#!/usr/bin/env python3
import json
import os
import time
import urllib.error
import urllib.request
from http.server import BaseHTTPRequestHandler, HTTPServer

RPC_URL = os.environ.get("BLOCKCHAIN_METRICS_RPC_URL", "http://anvil:8545")
LISTEN_ADDR = os.environ.get("BLOCKCHAIN_METRICS_ADDR", "0.0.0.0")
LISTEN_PORT = int(os.environ.get("BLOCKCHAIN_METRICS_PORT", "9109"))


def rpc(method):
    started = time.monotonic()
    body = json.dumps(
        {"jsonrpc": "2.0", "method": method, "params": [], "id": 1}
    ).encode("utf-8")
    request = urllib.request.Request(
        RPC_URL,
        data=body,
        headers={"content-type": "application/json"},
        method="POST",
    )
    with urllib.request.urlopen(request, timeout=3) as response:
        payload = json.loads(response.read().decode("utf-8"))
    if "error" in payload:
        raise RuntimeError(payload["error"])
    return payload.get("result"), time.monotonic() - started


def hex_to_int(value):
    if isinstance(value, str) and value.startswith("0x"):
        return int(value, 16)
    return int(value)


def collect_metrics():
    metrics = []
    latencies = {}
    values = {}
    up = 1

    for method in ["eth_chainId", "eth_blockNumber", "net_peerCount", "eth_gasPrice"]:
        try:
            result, latency = rpc(method)
            latencies[method] = latency
            values[method] = hex_to_int(result)
        except (OSError, RuntimeError, urllib.error.URLError, ValueError):
            up = 0
            latencies[method] = 0

    metrics.append("# HELP homelab_blockchain_rpc_up Blockchain RPC health.")
    metrics.append("# TYPE homelab_blockchain_rpc_up gauge")
    metrics.append(f"homelab_blockchain_rpc_up {up}")

    gauge_map = {
        "eth_chainId": "homelab_blockchain_chain_id",
        "eth_blockNumber": "homelab_blockchain_latest_block",
        "net_peerCount": "homelab_blockchain_peer_count",
        "eth_gasPrice": "homelab_blockchain_gas_price_wei",
    }
    for method, metric_name in gauge_map.items():
        if method in values:
            metrics.append(f"# TYPE {metric_name} gauge")
            metrics.append(f"{metric_name} {values[method]}")

    metrics.append("# TYPE homelab_blockchain_rpc_latency_seconds gauge")
    for method, latency in latencies.items():
        metrics.append(
            f'homelab_blockchain_rpc_latency_seconds{{method="{method}"}} {latency:.6f}'
        )

    return "\n".join(metrics) + "\n"


class MetricsHandler(BaseHTTPRequestHandler):
    def do_GET(self):
        if self.path not in ["/metrics", "/"]:
            self.send_response(404)
            self.end_headers()
            return

        body = collect_metrics().encode("utf-8")
        self.send_response(200)
        self.send_header("content-type", "text/plain; version=0.0.4")
        self.send_header("content-length", str(len(body)))
        self.end_headers()
        self.wfile.write(body)

    def log_message(self, fmt, *args):
        return


if __name__ == "__main__":
    server = HTTPServer((LISTEN_ADDR, LISTEN_PORT), MetricsHandler)
    server.serve_forever()