#!/usr/bin/env bash
#
#   This script allows CMAKE_CXX_COMPILER to be a standard
#   C++ compiler and Kokkos sets RULE_LAUNCH_COMPILE and
#   RULE_LAUNCH_LINK in CMake so that all compiler and link
#   commands are prefixed with this script followed by the
#   C++ compiler. Thus if $1 == $2 then we know the command
#   was intended for the C++ compiler and we discard both
#   $1 and $2 and redirect the command to NVCC_WRAPPER.
#   If $1 != $2 then we know that the command was not intended
#   for the C++ compiler and we just discard $1 and launch
#   the original command. Examples of when $2 will not equal
#   $1 are 'ar', 'cmake', etc. during the linking phase
#

set -e

# emit a message about the underlying command executed
: ${DEBUG:=0}
: ${KOKKOS_DEBUG_LAUNCH_COMPILER:=${DEBUG}}

debug-message()
{
    if [ "${KOKKOS_DEBUG_LAUNCH_COMPILER}" -ne 0 ]; then
        echo -e "##### $(basename ${BASH_SOURCE[0]}) executing: \"$@\"... #####"
    fi
}

# check the arguments for the KOKKOS_DEPENDENCE compiler definition
KOKKOS_DEPENDENCE=0
for i in ${@}
do
    if [ -n "$(echo ${i} | grep 'KOKKOS_DEPENDENCE$')" ]; then
        KOKKOS_DEPENDENCE=1
        break
    fi
done

# if Kokkos compiler is not passed, someone is probably trying to invoke it directly
if [ -z "${1}" ]; then
    echo -e "\n${BASH_SOURCE[0]} was invoked without the Kokkos compiler as the first argument."
    echo "This script is not indended to be directly invoked by any mechanism other"
    echo -e "than through a RULE_LAUNCH_COMPILE or RULE_LAUNCH_LINK property set in CMake.\n"
    exit 1
fi

# if Kokkos compiler is not passed, someone is probably trying to invoke it directly
if [ -z "${2}" ]; then
    echo -e "\n${BASH_SOURCE[0]} was invoked without the C++ compiler as the second argument."
    echo "This script is not indended to be directly invoked by any mechanism other"
    echo -e "than through a RULE_LAUNCH_COMPILE or RULE_LAUNCH_LINK property set in CMake.\n"
    exit 1
fi

# if there aren't two args, this isn't necessarily invalid, just a bit strange
if [ -z "${3}" ]; then exit 0; fi

# store the Kokkos compiler
KOKKOS_COMPILER=${1}

# remove the Kokkos compiler from the arguments
shift

# store the expected C++ compiler
CXX_COMPILER=$(which "${1}")

# remove the expected C++ compiler from the arguments
shift

# NOTE: in below, ${KOKKOS_COMPILER} is usually nvcc_wrapper
#
# after the above shifts, $1 is now the exe for the compile or link command, e.g.
#       kokkos_launch_compiler ${KOKKOS_COMPILER} g++ gcc -c file.c -o file.o
# becomes:
#       kokkos_launch_compiler gcc -c file.c -o file.o
# We check to see if the executable is the C++ compiler and if it is not, then
# just execute the command.
#
# Summary:
#       kokkos_launch_compiler ${KOKKOS_COMPILER} g++ gcc -c file.c -o file.o
# results in this command being executed:
#       gcc -c file.c -o file.o
# and
#       kokkos_launch_compiler ${KOKKOS_COMPILER} g++ g++ -c file.cpp -o file.o
# results in this command being executed:
#       ${KOKKOS_COMPILER} -c file.cpp -o file.o
if [[ "${KOKKOS_DEPENDENCE}" -eq "0" || "${CXX_COMPILER}" != $(which "${1}") ]]; then
    debug-message "$@"
    # the command does not depend on Kokkos so just execute the command w/o re-directing to ${KOKKOS_COMPILER}
    exec "$@"
else
    # the executable is the C++ compiler, so we need to re-direct to ${KOKKOS_COMPILER}
    if [ ! -f "${KOKKOS_COMPILER}" ]; then
        echo -e "\nError: the compiler redirect for Kokkos was not found at ${KOKKOS_COMPILER}\n"
        exit 1
    fi

    # find the nvcc_wrapper from the same build/install
    NVCC_WRAPPER="$(dirname ${BASH_SOURCE[0]})/nvcc_wrapper"
    if [ "${KOKKOS_COMPILER}" = "${NVCC_WRAPPER}" ]; then
        # this should only be valid in the install tree -- it will be set to CMAKE_CXX_COMPILER used using Kokkos installation
        if [ -z $(echo "@NVCC_WRAPPER_DEFAULT_COMPILER@" | grep 'NVCC_WRAPPER_DEFAULT_COMPILER') ]; then
            : ${NVCC_WRAPPER_DEFAULT_COMPILER:="@NVCC_WRAPPER_DEFAULT_COMPILER@"}
        fi

        # set default nvcc wrapper compiler if not specified
        : ${NVCC_WRAPPER_DEFAULT_COMPILER:=${CXX_COMPILER}}
        export NVCC_WRAPPER_DEFAULT_COMPILER

        # nvcc_wrapper calling itself will cause an infinitely long build
        if [ "${NVCC_WRAPPER}" = "${NVCC_WRAPPER_DEFAULT_COMPILER}" ]; then
            echo -e "\nError: NVCC_WRAPPER == NVCC_WRAPPER_DEFAULT_COMPILER. Terminating to avoid infinite loop!\n"
            exit 1
        fi
    fi

    # discard the compiler from the command
    shift

    debug-message ${KOKKOS_COMPILER} "$@"
    # execute ${KOKKOS_COMPILER} (again, usually nvcc_wrapper)
    ${KOKKOS_COMPILER} "$@"
fi
