import fs from 'fs/promises'
import path from 'node:path'
import childProcess from 'node:child_process'
import process from 'process'
import os from 'os'
import { Buffer } from 'node:buffer'

// Define constants.
const tmp = path.resolve('./build/tools')
const baseDirectory = path.resolve('./tools')

const kernelVersion = '5.15.159'
const gccVersion = '14.1.0'
const binutilsVersion = '2.42'
const glibcVersion = '2.39'

async function gccVerbose (gccBinary) {
  const env = {
    ...process.env,
    LANG: 'C'
  }
  const gccV = childProcess.spawn(gccBinary, ['--verbose'], { stdio: ['ignore', 'ignore', 'pipe'], env })
  const buffers = []

  gccV.stderr.on('data', function (data) {
    buffers.push(data)
  })

  return new Promise(function (resolve, reject) {
    gccV.on('exit', function () {
      resolve(Buffer.concat(buffers).toString())
    })
  })
}

async function findBuildTarget (gccVersion) {
  let gccBinary = 'gcc'
  let output = await gccVerbose(gccBinary)

  if (output.startsWith('Apple clang')) {
    gccBinary = `gcc-${gccVersion.split('.')[0]}`
    output = await gccVerbose(gccBinary)
  }
  return output
    .split('\n')
    .reduce(function (accumulator, line) {
      if (line.startsWith('Target: ')) {
        return {
          ...accumulator,
          build: line.split(' ')[1]
        }
      } else if (line.startsWith('COLLECT_GCC')) {
        return {
          ...accumulator,
          gcc: line.split('=')[1]
        }
      } else {
        return accumulator
      }
    }, {})
}

async function downloadAndUnarchive (url) {
  const response = await fetch(url)
  const bodyReader = response.body.getReader()
  const basename = path.basename(url.pathname)
  let archiveType = ''
  let rootDirectory = ''

  switch (path.extname(basename)) {
    case '.bz2':
      archiveType = '-j'
      rootDirectory = path.basename(basename, '.tar.bz2')
      break
    case '.xz':
      archiveType = '-J'
      rootDirectory = path.basename(basename, '.tar.xz')
      break
    default:
      break
  }

  return new Promise(async function (resolve, reject) {
    const untar = childProcess.spawn('tar', ['-C', tmp, archiveType, '-xv'], { stdio: ['pipe', 'inherit', 'inherit'] })
    let done = false

    untar.on('exit', function () {
      resolve(path.join(tmp, rootDirectory))
    })

    do {
      const chunk = await bodyReader.read()

      done = chunk.done
      if (chunk.value !== undefined) {
        untar.stdin.write(chunk.value)
      }
    } while (!done)

    untar.stdin.end()
  })
}

async function copyGlibcHeaders () {
  const sourceDirectory = await downloadAndUnarchive(
    new URL(`https://ftp.gnu.org/gnu/glibc/glibc-${glibcVersion}.tar.xz`)
  )
  const includeDirectory = path.join(tmp, 'include')

  await fs.mkdir(includeDirectory)
  await fs.cp(path.join(sourceDirectory, 'elf/elf.h'), path.join(includeDirectory, 'elf.h'))

  return sourceDirectory
}

async function buildKernel (rootfs, options) {
  const cwd = await downloadAndUnarchive(
    new URL(`https://cdn.kernel.org/pub/linux/kernel/v5.x/linux-${kernelVersion}.tar.xz`)
  )
  const env = {
    ...process.env,
    CROSS_COMPILE: `${options.target}-`,
    ARCH: 'riscv',
    PATH: `${path.join(rootfs, 'bin')}:${process.env['PATH']}`,
    HOSTCFLAGS: `-D_UUID_T -D__GETHOSTUUID_H -I${path.join(tmp, 'include')}`
  }
  childProcess.execFileSync('make', ['rv32_defconfig'], { stdio: 'inherit', env, cwd })
  childProcess.execFileSync('make', ['-j', os.availableParallelism()], { stdio: 'inherit', env, cwd })
  childProcess.execFileSync('make', ['headers'], { stdio: 'inherit', env, cwd })

  const userDirectory = path.join(options.sysroot, 'usr')
  await fs.cp(path.join(cwd, 'usr/include'), path.join(userDirectory, 'include'), { recursive: true })

  return path.join(cwd, 'arch/riscv/boot/Image')
}

async function buildInit (rootfs, options) {
  const env = {
    ...process.env,
    PATH: `${path.join(rootfs, 'bin')}:${process.env['PATH']}`
  }
  const compilerArguments = [
    '-ffreestanding', '-static',
    '-o', path.join(tmp, 'init'),
    path.join(baseDirectory, 'init.c')
  ]
  childProcess.execFileSync('riscv32-unknown-linux-gnu-gcc', compilerArguments, { stdio: 'inherit', env })
}

async function buildGlibc (sourceDirectory, rootfs, options) {
  const configureOptions = [
    '--prefix=/usr',
    `--host=${options.target}`,
    `--target=${options.target}`,
    `--build=${options.build}`,
    `--enable-kernel=${kernelVersion}`,
    `--with-headers=${path.join(options.sysroot, 'usr/include')}`,
    '--disable-nscd',
    '--disable-libquadmath',
    '--disable-libitm',
    '--disable-werror',
    'libc_cv_forced_unwind=yes'
  ]
  const bin = path.join(rootfs, 'bin')
  const env = {
    ...process.env,
    PATH: `${path.join(rootfs, 'bin')}:${process.env['PATH']}`
  }
  const cwd = path.join(path.dirname(sourceDirectory), 'build-glibc');
  await fs.mkdir(cwd)

  childProcess.execFileSync(path.join(path.relative(cwd, sourceDirectory), './configure'), configureOptions, {
    stdio: 'inherit',
    env,
    cwd
  })
  childProcess.execFileSync('make', ['-j', os.availableParallelism()], { stdio: 'inherit', env, cwd })
  childProcess.execFileSync('make', [`install_root=${options.sysroot}`, 'install'], { stdio: 'inherit', env, cwd })
}

async function buildCrossBinutils (rootfs, options) {
  const sourceDirectory = await downloadAndUnarchive(
    new URL(`https://ftp.gnu.org/gnu/binutils/binutils-${binutilsVersion}.tar.xz`)
  )
  const cwd = path.join(path.dirname(sourceDirectory), 'build-binutils');
  await fs.mkdir(cwd)

  const env = {
    ...process.env,
    CC: options.gcc,
    CXX: options.gxx
  }
  const configureOptions = [
    `--prefix=${rootfs}`,
    `--target=${options.target}`,
    '--disable-nls',
    '--enable-gprofng=no',
    '--disable-werror',
    '--enable-default-hash-style=gnu',
    '--disable-libquadmath'
  ]
  childProcess.execFileSync(path.join(path.relative(cwd, sourceDirectory), 'configure'), configureOptions, {
    stdio: 'inherit',
    cwd,
    env
  })
  childProcess.execFileSync('make', ['-j', os.availableParallelism()], { stdio: 'inherit', cwd, env })
  childProcess.execFileSync('make', ['install'], { stdio: 'inherit', cwd, env })

  return sourceDirectory
}

async function buildGCC1 (rootfs, options) {
  const sourceDirectory = await downloadAndUnarchive(
    new URL(`https://gcc.gnu.org/pub/gcc/releases/gcc-${gccVersion}/gcc-${gccVersion}.tar.xz`)
  )
  const cwd = path.join(path.dirname(sourceDirectory), 'build-gcc');
  await fs.mkdir(cwd)

  childProcess.execFileSync(path.join(sourceDirectory, 'contrib/download_prerequisites'), {
    stdio: 'inherit',
    cwd: sourceDirectory
  })
  const configureOptions = [
    `--prefix=${rootfs}`,
    `--with-sysroot=${options.sysroot}`,
    '--enable-languages=c,c++',
    '--disable-shared',
    '--with-arch=rv32imafdc',
    '--with-abi=ilp32d',
    '--with-tune=rocket',
    '--with-isa-spec=20191213',
    '--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=${options.build}`
  ]
  const flags = '-O2 -fPIC'
  const env = {
    ...process.env,
    CC: options.gcc,
    CXX: options.gxx,
    CFLAGS: flags,
    CXXFLAGS: flags,
    PATH: `${path.join(rootfs, 'bin')}:${process.env['PATH']}`
  }
  childProcess.execFileSync(path.join(path.relative(cwd, sourceDirectory), 'configure'), configureOptions, {
    stdio: 'inherit',
    env,
    cwd
  })
  childProcess.execFileSync('make', ['-j', os.availableParallelism()], { stdio: 'inherit', env, cwd })
  childProcess.execFileSync('make', ['install'], { stdio: 'inherit', env, cwd })

  return sourceDirectory
}

async function buildGCC2 (sourceDirectory, rootfs, options) {
  const cwd = path.join(path.dirname(sourceDirectory), 'build-gcc');
  await fs.rm(cwd, { recursive: true, force: true })
  await fs.mkdir(cwd)

  const configureOptions = [
    `--prefix=${rootfs}`,
    `--with-sysroot=${options.sysroot}`,
    '--enable-languages=c,c++,lto',
    '--enable-lto',
    '--enable-shared',
    '--with-arch=rv32imafdc',
    '--with-abi=ilp32d',
    '--with-tune=rocket',
    '--with-isa-spec=20191213',
    '--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=${options.build}`
  ]
  const flags = '-O2 -fPIC'
  const env = {
    ...process.env,
    CFLAGS: flags,
    CXXFLAGS: flags,
    PATH: `${path.join(rootfs, 'bin')}:${process.env['PATH']}`
  }
  childProcess.execFileSync(path.join(path.relative(cwd, sourceDirectory), 'configure'), configureOptions, {
    stdio: 'inherit',
    env,
    cwd
  })
  childProcess.execFileSync('make', ['-j', os.availableParallelism()], { stdio: 'inherit', env, cwd })
  childProcess.execFileSync('make', ['install'], { stdio: 'inherit', env, cwd })
}

const rootfs = path.join(tmp, 'rootfs')

const options = await findBuildTarget(gccVersion)
options.gxx = options.gcc.replaceAll('c', '+')
options.sysroot = path.join(tmp, 'sysroot')
options.target = 'riscv32-unknown-linux-gnu'

for (const targetDirectory of [tmp, rootfs]) {
  await fs.rm(targetDirectory, { recursive: true, force: true })
  await fs.mkdir(targetDirectory)
}

const binutilsSource = await buildCrossBinutils(rootfs, options)
const gccSource = await buildGCC1(rootfs, options)

const glibcSource = await copyGlibcHeaders()
const kernelImage = await buildKernel(rootfs, options)
await buildGlibc(glibcSource, rootfs, options)
await buildGCC2(gccSource, rootfs, options)
buildInit (rootfs, options)

console.log(kernelImage)