require 'pathname'
require 'rake/clean'
require 'open3'

M2C = 'gm2' # Modula-2 compiler.
BOOT_OBJECTS = FileList['boot/*.mod']
  .map do |source|
    Pathname.new(source).basename.sub_ext('.o')
  end

def source_for_object(out_file)
  path = Pathname.new(out_file).relative_path_from('build')
  result = ['build/boot']

  definition = File.join('boot', path.basename.sub_ext('.def'))
  result << definition if File.exist? definition

  implementation = path.sub_ext('.mod').to_path
  implementation = File.join 'build', implementation unless File.exist? implementation

  result << implementation
end

directory 'build/boot'
directory 'build/self'

CLEAN.include 'build'

rule(/build\/.+\.o$/ => ->(file) { source_for_object(file) }) do |t|
  sources = t.prerequisites.filter { |f| f.end_with? '.mod' }

  sh M2C, '-c', '-I', 'boot', '-o', t.name, *sources
end

rule(/build\/self\/.+\.mod$/ => [
  'build/self', 'build/boot/Compiler',
  ->(file) { File.join('boot', Pathname.new(file).basename) }
]) do |t|
  sources, compiler  = t.prerequisites
    .reject { |f| File.directory? f }
    .partition { |f| f.end_with? '.mod' }

  File.open t.name, 'w' do |output|
    puts
    puts(compiler * ' ')

    Open3.popen2(*compiler) do |cl_in, cl_out|
      cl_in.write File.read(*sources)
      cl_in.close

      IO.copy_stream cl_out, output
      cl_out.close
    end
  end
end

['boot', 'self'].each do |sub|
  compiler_binary = Pathname.new('build') + sub + 'Compiler'

  file compiler_binary.to_path => BOOT_OBJECTS.map { |file| File.join('build', sub, file) } do |t|
    sh M2C, '-o', t.name, *t.prerequisites
  end

  compiler_object = compiler_binary.sub_ext('.o')
  file compiler_object.to_path => source_for_object(compiler_object) do |t|
    sources = t.prerequisites.filter { |f| f.end_with? '.mod' }

    sh M2C, '-fscaffold-main', '-c', '-I', 'boot', '-o', t.name, *sources
  end
end

task default: 'build/self/Compiler'
task default: 'build/self/Compiler.mod'
task default: 'boot/Compiler.mod'
task :default do |t|
  exe, previous_output, source = t.prerequisites

  cat_arguments = ['cat', source]
  diff_arguments = ['diff', '-Nur', '--text', previous_output, '-']

  puts [cat_arguments * ' ', exe, diff_arguments * ' '].join(' | ')
  Open3.pipeline(cat_arguments, exe, diff_arguments)
end