"""On-chain metrics for the BTC bottom-reversal scanner.

Two providers, same interface (fetch_mvrv_z_score / fetch_sth_sopr → list[float]):

  BitcoinDataClient  — DEFAULT. bitcoin-data.com public API. FREE, no key.
                       Returns PRE-COMPUTED MVRV-Z and STH-SOPR (we don't
                       need realized-cap or local math — realized cap is an
                       on-chain quantity that CANNOT be derived from price
                       data, so a vendor is unavoidable; this is the free one).
                       Free tier: 10 requests/HOUR. The scanner runs once a
                       day and needs 2 calls — well within budget — but we
                       add a 6-hour in-process cache as a safety net against
                       restarts / manual re-runs hammering the limit.

  GlassnodeClient    — Optional paid fallback. Used automatically if
                       GLASSNODE_API_KEY is set (higher resolution / SLA).

get_onchain_client() picks the right one. btc_bottom_reversal.py only
depends on the interface, never the concrete class.
"""

from __future__ import annotations

import json
import logging
import os
import time
from datetime import datetime, timezone
from typing import Optional

import httpx

from app.config import settings

logger = logging.getLogger(__name__)


# ─── Provider 1: bitcoin-data.com (free, default) ───────────────────────────

BITCOIN_DATA_BASE = "https://bitcoin-data.com/v1"

# Endpoint → (path, json value key). Both return a full daily history list
# of {"d","unixTs",<key>} when called with no query params.
_BD_ENDPOINTS = {
    "mvrv_z": ("/mvrv-zscore", "mvrvZscore"),
    "sth_sopr": ("/sth-sopr", "sthSopr"),
}

# Fresh-fetch window: don't re-hit the API if the on-disk copy is younger
# than this. The scanner runs daily; 18h keeps it to ~1 fetch/day/metric
# (2 req/day total, vs the 10 req/HOUR free cap).
_BD_FRESH_S = 18 * 3600
# How stale on-disk data may be and still be USABLE when the API is down /
# rate-limited. A daily MVRV-Z / STH-SOPR barely moves over 2 days, so
# serving 48h-old data beats skipping a scan or, worse, acting on nothing.
_BD_STALE_OK_S = 48 * 3600

# Disk cache survives restarts — critical given the tight free rate limit.
_BD_CACHE_DIR = os.path.join(os.path.dirname(os.path.dirname(os.path.dirname(__file__))), ".cache")
_BD_CACHE_FILE = os.path.join(_BD_CACHE_DIR, "onchain_bitcoin_data.json")


def _load_disk_cache() -> dict:
    try:
        with open(_BD_CACHE_FILE) as f:
            return json.load(f)
    except (FileNotFoundError, json.JSONDecodeError, OSError):
        return {}


def _save_disk_cache(cache: dict) -> None:
    try:
        os.makedirs(_BD_CACHE_DIR, exist_ok=True)
        tmp = _BD_CACHE_FILE + ".tmp"
        with open(tmp, "w") as f:
            json.dump(cache, f)
        os.replace(tmp, _BD_CACHE_FILE)   # atomic
    except OSError as exc:
        logger.warning("onchain disk-cache write failed: %s", exc)


class BitcoinDataClient:
    """Free, key-less. Returns pre-computed metric series (already the
    Z-score / SOPR value — no local computation needed). Disk-cached so the
    10 req/hour free cap and process restarts can't starve the scanner."""

    async def _series(self, metric: str, days: int) -> list[float]:
        now = time.time()
        cache = _load_disk_cache()
        entry = cache.get(metric)            # {"ts": epoch, "values": [...]}
        age = (now - entry["ts"]) if entry else None

        # Fresh enough → no network call at all.
        if entry and age is not None and age < _BD_FRESH_S:
            vals = entry["values"]
            return vals[-days:] if days else vals

        path, key = _BD_ENDPOINTS[metric]
        try:
            async with httpx.AsyncClient(timeout=20) as client:
                resp = await client.get(f"{BITCOIN_DATA_BASE}{path}")
            if resp.status_code == 429:
                raise RuntimeError("rate_limited")
            resp.raise_for_status()
            rows = resp.json() or []
            values = [float(r[key]) for r in rows if r.get(key) is not None]
            if not values:
                raise RuntimeError("empty_response")
            cache[metric] = {"ts": now, "values": values}
            _save_disk_cache(cache)
            return values[-days:] if days else values
        except Exception as exc:
            # Network/limit failure: fall back to disk if it's still usable.
            if entry and age is not None and age < _BD_STALE_OK_S:
                logger.warning("bitcoin-data.com %s fetch failed (%s) — "
                               "serving disk cache aged %.1fh",
                               metric, exc, age / 3600)
                vals = entry["values"]
                return vals[-days:] if days else vals
            raise RuntimeError(
                f"bitcoin-data.com {metric} unavailable ({exc}) and no usable cache"
            ) from exc

    async def fetch_mvrv_z_score(self, asset: str = "BTC", days: int = 730) -> list[float]:
        if asset.upper() != "BTC":
            return []   # bitcoin-data.com is BTC-only
        return await self._series("mvrv_z", days)

    async def fetch_sth_sopr(self, asset: str = "BTC", days: int = 30) -> list[float]:
        if asset.upper() != "BTC":
            return []
        return await self._series("sth_sopr", days)


# ─── Provider 2: Glassnode (paid, optional) ─────────────────────────────────

GLASSNODE_BASE_URL = "https://api.glassnode.com/v1/metrics"


class GlassnodeClient:
    def __init__(self, api_key: Optional[str] = None):
        self.api_key = api_key if api_key is not None else settings.glassnode_api_key

    async def _get_series(self, path: str, asset: str, days: int) -> list[dict]:
        if not self.api_key:
            raise RuntimeError("GLASSNODE_API_KEY is not configured")
        end = int(datetime.now(timezone.utc).timestamp())
        start = end - days * 86_400
        async with httpx.AsyncClient(timeout=20) as client:
            resp = await client.get(
                f"{GLASSNODE_BASE_URL}{path}",
                params={"a": asset, "api_key": self.api_key,
                        "s": start, "u": end, "i": "24h"},
            )
            resp.raise_for_status()
            return resp.json() or []

    async def fetch_mvrv_z_score(self, asset: str = "BTC", days: int = 730) -> list[float]:
        rows = await self._get_series("/market/mvrv_z_score", asset, days)
        return [float(r["v"]) for r in rows if r.get("v") is not None]

    async def fetch_sth_sopr(self, asset: str = "BTC", days: int = 30) -> list[float]:
        rows = await self._get_series("/indicators/sopr_less_155", asset, days)
        return [float(r["v"]) for r in rows if r.get("v") is not None]


# ─── Factory ────────────────────────────────────────────────────────────────


def get_onchain_client():
    """Glassnode if a key is configured (paid, higher SLA), else the free
    bitcoin-data.com client. Both expose the same async interface."""
    if settings.glassnode_api_key:
        logger.info("On-chain provider: Glassnode (paid key configured)")
        return GlassnodeClient()
    logger.info("On-chain provider: bitcoin-data.com (free, no key)")
    return BitcoinDataClient()