#!/usr/bin/env ruby
# 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 'uri'
require 'net/http'
require 'open3'
require 'etc'
require 'pathname'
require 'rake/clean'

TMP = Pathname.new('./build')

CLOBBER.include 'build'

def gcc_verbose(gcc_binary)
  read, write = IO.pipe
  system({'LANG' => 'C'}, gcc_binary, '--verbose', err: write)
  write.close
  output = read.read
  read.close
  output
end

class BuildTarget
  def initialize(architecture)
    case architecture
    when /^r(isc)?v32$/
      @architecture = :rv32
    else
      raise "Unsupported architecture '#{architecture}'."
    end
  end

  def sysroot
    TMP + 'sysroot'
  end

  def rootfs
    TMP + 'rootfs'
  end

  def target
    case @architecture
    when :rv32
      'riscv32-unknown-linux-gnu'
    end
  end

  def build
    @build ||= gcc_verbose(ENV['CC']).lines
      .find { |line| line.start_with? 'Target: ' }
      .split(' ').last.strip
  end

  def configuration(prefix)
    case @architecture
    when :rv32
      ['arch=rv32imafdc', 'abi=ilp32d', 'tune=rocket', 'isa-spec=20191213'].map do |option|
        "-#{prefix}#{option}"
      end
    else
      []
    end
  end
end

def download_and_unarchive(url)
  case File.extname url.path
  when '.bz2'
    archive_type = '-j'
    root_directory = File.basename url.path, '.tar.bz2'
  when '.xz'
    archive_type = '-J'
    root_directory = File.basename url.path, '.tar.xz'
  else
    raise "Unsupported archive type #{url.path}."
  end
  target = TMP + 'tools'
  Net::HTTP.start(url.host, url.port, use_ssl: url.scheme == 'https') do |http|
    request = Net::HTTP::Get.new url.request_uri

    http.request request do |response|
      case response
      when Net::HTTPRedirection
        download_and_unarchive URI.parse(response['location'])
      when Net::HTTPSuccess
        Open3.popen2 'tar', '-C', target.to_path, archive_type, '-xv' do |stdin, stdout, wait_thread|
          Thread.new do
            stdout.each { |line| puts line }
          end

          response.read_body do |chunk|
            stdin.write chunk
          end
          stdin.close

          wait_thread.value
        end
      else
        response.error!
      end
    end
  end
  target + root_directory
end

def configure_make_install(source_directory, configure_options, env, cwd)
  configure = source_directory.relative_path_from(cwd) + 'configure'
  sh env, configure.to_path, *configure_options, chdir: cwd.to_path
  sh 'make', '-j', Etc.nprocessors.to_s, chdir: cwd.to_path
  sh env, 'make', 'install', chdir: cwd.to_path
end

directory(TMP + 'tools')

namespace :cross do
  BINUTILS_VERSION = '2.44'
  GLIBC_VERSION = '2.41'
  KERNEL_VERSION = '5.15.185'
  GCC_VERSION = "15.1.0"

  task :environment, :target do |t, args|
    binary_suffix = ''
    output = gcc_verbose 'gcc'

    if output.start_with? 'Apple clang'
      binary_suffix = "-#{GCC_VERSION.split('.').first}"
    end

    ENV['CC'] = "gcc#{binary_suffix}"
    ENV['CXX'] = "g++#{binary_suffix}"
  end

  desc 'Build cross binutils'
  task :binutils, [:target] => :environment do |t, args|
    options = BuildTarget.new args[:target]
    source_directory = download_and_unarchive(
      URI.parse("https://ftp.gnu.org/gnu/binutils/binutils-#{BINUTILS_VERSION}.tar.xz"))

    cwd = source_directory.dirname + 'build-binutils'
    cwd.mkpath
    options.rootfs.mkpath

    env = ENV.slice 'CC', 'CXX'
    configure_options = [
      "--prefix=#{options.rootfs.realpath}",
      "--target=#{options.target}",
      '--disable-nls',
      '--enable-gprofng=no',
      '--disable-werror',
      '--enable-default-hash-style=gnu',
      '--disable-libquadmath'
    ]
    configure_make_install source_directory, configure_options, env, cwd
  end

  desc 'Build stage 1 GCC'
  task :gcc1, [:target] => :environment do |t, args|
    options = BuildTarget.new args[:target]
    source_directory = download_and_unarchive(
      URI.parse("https://gcc.gnu.org/pub/gcc/releases/gcc-#{GCC_VERSION}/gcc-#{GCC_VERSION}.tar.xz"))

    cwd = source_directory.dirname + 'build-gcc'
    cwd.mkpath
    options.rootfs.mkpath
    options.sysroot.mkpath

    sh 'contrib/download_prerequisites', chdir: source_directory.to_path
    configure_options = options.configuration('-with-') + [
      "--prefix=#{options.rootfs.realpath}",
      "--with-sysroot=#{options.sysroot.realpath}",
      '--enable-languages=c,c++',
      '--disable-shared',
      '--disable-bootstrap',
      '--disable-multilib',
      '--disable-libmudflap',
      '--disable-libssp',
      '--disable-libquadmath',
      '--disable-libsanitizer',
      '--disable-threads',
      '--disable-libatomic',
      '--disable-libgomp',
      '--disable-libvtv',
      '--disable-libstdcxx',
      '--disable-nls',
      '--with-newlib',
      '--without-headers',
      "--target=#{options.target}",
      "--build=#{options.build}",
      "--host=#{options.build}"
    ]
    flags = '-O2 -fPIC'
    env = {
      'CC' => ENV['CC'],
      'CXX' => ENV['CXX'],
      'CFLAGS' => flags,
      'CXXFLAGS' => flags,
      'PATH' => "#{options.rootfs.realpath + 'bin'}:#{ENV['PATH']}"
    }
    configure_make_install source_directory, configure_options, env, cwd
  end

  desc 'Copy glibc headers'
  task :headers, [:target] => :environment do |t, args|
    options = BuildTarget.new args[:target]
    source_directory = download_and_unarchive(
      URI.parse("https://ftp.gnu.org/gnu/glibc/glibc-#{GLIBC_VERSION}.tar.xz"))
    include_directory = TMP + 'tools/include'

    include_directory.mkpath
    cp (source_directory + 'elf/elf.h'), (include_directory + 'elf.h')
  end

  desc 'Build linux kernel'
  task :kernel, [:target] => :environment do |t, args|
    options = BuildTarget.new args[:target]
    cwd = download_and_unarchive(
      URI.parse("https://cdn.kernel.org/pub/linux/kernel/v5.x/linux-#{KERNEL_VERSION}.tar.xz"))

    env = {
      'CROSS_COMPILE' => "#{options.target}-",
      'ARCH' => 'riscv',
      'PATH' => "#{options.rootfs.realpath + 'bin'}:#{ENV['PATH']}",
      'HOSTCFLAGS' => "-D_UUID_T -D__GETHOSTUUID_H -I#{TMP + 'tools/include'}"
    }
    sh env, 'make', 'rv32_defconfig', chdir: cwd.to_path
    sh env, 'make', '-j', Etc.nprocessors.to_s, chdir: cwd.to_path
    sh env, 'make', 'headers', chdir: cwd.to_path

    user_directory = options.sysroot + 'usr'

    user_directory.mkpath
    cp_r (cwd + 'usr/include'), (user_directory + 'include')
  end

  desc 'Build glibc'
  task :glibc, [:target] => :environment do |t, args|
    options = BuildTarget.new args[:target]
    source_directory = TMP + "tools/glibc-#{GLIBC_VERSION}"
    configure_options = [
      '--prefix=/usr',
      "--host=#{options.target}",
      "--target=#{options.target}",
      "--build=#{options.build}",
      "--enable-kernel=#{KERNEL_VERSION}",
      "--with-headers=#{options.sysroot.realpath + 'usr/include'}",
      '--disable-nscd',
      '--disable-libquadmath',
      '--disable-libitm',
      '--disable-werror',
      'libc_cv_forced_unwind=yes'
    ]
    bin = options.rootfs.realpath + 'bin'
    env = {
      'PATH' => "#{bin}:#{ENV['PATH']}",
      'MAKE' => 'make', # Otherwise it uses gnumake which can be different and too old.
      'CC' => "#{options.target}-gcc",
      'CXX' => "#{options.target}-g++"
    }
    cwd = source_directory.dirname + 'build-glibc'
    cwd.mkpath

    configure = source_directory.relative_path_from(cwd) +'./configure'
    system env, configure.to_path, *configure_options, chdir: cwd.to_path, exception: true
    system env, 'make', '-j', Etc.nprocessors.to_s, chdir: cwd.to_path, exception: true
    system env, 'make', "install_root=#{options.sysroot.realpath}", 'install', chdir: cwd.to_path, exception: true
  end

  desc 'Build stage 2 GCC'
  task :gcc2, [:target] => :environment do |t, args|
    options = BuildTarget.new args[:target]
    source_directory = TMP + "tools/gcc-#{GCC_VERSION}"
    cwd = TMP + 'tools/build-gcc'

    rm_rf cwd
    cwd.mkpath
    cp_r '../elna', source_directory + 'gcc'

    configure_options = options.configuration('-with-') + [
      "--prefix=#{options.rootfs.realpath}",
      "--with-sysroot=#{options.sysroot.realpath}",
      '--enable-languages=c,c++,lto,elna',
      '--enable-lto',
      '--enable-shared',
      '--disable-bootstrap',
      '--disable-multilib',
      '--enable-checking=release',
      '--disable-libssp',
      '--disable-libquadmath',
      '--enable-threads=posix',
      '--with-default-libstdcxx-abi=new',
      '--disable-nls',
      "--target=#{options.target}",
      "--build=#{options.build}",
      "--host=#{options.build}"
    ]
    flags = '-O2 -fPIC'
    env = {
      'CFLAGS' => flags,
      'CXXFLAGS' => flags,
      'PATH' => "#{options.rootfs.realpath + 'bin'}:#{ENV['PATH']}"
    }
    configure_make_install source_directory, configure_options, env, cwd
  end
end

task cross: TMP + 'tools'
task :cross, :target do |t, args|
  args.with_defaults target: 'riscv32'

  Rake::Task['cross:binutils'].invoke args[:target]
  Rake::Task['cross:gcc1'].invoke args[:target]
  Rake::Task['cross:headers'].invoke args[:target]
  Rake::Task['cross:kernel'].invoke args[:target]
  Rake::Task['cross:glibc'].invoke args[:target]
  Rake::Task['cross:gcc2'].invoke args[:target]
end

def relative_from_tmp(path)
  Pathname.new(path).relative_path_from(TMP).each_filename
end

CLEAN.include(TMP + 'riscv32')
directory(TMP + 'riscv32')

rule '.s.o' => ->(match) {
  architecture, *path_components = relative_from_tmp(match).to_a
  path_components[-1] = path_components.last.ext('')

  [File.join(path_components), TMP + architecture]
} do |t|
  options = BuildTarget.new relative_from_tmp(t.name).first
  compiler = options.rootfs + "bin/#{options.target}-gcc"
  flags = ['-ffreestanding'] + options.configuration('m')
  sources = t.prerequisites.select { |prerequisite| File.extname(prerequisite) == '.s' }

  system compiler.to_s, *flags, '-c', '-o', t.name, *sources, exception: true
end

rule '.elna.o' => ->(match) {
  architecture, *path_components = relative_from_tmp(match).to_a
  path_components[-1] = path_components.last.ext('')

  [File.join(path_components), TMP + architecture]
} do |t|
  options = BuildTarget.new relative_from_tmp(t.name).first
  compiler = options.rootfs + "bin/#{options.target}-gcc"
  flags = ['-O2', '-g3', '-fno-stack-protector'] + options.configuration('m')
  sources = t.prerequisites.select { |prerequisite| File.extname(prerequisite) == '.elna' }

  system compiler.to_s, *flags, '-c', '-o', t.name, *sources, exception: true
end

rule 'kernel.elf' => ->(match) {
  architecture_tmp = TMP + relative_from_tmp(match).first

  FileList['*.s', '*.elna'].map { |source| (architecture_tmp + source).to_path + '.o' } << 'kernel.ld'
} do |t|
  options = BuildTarget.new relative_from_tmp(t.name).first
  compiler = options.rootfs + "bin/#{options.target}-gcc"
  flags = options.configuration('m')
  objects, linker_script = t.prerequisites.partition { |prerequisite| File.extname(prerequisite) == '.o' }

  system compiler.to_s, '-nostdlib', '-T', *linker_script, '-o', t.name, *objects, exception: true
end

task default: 'build/riscv32/kernel.elf'
task :default do |t|
  QEMU = 'qemu-system-riscv32'

  system QEMU, '-machine', 'virt', '-bios', 'default', '-nographic', '-serial', 'mon:stdio', '--no-reboot',
    '-kernel', *t.prerequisites
end