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

M2C = 'gm2' # Modula-2 compiler.

stage_compiler = Pathname.new 'build/stage1/elna'

directory 'build/stage1'
directory 'build/source'
directory 'build/self'

CLEAN.include 'build'

rule(/build\/stage1\/.+\.o$/ => ->(file) {
  path = Pathname.new('boot/stage1/source') + Pathname.new(file).basename

  ['build/stage1', path.sub_ext('.def'), path.sub_ext('.mod')]
}) do |t|
  sources = t.prerequisites.filter { |f| f.end_with? '.mod' }

  sh M2C, '-c', '-I', 'boot/stage1/source', '-o', t.name, *sources
end

file 'build/stage1/elna' => FileList['boot/stage1/source/*'].map { |file|
  File.join 'build', 'stage1', Pathname.new(file).basename.sub_ext('.o')
} do |t|
  sh M2C, '-o', t.name, *t.prerequisites
end

file 'build/stage1/Compiler.o' => ['build/stage1', 'boot/stage1/source/Compiler.mod'] do |t|
  sources = t.prerequisites.filter { |f| f.end_with? '.mod' }

  sh M2C, '-fscaffold-main', '-c', '-I', 'boot/stage1/source', '-o', t.name, *sources
end

['source', 'self'].each do |sub|
  rule(/build\/#{sub}\/.+\.mod$/ => [
    "build/#{sub}", stage_compiler.to_path,
    ->(file) { File.join('source', Pathname.new(file).basename.sub_ext('.elna')) }
  ]) do |t|
    sources, compiler  = t.prerequisites
      .reject { |f| File.directory? f }
      .partition { |f| f.end_with? '.elna' }

    File.open t.name, 'w' do |output|
      compiler_command = compiler + sources

      puts
      puts(compiler_command * ' ')

      Open3.popen2(*compiler_command) do |cl_in, cl_out|
        cl_in.close

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

  rule(/build\/#{sub}\/.+\.o$/ => ->(file) {
    path = Pathname.new(file).relative_path_from('build')
    result = []

    result << File.join('source', path.basename.sub_ext('.def'))
    result << File.join('build', path.sub_ext('.mod'))
  }) do |t|
    sources = t.prerequisites.filter { |f| f.end_with? '.mod' }

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

  file "build/#{sub}/Compiler.o" => ["build/#{sub}/Compiler.mod"] do |t|
    sh M2C, '-fscaffold-main', '-c', '-I', 'source', '-o', t.name, *t.prerequisites
  end
  stage_compiler = Pathname.new('build') + sub + 'elna'

  file stage_compiler => FileList["source/*.elna"].map { |file|
    File.join 'build', sub, Pathname.new(file).basename.sub_ext('.o')
  } do |t|
    sh M2C, '-o', t.name, *t.prerequisites
  end
end

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

  exe_arguments = [exe, source]
  diff_arguments = ['diff', '-Nur', '--text', previous_output, '-']

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

task :backport do
  FileList['source/*.elna'].each do |file|
    source_path = Pathname.new file
    source = File.read source_path
    current_procedure = nil
    target = ''

    source
      .gsub(/^(var|type|const|begin)/) { |match| match.upcase }
      .gsub(/^[[:alnum:]]* ?module/) { |match| match.upcase }
      .gsub(/\b(record|nil|or|false|true)\b/) { |match| match.upcase }
      .gsub(/proc\(/, 'PROCEDURE(')
      .gsub(/ & /, ' AND ')
      .gsub(/ -> /, ': ')
      .gsub(/end\./, "END #{source_path.basename.sub_ext('')}.")
      .gsub(/([[:space:]]*)end(;?)$/, '\1END\2')
      .gsub(/^([[:space:]]*)(while|return|if)\b/) { |match| match.upcase }
      .gsub(/^from ([[:alnum:]]+) import/, 'FROM \1 IMPORT')
      .gsub(/ \^([[:alnum:]])/, ' POINTER TO \1')
      .gsub(/(then|do)$/) { |match| match.upcase }
      .gsub(/(:|=) \[([[:digit:]]+)\]/, '\1 ARRAY[1..\2] OF ')
      .each_line do |line|
        if line.start_with? 'proc'
          current_procedure = line[5...line.index('(')]

          line = 'PROCEDURE ' + line[5..].gsub(',', ';')
        elsif line.start_with?('END;') && !current_procedure.nil?
          line = "END #{current_procedure};"
          current_proceure = nil
        elsif line.start_with?('end')
          line = 'END ' + line[4..]
        end
        target += line
      end

    target_path = Pathname.new('boot/stage1/source') + source_path.basename.sub_ext('.mod')
    File.write target_path, target
  end
  FileList['source/*.def'].each do |file|
    cp file, File.join('boot/stage1/source', Pathname.new(file).basename)
  end
end