#!/usr/bin/env python3
"""Render ${VAR} placeholders in the live SearXNG settings.yml from the
host-side env file.

Why this exists: SearXNG does NOT expand environment variables inside
settings.yml. The repo-tracked shared/searxng/settings.yml deliberately keeps
secrets as "${KAGI_API_KEY}"-style placeholders so no key ever enters git; the
deployer copies that file to /opt/searxng/config/settings.yml and runs this
script to bake in the real values. Without it the app runs with the literal
placeholder strings (observed 2026-09-26: secret_key literally
"${SEARXNG_SECRET}" and the Kagi engine failing setup() on an empty key).

Only the allowlisted names are substituted. A placeholder that has no value in
the env file is a deploy-blocking error: serving a paid-API engine with a
literal "${KAGI_API_KEY}" bearer would waste requests and hide the misconfig.

Usage: searxng-render-settings.py ENV_FILE SETTINGS_FILE
Both paths are taken as arguments; secrets never appear in any argv.
Exit codes: 0 rendered (idempotent on an already-rendered file), 1 unresolved
placeholder, 2 usage error.
"""

import sys

ALLOWED = ("KAGI_API_KEY", "SEARXNG_SECRET", "SEARXNG_BASE_URL")


def load_env(path: str) -> dict[str, str]:
    values: dict[str, str] = {}
    with open(path, encoding="utf-8") as fh:
        for line in fh:
            line = line.strip()
            if not line or line.startswith("#") or "=" not in line:
                continue
            key, _, value = line.partition("=")
            if key in ALLOWED:
                values[key] = value
    return values


def main(argv: list[str]) -> int:
    args = [a for a in argv[1:]]
    if len(args) != 2:
        print(
            "usage: searxng-render-settings.py ENV_FILE SETTINGS_FILE",
            file=sys.stderr,
        )
        return 2
    env_file, settings_file = args

    values = load_env(env_file)
    with open(settings_file, encoding="utf-8") as fh:
        text = fh.read()

    for name in ALLOWED:
        if name in values:
            text = text.replace("${%s}" % name, values[name])

    unresolved = [n for n in ALLOWED if "${%s}" % n in text]
    if unresolved:
        print(
            "unresolved placeholders in %s: %s (missing from %s)"
            % (settings_file, ", ".join(unresolved), env_file),
            file=sys.stderr,
        )
        return 1

    with open(settings_file, "w", encoding="utf-8") as fh:
        fh.write(text)
    return 0


if __name__ == "__main__":
    sys.exit(main(sys.argv))