# 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 'fileutils'
require 'uri'
require 'faraday'
require 'faraday/follow_redirects'
require 'English'
require_relative 'support/ui'

# Dependencies.
GCC_VERSION = '16.2.0'
GCC_HOST = 'build/host/gcc'
GCC_HOST_INSTALL = Pathname.new 'build/host/install'
GCC_TREE = Pathname.new "build/tools/gcc-#{GCC_VERSION}"
GCC_PATCH =
  "https://raw.githubusercontent.com/Homebrew/homebrew-core/refs/heads/main/Patches/gcc/gcc-#{GCC_VERSION}.diff".freeze

# Use Homebrew GCC if available (it uses libstdc++, avoiding
# macOS-specific libc++ incompatibilities in GCC's own sources).
class GCCConfiguration
  attr_reader :target

  def initialize(suffix, target, sysroot_sdk)
    @suffix = suffix
    @target = target
    @sysroot_sdk = sysroot_sdk
  end

  def cc
    "gcc#{@suffix}"
  end

  def cxx
    "g++#{@suffix}"
  end

  def configure
    @sysroot_sdk.nil? ? [] : ["--with-sysroot=#{@sysroot_sdk}"]
  end
end

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

def target_triple(cc_name)
  gcc_verbose(cc_name)
    .lines
    .find { |line| line.start_with? 'Target: ' }
    .split
    .last
    .strip
end

def find_build_target(gcc_version)
  is_darwin = RUBY_PLATFORM =~ /darwin/
  suffix = is_darwin ? "-#{gcc_version.split('.').first}" : ''
  mac_os_sdk = '/Library/Developer/CommandLineTools/SDKs/MacOSX.sdk' if is_darwin
  build_target = target_triple(ENV.fetch('CC', "gcc#{suffix}"))

  GCCConfiguration.new suffix, build_target, mac_os_sdk
end

def pipe_to_command(command, chdir:, &)
  IO.popen(command, 'w', chdir:, &)
  UI.fatal "Command #{command.join(' ')} failed" unless $CHILD_STATUS.success?
end

def stream_http(url, &)
  conn = Faraday.new do |f|
    f.response :follow_redirects
    f.response :raise_error
  end
  conn.get(url) do |req|
    req.options.on_data = ->(chunk, _, env) { yield chunk if (200..299).cover?(env.status) && !chunk.empty? }
  end
end

def download_and_pipe(url, target, command)
  target.mkpath
  pipe_to_command(command, chdir: target.to_path) do |stdin|
    stream_http(url) { |chunk| stdin.write chunk }
  end
end

# Makes a link from the source tree in the GCC tree.
def link_frontend(source, destination)
  File.symlink Pathname.new(source).relative_path_from(destination), (destination + File.basename(source))
end

# Replaces an elna-native directive in the line with its dg-* equivalent,
# escaping the directive argument for dejagnu's Tcl evaluation.
def convert_directive(line, directive, dg_name)
  line.sub(/\(\*\s*#{Regexp.escape directive}\s+(.*?)\s*\*\)/) do
    escaped = Regexp.last_match(1).gsub(/[\\\[\]$"]/) { |character| "\\#{character}" }
    "(* { #{dg_name} \"#{escaped}\" } *)"
  end
end

def test_trailer_lines(category, extra_lines = [])
  lines = []
  lines << '(* { dg-do run } *)' if category == 'runnable'
  lines.concat extra_lines
  lines << '(* { dg-prune-output .* } *)'
  case category
  when 'compilable' then lines << '(* { dg-final { output-exists } } *)'
  when 'fail_compilation' then lines << '(* { dg-final { output-exists-not } } *)'
  end
  lines
end

def convert_test(source, target, category, extra_lines = [])
  File.open(target, 'wb') do |output|
    File.foreach(source) do |line|
      line = convert_directive(line, '@Error', 'dg-error')
      output.puts convert_directive(line, '@Flags', 'dg-additional-options')
    end

    test_trailer_lines(category, extra_lines).each { |line| output.puts line }
  end
end

def multi_module_extra_sources(test_target)
  sources = test_target.glob('**/*.elna')
    .map { |extra| extra.relative_path_from(test_target) }
    .sort
  "(* { dg-additional-sources \"#{sources * ' '}\" } *)"
end

def convert_multi_module_test(test_path, test_target, category)
  main = test_path / 'sut.elna'
  UI.fatal "Multi-module test directory \"#{test_path}\" must contain sut.elna." unless main.file?

  test_target.mkdir
  (test_path.children - [main]).each { |extra| cp_r extra, test_target }
  extra_lines = ["(* { dg-additional-options \"-I#{test_target.expand_path}\" } *)"]
  extra_lines << multi_module_extra_sources(test_target) if category == 'runnable'

  convert_test main, test_target / 'sut.elna', category, extra_lines
end

namespace :gcc do
  directory GCC_HOST
  directory GCC_HOST_INSTALL.to_path
  directory 'build/tools'

  desc 'Download the bootstrap compiler and its prerequisites'
  task download: 'build/tools' do
    UI.step "Downloading bootstrap compiler and prerequisites (GCC #{GCC_VERSION})..."
    url = URI.parse "https://gcc.gnu.org/pub/gcc/releases/gcc-#{GCC_VERSION}/gcc-#{GCC_VERSION}.tar.xz"

    UI.debug "Downloading #{url}..."
    download_and_pipe url, GCC_TREE.dirname, ['tar', '-Jxv']
    UI.debug "Downloading and applying patch #{GCC_PATCH}..."
    download_and_pipe URI.parse(GCC_PATCH), GCC_TREE, ['patch', '-p1']

    # GCC 16.1.0 registers 17 languages but CL_PARAMS is at bit 16,
    # which collides with the 17th language class (CL_Rust). Shift
    # every CL_* constant from bit 16 upward by one position.
    UI.debug 'Patching gcc/opts.h to shift CL_* flags...'
    File.open(GCC_TREE / 'gcc/opts.h', 'r+') do |opts_h|
      content = opts_h.read.gsub(/\(1U << (\d+)\)/) do
        "(1U << #{Regexp.last_match(1).to_i + 1})"
      end
      opts_h.seek 0, IO::SEEK_SET
      opts_h.write content
    end

    sh 'contrib/download_prerequisites', chdir: GCC_TREE.to_path
  end

  desc 'Link the frontend into the GCC source tree'
  task :link do
    UI.step 'Linking Elna frontend into the GCC source tree...'
    source_destination = GCC_TREE / 'gcc/elna'
    test_destination = GCC_TREE / 'gcc/testsuite/elna.dg'

    rm_rf [source_destination, test_destination]
    mkdir_p [source_destination, test_destination]

    FileList['boot', 'include', 'COPYING3', 'README.md', 'gcc/gcc', 'gcc/*.in', 'gcc/lang*'].each do |file|
      link_frontend file, source_destination
    end
    FileList['gcc/dg.exp', 'README.md'].each do |file|
      link_frontend file, test_destination
    end
    destination = GCC_TREE / 'gcc/testsuite/lib'
    FileList['gcc/testlib/*'].each do |file|
      rm_f destination / File.basename(file)
      link_frontend file, destination
    end
  end

  desc 'Configure the bootstrap compiler'
  task configure: [GCC_HOST, GCC_HOST_INSTALL.to_path] do |t|
    build_target = find_build_target GCC_VERSION
    UI.step "Configuring bootstrap compiler for #{build_target.target}..."
    configure_options = [
      "--prefix=#{File.realpath t.prerequisites.last}",
      '--enable-languages=c,c++,jit,elna',
      '--disable-bootstrap',
      '--disable-multilib',
      '--enable-host-shared',
      '--with-system-zlib',
      "--target=#{build_target.target}",
      "--build=#{build_target.target}",
      "--host=#{build_target.target}",
      *build_target.configure
    ]
    env = {
      'CC' => ENV['CC'] || build_target.cc,
      'CXX' => ENV['CXX'] || build_target.cxx
    }
    env['CFLAGS'] = env['CXXFLAGS'] = '-O0 -g -fPIC -I/opt/homebrew/opt/flex/include'

    configure = GCC_TREE.relative_path_from(GCC_HOST) / 'configure'
    sh env, configure.to_path, *configure_options, chdir: GCC_HOST
  end

  desc 'Make and install the bootstrap compiler'
  task :make do
    UI.step "Building bootstrap compiler (jobs: #{Etc.nprocessors})..."
    sh 'make', '-j', Etc.nprocessors.to_s, chdir: GCC_HOST
    sh 'make', 'install', chdir: GCC_HOST
  end

  desc 'Convert the testsuite into dejagnu format'
  task :convert do
    UI.step 'Converting testsuite to DejaGnu format...'
    destination = GCC_TREE / 'gcc/testsuite/elna.dg'
    destination.mkpath
    source = Pathname.new 'testsuite'

    # Regenerate the category directories from scratch: this removes
    # converted tests whose sources are gone and adds new ones.
    %w[compilable fail_compilation runnable].each do |category|
      UI.debug "Converting #{category} tests..."
      category_destination = destination + category
      category_source = source + category

      rm_rf category_destination
      mkdir_p category_destination

      category_source.each_child do |test_path|
        test_target = category_destination + test_path.basename
        if test_path.directory?
          convert_multi_module_test test_path, test_target, category
        else
          convert_test test_path, test_target, category
        end
      end
    end
  end

  desc 'Run tests'
  task check: 'gcc:convert' do
    UI.step 'Running DejaGnu testsuite...'
    log_file = Pathname.new(GCC_HOST) / 'gcc/testsuite/elna/elna.log'

    sh 'make', 'check-elna', chdir: File.join(GCC_HOST, 'gcc')
    UI.fatal "See #{log_file}." if log_file.file? && log_file.read =~ /^(FAIL|XPASS|UNRESOLVED|ERROR):/
  end

  desc 'Run clang-tidy'
  task :tidy do
    compile_db = Pathname.new 'compile_commands.json'

    UI.fatal "#{compile_db} is missing.", hint: 'Run: bear -- rake gcc:make' unless compile_db.exist?

    sources = FileList['boot/*.cc', 'gcc/gcc/*.cc', 'include/elna/**/*.h']
      .reject do |file|
        ['/elna1.', '/elna-spec.'].any? { |pattern| file.include? pattern }
      end
    UI.step "Running clang-tidy on #{sources.size} files..."
    build_target = find_build_target GCC_VERSION
    includes = ['.', build_target.target].collect do |inc|
      GCC_HOST_INSTALL / 'include/c++' / GCC_VERSION / inc
    end

    sh 'clang-tidy', '-p', compile_db.to_path, '--extra-arg=-w', '--warnings-as-errors=*',
      *includes.collect { |inc| "--extra-arg=-cxx-isystem#{inc.realpath}" },
      '--extra-arg=-stdlib=libstdc++', *sources
  end

  desc 'Build documentation'
  task :doc do
    sh 'make', 'html', chdir: File.join(GCC_HOST, 'gcc')
  end

  desc 'Run GCC linters and tests'
  task test: %w[gcc:tidy gcc:check]
end

desc 'Build the bootstrap compiler'
task gcc: %w[gcc:download gcc:link gcc:configure gcc:make]