS_PART_SIZE * 1024} -d #{tmpdir}/ext2 #{tmpdir}/ext2.part])
        # Create full disk image.
        system(*%W[dd if=/dev/zero of=#{@target} bs=1M count=#{EFI_PART_SIZE + HOS_PART_SIZE + 2}], err: "/dev/null")
        system(*%W[parted -s #{@target} mklabel gpt])
        system(*%W[parted -s #{@target} mkpart efi 1MiB #{EFI_PART_SIZE + 1}MiB])
        system(*%W[parted -s #{@target} mkpart hos #{EFI_PART_SIZE + 1}MiB #{EFI_PART_SIZE + HOS_PART_SIZE + 1}MiB])
        system(*%W[dd if=#{tmpdir}/efi.part of=#{@target} bs=1M seek=1 conv=notrunc], err: "/dev/null")
        system(*%W[dd if=#{tmpdir}/ext2.part of=#{@target} bs=1M seek=#{1 + EFI_PART_SIZE} conv=notrunc], err: "/dev/null")
      end
      @cache.register_build(@target, nil, @sources, @env)
    end
    true
  end
end

class FontGen < Builder
  def run(options)
    if @command
      finalize_command
    else
      fontgen = @vars["fontgen"]
      @sources += [fontgen]
      command = %W[#{fontgen} #{@sources.first} #{KFONT_SIZE} #{@target}]
      standard_command("FontGen <target>#{@target}<reset>", command, {})
    end
  end
end

class Size < Builder
  def run(options)
    if @command
      finalize_command
    else
      @vars["_SOURCES"] = @sources
      @vars["_TARGET"] = @target
      command = @env.build_command(%w[${SIZE} ${_SOURCES}], @vars)
      standard_command("Size <target>#{@target}<reset>", command, stdout: @target)
    end
  end
end

# FontGen Environment
fontgen_env = env "fontgen", use: "freetype" do |env|
  env["CC"] = "gcc"
  env.Program("^/fontgen.bin", glob("fontgen/**/*.c"))
end

# Kernel Environment
kernel_env = env "kernel" do |env|
  env.add_builder(EfiImage)
  env.add_builder(BiosImage)
  env.add_builder(FontGen)
  env.add_builder(Size)
  env["OBJDUMP"] = "i686-elf-objdump"
  env["SIZE"] = "i686-elf-size"
  env["CCFLAGS"] += %w[-ffreestanding -Wall -O2]
  env["LDFLAGS"] += %w[-ffreestanding -nostdlib -T src/link.ld]
  env["LDFLAGS"] += %W[-Wl,-Map,${_TARGET}.map]
  env["LIBS"] += %w[gcc]
  env.FontGen("^/kfont/kfont.c", "font/Hack-Regular.ttf",
             "fontgen" => fontgen_env.expand("^/fontgen.bin"))
  env.barrier
  env["CPPPATH"] += ["#{env.build_root}/kfont"]
  env.Program("^/hos.elf", glob("src/**/*.{S,c}") + ["^/kfont/kfont.c"])
  env.depends("#{env.build_root}/hos.elf", "src/link.ld")
  env.Disassemble("^/hos.elf.txt", "^/hos.elf")
  env.Size("^/hos.elf.size", "^/hos.elf")
  env.EfiImage("^/hos-efi.img", %w[^/hos.elf])
  env.BiosImage("^/hos.img", %w[^/hos.elf])
end

task "run", desc: "Run HOS in QEMU" do
  img = kernel_env.expand("^/hos.img")
  sh %W[qemu-system-x86_64 -hda #{img}]
end

task "run-efi", desc: "Run HOS EFI in QEMU" do
  img = kernel_env.expand("^/hos-efi.img")
  sh %W[qemu-system-x86_64 -bios OVMF.fd -hda #{img}]
end