BUILD_DIR="./target"
BIN="$BUILD_DIR/poppin.bin"
ISO="$BUILD_DIR/poppin.iso"

set -e

function cmd_exists() {
    if ! command -v $1 &> /dev/null
    then
        echo "The command '$1' could not be found please install it"
        exit 1
    fi
}

function pre_build() {
    cmd_exists cargo
    cmd_exists xorriso
    cmd_exists grub-file
    cmd_exists ld
    cmd_exists grub-mkrescue
    cmd_exists qemu-system-x86_64
}

function build_kernel() {
    echo "INFO: Building poppin-kernel"
    pushd kernel > /dev/null
    case $1 in
        dev)
            cargo build --target-dir ../${BUILD_DIR}
        ;;
        *)
            cargo build --release --target-dir ../${BUILD_DIR}
        ;;
    esac
    popd > /dev/null
}


function build_boot() {
    echo "INFO: Building boot code"
    nasm -felf64 -o $BUILD_DIR/long_mode.o boot/long_mode.s
    nasm -felf64 -o $BUILD_DIR/boot.o boot/boot.s
    nasm -felf64 -o $BUILD_DIR/multiboot.o boot/multiboot.s
}



function link(){
    echo "INFO: Linking"
    ld -melf_x86_64 -n \
        -T linker.ld   \
        -o ${BIN}      \
        ${BUILD_DIR}/multiboot.o \
        ${BUILD_DIR}/boot.o \
        ${BUILD_DIR}/long_mode.o \
        $1 # kernel path
}

function check_mb() {
    if grub-file --is-x86-multiboot2 $BIN; then
        echo "INFO: Kernel conatins multiboot2"
    else
        echo "ERROR: Kernel doesnt contain multiboot2"
        exit 1
    fi
}

function make_iso() {
    echo "INFO: Building ISO" 
    mkdir -p ${BUILD_DIR}/iso/boot/grub
    cp ${BUILD_DIR}/poppin.bin ${BUILD_DIR}/iso/boot/poppin.bin 
    cp boot/grub.cfg ${BUILD_DIR}/iso/boot/grub/grub.cfg
    grub-mkrescue -o ${ISO} ${BUILD_DIR}/iso > /dev/null 2>&1
}

function run_qemu() {
    qemu-system-x86_64 \
        -cdrom $ISO \
        -serial stdio \
        -device VGA
        # -d int        \
}

function run_qemu_gdb {
    qemu-system-x86_64 \
        -cdrom $ISO \
        -device VGA \
        -d int    \
        -s -S -monitor stdio
}

function print_help() {
    echo "Usage: ./build.sh [command]"
    echo "Commands:"
    echo "    run-qemu - Compiles and Runs the built iso with qemu"
    echo "    build    - Compiles everything"
}

function build() {
    pre_build
    build_kernel
    build_boot
    link ${BUILD_DIR}/x86_64-unknown-none/release/libkernel.a
    check_mb
    make_iso
}

function build_dev() {
    pre_build
    build_kernel dev
    build_boot
    link ${BUILD_DIR}/x86_64-unknown-none/debug/libkernel.a
    check_mb
    make_iso

}


case $1 in
    run-qemu)
        build
        run_qemu
    ;;
    build)
        build
    ;;
    build-dev)
        build_dev
    ;;
    run-qemu-gdb)
        build
        run_qemu_gdb
    ;;
    *)
        if [ $# -gt 0 ]; then
            echo "ERROR: Unknown option '$1'"
        fi
        print_help
        exit 1
    ;;
esac