import subprocess
from pathlib import Path

# Maximum time (seconds) a subprocess is allowed to run before being killed.
RUN_TIMEOUT = 30


class ExecutionEngine:
    """Runs files from the editor in a subprocess and returns the output.

    Currently supports Python (.py) and LaTeX (.tex) files.
    Returns a dict with keys: stdout, stderr, rc (return code).
    """

    def __init__(self):
        pass

    def run_code(self, active_file: Path) -> dict:
        """Execute the given file and return its output.

        Args:
            active_file: Absolute path to the file that should be run.

        Returns:
            {"stdout": str, "stderr": str, "rc": int}
            rc == 0 means success, anything else is an error.
        """
        suffix = active_file.suffix
        current_dir = active_file.parent.resolve()

        # Build the shell command depending on file type
        if suffix == ".py":
            cmd = ["py", active_file.name]
        elif suffix == ".tex":
            # pdflatex in non-interactive mode so it never waits for input
            cmd = [
                "pdflatex",
                "-interaction=nonstopmode",
                f"-output-directory={current_dir}",
                active_file.name,
            ]
        else:
            return {"stdout": "", "stderr": f"Unsupported file type: {suffix}", "rc": 1}

        try:
            proc = subprocess.run(
                cmd,
                cwd=current_dir,        # run inside the file's own directory
                capture_output=True,
                text=True,
                timeout=RUN_TIMEOUT,
            )
            return {"stdout": proc.stdout, "stderr": proc.stderr, "rc": proc.returncode}

        except subprocess.TimeoutExpired:
            return {"stdout": "", "stderr": f"Timed out after {RUN_TIMEOUT}s", "rc": -1}
        except FileNotFoundError as e:
            # Raised when the interpreter/compiler binary is not found on PATH
            return {"stdout": "", "stderr": str(e), "rc": -1}
        except Exception as e:
            return {"stdout": "", "stderr": str(e), "rc": -1}