"""Readiness checks backing the pre-run validation checklist.

Each function returns a plain dict so the same result can be logged as Dagster
metadata (evidence for the checklist) or asserted in a test.
"""

from __future__ import annotations

import os
import socket
from urllib.parse import urlparse

# Runtime dependencies a tightly coupled execution pod must be able to resolve.
TIGHTLY_COUPLED_ENV_VARS = (
    "DAGSTER_POSTGRES_HOST",
    "DAGSTER_POSTGRES_USER",
    "DAGSTER_POSTGRES_DB",
)


def check_env_vars(names: tuple[str, ...] | list[str]) -> dict:
    """Report which of ``names`` are present, without echoing their values."""
    present = [name for name in names if os.environ.get(name)]
    missing = [name for name in names if not os.environ.get(name)]
    return {
        "check": "env_vars",
        "passed": not missing,
        "present": present,
        "missing": missing,
    }


def check_tcp_reachable(host: str, port: int, timeout: float = 3.0) -> dict:
    """Open a TCP connection to prove the execution pod can reach a dependency."""
    result = {"check": "tcp_reachable", "target": f"{host}:{port}", "passed": False, "error": None}
    try:
        with socket.create_connection((host, port), timeout=timeout):
            result["passed"] = True
    except OSError as exc:
        result["error"] = str(exc)
    return result


def check_endpoint_reachable(url: str, timeout: float = 3.0) -> dict:
    """TCP-level reachability for an endpoint expressed as a URL."""
    parsed = urlparse(url)
    if not parsed.hostname:
        return {"check": "tcp_reachable", "target": url, "passed": False, "error": "no hostname in URL"}
    port = parsed.port or (443 if parsed.scheme == "https" else 80)
    return check_tcp_reachable(parsed.hostname, port, timeout=timeout)


def describe_pod_identity() -> dict:
    """Where this process is actually running - the primary execution-target evidence."""
    hostname = socket.gethostname()
    return {
        "hostname": hostname,
        "pid": os.getpid(),
        # Distinguishes processes on one host, so multiprocess fan-out is visible locally.
        "worker": f"{hostname}#{os.getpid()}",
        "namespace": os.environ.get("DAGSTER_K8S_PIPELINE_RUN_NAMESPACE", "<not-in-kubernetes>"),
        "run_id": os.environ.get("DAGSTER_RUN_ID", "<unset>"),
        "image": os.environ.get("DAGSTER_K8S_PIPELINE_RUN_IMAGE", "<unset>"),
    }