# This Source Code Form is subject to the terms of the Mozilla Public License,
# v. 2.0. If a copy of the MPL was not distributed with this file, You can
# obtain one at https://mozilla.org/MPL/2.0/.
# frozen_string_literal: true

require 'open3'
require 'pathname'
require 'rake/clean'
require 'asciidoctor-pdf'

STAGES = Dir.glob('boot/stage*')
  .collect { |stage| File.basename stage }
  .sort { |a, b| a.delete_prefix('stage').to_i <=> b.delete_prefix('stage').to_i }
  .drop(1) # First assembly stage does not count.

CLEAN.include 'build/boot', 'build/valid'
CLEAN.include 'doc/*.pdf'
CLOBBER.include 'build'

def run(exe)
  ENV.fetch('QEMU', '').split << exe
end

task default: :boot

desc 'Final stage'
task boot: "build/valid/#{STAGES.last}/cl"
task boot: "boot/#{STAGES.last}/cl.elna" do |t|
  groupped = t.prerequisites.group_by { |stage| File.extname stage }.transform_values(&:first)
  exe = groupped['']
  expected = groupped[''] + '.s'
  source = groupped['.elna']

  cat_arguments = ['cat', source]
  diff_arguments = ['diff', '-Nur', '--text', expected, '-']
  Open3.pipeline(cat_arguments, run(exe), diff_arguments)
end

desc 'Convert previous stage language into the current stage language'
task :convert do
  File.open('boot/stage18/cl.elna', 'w') do |current_stage|
    File.readlines('boot/stage17/cl.elna').each do |line|
        current_stage << line
    end
  end
end

file "build/valid/#{STAGES.last}/cl" => 'build/build.ninja' do |t|
  sh 'ninja', '-f', t.prerequisites.first
end

file 'build/build.ninja' => ['build'] do |t|
  File.open t.name, 'w' do |f|
    f << <<~NINJA
      builddir = build
      cflags = -fpie -g

      rule cc
        command = gcc $cflags -nostdlib -o $out $in

      rule as
        command = gcc $cflags -c -o $out $in

      rule link1
        command = ld -o $out $in

      rule link2
        command = ld -o $out --dynamic-linker /lib32/ld-linux-riscv32-ilp32d.so.1 /usr/lib/crt1.o /usr/lib/crti.o -lc $in /usr/lib/crtn.o

      rule bootstrap
        command = $bootstrap < \$in > \$out
    NINJA
    f << <<~NINJA

      build build/boot/stage1/cl: cc boot/stage1.s
      build build/valid/stage1/cl.s: bootstrap boot/stage1.s | build/boot/stage1/cl
        bootstrap = build/boot/stage1/cl

      build build/valid/stage1/cl.o: as build/valid/stage1/cl.s
      build build/valid/stage1/cl: link1 build/valid/stage1/cl.o
    NINJA
    STAGES.each do |stage|
      stage_number = stage.delete_prefix('stage').to_i

      arguments_path = Pathname.new('boot') + stage + 'linker.arg'
      if arguments_path.exist?
        link = 'link2'
      else
        link = 'link1'
      end
      boot_stage = "build/boot/stage#{stage_number}"
      valid_stage = "build/valid/stage#{stage_number}"
      f << <<~NINJA

        build #{boot_stage}/cl.s: bootstrap boot/stage#{stage_number}/cl.elna | build/valid/stage#{stage_number.pred}/cl
          bootstrap = build/valid/stage#{stage_number.pred}/cl

        build #{boot_stage}/cl.o: as #{boot_stage}/cl.s
        build #{boot_stage}/cl: #{link} #{boot_stage}/cl.o

        build #{valid_stage}/cl.s: bootstrap boot/stage#{stage_number}/cl.elna | #{boot_stage}/cl
          bootstrap = build/boot/stage#{stage_number}/cl

        build #{valid_stage}/cl.o: as #{valid_stage}/cl.s
        build #{valid_stage}/cl: #{link} #{valid_stage}/cl.o
      NINJA
    end
    f << "\ndefault build/valid/stage18/cl\n"
  end
end

rule '.pdf' => '.adoc' do |t|
  Asciidoctor.convert_file t.source, backend: 'pdf', safe: :safe
end

desc 'Generate documentation'
task doc: 'doc/language.pdf'