"""Low-level HTTP client implementing Dragonchain's DC1-HMAC-SHA256 auth.

This is a direct port of the Go SDK's ``client/client.go``. The signing scheme
must match the prime-node authorizer byte-for-byte: the signed message is six
fields joined by ``\\n`` (no trailing newline) in this exact order::

    UPPER(method)
    path                      # full path incl. /api/v1/..., no query string
    publicId
    timestamp
    contentType
    base64(sha256(body))
"""

import base64
import hashlib
import hmac
import json
import time
from typing import Any, Optional, Type, TypeVar

import requests

from .errors import DragonchainAPIError

T = TypeVar("T")

CONTENT_TYPE_JSON = "application/json"
DEFAULT_TIMEOUT = 30  # seconds


class Client:
    """Authenticated HTTP client for a single Dragonchain node."""

    def __init__(
        self,
        public_id: str,
        auth_key_id: str,
        auth_key: str,
        base_url: str,
        timeout: int = DEFAULT_TIMEOUT,
    ):
        self.public_id = public_id
        self.auth_key_id = auth_key_id
        self.auth_key = auth_key
        self.base_url = base_url.rstrip("/")
        self.timeout = timeout
        self._session = requests.Session()

    # -- introspection helpers (mirror the Go accessors) --------------------

    def internal_id(self) -> str:
        return self.public_id

    def get_public_id(self) -> str:
        return self.public_id

    def get_auth_key_id(self) -> str:
        return self.auth_key_id

    def endpoint(self) -> str:
        return self.base_url

    # -- auth ---------------------------------------------------------------

    def _hmac_message(
        self, method: str, path: str, timestamp: str, content_type: str, body: bytes
    ) -> str:
        b64_content = base64.b64encode(hashlib.sha256(body).digest()).decode("ascii")
        return "\n".join(
            [
                method.upper(),
                path,
                self.public_id,
                timestamp,
                content_type,
                b64_content,
            ]
        )

    def _generate_auth_header(
        self, method: str, path: str, timestamp: str, content_type: str, body: bytes
    ) -> str:
        msg = self._hmac_message(method, path, timestamp, content_type, body)
        digest = hmac.new(
            self.auth_key.encode("utf-8"), msg.encode("utf-8"), hashlib.sha256
        ).digest()
        b64_hmac = base64.b64encode(digest).decode("ascii")
        return f"DC1-HMAC-SHA256 {self.auth_key_id}:{b64_hmac}"

    # -- request plumbing ---------------------------------------------------

    def _do_request(
        self,
        method: str,
        path: str,
        content_type: str = "",
        body: Any = None,
        response_cls: Optional[Type[T]] = None,
    ) -> Optional[T]:
        if isinstance(body, (bytes, bytearray)):
            body_bytes = bytes(body)
        elif body is not None:
            body_bytes = json.dumps(_to_jsonable(body)).encode("utf-8")
            content_type = CONTENT_TYPE_JSON
        else:
            body_bytes = b""

        timestamp = str(int(time.time()))
        auth_header = self._generate_auth_header(
            method, path, timestamp, content_type, body_bytes
        )

        headers = {
            "Authorization": auth_header,
            "Dragonchain": self.public_id,
            "Timestamp": timestamp,
        }
        if content_type:
            headers["Content-Type"] = content_type

        url = self.base_url + path
        resp = self._session.request(
            method, url, data=body_bytes, headers=headers, timeout=self.timeout
        )

        resp_text = resp.text
        if resp.status_code >= 400:
            raise DragonchainAPIError(resp.status_code, resp_text.strip())

        if response_cls is not None and resp_text:
            parsed = json.loads(resp_text)
            return response_cls.from_dict(parsed)  # type: ignore[attr-defined]
        return None

    # -- verb helpers -------------------------------------------------------

    def get(self, path: str, response_cls: Optional[Type[T]] = None) -> Optional[T]:
        return self._do_request("GET", path, response_cls=response_cls)

    def post(
        self,
        path: str,
        content_type: str,
        body: Any,
        response_cls: Optional[Type[T]] = None,
    ) -> Optional[T]:
        return self._do_request("POST", path, content_type, body, response_cls)

    def put(
        self,
        path: str,
        content_type: str,
        body: Any,
        response_cls: Optional[Type[T]] = None,
    ) -> Optional[T]:
        return self._do_request("PUT", path, content_type, body, response_cls)

    def delete(self, path: str, response_cls: Optional[Type[T]] = None) -> Optional[T]:
        return self._do_request("DELETE", path, response_cls=response_cls)


def _to_jsonable(body: Any) -> Any:
    """Convert request models (which expose ``to_dict``) to JSON-ready data."""
    if hasattr(body, "to_dict"):
        return body.to_dict()
    return body