romm/backend/endpoints/roms/patch.py

import shutil
import tempfile
from pathlib import Path
from typing import Annotated
from urllib.parse import quote

from fastapi import Body, HTTPException
from fastapi import Path as PathVar
from fastapi import Request, status
from pydantic import BaseModel, Field
from starlette.background import BackgroundTask
from starlette.responses import FileResponse

from config import ROM_PATCHER_MAX_FILE_SIZE_BYTES
from decorators.auth import protected_route
from handler.auth.constants import Scope
from handler.database import db_rom_handler
from handler.filesystem import fs_rom_handler
from logger.formatter import BLUE
from logger.formatter import highlight as hl
from logger.logger import log
from utils.rom_patcher import SUPPORTED_PATCH_EXTENSIONS, PatcherError, apply_patch
from utils.router import APIRouter

router = APIRouter()


class PatchRequest(BaseModel):
    patch_file_id: int = Field(description="ID of the patch file (RomFile) to apply.")
    output_file_name: str | None = Field(
        default=None,
        description="Custom output file name. If omitted, derived from ROM + patch names.",
    )


class PatchResponse(BaseModel):
    message: str
    output_file_name: str
    output_file_size: int


@protected_route(
    router.post,
    "/{id}/patch",
    [Scope.ROMS_READ],
    responses={
        status.HTTP_400_BAD_REQUEST: {},
        status.HTTP_404_NOT_FOUND: {},
        status.HTTP_500_INTERNAL_SERVER_ERROR: {},
    },
)
async def patch_rom(
    request: Request,
    id: Annotated[int, PathVar(description="ROM file ID (the base game file).", ge=1)],
    patch_request: Annotated[PatchRequest, Body()],
):
    """Apply a patch to a ROM file server-side and return the patched file.

    Both the ROM file and the patch file must already exist in the library.
    The patched ROM is streamed back as a download.
    """

    current_username = (
        request.user.username if request.user.is_authenticated else "unknown"
    )

    rom_file = db_rom_handler.get_rom_file_by_id(id)
    if not rom_file:
        raise HTTPException(
            status_code=status.HTTP_404_NOT_FOUND,
            detail=f"ROM file with id {id} not found",
        )
    if rom_file.missing_from_fs:
        raise HTTPException(
            status_code=status.HTTP_404_NOT_FOUND,
            detail=f"ROM file '{rom_file.file_name}' is missing from filesystem",
        )

    patch_file = db_rom_handler.get_rom_file_by_id(patch_request.patch_file_id)
    if not patch_file:
        raise HTTPException(
            status_code=status.HTTP_404_NOT_FOUND,
            detail=f"Patch file with id {patch_request.patch_file_id} not found",
        )
    if patch_file.missing_from_fs:
        raise HTTPException(
            status_code=status.HTTP_404_NOT_FOUND,
            detail=f"Patch file '{patch_file.file_name}' is missing from filesystem",
        )

    patch_ext = Path(patch_file.file_name).suffix.lower()
    if patch_ext not in SUPPORTED_PATCH_EXTENSIONS:
        raise HTTPException(
            status_code=status.HTTP_400_BAD_REQUEST,
            detail=f"Unsupported patch format '{patch_ext}'. Supported: {', '.join(sorted(SUPPORTED_PATCH_EXTENSIONS))}",
        )

    # RomPatcher.js loads the whole ROM into memory, so reject oversized inputs.
    for label, file in (("ROM", rom_file), ("Patch", patch_file)):
        if file.file_size_bytes > ROM_PATCHER_MAX_FILE_SIZE_BYTES:
            raise HTTPException(
                status_code=status.HTTP_400_BAD_REQUEST,
                detail=(
                    f"{label} file is too large to patch "
                    f"({file.file_size_bytes} bytes, max {ROM_PATCHER_MAX_FILE_SIZE_BYTES})"
                ),
            )

    rom_path = fs_rom_handler.validate_path(rom_file.full_path)
    patch_path = fs_rom_handler.validate_path(patch_file.full_path)

    rom_ext = Path(rom_file.file_name).suffix
    if patch_request.output_file_name:
        output_file_name = f"{Path(patch_request.output_file_name).stem}{rom_ext}"
    else:
        rom_base = Path(rom_file.file_name).stem
        patch_base = Path(patch_file.file_name).stem
        output_file_name = f"{rom_base} (patched-{patch_base}){rom_ext}"

    log.info(
        f"User {hl(current_username, color=BLUE)} is patching "
        f"ROM file {hl(rom_file.file_name)} with patch {hl(patch_file.file_name)}"
    )

    tmp_dir = tempfile.mkdtemp(prefix="romm_patch_")
    output_path = Path(tmp_dir) / output_file_name

    try:
        validated = await apply_patch(rom_path, patch_path, output_path)
    except PatcherError as e:
        shutil.rmtree(tmp_dir, ignore_errors=True)
        # Detail may contain server paths from node/RomPatcher.js; keep it server-side.
        log.error(f"Patching failed: {e}")
        raise HTTPException(
            status_code=status.HTTP_500_INTERNAL_SERVER_ERROR,
            detail="Patching failed",
        ) from e
    except Exception as e:
        shutil.rmtree(tmp_dir, ignore_errors=True)
        log.error(f"Unexpected patching error: {e}")
        raise HTTPException(
            status_code=status.HTTP_500_INTERNAL_SERVER_ERROR,
            detail="Patching failed",
        ) from e

    output_size = output_path.stat().st_size
    log.info(
        f"Successfully patched ROM for user {hl(current_username, color=BLUE)}: "
        f"{hl(output_file_name)} ({output_size} bytes)"
    )
    if not validated:
        log.warning(
            f"Patch {hl(patch_file.file_name)} source checksum did not match "
            f"ROM {hl(rom_file.file_name)}; output may be incorrect"
        )

    return FileResponse(
        path=str(output_path),
        filename=output_file_name,
        media_type="application/octet-stream",
        headers={
            "Content-Disposition": f"attachment; filename*=UTF-8''{quote(output_file_name)}; filename=\"{quote(output_file_name)}\"",
            "Content-Length": str(output_size),
            # Lets callers warn when the patch's source checksum didn't match the ROM.
            "X-Patch-Validated": "true" if validated else "false",
        },
        background=BackgroundTask(shutil.rmtree, tmp_dir, True),
    )