#!/bin/sh

die() {
    echo "$0: Error: $*" >&2
    exit 1
}

prihelp() {
    host="[$(cc -dumpmachine)]"
    : ${host:=""}
    cat << EOF
Usage: $0 [options]
Options:
  --help                    Print this help mesage
  --host=target-triple      $host
  --cc=cc                   C compiler [cc]
  --ld=ld                   Linker [ld]
  --prefix=PREFIX           Installation path [/usr/local]
  --sysroot=/path           System root []
  --includedir="/a/b",...   System include dirs
EOF
}

sysroot=
prefix=/usr/local
host=
linker=

for arg ; do
	case "$arg" in
	--host=*) host=${arg#*=} ;;
    --sysroot=*) sysroot=${arg#*=} ;;
    --includedir=*) host_include_dirs=${arg#*=} ;;
	CC=*) CC=${arg#*=} ;;
	--cc=*) CC=${arg#*=} ;;
	--ld=*) linker=${arg#*=} ;;
	CFLAGS=*) CFLAGS=${arg#*=} ;;
	--cflags=*) CFLAGS=${arg#*=} ;;
    --prefix=*) prefix=$(sh -c "echo ${arg#*=}") ;;
    --help) prihelp ; exit ;;
	*) die "$0: unknown option '$arg'"
	esac
done

: ${CC:=cc}
if ! test -n "$host"; then
    host=$($CC -dumpmachine)
else
    # try target-triple-ld (cross compiling)
    if ! test -n "$linker" && command -v "$host"-ld >/dev/null; then
        linker="$host"-ld
        sysroot=$( ($host-cc -print-sysroot || $host-gcc -print-sysroot) 2>/dev/null)
    fi
fi
: ${linker:=ld}
test -n "$host" || die "cannot determine host"

host_arch=
host_os=unknown
host_abi=none
host_predefs=

echo "host: $host"
case "$host" in
x86_64-*) host_arch=x86_64 ;;
amd64-*) host_arch=x86_64 ;;
aarch64-*) host_arch=aarch64 ;;
arm64-*) host_arch=aarch64 ;;
*) die "unsupported target '$host'"
esac

linkflags=

findgcclibdir () {
    : ${GCCLIBDIR:=$(dirname $( ("$host"-gcc -print-file-name=crtbegin.o || $CC -print-file-name=crtbegin.o) 2>/dev/null) )}
    if ! test -n $GCCLIBDIR; then
        die "cannot determine gcclibdir"
    fi
}

link_with_cc=0

case "$host" in
*-linux-*gnu*)
    host_os=linux
    host_abi=gnu
    case $host_arch in
    x86_64) DYNAMIC_LINKER=$sysroot/lib64/ld-linux-x86-64.so.2 ;;
    aarch64) DYNAMIC_LINKER=$sysroot/lib/ld-linux-aarch64.so.1
    esac
    ldstartfiles='"-l:crt1.o", "-l:crti.o", "-l:crtbegin.o"'
    ldendfiles='"-lc", "-lgcc", "-l:crtend.o", "-l:crtn.o"'
    ldstartfiles_pie='"-l:Scrt1.o", "-l:crti.o", "-l:crtbeginS.o"'
    ldendfiles_pie='"-lc", "-lgcc", "-l:crtendS.o", "-l:crtn.o"'
    findgcclibdir
    linkflags='"-L", "'$GCCLIBDIR'",'
    host_predefs=''
    ;;
*-linux-*musl*)
    host_os=linux
    host_abi=musl
    case $host_arch in
    x86_64) DYNAMIC_LINKER=$sysroot/lib/ld-musl-x86_64.so.1 ;;
    aarch64) DYNAMIC_LINKER=$sysroot/lib/ld-linux-aarch64.so.1 ;;
    esac
    if test -d $sysroot/usr/lib/musl/lib; then
        # musl cross compiler in glibc system (probably)
        findgcclibdir
        linkflags='"-nostdlib", "-L", "'$sysroot'/usr/lib/musl/lib", "-L", "'$GCCLIBDIR'",'
        ldstartfiles='"'$sysroot'/usr/lib/musl/lib/crt1.o","'$sysroot'/usr/lib/musl/lib/crti.o", "-l:crtbeginS.o"'
        ldendfiles='"-lc", "-lgcc", "-l:crtendS.o", "'$sysroot'/usr/lib/musl/lib/crtn.o"'
        ldstartfiles_pie='"'$sysroot'/usr/lib/musl/lib/Scrt1.o", "'$sysroot'/usr/lib/musl/lib/crti.o", "-l:crtbeginS.o"'
        ldendfiles_pie="$ldendfiles"
    else
        ldstartfiles='"-l:crt1.o", "-l:crti.o"'
        ldendfiles='"-lc", "-lgcc", "-l:crtn.o"'
        ldstartfiles_pie='"-l:Scrt1.o", "-l:crti.o"'
        ldendfiles_pie="$ldendfiles"
    fi
    ;;
*-openbsd*)
    host_os=openbsd
    DYNAMIC_LINKER=$sysroot/usr/libexec/ld.so
    ldstartfiles='"-l:crt0.o", "-l:crtbegin.o"'
    ldendfiles='"-lc", "-lgcc", "-l:crtend.o"'
    ldstartfiles_pie="$ldstartfiles"
    ldendfiles_pie="$ldendfiles"
    linkflags='"-L'$sysroot'/usr/lib"'
    host_predefs='
    "_ANSI_LIBRARY", /* works around __only_inline functions in libc headers */
    '
    ;;
*)
    link_with_cc=1
    echo "warning: unknown/unsupported target '$host'" >&2
esac
echo dynamic linker: $DYNAMIC_LINKER

tryincldir() {
    if stat "$1"/ >/dev/null 2>/dev/null; then
        host_include_dirs="$host_include_dirs\"$1\","
    fi
}

if ! test -n "$host_include_dirs"; then
    # try to query host toolchain first
    for sfx in cc gcc; do
        if command -v "$host"-$sfx > /dev/null; then
            cc="$host"-$sfx
        fi
    done
    : ${cc:=$CC}
    if hostccdirs=$($cc -E -v -xc /dev/null 2>&1 | sed -n '/#include <...> search starts here:/,/End of search list./{
    s/^[[:space:]]*//
    /^\/.*/p
}') && test -n "$hostccdirs"; then
        echo "Using $cc's system include paths:"
        for d in $hostccdirs; do
            dir=$(realpath "$d")
            case "$dir" in
                #exclude internal compiler headers, we have our own
                */gcc/*) ;; */clang/*) ;;
                *) echo "    $dir"
                   tryincldir "$dir" ;;
            esac
        done
    else
        echo "Falling back to generic system include paths"
        tryincldir "$sysroot/usr/local/include/$host"
        tryincldir "$sysroot/usr/local/include"
        tryincldir "$sysroot/usr/include/$host"
        tryincldir "$sysroot/usr/include"
    fi
fi

set -e

echo using linker: "$linker"
echo using arch: "$host_arch"
echo using os: "$host_os"
echo using abi: "$host_abi"
echo host include paths: "$host_include_dirs"

if test -n "$DYNAMIC_LINKER"; then
    linkflags="\"--dynamic-linker=$DYNAMIC_LINKER\", $linkflags"
fi

echo "/** GENERATED WITH $0 $* **/
#define HOST_TRIPLE \"$host\"
#define HOST_ARCH   IS$host_arch
#define HOST_OS     OS$host_os
#define HOST_ABI    ABI$host_abi
#define HOST_INCLUDE_DIRS $host_include_dirs
#define HOST_LD \"$linker\"
#define HOST_CC \"$CC\"
static const char *const host_predefs[] = {$host_predefs 0
};
#define HOST_LINK_WITH_CC $link_with_cc
static const char *const host_linkcmd[] = {${linkflags:=0}};
static const char *const host_ldstartfiles[] = {${ldstartfiles:=0}};
static const char *const host_ldendfiles[] = {${ldendfiles:=0}};
static const char *const host_ldstartfiles_pie[] = {${ldstartfiles_pie:=0}};
static const char *const host_ldendfiles_pie[] = {${ldendfiles_pie:=0}};
"  > src/hostconfig.h

echo "# GENERATED WITH $0 $*
PREFIX = $prefix
CC     = $CC
CFLAGS = ${CFLAGS:--Wall -std=c11 -pedantic}" > config.mk

echo config written to src/hostconfig.h, config.mk