import os


def exists(env):
    return "EM_CONFIG" in os.environ


def generate(env):
    if env["arch"] not in ("wasm32"):
        print("Only wasm32 supported on web. Exiting.")
        Exit()

    if "EM_CONFIG" in os.environ:
        env["ENV"] = os.environ

    env["CC"] = "emcc"
    env["CXX"] = "em++"
    env["AR"] = "emar"
    env["RANLIB"] = "emranlib"
    env.Append(CPPFLAGS=["-s", "SIDE_MODULE=1"])
    env.Append(LINKFLAGS=["-s", "SIDE_MODULE=1"])
    env["SHOBJSUFFIX"] = ".bc"
    env["SHLIBSUFFIX"] = ".wasm"
    # Use TempFileMunge since some AR invocations are too long for cmd.exe.
    # Use POSIX-style paths, required with TempFileMunge.
    env["ARCOM_POSIX"] = env["ARCOM"].replace("$TARGET", "$TARGET.posix").replace("$SOURCES", "$SOURCES.posix")
    env["ARCOM"] = "${TEMPFILE(ARCOM_POSIX)}"

    # All intermediate files are just LLVM bitcode.
    env["OBJPREFIX"] = ""
    env["OBJSUFFIX"] = ".bc"
    env["PROGPREFIX"] = ""
    # Program() output consists of multiple files, so specify suffixes manually at builder.
    env["PROGSUFFIX"] = ""
    env["LIBPREFIX"] = "lib"
    env["LIBSUFFIX"] = ".a"
    env["LIBPREFIXES"] = ["$LIBPREFIX"]
    env["LIBSUFFIXES"] = ["$LIBSUFFIX"]
    env.Replace(SHLINKFLAGS="$LINKFLAGS")
    env.Replace(SHLINKFLAGS="$LINKFLAGS")

    if env["target"] == "debug":
        env.Append(CCFLAGS=["-O0", "-g"])
    elif env["target"] == "release":
        env.Append(CCFLAGS=["-O3"])