"""Validate the neutral model boundary before calling provider adapters."""
from backend.errors import InvalidInputError


def object_fields(value, required, optional=()):
    if not isinstance(value, dict) or not set(required) <= set(value) or set(value) - set(required) - set(optional):
        raise InvalidInputError("Invalid model boundary fields")


def validate_content(content, user=False):
    if not isinstance(content, list):
        raise InvalidInputError("Model content must be an array")
    for item in content:
        if not isinstance(item, dict):
            raise InvalidInputError("Invalid model content")
        if item.get("type") == "text":
            object_fields(item, ("type", "text"))
            if not isinstance(item["text"], str):
                raise InvalidInputError("Model text must be a string")
        elif not user and item.get("type") == "tool_call":
            object_fields(item, ("type", "id", "name", "arguments"))
            if not all(isinstance(item[k], str) and item[k] for k in ("id", "name")) or not isinstance(item["arguments"], dict):
                raise InvalidInputError("Invalid model tool call")
        else:
            raise InvalidInputError("Unsupported model content type")


def validate_model_request(payload):
    object_fields(payload, ("messages", "tools"))
    if not isinstance(payload["messages"], list) or not isinstance(payload["tools"], list):
        raise InvalidInputError("Model messages and tools must be arrays")
    for message in payload["messages"]:
        if not isinstance(message, dict):
            raise InvalidInputError("Invalid model message")
        role = message.get("role")
        if role in ("user", "assistant"):
            object_fields(message, ("role", "content"), ("provider_state",) if role == "assistant" else ())
            validate_content(message["content"], user=role == "user")
            if "provider_state" in message and (not isinstance(message["provider_state"], str) or not message["provider_state"]):
                raise InvalidInputError("Invalid provider_state handle")
        elif role == "tool":
            object_fields(message, ("role", "tool_call_id", "name", "content", "is_error"))
            if not all(isinstance(message[k], str) for k in ("tool_call_id", "name", "content")) or type(message["is_error"]) is not bool:
                raise InvalidInputError("Invalid model tool result")
        else:
            raise InvalidInputError("Unsupported model message role")
    for tool in payload["tools"]:
        object_fields(tool, ("name", "description", "input_schema"))
        if not isinstance(tool["name"], str) or not tool["name"] or not isinstance(tool["description"], str) or not isinstance(tool["input_schema"], dict):
            raise InvalidInputError("Invalid model tool declaration")