#!/usr/bin/env python3
# Copyright (C) 1994-1995 Andrew Cagney <cagney@highland.com.au>
# Copyright (C) 1996-2023 Free Software Foundation, Inc.
#
# This file is part of the GNU simulators.
#
# This program is free software; you can redistribute it and/or modify
# it under the terms of the GNU General Public License as published by
# the Free Software Foundation; either version 3 of the License, or
# (at your option) any later version.
#
# This program is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
# GNU General Public License for more details.
#
# You should have received a copy of the GNU General Public License
# along with this program.  If not, see <http://www.gnu.org/licenses/>.

"""Helper to generate spreg.[ch] files."""

import argparse
from pathlib import Path
import sys
from typing import NamedTuple, TextIO


FILE = Path(__file__).resolve()
DIR = FILE.parent


NR_OF_SPRS = 1024

SPREG_ATTRIBUTES = (
    "is_valid",
    "is_readonly",
    "name",
    "index",
    "length",
)


class Spreg(NamedTuple):
    """A single spreg entry."""

    name: str
    reg_nr: int
    is_readonly: int
    length: int


def load_table(source: Path) -> list[Spreg]:
    """Load the spreg table & return all entries in it."""
    ret = []

    with source.open("r", encoding="utf-8") as fp:
        for i, line in enumerate(fp):
            line = line.split("#", 1)[0].strip()
            if not line:
                # Skip blank & comment lines.
                continue

            fields = line.split(":")
            assert len(fields) == 4, f"{source}:{i}: bad line: {line}"
            spreg = Spreg(
                name=fields[0].lower(),
                reg_nr=int(fields[1]),
                is_readonly=int(fields[2]),
                length=int(fields[3]),
            )
            ret.append(spreg)

    return sorted(ret, key=lambda x: x[1])


def print_copyleft(fp: TextIO) -> None:
    """Write out the standard copyright & license file block."""
    fp.write(
        f"""\
/* DO NOT EDIT: GENERATED BY {FILE.name}.

   Copyright (C) 1994-1995 Andrew Cagney <cagney@highland.com.au>
   Copyright (C) 1996-2023 Free Software Foundation, Inc.

   This file is part of the GNU simulators.

   This program is free software; you can redistribute it and/or modify
   it under the terms of the GNU General Public License as published by
   the Free Software Foundation; either version 3 of the License, or
   (at your option) any later version.

   This program is distributed in the hope that it will be useful,
   but WITHOUT ANY WARRANTY; without even the implied warranty of
   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
   GNU General Public License for more details.

   You should have received a copy of the GNU General Public License
   along with this program.  If not, see <http://www.gnu.org/licenses/>.  */
"""
    )


def gen_header(table: list[Spreg], output: Path) -> None:
    """Write header to |output| from spreg |table|."""
    with output.open("w", encoding="utf-8") as fp:
        print_copyleft(fp)
        fp.write(
            """
#ifndef _SPREG_H_
#define _SPREG_H_

typedef unsigned_word spreg;

typedef enum {
"""
        )

        for spreg in table:
            fp.write(f"  spr_{spreg.name} = {spreg.reg_nr},\n")

        fp.write(
            f"""\
  nr_of_sprs = {NR_OF_SPRS}
}} sprs;

"""
        )

        for attr in SPREG_ATTRIBUTES:
            ret_type = "const char *" if attr == "name" else "int"
            fp.write(f"INLINE_SPREG({ret_type}) spr_{attr}(sprs spr);\n")

        fp.write(
            """
#endif /* _SPREG_H_ */
"""
        )


def gen_switch_is_valid(table: list[Spreg], fp: TextIO) -> None:
    """Generate switch table for is_valid property."""
    fp.write("  switch (spr) {\n")
    # Output all the known registers.  We'll return 1 for them.
    for spreg in table:
        fp.write(f"    case {spreg.reg_nr}:\n")
    # All other registers return 0.
    fp.write(
        """\
      return 1;
    }
    return 0;
"""
    )


def gen_switch_is_readonly(table: list[Spreg], fp: TextIO) -> None:
    """Generate switch table for is_readonly property."""
    # Find any readonly registers and output a switch for them.
    # If there aren't any, we can optimize this away to a single return.
    output_switch = False
    has_readonly = False
    for spreg in table:
        if spreg.is_readonly:
            if not output_switch:
                fp.write("  switch (spr) {\n")
                output_switch = True
            has_readonly = True
            fp.write(f"    case {spreg.reg_nr}:\n")
    if has_readonly:
        fp.write("      return 1;\n")

    if output_switch:
        fp.write("  }\n")
    fp.write("  return 0;\n")


def gen_switch_length(table: list[Spreg], fp: TextIO) -> None:
    """Generate switch table for length property."""
    # Find any registers with a length property and output a switch for them.
    # If there aren't any, we can optimize this away to a single return.
    output_switch = False
    for spreg in table:
        if spreg.length:
            if not output_switch:
                fp.write("  switch (spr) {\n")
                output_switch = True
            fp.write(f"    case {spreg.reg_nr}:\n")
            fp.write(f"      return {spreg.length};\n")

    if output_switch:
        fp.write("  }\n")
    fp.write("  return 0;\n")


def gen_source(table: list[Spreg], output: Path) -> None:
    """Write header to |output| from spreg |table|."""
    with output.open("w", encoding="utf-8") as fp:
        print_copyleft(fp)
        fp.write(
            """
#ifndef _SPREG_C_
#define _SPREG_C_

#include "basics.h"
#include "spreg.h"

typedef struct _spreg_info {
  const char *name;
  int is_valid;
  int length;
  int is_readonly;
  int index;
} spreg_info;

static const spreg_info spr_info[nr_of_sprs+1] = {
"""
        )

        entries = iter(table)
        entry = next(entries)
        for spreg_nr in range(0, NR_OF_SPRS + 1):
            if entry is None or spreg_nr < entry.reg_nr:
                fp.write(f"  {{ 0, 0, 0, 0, {spreg_nr} }},\n")
            else:
                fp.write(
                    f'  {{ "{entry.name}", 1, {entry.length}, {entry.is_readonly}, spr_{entry.name} /*{spreg_nr}*/ }},\n'
                )
                entry = next(entries, None)
        fp.write("};\n")

        for attr in SPREG_ATTRIBUTES:
            ret_type = "const char *" if attr == "name" else "int"
            fp.write(
                f"""
INLINE_SPREG({ret_type}) spr_{attr}(sprs spr)
{{
"""
            )

            if attr not in ("index", "name"):
                fp.write(
                    """\
#ifdef WITH_SPREG_SWITCH_TABLE
"""
                )
                if attr == "is_valid":
                    gen_switch_is_valid(table, fp)
                elif attr == "is_readonly":
                    gen_switch_is_readonly(table, fp)
                elif attr == "length":
                    gen_switch_length(table, fp)
                else:
                    assert False, f"{attr}: Unknown attribute"
                fp.write("#else\n")
            fp.write(f"  return spr_info[spr].{attr};\n")
            if attr not in ("index", "name"):
                fp.write("#endif\n")
            fp.write("}\n")

        fp.write("\n#endif /* _SPREG_C_ */\n")


def get_parser() -> argparse.ArgumentParser:
    """Get CLI parser."""
    parser = argparse.ArgumentParser(
        description=__doc__,
        formatter_class=argparse.RawDescriptionHelpFormatter,
    )
    parser.add_argument(
        "--table",
        type=Path,
        default=DIR / "ppc-spr-table",
        help="path to source table",
    )
    parser.add_argument("--header", type=Path, help="path to header (.h) file")
    parser.add_argument("--source", type=Path, help="path to source (.c) file")
    return parser


def parse_args(argv: list[str]) -> argparse.Namespace:
    """Process the command line & default options."""
    parser = get_parser()
    opts = parser.parse_args(argv)

    if not opts.header and not opts.source:
        opts.header = DIR / "spreg.h"
        opts.source = DIR / "spreg.c"

    return opts


def main(argv: list[str]) -> int:
    """The main entry point for scripts."""
    opts = parse_args(argv)

    table = load_table(opts.table)
    if opts.header:
        gen_header(table, opts.header)
    if opts.source:
        gen_source(table, opts.source)
    return 0


if __name__ == "__main__":
    sys.exit(main(sys.argv[1:]))