#!/usr/bin/env python3
"""GODSIGH dev server: static files + same-origin proxy for feeds that block CORS."""
import sys
import urllib.error
import urllib.request
from http.server import SimpleHTTPRequestHandler, ThreadingHTTPServer

UPSTREAMS = {
    # OpenSky pins Access-Control-Allow-Origin to its own domain, so the browser
    # can't call it directly — we forward it here instead.
    "opensky": "https://opensky-network.org/api/states/all",
    # Celestrak sends ACAO:* today; proxied too so the app keeps working if that changes.
    "celestrak": "https://celestrak.org/NORAD/elements/gp.php",
}


class Handler(SimpleHTTPRequestHandler):
    def do_GET(self):
        if not self.path.startswith("/proxy/"):
            return super().do_GET()
        name, _, query = self.path[len("/proxy/"):].partition("?")
        base = UPSTREAMS.get(name)
        if not base:
            return self.send_error(404, f"unknown upstream {name!r}")
        url = base + ("?" + query if query else "")
        # Forward these upstream headers so the client can show quota state.
        passthrough = {}

        def grab(hdrs):
            for k in ("X-Rate-Limit-Remaining", "X-Rate-Limit-Limit", "X-Expires-After"):
                if hdrs.get(k) is not None:
                    passthrough[k] = hdrs.get(k)

        try:
            req = urllib.request.Request(url, headers={"User-Agent": "godsigh-dev/0.1"})
            with urllib.request.urlopen(req, timeout=45) as r:
                body = r.read()
                status, ctype = r.status, r.headers.get("Content-Type", "text/plain")
                grab(r.headers)
        except urllib.error.HTTPError as e:
            body = e.read() or str(e).encode()
            status, ctype = e.code, "text/plain"
            grab(e.headers)
        except Exception as e:
            body, status, ctype = str(e).encode(), 502, "text/plain"
        self.send_response(status)
        self.send_header("Content-Type", ctype)
        self.send_header("Access-Control-Allow-Origin", "*")
        self.send_header("Access-Control-Expose-Headers", "X-Rate-Limit-Remaining, X-Rate-Limit-Limit, X-Expires-After")
        self.send_header("Cache-Control", "no-store")
        for k, v in passthrough.items():
            self.send_header(k, v)
        self.send_header("Content-Length", str(len(body)))
        self.end_headers()
        self.wfile.write(body)

    def log_message(self, fmt, *args):
        sys.stderr.write("%s - %s\n" % (self.address_string(), fmt % args))


if __name__ == "__main__":
    port = int(sys.argv[1]) if len(sys.argv) > 1 else 8137
    print(f"GODSIGH serving on http://127.0.0.1:{port}")
    ThreadingHTTPServer(("127.0.0.1", port), Handler).serve_forever()