#!/usr/bin/env bash
  
  CXX=${CXX:-g++}
  status=0
  
  # at some point we could try to add packages for Cywgin or macports(?) to this
  # script.
  redhat_packages=
  debian_packages=
  opensuse_packages=
  
  function add_packages {
    redhat_packages="$redhat_packages $1"
    debian_packages="$debian_packages ${2:-$1}"
    opensuse_packages="$opensuse_packages ${3:-$1}"
  }
  
  function have { type -t "$1" >/dev/null; }
  
  compiler_ver_info=$($CXX --version 2>/dev/null)
  case $compiler_ver_info in
    "")
      echo "$0: Compiler '$CXX' is not installed."
      echo "$0: You need g++ >= 4.8.3, Apple Xcode >= 5.0 or clang >= 3.3."
      add_packages gcc-c++ g++
      status=1
      ;;
    "g++ "* )
      gcc_ver=$($CXX -dumpversion)
      gcc_ver_num=$(echo $gcc_ver | sed 's/\./ /g' | xargs printf "%d%02d%02d")
      if [ $gcc_ver_num -lt 40803 ]; then
          echo "$0: Compiler '$CXX' (g++-$gcc_ver) is not supported."
          echo "$0: You need g++ >= 4.8.3, Apple clang >= 5.0 or LLVM clang >= 3.3."
          status=1
      fi
      ;;
    "Apple LLVM "* )
      # See https://gist.github.com/yamaya/2924292
      clang_ver=$(echo $compiler_ver_info | grep version | sed "s/.*version \([0-9\.]*\).*/\1/")
      clang_ver_num=$(echo $compiler_ver_info | grep version | sed "s/.*clang-\([0-9]*\).*/\1/")
      if [ $clang_ver_num -lt 500 ]; then
          echo "$0: Compiler '$CXX' (Apple clang-$clang_ver) is not supported."
          echo "$0: You need g++ >= 4.8.3, Apple clang >= 5.0 or LLVM clang >= 3.3."
          status=1
      fi
      ;;
    "clang "* )
      clang_ver=$(echo $compiler_ver_info | grep version | sed "s/.*version \([0-9\.]*\).*/\1/")
      clang_ver_num=$(echo $clang_ver | sed 's/\./ /g' | xargs printf "%d%02d")
      if [ $clang_ver_num -lt 303 ]; then
          echo "$0: Compiler '$CXX' (LLVM clang-$clang_ver) is not supported."
          echo "$0: You need g++ >= 4.8.3, Apple clang >= 5.0 or LLVM clang >= 3.3."
          status=1
      fi
      ;;
    *)
      echo "$0: WARNING: unknown compiler $CXX."
      ;;
  esac
  
  # Cannot check this without a compiler.
  if have "$CXX" && ! echo "#include <zlib.h>" | $CXX -E - >&/dev/null; then
    echo "$0: zlib is not installed."
    add_packages zlib-devel zlib1g-dev
  fi
  
  for f in make automake autoconf patch grep bzip2 gzip unzip wget git sox; do
    if ! have $f; then
      echo "$0: $f is not installed."
      add_packages $f
    fi
  done
  
  if ! have libtoolize && ! have glibtoolize; then
    echo "$0: neither libtoolize nor glibtoolize is installed"
    add_packages libtool
  fi
  
  if ! have svn; then
    echo "$0: subversion is not installed"
    add_packages subversion
  fi
  
  if ! have awk; then
    echo "$0: awk is not installed"
    add_packages gawk
  fi
  
  pythonok=true
  if ! have python2.7; then
    echo "$0: python2.7 is not installed"
    add_packages python2.7
    pythonok=false
  fi
  
  if ! have python3; then
    echo "$0: python3 is not installed"
    add_packages python3
    pythonok=false
  fi
  
  (
  #Use a subshell so that sourcing env.sh does not have an influence on the rest of the script
  [ -f ./env.sh ] && . ./env.sh
  if $pythonok && ! have python2; then
    mkdir -p $PWD/python
    echo "$0: python2.7 is installed, but the python2 binary does not exist." \
         "Creating a symlink and adding this to tools/env.sh"
    ln -s $(command -v python2.7) $PWD/python/python2
    echo "export PATH=$PWD/python:\${PATH}" >> env.sh
  fi
  
  if [[ -f $PWD/python/.use_default_python && -f $PWD/python/python ]]; then
    rm $PWD/python/python
  fi
  
  if $pythonok && have python && [[ ! -f $PWD/python/.use_default_python ]]; then
    version=$(python 2>&1 --version | awk '{print $2}')
    if [[ $version != "2.7"* ]] ; then
      echo "$0: WARNING python 2.7 is not the default python. We fixed this by" \
           "adding a correct symlink more prominently on the path."
      echo " ... If you really want to use python $version as default, add an" \
           "empty file $PWD/python/.use_default_python and run this script again."
      mkdir -p $PWD/python
      ln -s $(command -v python2.7) $PWD/python/python
      echo "export PATH=$PWD/python:\${PATH}" >> env.sh
    fi
  fi
  )
  
  mathlib_missing=false
  case $(uname -m) in
    x86_64)  # Suggest MKL on an Intel64 system (configure does not like i?86 hosts).
      # We do not know if compiler exists at this point, so double-check the
      # well-known mkl.h file location. The compiler test would still find it if
      # installed in an alternative location (this is unlikely).
      if [ ! -f /opt/intel/mkl/include/mkl.h ] &&
           ! echo '#include <mkl.h>' | $CXX -I /opt/intel/mkl/include -E - >&/dev/null; then
        if [[ $(uname) == Linux ]]; then
          echo "$0: Intel MKL is not installed. Run extras/install_mkl.sh to install it."
        else
          echo "$0: Intel MKL is not installed. Download the installer package for your
   ... system from: https://software.intel.com/mkl/choose-download."
        fi
        mathlib_missing=true
      fi
        ;;
    *)  # Suggest OpenBLAS on other hardware.
      if [ ! -f $(pwd)/OpenBLAS/install/include/openblas_config.h ] &&
           ! echo '#include <openblas_config.h>' |
              $CXX -I $(pwd)/OpenBLAS/install/include -E - >&/dev/null; then
        echo "$0: OpenBLAS not detected. Run extras/install_openblas.sh
   ... to compile it for your platform, or configure with --openblas-root= if you
   ... have it installed in a location we could not guess. Note that packaged
   ... library may be significantly slower and/or older than the one the above
   ... would build."
        mathlib_missing=true
      fi
        ;;
  esac
  $mathlib_missing &&
    echo "\
   ... You can also use other matrix algebra libraries. For information, see:
   ...   http://kaldi-asr.org/doc/matrixwrap.html"
  
  # Report missing programs and libraries.
  if [ -n "$debian_packages" ]; then
    install_pkg_command=$(
      # Guess package manager from user's distribution type. Use a subshell
      # because we are potentially importing a lot of dirt here.
      eval $(grep 2>/dev/null ^ID /etc/os-release) 2>/dev/null
      for rune in ${ID-} ${ID_LIKE-}; do
        # The case '(pattern)' syntax is necessary in subshell for bash 3.x.
        case $rune in
          (rhel|centos|redhat) echo "yum install $redhat_packages"; break;;
          (fedora) echo "dnx install $redhat_packages"; break;;
          (suse) echo "zypper install $opensuse_packages"; break;;
          (debian) echo "apt-get install $debian_packages"; break;;
        esac
      done
    )
  
    # Print the suggestion to install missing packages.
    if [ -n "$install_pkg_command" ]; then
      echo "$0: Some prerequisites are missing; install them using the command:"
      echo "  sudo" $install_pkg_command
    else
      echo "$0: The following prerequisites are missing; install them first:"
      echo "  " $debian_packages
    fi
    status=1
  fi
  
  if [ $(pwd | wc -w) -gt 1 ]; then
    echo "*** $0: Warning: Kaldi scripts will fail if the directory name contains a space."
    echo "***  (it's OK if you just want to compile a few tools -> disable this check)."
    status=1
  fi
  
  if pwd | grep -E 'JOB|LMWT' >/dev/null; then
    echo "*** $0: Kaldi scripts will fail if the directory name contains"
    echo "***  either of the strings 'JOB' or 'LMWT'."
    status=1
  fi
  
  if ! $mathlib_missing && [ $status -eq 0 ]; then
    echo "$0: all OK."
  fi
  
  exit $status