#!/usr/bin/env python3
"""Generate the Android guest's OpenGL ES entry points.

The guest (ILP32 code, see port/android/README.md) cannot link against the
host's libGLESv3, but it can call it: a host function receives the guest's
pointer arguments zero-extended, and 32-bit integers and floats go in the
same registers under both ABIs. What differs is

- GLsizeiptr and GLintptr, 32-bit in the guest and 64-bit in the host;
- arguments passed on the stack (beyond the eighth integer argument), which
  the guest packs by size while the host expects 8-byte slots;
- returned pointers, which point at host memory.

For each function in the Android list in port/linux/src/gl.h this writes a
guest wrapper that widens such arguments and calls an import named
hostgl_<function>, which the host resolves to the real entry point. Functions
returning a string go through host_gl_get_string instead.

Usage: android_gl_stubs.py gl.h gl32.h gl2ext.h output.c imports.list
"""

import re
import sys

INTEGER_REGISTER_COUNT = 8
WIDE_TYPES = {"GLsizeiptr", "GLintptr", "GLint64", "GLuint64", "GLint64EXT", "GLuint64EXT"}
FLOAT_TYPES = {"GLfloat", "GLclampf", "GLdouble", "GLclampd", "float", "double"}


def android_functions(gl_header: str):
    text = open(gl_header, encoding="utf-8").read()
    start = text.index("/* ANDROID_GL_FUNCTIONS_BEGIN */")
    end = text.index("/* ANDROID_GL_FUNCTIONS_END */")
    return re.findall(r"X\((\w+)\)", text[start:end])


def prototypes(*headers):
    result = {}
    pattern = re.compile(r"GL_APICALL\s+(.+?)\s*GL_APIENTRY\s+(\w+)\s*\((.*?)\);", re.S)
    for header in headers:
        text = open(header, encoding="utf-8").read()
        for ret, name, params in pattern.findall(text):
            params = " ".join(params.split())
            result.setdefault(name, (ret.strip(), params))
    return result


def split_parameter(param: str):
    param = param.strip()
    m = re.match(r"(.*?)(\w+)\s*$", param)
    ptype, pname = m.group(1).strip(), m.group(2)
    if not ptype:  # unnamed
        ptype, pname = param, None
    return ptype, pname


def main():
    gl_header, gl32, gl2ext, output, imports = sys.argv[1:6]
    functions = android_functions(gl_header)
    protos = prototypes(gl32, gl2ext)
    out = [
        "/* generated by tools/android_gl_stubs.py from port/linux/src/gl.h; do not edit */",
        "#include <GLES3/gl32.h>",
        "#include <GLES2/gl2ext.h>",
        "#include <string.h>",
        "",
        "void host_gl_get_string(unsigned int name, int index, char *buffer, unsigned int size);",
        "",
    ]
    table = []
    import_names = []
    for name in functions:
        if name not in protos:
            raise SystemExit(f"{name}: no prototype in the GLES headers")
        ret, params = protos[name]
        if params in ("void", ""):
            plist = []
        else:
            plist = [split_parameter(p) for p in params.split(",")]
        if name == "glGetString":
            out += [
                "static const GLubyte *GL_APIENTRY guest_glGetString(GLenum name)",
                "{",
                "\tstatic __thread char buffer[4][4096];",
                "\tstatic __thread int next;",
                "\tchar *result = buffer[next++ & 3];",
                "",
                "\thost_gl_get_string(name, -1, result, sizeof(buffer[0]));",
                "\treturn (const GLubyte *)result;",
                "}",
                "",
            ]
            table.append(name)
            continue
        if name == "glShaderSource":
            # an array of pointers: widen each to a host pointer
            import_names.append("hostgl_glShaderSource")
            out += [
                "void hostgl_glShaderSource(GLuint shader, GLsizei count, const unsigned long long *strings, "
                "const GLint *lengths);",
                "static void GL_APIENTRY guest_glShaderSource(GLuint shader, GLsizei count, "
                "const GLchar *const *strings, const GLint *lengths)",
                "{",
                "\tunsigned long long wide[16];",
                "\tGLsizei index;",
                "",
                "\tif (count > 16)",
                "\t\tcount = 16;",
                "\tfor (index = 0; index < count; index++)",
                "\t\twide[index] = (unsigned long long)(unsigned int)strings[index];",
                "\thostgl_glShaderSource(shader, count, wide, lengths);",
                "}",
                "",
            ]
            table.append(name)
            continue
        if "*" in ret:
            raise SystemExit(f"{name}: returns a pointer; add a special case")
        if any(p.count("*") > 1 for p, _ in plist):
            raise SystemExit(f"{name}: takes an array of pointers; add a special case")
        decl_params, host_params, call_args = [], [], []
        integer_index = 0
        for index, (ptype, pname) in enumerate(plist):
            arg = f"a{index}"
            decl_params.append(f"{ptype} {arg}")
            is_pointer = "*" in ptype
            base = ptype.replace("const", "").strip()
            if base in FLOAT_TYPES and not is_pointer:
                host_params.append(ptype)
                call_args.append(arg)
                continue
            wide = base in WIDE_TYPES and not is_pointer
            on_stack = integer_index >= INTEGER_REGISTER_COUNT
            integer_index += 1
            if is_pointer:
                if on_stack:
                    host_params.append("unsigned long long")
                    call_args.append(f"(unsigned long long)(unsigned int){arg}")
                else:
                    host_params.append(ptype)
                    call_args.append(arg)
            elif wide or on_stack:
                host_params.append("long long")
                call_args.append(f"(long long){arg}")
            else:
                host_params.append(ptype)
                call_args.append(arg)
        host_name = "hostgl_" + name
        import_names.append(host_name)
        out.append(f"{ret} {host_name}({', '.join(host_params) or 'void'});")
        out.append(f"static {ret} GL_APIENTRY guest_{name}({', '.join(decl_params) or 'void'})")
        out.append("{")
        call = f"{host_name}({', '.join(call_args)})"
        out.append(f"\t{'return ' if ret != 'void' else ''}{call};")
        out.append("}")
        out.append("")
        table.append(name)
    out.append("static const struct { const char *name; void *function; } guest_gl_functions[] =")
    out.append("{")
    for name in table:
        out.append(f'\t{{ "{name}", (void *)guest_{name} }},')
    out.append("};")
    out.append("")
    out.append("typedef void (*guest_gl_function)(void);")
    out.append("guest_gl_function guest_gl_get_proc_address(const char *name)")
    out.append("{")
    out.append("\tunsigned long index;")
    out.append("")
    out.append("\tfor (index = 0; index < sizeof(guest_gl_functions) / sizeof(guest_gl_functions[0]); index++)")
    out.append("\t{")
    out.append("\t\tif (!strcmp(guest_gl_functions[index].name, name))")
    out.append("\t\t\treturn (guest_gl_function)guest_gl_functions[index].function;")
    out.append("\t}")
    out.append("\treturn 0;")
    out.append("}")
    with open(output, "w", encoding="utf-8") as f:
        f.write("\n".join(out) + "\n")
    with open(imports, "w", encoding="utf-8") as f:
        f.write("\n".join(import_names) + "\n")


if __name__ == "__main__":
    main()