#!/usr/bin/env python3

"""
This script will regenerate and update GLConsts.h.

Step 1:
  Download the last gl.xml, egl.xml, glx.xml and wgl.xml from
  http://www.opengl.org/registry/#specfiles into some XML_DIR:
    wget https://www.khronos.org/registry/OpenGL/xml/gl.xml
    wget https://www.khronos.org/registry/OpenGL/xml/glx.xml
    wget https://www.khronos.org/registry/OpenGL/xml/wgl.xml
    wget https://www.khronos.org/registry/EGL/api/egl.xml

Step 2:
  `py ./GLConsts.py <XML_DIR>`

Step 3:
  Do not add the downloaded XML in the patch

Step 4:
  Enjoy =)
"""

# includes
import pathlib
import sys
import xml.etree.ElementTree

# -

(_, XML_DIR_STR) = sys.argv
XML_DIR = pathlib.Path(XML_DIR_STR)

# -

HEADER = b"""
/* This Source Code Form is subject to the terms of the Mozilla Public
 * License, v. 2.0. If a copy of the MPL was not distributed with this
 * file, You can obtain one at http://mozilla.org/MPL/2.0/. */

// clang-format off

#ifndef GLCONSTS_H_
#define GLCONSTS_H_

/**
 * GENERATED FILE, DO NOT MODIFY DIRECTLY.
 * This is a file generated directly from the official OpenGL registry
 * xml available http://www.opengl.org/registry/#specfiles.
 *
 * To generate this file, see tutorial in \'GLConsts.py\'.
 */
"""[
    1:
]

FOOTER = b"""
#endif // GLCONSTS_H_

// clang-format on
"""[
    1:
]

# -


def format_lib_constant(lib, name, value):
    # lib would be 'GL', 'EGL', 'GLX' or 'WGL'
    # name is the name of the const (example: MAX_TEXTURE_SIZE)
    # value is the value of the const (example: 0xABCD)

    define = "#define LOCAL_" + lib + "_" + name
    whitespace = 60 - len(define)
    if whitespace < 0:
        whitespace = whitespace % 8

    return define + " " * whitespace + " " + value


class GLConst:
    def __init__(self, lib, name, value, type):
        self.lib = lib
        self.name = name
        self.value = value
        self.type = type


class GLDatabase:
    LIBS = ["GL", "EGL", "GLX", "WGL"]

    def __init__(self):
        self.consts = {}
        self.libs = set(GLDatabase.LIBS)
        self.vendors = set(["EXT", "ATI"])
        # there is no vendor="EXT" and vendor="ATI" in gl.xml,
        # so we manualy declare them

    def load_xml(self, xml_path):
        tree = xml.etree.ElementTree.parse(xml_path)
        root = tree.getroot()

        for enums in root.iter("enums"):
            vendor = enums.get("vendor")
            if not vendor:
                # there some standart enums that do have the vendor attribute,
                # so we fake them as ARB's enums
                vendor = "ARB"

            if vendor not in self.vendors:
                # we map this new vendor in the vendors set.
                self.vendors.add(vendor)

            namespaceType = enums.get("type")

            for enum in enums:
                if enum.tag != "enum":
                    # this is not an enum => we skip it
                    continue

                lib = enum.get("name").split("_")[0]

                if lib not in self.libs:
                    # unknown library => we skip it
                    continue

                name = enum.get("name")[len(lib) + 1 :]
                value = enum.get("value")
                type = enum.get("type")

                if not type:
                    # if no type specified, we get the namespace's default type
                    type = namespaceType

                self.consts[lib + "_" + name] = GLConst(lib, name, value, type)


# -

db = GLDatabase()
db.load_xml(XML_DIR / "gl.xml")
db.load_xml(XML_DIR / "glx.xml")
db.load_xml(XML_DIR / "wgl.xml")
db.load_xml(XML_DIR / "egl.xml")

# -

lines: list[str] = []

keys = sorted(db.consts.keys())

for lib in db.LIBS:
    lines.append("// " + lib)

    for k in keys:
        const = db.consts[k]

        if const.lib != lib:
            continue

        const_str = format_lib_constant(lib, const.name, const.value)
        lines.append(const_str)

    lines.append("")

# -

b_lines: list[bytes] = [HEADER] + [x.encode() for x in lines] + [FOOTER]
b_data: bytes = b"\n".join(b_lines)

dest = pathlib.Path("GLConsts.h")
dest.write_bytes(b_data)

print(f"Wrote {len(b_data)} bytes.")  # Some indication that we're successful.