"""JSON-RPC 2.0 server primitives for I2PControl."""
from __future__ import annotations

import json
from dataclasses import dataclass, field
from typing import Any

# Standard JSON-RPC 2.0 error codes
PARSE_ERROR = -32700
INVALID_REQUEST = -32600
METHOD_NOT_FOUND = -32601
INTERNAL_ERROR = -32603


@dataclass
class JSONRPCRequest:
    """Parsed JSON-RPC 2.0 request."""

    method: str
    params: dict = field(default_factory=dict)
    id: int | str | None = None
    jsonrpc: str = "2.0"


@dataclass
class JSONRPCResponse:
    """JSON-RPC 2.0 response."""

    result: dict | None = None
    error: dict | None = None
    id: int | str | None = None
    jsonrpc: str = "2.0"

    def to_dict(self) -> dict[str, Any]:
        d: dict[str, Any] = {"jsonrpc": self.jsonrpc, "id": self.id}
        if self.error is not None:
            d["error"] = self.error
        else:
            d["result"] = self.result
        return d


def parse_jsonrpc_request(data: str) -> JSONRPCRequest:
    """Parse a JSON-RPC 2.0 request string.

    Raises ``ValueError`` on invalid JSON, missing ``jsonrpc`` field,
    or missing ``method`` field.
    """
    try:
        obj = json.loads(data)
    except (json.JSONDecodeError, TypeError) as exc:
        raise ValueError("Parse error: invalid JSON") from exc

    if not isinstance(obj, dict):
        raise ValueError("Parse error: request must be a JSON object")

    if "jsonrpc" not in obj or obj["jsonrpc"] != "2.0":
        raise ValueError("Invalid request: missing or wrong jsonrpc field")

    if "method" not in obj:
        raise ValueError("Invalid request: missing method field")

    return JSONRPCRequest(
        method=obj["method"],
        params=obj.get("params", {}),
        id=obj.get("id"),
        jsonrpc=obj["jsonrpc"],
    )


def build_jsonrpc_response(
    result: dict | None = None,
    error: dict | None = None,
    request_id: int | str | None = None,
) -> dict[str, Any]:
    """Build a JSON-RPC 2.0 response dict."""
    resp: dict[str, Any] = {"jsonrpc": "2.0", "id": request_id}
    if error is not None:
        resp["error"] = error
    else:
        resp["result"] = result
    return resp


def build_jsonrpc_error(
    code: int,
    message: str,
    request_id: int | str | None = None,
) -> dict[str, Any]:
    """Build a JSON-RPC 2.0 error response."""
    return build_jsonrpc_response(
        error={"code": code, "message": message},
        request_id=request_id,
    )