computer-playbook/utils/cache/render.py

"""Render what the package cache needs beside its role, from the declarations.

The role deploys the frontend and owns the templates and their tuning; the dev
compose stack has no inventory to render them with and comes through here
instead. Every value still has one home: the hosts and repositories come from
the ``cache:`` declarations, the nginx tuning from the role's ``vars/main.yml``,
and only the backend address differs, because the dev stack reaches Nexus over
a compose network alias while the role reaches it by its configured container.
"""

from __future__ import annotations

from typing import TYPE_CHECKING

from jinja2 import Environment, FileSystemLoader

from utils.cache.hosts import (
    host_records,
    hosts_serving,
    origin_of,
    repo_named,
    repo_records,
)
from utils.cache.yaml import load_yaml_any
from utils.distros import distro_names
from utils.roles.mapping import ROLE_FILE_META_VOLUMES, ROLE_FILE_VARS_MAIN

from . import PROJECT_ROOT

if TYPE_CHECKING:
    from pathlib import Path

ROLE = "svc-cache-package"
ROLE_DIR = PROJECT_ROOT / "roles" / ROLE
ROLE_VARS = ROLE_DIR / ROLE_FILE_VARS_MAIN
TEMPLATE_DIRS = (ROLE_DIR / "templates", PROJECT_ROOT / "compose" / "templates")
UPSTREAMS_TEMPLATE = "upstreams.conf.j2"
CONSUMER_TEMPLATE = "cache-consumer.yml.jinja"
CONSUMER = "compose.cache-consumer.yml"

PYPI_REPO = "pypi-proxy"
NPM_REPO = "npm-proxy"

BACKEND = "http://package-cache:8081"
TEMPLATED = "{{"


def _mount_target(volume: str, service: str) -> str:
    """Return where *volume* is mounted on *service*, from meta/volumes.yml.

    The role reads the same value through the ``volume`` lookup, which needs
    an inventory; the dev stack has none and reads the declaration directly,
    so the mount point still has one home.

    Args:
        volume: the key in meta/volumes.yml.
        service: the service whose mount to return.
    """
    declared = load_yaml_any(str(ROLE_DIR / ROLE_FILE_META_VOLUMES)) or {}
    mounts = (declared.get(volume) or {}).get("mounts") or []
    return next(
        (
            m["target"]
            for m in mounts
            if m.get("service") == service and m.get("target")
        ),
        "",
    )


def _tuning() -> dict[str, str]:
    """Return the role's plain nginx settings, keyed as the template names them.

    A value the role builds from its inventory is skipped: it has no meaning
    without one, and the dev stack supplies its own.
    """
    loaded = load_yaml_any(str(ROLE_VARS), default_if_missing={}) or {}
    return {
        key: value
        for key, value in loaded.items()
        if key.startswith("CACHE_PACKAGE_") and TEMPLATED not in str(value)
    }


def _render(template: str, **context) -> str:
    env = Environment(
        loader=FileSystemLoader([str(path) for path in TEMPLATE_DIRS]),
        trim_blocks=True,
        keep_trailing_newline=True,
        autoescape=False,  # noqa: S701 - nginx and compose config, not markup
    )
    return env.get_template(template).render(**context)


def upstreams_conf() -> str:
    """Return the nginx frontend configuration the declarations produce."""
    return _render(
        UPSTREAMS_TEMPLATE,
        CACHE_PACKAGE_UPSTREAMS=list(host_records().values()),
        CACHE_PACKAGE_REPOS=repo_records(),
        CACHE_PACKAGE_BACKEND=BACKEND,
        CACHE_PACKAGE_CERTS_DIR=_mount_target("frontend_certs", "frontend"),
        **_tuning(),
    )


def cache_consumer_yml() -> str:
    """Return the compose override that points every cached host at the frontend."""
    return _render(CONSUMER_TEMPLATE, CACHE_PACKAGE_HOSTNAMES=list(host_records()))


def pip_conf() -> str:
    """Return the pip configuration pointing at the cached PyPI hosts."""
    repo = repo_named(PYPI_REPO)
    hosts = hosts_serving(PYPI_REPO)
    origin = origin_of(repo) if repo else ""
    index = next((entry for entry in hosts if entry.host == origin), None)
    if index is None:
        raise SystemExit(
            f"no cache: host declares itself the origin of {PYPI_REPO}, so pip "
            "has no index URL to point at"
        )
    return _render(
        "pip.conf.jinja",
        CACHE_PACKAGE_PYPI_INDEX=f"{index.scheme()}://{index.host}/simple/",
        CACHE_PACKAGE_PYPI_HOSTS=[entry.host for entry in hosts],
    )


def npmrc() -> str:
    """Return the npm configuration pointing at the cached registry."""
    hosts = hosts_serving(NPM_REPO)
    if not hosts:
        raise SystemExit(f"no cache: host serves {NPM_REPO}, so npm has no registry")
    registry = hosts[0]
    return _render(
        "npmrc.jinja",
        CACHE_PACKAGE_NPM_REGISTRY=f"{registry.scheme()}://{registry.host}/",
    )


def apt_list(distro: str) -> str:
    """Return one distribution's apt source, empty where it does not use apt.

    Args:
        distro: the value INFINITO_DISTRO carries.
    """
    name = f"apt-{distro}"
    repo = repo_named(name)
    hosts = hosts_serving(name)
    source = ""
    if repo and hosts:
        entry = hosts[0]
        path = entry.path_of(name).rstrip("/")
        source = f"{entry.scheme()}://{entry.host}{path}"
    return _render(
        "apt.list.jinja",
        CACHE_PACKAGE_APT_SOURCE=source,
        CACHE_PACKAGE_APT_SUITE=repo.distribution if repo else "",
    )


def _write(target: Path, content: str) -> Path:
    target.parent.mkdir(parents=True, exist_ok=True)
    target.write_text(content, encoding="utf-8")
    return target


def render_artifacts(repo_root: Path, conf_path: Path) -> list[Path]:
    """Write every generated cache file and return what was written.

    A worktree configured to follow the primary checkout reads that
    checkout's map without writing it: rendering there would push this
    branch's declarations into another tree, which is the isolation the
    setting exists to provide.

    Args:
        repo_root: the checkout being generated for.
        conf_path: where INFINITO_CACHE_PACKAGE_FRONTEND_CONF points.
    """
    consumer_dir = repo_root / "compose" / "package-cache"
    written = [
        _write(repo_root / CONSUMER, cache_consumer_yml()),
        _write(consumer_dir / "pip.conf", pip_conf()),
        _write(consumer_dir / "npmrc", npmrc()),
    ]
    written += [
        _write(consumer_dir / "apt" / f"{distro}.list", apt_list(distro))
        for distro in distro_names()
    ]
    if conf_path.is_relative_to(repo_root):
        written.append(_write(conf_path, upstreams_conf()))
    return written