import json
import subprocess
import tempfile
from pathlib import Path

from core_domain import CodeExecutionRequestContract, CodeExecutionResponseContract
from core_shared import JSONValue

from app.bootstrap.settings import CodeRunnerServiceSettings


class CodeRunnerError(Exception):
    pass


class PythonCodeRunner:
    def __init__(self, *, settings: CodeRunnerServiceSettings) -> None:
        self.settings = settings

    def execute(self, payload: CodeExecutionRequestContract) -> CodeExecutionResponseContract:
        script_content = _build_python_runner_script(payload.code)
        with tempfile.TemporaryDirectory(prefix="agent-platform-code-") as temp_dir:
            temp_path = Path(temp_dir)
            script_file = temp_path / "runner.py"
            input_file = temp_path / "input.json"

            script_file.write_text(script_content, encoding="utf-8")
            input_file.write_text(
                json.dumps(payload.input_json, ensure_ascii=False),
                encoding="utf-8")

            try:
                completed = subprocess.run(
                    [self.settings.python_bin, str(script_file), str(input_file)],
                    capture_output=True,
                    text=True,
                    encoding="utf-8",
                    timeout=payload.timeout_seconds,
                    check=False)
            except subprocess.TimeoutExpired as exc:
                return CodeExecutionResponseContract(
                    success=False,
                    stderr=exc.stderr or "",
                    error_message=f"code execution timed out after {payload.timeout_seconds} seconds")
            except OSError as exc:
                raise CodeRunnerError(f"failed to start python runner: {exc}") from exc

        stdout = completed.stdout
        stderr = completed.stderr
        output_json = _extract_result_json(stdout)
        success = completed.returncode == 0
        error_message = None if success else f"python exited with code {completed.returncode}"
        return CodeExecutionResponseContract(
            success=success,
            stdout=stdout,
            stderr=stderr,
            output_json=output_json,
            error_message=error_message)


def _build_python_runner_script(user_code: str) -> str:
    escaped_code = json.dumps(user_code)
    return (
        "import json\n"
        "import pathlib\n"
        "import sys\n"
        "\n"
        "input_path = pathlib.Path(sys.argv[1])\n"
        "payload = json.loads(input_path.read_text(encoding='utf-8'))\n"
        "namespace = {\n"
        "    'payload': payload,\n"
        "    'result': None,\n"
        "}\n"
        f"exec({escaped_code}, namespace, namespace)\n"
        "print('\\n__RESULT_JSON__=' + json.dumps(namespace.get('result'), ensure_ascii=False))\n"
    )


def _extract_result_json(stdout: str) -> dict[str, JSONValue]:
    marker = "__RESULT_JSON__="
    lines = stdout.splitlines()
    for index in range(len(lines) - 1, -1, -1):
        line = lines[index]
        if not line.startswith(marker):
            continue
        raw_payload = line[len(marker) :]
        try:
            payload = json.loads(raw_payload)
        except json.JSONDecodeError:
            return {}
        if isinstance(payload, dict):
            return {str(key): value for key, value in payload.items()}
        return {"result": payload}
    return {}