"""Envelope + camelCase renderer (``API-STANDARD.md`` §3, §4)."""

from __future__ import annotations

from typing import Any

from django.utils import timezone
from djangorestframework_camel_case.render import CamelCaseJSONRenderer

__all__ = ["EnvelopeJSONRenderer"]

_PAGINATED_KEYS = {"results", "next", "previous"}


class EnvelopeJSONRenderer(CamelCaseJSONRenderer):
    """Wraps every response in the standard envelope and camelCases its keys.

    * success (status < 400): ``{success: true, data, error: null, meta}``
    * error (status >= 400): ``{success: false, data: null, error, meta}``

    ``meta`` always carries ``requestId`` and ``timestamp``; it carries
    ``tenantId`` when a tenant is resolved and ``pagination`` for list
    responses produced by :class:`infrasynth.api.pagination.CursorPagination`.
    """

    def render(
        self,
        data: Any,
        accepted_media_type: str | None = None,
        renderer_context: dict[str, Any] | None = None,
    ) -> bytes:
        renderer_context = renderer_context or {}
        response = renderer_context.get("response")
        request = renderer_context.get("request")
        status_code = getattr(response, "status_code", 200) or 200

        meta: dict[str, Any] = {
            "requestId": getattr(request, "request_id", "") if request else "",
            "timestamp": timezone.now().isoformat().replace("+00:00", "Z"),
        }
        tenant = getattr(request, "tenant", None) if request else None
        if tenant is not None:
            meta["tenantId"] = str(getattr(tenant, "pk", tenant))

        if status_code >= 400:
            body: dict[str, Any] = {"success": False, "data": None, "error": data, "meta": meta}
        else:
            payload = data
            if isinstance(payload, dict) and _PAGINATED_KEYS.issubset(payload.keys()):
                meta["pagination"] = {
                    "nextCursor": payload.get("next"),
                    "prevCursor": payload.get("previous"),
                    "pageSize": payload.get("page_size"),
                }
                payload = payload.get("results")
            body = {"success": True, "data": payload, "error": None, "meta": meta}

        return super().render(body, accepted_media_type, renderer_context)