"""Market data in your app: a small backend that fetches Blockmetric data on the server, caches it and hands your
frontend exactly what it shows, with the credit line the licence asks for. Python 3.9+, standard library only.
Your key never reaches the browser, and 1,000 visitors cost the same few API requests as one.

    export BLOCKMETRIC_API_KEY=bm_live_...            # API Pro: display licence for data shown to your users
    export BLOCKMETRIC_BASE_URL=https://<domain>/api/v1
    python server.py                                   # http://localhost:8080/api/market

Options: PORT (8080), CACHE_SECONDS (30), TOP (10), ONCE=1 (print the JSON once, then exit).
"""
import json
import os
import threading
import time
import urllib.error
import urllib.request
from http.server import BaseHTTPRequestHandler, ThreadingHTTPServer

BASE = os.environ.get("BLOCKMETRIC_BASE_URL", "").rstrip("/")
KEY = os.environ.get("BLOCKMETRIC_API_KEY")
PORT = int(os.environ.get("PORT", "8080"))
CACHE_SECONDS = float(os.environ.get("CACHE_SECONDS", "30"))
TOP = int(os.environ.get("TOP", "10"))
etags = {}  # path -> (etag, body): an unchanged answer comes back as 304 without a body


def api(path):
    headers = {"Authorization": f"Bearer {KEY}"} if KEY else {"X-Blockmetric-Access": "public"}
    if path in etags:
        headers["If-None-Match"] = etags[path][0]
    try:
        with urllib.request.urlopen(urllib.request.Request(BASE + path, headers=headers), timeout=20) as res:
            body = json.load(res)
            if res.headers.get("ETag"):
                etags[path] = (res.headers["ETag"], body)
            return body
    except urllib.error.HTTPError as e:
        if e.code == 304 and path in etags:
            return etags[path][1]
        err = json.load(e).get("error", {})
        raise RuntimeError(f"{e.code} {err.get('code')}: {err.get('message')}")


def credit(lines):
    """"Data by Blockmetric · Source: A · B" from several credit lines (the sources of every answer, each named once)."""
    sources = []
    for line in lines:
        for s in (line.split(" · Source: ") + [""])[1].split(" · "):
            if s and s not in sources:
                sources.append(s)
    head = lines[0].split(" · Source: ")[0]
    return f"{head} · Source: {' · '.join(sources)}" if sources else head


def build():
    """What the frontend needs, nothing more: top markets by open interest, 24h liquidations and the credit line."""
    markets = api("/markets?venue=hyperliquid")
    liq = api("/liquidations/summary?hours=24")
    keep = ("coin", "mark", "fundingApr", "openInterestUsd", "volume24hUsd")
    return {
        "updatedAt": markets["meta"]["updatedAt"],
        "markets": [{k: m.get(k) for k in keep} for m in markets["data"][:TOP]],
        "liquidations24h": {k: liq["data"][k] for k in ("totalUsd", "longUsd", "shortUsd")},
        # Show this credit next to the data; it names the sources of both answers.
        "attribution": {"text": credit([markets["meta"]["attribution"]["text"], liq["meta"]["attribution"]["text"]]), "url": markets["meta"]["attribution"]["url"]},
        "license": markets["meta"]["license"]["id"],
    }


cache = {"at": 0.0, "value": None}
lock = threading.Lock()


def cached():
    with lock:  # one refresh at a time, every visitor gets the same answer
        if cache["value"] is None or time.time() - cache["at"] >= CACHE_SECONDS:
            try:
                cache.update(at=time.time(), value=build())
            except (RuntimeError, urllib.error.URLError):
                if cache["value"] is None:
                    raise  # serve the last good answer while the API is unreachable
        return cache["value"]


class Handler(BaseHTTPRequestHandler):
    def do_GET(self):
        if self.path != "/api/market":
            self.send_response(404)
            self.end_headers()
            return
        try:
            body, status = json.dumps(cached()).encode(), 200
        except Exception as e:  # noqa: BLE001 - report any upstream problem as 502
            body, status = json.dumps({"error": str(e)}).encode(), 502
        self.send_response(status)
        self.send_header("Content-Type", "application/json")
        self.send_header("Cache-Control", f"public, max-age={int(CACHE_SECONDS)}")
        self.end_headers()
        self.wfile.write(body)


if __name__ == "__main__":
    if os.environ.get("ONCE") == "1":
        print(json.dumps(cached(), indent=2, ensure_ascii=False))
    else:
        print(f"http://localhost:{PORT}/api/market", flush=True)
        ThreadingHTTPServer(("", PORT), Handler).serve_forever()