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# Converts GLSL shader to SPIR-V library 

from __future__ import annotations
import argparse
import subprocess
import sys
import os
import typing as T

if T.TYPE_CHECKING:

    class Arguments(T.Protocol):
        input: str
        output: str
        create_entry: T.Optional[str]
        glsl_ver: T.Optional[str]
        Olib: bool
        extra: T.Optional[str]
        vn: str
        stage: str


def get_args() -> Arguments:
    parser = argparse.ArgumentParser()
    parser.add_argument('input', help="Name of input file.")
    parser.add_argument('output', help="Name of output file.")

    parser.add_argument("--create-entry",
                        dest="create_entry",
                        help="Create a new entry point and put to the end of a file.")

    parser.add_argument('--glsl-version',
                        dest="glsl_ver",
                        choices=['100', '110', '120', '130', '140', '150', '300es', '310es', '330', '400', '410', '420', '430', '440', '450', '460'],
                        help="Override GLSL #version declaration in source.")

    parser.add_argument("-Olib",
                        action='store_true',
                        help="Any optimizations are disabled and unused functions are saved.")

    parser.add_argument("--extra-flags",
                        dest="extra",
                        help="Pass additional flags to glslangValidator.")

    parser.add_argument("--vn",
                        dest="vn",
                        required=True,
                        help="Variable name. Creates a C header file that contains a uint32_t array.")

    parser.add_argument("--stage",
                        default="vert",
                        choices=['vert', 'tesc', 'tese', 'geom', 'frag', 'comp'],
                        help="Uses specified stage rather than parsing the file extension")
    args = parser.parse_args()
    return args


def create_include_guard(lines: T.List[str], filename: str) -> T.List[str]:
    filename = filename.replace('.', '_')
    upper_name = filename.upper()

    guard_head = ["#ifndef {}\n".format(upper_name),
                  "#define {}\n".format(upper_name)]
    guard_tail = ["\n#endif // {}\n".format(upper_name)]

    # remove '#pragma once'
    for idx, l in enumerate(lines):
        if l.find('#pragma once') != -1:
            lines.pop(idx)
            break

    return guard_head + lines + guard_tail


def convert_to_static_variable(lines: T.List[str], varname: str) -> T.List[str]:
    for idx, l in enumerate(lines):
        if l.find(varname) != -1:
            lines[idx] = "static " + lines[idx]
            return lines
    raise RuntimeError(f'Did not find {varname}, this is unexpected')


def override_version(lines: T.List[str], glsl_version: str) -> T.List[str]:
    for idx, l in enumerate(lines):
        if l.find('#version ') != -1:
            lines[idx] = "#version {}\n".format(glsl_version)
            return lines
    raise RuntimeError('Did not find #version directive, this is unexpected')


def postprocess_file(args: Arguments) -> None:
    with open(args.output, "r") as r:
        lines = r.readlines()

    # glslangValidator creates a variable without the static modifier.
    lines = convert_to_static_variable(lines, args.vn)

    # '#pragma once' is unstandardised.
    lines = create_include_guard(lines, os.path.basename(r.name))

    with open(args.output, "w") as w:
        w.writelines(lines)


def preprocess_file(args: Arguments, origin_file: T.TextIO) -> str:
    with open(origin_file.name + ".copy", "w") as copy_file:
        lines = origin_file.readlines()

        if args.create_entry is not None:
            lines.append("\nvoid {}()".format(args.create_entry) + "{}\n")

        if args.glsl_ver is not None:
            override_version(lines, args.glsl_ver)

        copy_file.writelines(lines)

    return copy_file.name


def process_file(args: Arguments) -> None:
    with open(args.input, "r") as infile:
        copy_file = preprocess_file(args, infile)

    cmd_list = ["glslangValidator"]

    if args.Olib:
        cmd_list += ["--keep-uncalled"]

    if args.vn is not None:
        cmd_list += ["--variable-name", args.vn]

    if args.extra is not None:
        cmd_list.append(args.extra)

    if args.create_entry is not None:
        cmd_list += ["--entry-point", args.create_entry]

    cmd_list.append("-V")
    cmd_list += ["-o", args.output]
    cmd_list += ["-S", args.stage]

    cmd_list.append(copy_file)

    ret = subprocess.run(cmd_list, stdout=subprocess.PIPE, stderr=subprocess.PIPE, timeout=30)
    if ret.returncode != 0:
        print(ret.stdout)
        print(ret.stderr, file=sys.stderr)
        sys.exit(1)

    if args.vn is not None:
        postprocess_file(args)

    if args.create_entry is not None:
        os.remove(copy_file)


def main() -> None:
    args = get_args()
    process_file(args)


if __name__ == "__main__":
    main()