"""Discover instances, save one address, and compare cached/fresh requests."""
import argparse
import json
from pathlib import Path
import sys
import time
from urllib.request import urlopen

BASE = "http://consul:8500"
CACHE = Path("/work/consul-address.json")


def get(url):
    with urlopen(url, timeout=2) as response:
        return json.load(response)


def discover():
    rows = get(BASE + "/v1/health/service/orders?passing=true")
    return sorted([{"id": r["Service"]["ID"], "address": r["Service"]["Address"],
                    "port": r["Service"]["Port"]} for r in rows], key=lambda r: r["id"])


def main():
    parser = argparse.ArgumentParser(description=__doc__)
    parser.add_argument("action", choices=["list", "save", "cached", "fresh", "wait"])
    parser.add_argument("--ids", default="app-a,app-b", help="Expected passing IDs for wait")
    args = parser.parse_args()
    if args.action == "wait":
        expected = sorted(args.ids.split(","))
        deadline = time.monotonic() + 30
        while time.monotonic() < deadline:
            try:
                rows = discover()
                if [r["id"] for r in rows] == expected:
                    print(json.dumps(rows, indent=2))
                    return
            except OSError:
                pass
            time.sleep(0.5)
        raise RuntimeError("Passing instances did not reach " + str(expected))
    if args.action == "list":
        print(json.dumps(discover(), indent=2))
        return
    if args.action == "cached":
        endpoint = json.loads(CACHE.read_text())
    else:
        rows = discover()
        if not rows:
            raise RuntimeError("No passing instances")
        endpoint = rows[0]
    if args.action == "save":
        CACHE.parent.mkdir(parents=True, exist_ok=True)
        CACHE.write_text(json.dumps(endpoint), encoding="utf-8")
        print("SAVED", endpoint)
        return
    url = f"http://{endpoint['address']}:{endpoint['port']}/"
    print(("CACHED" if args.action == "cached" else "FRESH"), endpoint["id"], url, flush=True)
    print(json.dumps(get(url), indent=2))


if __name__ == "__main__":
    try:
        main()
    except (OSError, ValueError, RuntimeError) as error:
        print("REQUEST FAILED:", error, file=sys.stderr)
        sys.exit(1)