"""Env validation policy: fail-fast per mandatory, soft per optional.

Usage al boot di ogni mcp `__main__.py`:

    from mcp_common.env_validation import require_env, optional_env, summarize

    creds_file = require_env("CREDENTIALS_FILE", "deribit credentials JSON path")
    host = optional_env("HOST", default="0.0.0.0")
    summarize(["CREDENTIALS_FILE", "HOST", "PORT"])
"""

from __future__ import annotations

import logging
import os
import sys

logger = logging.getLogger(__name__)


class MissingEnvError(RuntimeError):
    """Mandatory env var absent or empty."""


def require_env(name: str, description: str = "") -> str:
    val = (os.environ.get(name) or "").strip()
    if not val:
        msg = f"missing mandatory env var: {name}"
        if description:
            msg += f" ({description})"
        logger.error(msg)
        raise MissingEnvError(msg)
    return val


def optional_env(name: str, *, default: str = "") -> str:
    val = (os.environ.get(name) or "").strip()
    if not val:
        if default:
            logger.info("env %s not set, using default=%r", name, default)
        return default
    return val


def summarize(names: list[str]) -> None:
    sensitive_tokens = ("SECRET", "KEY", "TOKEN", "PASSWORD", "CREDENTIAL", "WALLET")
    for n in names:
        val = os.environ.get(n)
        if val is None:
            logger.info("env[%s]: <unset>", n)
            continue
        if any(t in n.upper() for t in sensitive_tokens):
            logger.info("env[%s]: <set, %d chars>", n, len(val))
        else:
            logger.info("env[%s]: %s", n, val)


def fail_fast_if_missing(names: list[str]) -> None:
    missing: list[str] = []
    for n in names:
        if not (os.environ.get(n) or "").strip():
            missing.append(n)
    if missing:
        logger.error("boot aborted: missing mandatory env vars: %s", missing)
        print(
            f"FATAL: missing mandatory env vars: {missing}",
            file=sys.stderr,
        )
        sys.exit(2)