import time
from typing import Any, Literal, Optional

import requests

from infrastructure.http_retry import TransientHttpError, call_with_retry


class BuildingInsightsNotFoundError(Exception):
    pass


class GoogleSolarApiClient:
    base_url: str = "https://solar.googleapis.com/v1"
    # Bounded retries (NOT Google's infinite-loop example). With the 60s max
    # backoff below, 6 retries span ~2 of the Solar API's per-minute (600 QPM)
    # windows — enough to ride out a transient 429 burst, then give up so a
    # stuck request can't blow the container timeout; the subtask fails and is
    # re-triggered.
    MAX_RETRIES: int = 6
    MAX_BACKOFF_SECONDS: float = 60.0
    ENTITY_NOT_FOUND_ERROR: str = "Requested entity was not found."

    def __init__(
        self, api_key: str, min_request_interval_seconds: float = 0.0
    ) -> None:
        # Per-instance min-interval throttle. The Solar API caps the whole GCP
        # project at a hard 600 QPM shared across Building Insights + Data Layers
        # (https://developers.google.com/maps/documentation/solar/usage-and-billing).
        # The modelling_e2e fleet runs up to `maximum_concurrency` (32) containers,
        # each looping its ~50-property batch sequentially — so without pacing the
        # fleet offers multiples of the quota and a steady fraction of calls 429
        # for a sustained window that #1327's jittered backoff can't ride out.
        # Each container holding >= quota/N seconds between its OWN consecutive
        # calls keeps the fleet sum under the ceiling. Default 0.0 = no throttle,
        # so the interactive backend path and tests are unchanged; the scaled
        # caller (the Lambda) opts in via env.
        self._api_key = api_key
        self._min_request_interval_seconds = min_request_interval_seconds
        self._last_request_monotonic: Optional[float] = None

    def _await_rate_limit(self) -> None:
        """Block until at least ``min_request_interval_seconds`` has elapsed since
        this instance's previous call, so the container never exceeds its share of
        the fleet's 600 QPM Solar budget. A no-op when the interval is 0 (the
        default / interactive path). The call's own latency counts toward the gap
        (we sleep only the *remainder*), so we don't double-pay the request time."""
        if self._min_request_interval_seconds <= 0:
            return
        now = time.monotonic()
        if self._last_request_monotonic is not None:
            wait = self._min_request_interval_seconds - (
                now - self._last_request_monotonic
            )
            if wait > 0:
                time.sleep(wait)
                now = time.monotonic()
        self._last_request_monotonic = now

    @staticmethod
    def _parse_retry_after(response: requests.Response) -> Optional[float]:
        header = response.headers.get("Retry-After")
        if header is None:
            return None
        try:
            return float(header)
        except (TypeError, ValueError):
            return None

    def get_building_insights(
        self,
        longitude: float,
        latitude: float,
        required_quality: Literal["HIGH", "MEDIUM", "LOW"] = "MEDIUM",
    ) -> dict[str, Any]:
        self._await_rate_limit()
        insights_url = f"{self.base_url}/buildingInsights:findClosest"
        params: dict[str, str] = {
            "location.latitude": f"{latitude:.5f}",
            "location.longitude": f"{longitude:.5f}",
            "requiredQuality": required_quality,
            "key": self._api_key,
        }

        def _fetch() -> dict[str, Any]:
            try:
                response = requests.get(insights_url, params=params)
                response.raise_for_status()
                result: dict[str, Any] = response.json()
                return result
            except requests.exceptions.RequestException as e:
                response = e.response
                if response is None:
                    # No response = a transport-level failure (connection reset /
                    # read or connect timeout) — transient, retry.
                    raise TransientHttpError(f"Solar API transport error: {e}") from e
                status = response.status_code
                if (
                    status == 404
                    and response.json().get("error", {}).get("message")
                    == self.ENTITY_NOT_FOUND_ERROR
                ):
                    raise BuildingInsightsNotFoundError() from e
                if status == 429 or status >= 500:
                    # Rate-limit (429) and server errors (5xx) are transient.
                    # Honour the server's Retry-After when present (jittered
                    # exponential backoff otherwise — see `call_with_retry`).
                    raise TransientHttpError(
                        f"Solar API {status}",
                        retry_after=self._parse_retry_after(response),
                    ) from e
                # Other 4xx are the caller's fault — non-transient, propagate.
                raise

        return call_with_retry(
            _fetch,
            max_retries=self.MAX_RETRIES,
            max_backoff=self.MAX_BACKOFF_SECONDS,
            jitter=True,
        )