#!/usr/bin/env python3
"""Render the nginx vhost (asset/nginx/site.conf.tmpl) from the environment.

Both .gitea/workflows/deploy.yml (deploy-web) and refresh.yml call this, so the
two pipelines can never disagree about what they substitute. They did once: the
WEB_LISTEN placeholder was added to the template and to deploy.yml but not to
refresh.yml, so the nightly refresh shipped a literal `listen {{WEB_LISTEN}};`
to oolon. `nginx -t` then failed for the whole edge, and because the file is
rsynced straight into the live conf.d before it is tested, every vhost's reload
-- including the step@ cert renewals -- stayed frozen for days while renewed
certs piled up unserved on disk.

Guard rails, so that can't recur:
  * every {{PLACEHOLDER}} in the template must have a matching environment
    variable, or the render fails before anything leaves the runner;
  * no {{...}} may survive substitution.
A forgotten or misnamed variable is now a red build, not a broken edge.

usage: render-site-conf.py [OUTPUT]   (default: rendered/site.conf)
"""
import os
import re
import sys

TEMPLATE = "asset/nginx/site.conf.tmpl"
PLACEHOLDER = re.compile(r"\{\{(\w+)\}\}")


def main() -> int:
    out = sys.argv[1] if len(sys.argv) > 1 else "rendered/site.conf"
    with open(TEMPLATE, encoding="utf-8") as fh:
        text = fh.read()

    names = sorted(set(PLACEHOLDER.findall(text)))
    missing = [n for n in names if n not in os.environ]
    if missing:
        sys.stderr.write(
            "render-site-conf: no environment value for placeholder(s): "
            + ", ".join(missing) + "\n")
        return 1

    for name in names:
        text = text.replace("{{%s}}" % name, os.environ[name])

    leftover = sorted(set(PLACEHOLDER.findall(text)))
    if leftover:
        sys.stderr.write(
            "render-site-conf: unrendered placeholder(s) after substitution: "
            + ", ".join(leftover) + "\n")
        return 1

    os.makedirs(os.path.dirname(out) or ".", exist_ok=True)
    with open(out, "w", encoding="utf-8") as fh:
        fh.write(text)
    sys.stderr.write(
        "render-site-conf: wrote %s (%d substitutions: %s)\n"
        % (out, len(names), ", ".join(names)))
    return 0


if __name__ == "__main__":
    raise SystemExit(main())