"""Loki HTTP API Client.

Handles all communication with Loki's query endpoints:
  - /loki/api/v1/query_range  (log queries over a time window)
  - /loki/api/v1/labels       (list all label names)
  - /loki/api/v1/label/{name}/values  (values for a specific label)
  - /loki/api/v1/series       (active label sets / streams)
"""

import logging
from datetime import datetime, timedelta, timezone
from typing import Any, Dict, List, Optional

import httpx

from mcp_servers.loki.config import (
    LOKI_URL,
    LOKI_TIMEOUT,
    DEFAULT_LIMIT,
    DEFAULT_RANGE_HOURS,
)

logger = logging.getLogger(__name__)


class LokiClient:
    """Async HTTP client for Loki's query API."""

    def __init__(
        self,
        url: Optional[str] = None,
        timeout: Optional[int] = None,
    ):
        self.url = url or LOKI_URL
        self.timeout = timeout or LOKI_TIMEOUT
        self._client: Optional[httpx.AsyncClient] = None

    async def _get_client(self) -> httpx.AsyncClient:
        """Lazy-init the async HTTP client."""
        if self._client is None or self._client.is_closed:
            self._client = httpx.AsyncClient(
                base_url=self.url,
                timeout=self.timeout,
            )
        return self._client

    async def close(self):
        """Close the HTTP client."""
        if self._client and not self._client.is_closed:
            await self._client.aclose()

    # ------------------------------------------------------------------
    # Time helpers
    # ------------------------------------------------------------------

    @staticmethod
    def _to_nano_ts(dt: datetime) -> str:
        """Convert a datetime to Loki's nanosecond-epoch string."""
        return str(int(dt.timestamp() * 1_000_000_000))

    @staticmethod
    def _default_range(hours: Optional[int] = None):
        """Return (start, end) as nano-epoch strings for the last N hours."""
        now = datetime.now(timezone.utc)
        hrs = hours or DEFAULT_RANGE_HOURS
        start = now - timedelta(hours=hrs)
        return (
            LokiClient._to_nano_ts(start),
            LokiClient._to_nano_ts(now),
        )

    # ------------------------------------------------------------------
    # Core queries
    # ------------------------------------------------------------------

    async def query_range(
        self,
        query: str,
        start: Optional[str] = None,
        end: Optional[str] = None,
        limit: Optional[int] = None,
        hours: Optional[int] = None,
    ) -> Dict[str, Any]:
        """Run a LogQL query over a time range.

        Args:
            query:  LogQL expression, e.g. '{job="varlogs"} |= "error"'
            start:  Nano-epoch start (optional — defaults to now-<hours>).
            end:    Nano-epoch end (optional — defaults to now).
            limit:  Max log lines to return.
            hours:  Shorthand for "last N hours" (ignored if start/end given).

        Returns:
            Raw JSON response from Loki (dict).
        """
        if not start or not end:
            start, end = self._default_range(hours)

        params = {
            "query": query,
            "start": start,
            "end": end,
            "limit": limit or DEFAULT_LIMIT,
        }

        client = await self._get_client()
        logger.debug("[Loki] query_range: %s", params)
        resp = await client.get("/loki/api/v1/query_range", params=params)
        resp.raise_for_status()
        return resp.json()

    async def labels(self) -> List[str]:
        """List all known label names."""
        client = await self._get_client()
        resp = await client.get("/loki/api/v1/labels")
        resp.raise_for_status()
        data = resp.json()
        return data.get("data", [])

    async def label_values(self, label: str) -> List[str]:
        """List values for a specific label (e.g. 'job', 'host')."""
        client = await self._get_client()
        resp = await client.get(f"/loki/api/v1/label/{label}/values")
        resp.raise_for_status()
        data = resp.json()
        return data.get("data", [])

    async def series(
        self,
        match: Optional[List[str]] = None,
        hours: Optional[int] = None,
    ) -> List[Dict[str, str]]:
        """List active streams/series matching optional selectors.

        Args:
            match: List of LogQL stream selectors, e.g. ['{job="varlogs"}'].
            hours: Time window to search (default: DEFAULT_RANGE_HOURS).
        """
        start, end = self._default_range(hours)
        params: Dict[str, Any] = {"start": start, "end": end}
        if match:
            params["match[]"] = match

        client = await self._get_client()
        resp = await client.get("/loki/api/v1/series", params=params)
        resp.raise_for_status()
        data = resp.json()
        return data.get("data", [])

    async def health(self) -> bool:
        """Quick health check — hits /ready endpoint."""
        try:
            client = await self._get_client()
            resp = await client.get("/ready")
            return resp.status_code == 200
        except Exception as e:
            logger.warning("[Loki] Health check failed: %s", e)
            return False

    # ------------------------------------------------------------------
    # Convenience: extract just the log lines from a query_range result
    # ------------------------------------------------------------------

    @staticmethod
    def extract_lines(result: Dict[str, Any]) -> List[Dict[str, str]]:
        """Pull log lines from a query_range response.

        Returns list of {"timestamp": ..., "line": ..., "labels": ...} dicts,
        sorted newest-first.
        """
        lines = []
        data = result.get("data", {})
        for stream in data.get("result", []):
            labels = stream.get("stream", {})
            label_str = ", ".join(f'{k}="{v}"' for k, v in labels.items())
            for ts, line in stream.get("values", []):
                # Convert nano-epoch to human-readable
                dt = datetime.fromtimestamp(
                    int(ts) / 1_000_000_000, tz=timezone.utc
                )
                lines.append({
                    "timestamp": dt.strftime("%Y-%m-%d %H:%M:%S UTC"),
                    "line": line,
                    "labels": label_str,
                })

        # Newest first
        lines.sort(key=lambda x: x["timestamp"], reverse=True)
        return lines