# Copyright (c) 2025-2026 Advanced Micro Devices, Inc.
# SPDX-License-Identifier: MIT

"""C++ file emission for generated ISA code."""

from __future__ import annotations

import os
import re

import cgen

from collections.abc import Sequence
from datetime import datetime
from typing import TextIO


class CppFile:
    """A generated C++ file (.h or .cpp).

    Defines a common structure: copyright, includes, namespace, forward
    declarations, and source code objects.

    The top-level namespace is currently hardcoded to ``rocjitsu``.
    Namespace is configurable via ``CodegenConfig.namespace``.

    Attributes:
        name: File name without extension.
        out_path: Output directory for generated files.
        is_header: True if this is a header file.
        includes: List of (include_name, is_system_header) pairs.
        fwd_decls: Forward declarations within the namespace.
        src_code: Source code objects (strings or cgen objects).
        arch_name: ISA architecture name.
        replace_structs: If True, replace 'struct' with 'class' in output.
        file_name: File name with extension.
    """

    @staticmethod
    def _prologue_comment() -> str:
        year = datetime.now().strftime('%Y')
        return (
            f'// Copyright (c) 2025-{year} Advanced Micro Devices, Inc.\n'
            f'// SPDX-License-Identifier: MIT\n'
            f'//\n'
            f'// AUTO-GENERATED by the amdisa codegen pipeline. DO NOT EDIT.\n'
            f'// See lib/python/amdisa/README.md for regeneration instructions.\n\n'
        )

    def __init__(
        self,
        name: str,
        out_path: str,
        is_header: bool,
        includes: list[tuple[str, bool]],
        fwd_decls: list[str],
        src_code: Sequence[object],
        arch_name: str,
        replace_structs: bool = False,
    ) -> None:
        self.name = name
        self.out_path = out_path
        self.is_header = is_header
        self.includes = includes
        self.fwd_decls = fwd_decls
        self.src_code = src_code
        self.arch_name = arch_name
        self.replace_structs = replace_structs
        self.file_name = self.name

        if self.is_header:
            self.file_name += '.h'
            include_guard_components = [s.upper() for s in self.name.split('_')]
            self.include_guard = (
                f'ROCJITSU_ISA_ARCH_AMDGPU_{self.arch_name.upper()}_'
                + '_'.join(include_guard_components)
                + '_H_'
            )
        else:
            self.file_name += '.cpp'

    def gen_prologue(self, f: TextIO) -> None:
        """Write copyright, include guard, includes, and namespace opener."""
        f.write(CppFile._prologue_comment())
        if self.is_header:
            f.write(f'#ifndef {self.include_guard}\n')
            f.write(f'#define {self.include_guard}\n\n')
        f.writelines([f'{cgen.Include(x[0], x[1])}\n' for x in self.includes])
        f.write('\n')
        f.write('namespace rocjitsu {\n')
        f.writelines(
            [f'\n{cgen.Statement("class " + x)}' + '\n\n' for x in self.fwd_decls]
        )
        f.write(f'namespace {self.arch_name} {{\n')
        f.write('\n')

    def gen_header(self, f: TextIO) -> None:
        """Write header body and closing guards."""
        if self.replace_structs:
            f.writelines(
                [re.sub(r'^struct\s', 'class ', f'{e}\n\n') for e in self.src_code]
            )
        else:
            f.writelines([f'{e}\n\n' for e in self.src_code])
        f.write(f'}} // namespace {self.arch_name}\n}}' f' // namespace rocjitsu\n')
        f.write(f'\n#endif // {self.include_guard}\n')

    def gen_cpp(self, f: TextIO) -> None:
        """Write source file body and closing namespaces."""
        f.writelines([f'{e}\n\n' for e in self.src_code])
        f.write(f'}} // namespace {self.arch_name}' f'\n}} // namespace rocjitsu\n')

    def gen_code(self) -> None:
        """Generate the file (header or source)."""
        arch_out_path = os.path.join(self.out_path, self.arch_name)
        os.makedirs(arch_out_path, exist_ok=True)
        with open(os.path.join(arch_out_path, self.file_name), 'w') as f:
            self.gen_prologue(f)
            if self.is_header:
                self.gen_header(f)
            else:
                self.gen_cpp(f)