backend/app/utils/json_utils.py

import json
import re
from typing import Any, TypeVar

from pydantic import BaseModel, ValidationError

T = TypeVar("T", bound=BaseModel)


def safe_json_loads(text: str) -> dict[str, Any]:
    stripped = text.strip()

    # Try direct parse first
    try:
        payload = json.loads(stripped)
        if isinstance(payload, dict):
            return payload
    except json.JSONDecodeError:
        pass

    # Try extracting from markdown fences ```json ... ``` or ``` ... ```
    fence_match = re.search(r"```(?:json)?\s*\n?(.*?)\n?```", stripped, re.DOTALL)
    if fence_match:
        try:
            payload = json.loads(fence_match.group(1).strip())
            if isinstance(payload, dict):
                return payload
        except json.JSONDecodeError:
            pass

    # Try finding the first { ... } block
    brace_start = stripped.find("{")
    if brace_start != -1:
        brace_end = stripped.rfind("}")
        if brace_end > brace_start:
            try:
                payload = json.loads(stripped[brace_start : brace_end + 1])
                if isinstance(payload, dict):
                    return payload
            except json.JSONDecodeError:
                pass

    raise ValueError("Response is not valid JSON — tried direct parse, markdown fences, and brace extraction.")


def validate_json_plan(payload: dict[str, Any], model: type[T]) -> T:
    try:
        return model.model_validate(payload)
    except ValidationError as exc:
        raise ValueError("Invalid JSON analysis plan.") from exc