import subprocess
import re
import time
import itertools
from db import init_ping_db, insert_ping_result
from config import PING_INTERVAL

# Curated pool of well-known, stable IPs across DNS resolvers, CDNs, and captive-portal check targets.
# Cycling 3 at a time means each IP is hit at most once every ~(len(pool)/3 * PING_INTERVAL) seconds.
IP_POOL = [
    # DNS resolvers
    "1.1.1.1",          # Cloudflare
    "1.0.0.1",          # Cloudflare
    "8.8.8.8",          # Google
    "8.8.4.4",          # Google
    "9.9.9.9",          # Quad9
    "149.112.112.112",  # Quad9
    "208.67.222.222",   # OpenDNS
    "208.67.220.220",   # OpenDNS
    "64.6.64.6",        # Verisign
    "84.200.69.80",     # DNS.WATCH
]

TARGETS_PER_ITERATION = 3

_LATENCY_RE = re.compile(r"time[=<](\d+(?:\.\d+)?)\s*ms")


def detect_gateway() -> str | None:
    try:
        with open("/proc/net/route") as f:
            for line in f.readlines()[1:]:  # skip header row
                fields = line.strip().split()
                # Destination == "00000000" means 0.0.0.0 — the default/catch-all route
                if fields[1] == "00000000":
                    addr = int(fields[2], 16)  # little-endian hex
                    return ".".join(str((addr >> (8 * i)) & 0xFF) for i in range(4))
    except Exception as e:
        print(f"WARNING: gateway detection failed: {e}", flush=True)
    return None


def ping_once(ip: str) -> tuple[bool, float | None]:
    result = subprocess.run(
        ["ping", "-c", "1", "-W", "2", ip],
        capture_output=True, text=True
    )
    if result.returncode != 0:
        return False, None
    m = _LATENCY_RE.search(result.stdout)
    latency = float(m.group(1)) if m else None
    return True, latency


def run():
    init_ping_db()
    gateway_ip = detect_gateway()
    if gateway_ip:
        print(f"Gateway detected: {gateway_ip}", flush=True)
    else:
        print("WARNING: No gateway detected, skipping gateway checks", flush=True)

    pool = itertools.cycle(IP_POOL)

    while True:
        if gateway_ip:
            success, latency_ms = ping_once(gateway_ip)
            insert_ping_result(gateway_ip, success, latency_ms, is_gateway=True)
            status = f"{latency_ms:.1f}ms" if latency_ms is not None else "FAIL"
            print(f"[GW] {gateway_ip}: {status}", flush=True)

        targets = [next(pool) for _ in range(TARGETS_PER_ITERATION)]
        for ip in targets:
            success, latency_ms = ping_once(ip)
            insert_ping_result(ip, success, latency_ms)
            status = f"{latency_ms:.1f}ms" if latency_ms is not None else "FAIL"
            print(f"{ip}: {status}", flush=True)
        time.sleep(PING_INTERVAL)


if __name__ == "__main__":
    run()