# 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'

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'

def compile(*arguments)
  sh(ENV.fetch('CC', 'gcc'), '-fpie', '-g', *arguments)
end

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

task default: :boot

desc 'Final stage'
task boot: "build/valid/#{STAGES.last}/cl"
task boot: "build/valid/#{STAGES.last}/cl.s"
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/stage16.elna', 'w') do |current_stage|
    skip = false

    File.readlines('boot/stage15.elna').each do |line|
      if line.strip == 'type'
        current_stage << <<~SNIP
          type
          	_elna_tac_declaration = record
          		next: Word;
          		name: Word;
          		length: Word;
          		body: Word
          	end;
		_integer_literal_node = record
			kind: Word;
			value: Word;
			length: Word
		end;
        SNIP
      elsif line.start_with?('proc _elna_tac_declaration_size')
        skip = true
      elsif line.start_with?('proc _elna_tac_declaration_get_')
        skip = true
      elsif line.start_with?('proc _elna_tac_declaration_set_')
        skip = true
      elsif line.start_with?('proc _integer_literal_node_size')
        skip = true
      elsif line.start_with?('proc _integer_literal_node_get_')
        skip = true
      elsif line.start_with?('proc _integer_literal_node_set_')
        skip = true
      elsif line.start_with?('end') && skip
        skip = false
      elsif !skip
        current_stage << line
      end
    end
  end
end

rule /^build\/[[:alpha:]]+\/stage[[:digit:]]+\/cl$/ => ->(match) {
  "#{match}.o"
} do |t|
  arguments_path = Pathname.new('boot') + Pathname.new(t.name).dirname.basename + 'linker.arg'
  if arguments_path.exist?
    arguments1 = ['--dynamic-linker', '/lib32/ld-linux-riscv32-ilp32d.so.1', '/usr/lib/crt1.o', '/usr/lib/crti.o', '-lc']
    arguments2 = ['/usr/lib/crtn.o']
  else
    arguments1 = arguments2 = []
  end

  sh(ENV.fetch('LD', 'ld'), '-o', t.name, *arguments1, *t.prerequisites, *arguments2)
end

rule /^build\/[[:alpha:]]+\/stage[[:digit:]]+\/cl.o$/ => ->(match) {
  match.ext('.s')
} do |t|
  compile('-c', '-o', t.name, *t.prerequisites)
end

STAGES.each do |stage|
  previous = stage.delete_prefix('stage').to_i.pred

  directory "build/valid/#{stage}"
  directory "build/boot/#{stage}"

  file "build/valid/#{stage}/cl.s" => ["build/boot/#{stage}/cl", "boot/#{stage}/cl.elna", "build/valid/#{stage}"] do |t|
    exe, source = t.prerequisites

    cat_arguments = ['cat', source]
    last_stdout, wait_threads = Open3.pipeline_r(cat_arguments, run(exe))

    IO.copy_stream last_stdout, t.name
  end

  file "build/boot/#{stage}/cl.s" => ["build/valid/stage#{previous}/cl", "boot/#{stage}/cl.elna", "build/boot/#{stage}"] do |t|
    exe, source = t.prerequisites

    cat_arguments = ['cat', source]
    last_stdout, wait_threads = Open3.pipeline_r(cat_arguments, run(exe))

    IO.copy_stream last_stdout, t.name
  end
end

#
# Stage 1.
#

directory 'build/valid/stage1'
directory 'build/boot/stage1'

file 'build/valid/stage1/cl' => ['build/valid/stage1.s'] do |t|
  compile('-nostdlib', '-o', t.name, *t.prerequisites)
end

file 'build/valid/stage1.s' => ['build/boot/stage1/cl', 'boot/stage1.s', 'build/valid/stage1'] do |t|
  source, exe, = t.prerequisites.partition { |prerequisite| prerequisite.end_with? '.s' }

  cat_arguments = ['cat', *source]
  last_stdout, wait_threads = Open3.pipeline_r(cat_arguments, run(exe.first))

  IO.copy_stream last_stdout, t.name
end

file 'build/boot/stage1/cl' => ['build/boot/stage1', 'boot/stage1.s'] do |t|
  source = t.prerequisites.select { |prerequisite| prerequisite.end_with? '.s' }

  compile('-nostdlib', '-o', t.name, *source)
end