"""Build a minimal, offline, hand-rolled crate and its sparse registry index
entry, for integration-testing the `rust` module of id-configurator.

No network access and no build backend (cargo) is used: the crate is a
plain gzipped tar assembled with the standard library only, so this script
can run in a minimal Python image with nothing installed.

See https://doc.rust-lang.org/cargo/reference/registries.html#index-format
for the sparse registry index/config.json format this reproduces.
"""

from __future__ import annotations

import hashlib
import io
import json
import pathlib
import tarfile

CRATE = "idconfiguratortestpkg"
VERSION = "0.0.1"
CRATE_FILE = f"{CRATE}-{VERSION}.crate"
OUT_DIR = pathlib.Path("/srv")

CARGO_TOML = f"""[package]
name = "{CRATE}"
version = "{VERSION}"
edition = "2021"
"""
LIB_RS = "// test-only crate served by the id-configurator integration tests\n"


def _add_file(archive: tarfile.TarFile, name: str, content: bytes) -> None:
    info = tarfile.TarInfo(name=f"{CRATE}-{VERSION}/{name}")
    info.size = len(content)
    archive.addfile(info, io.BytesIO(content))


def build_crate() -> bytes:
    buffer = io.BytesIO()
    with tarfile.open(fileobj=buffer, mode="w:gz") as archive:
        _add_file(archive, "Cargo.toml", CARGO_TOML.encode("utf-8"))
        _add_file(archive, "src/lib.rs", LIB_RS.encode("utf-8"))
    return buffer.getvalue()


def index_path(name: str) -> pathlib.Path:
    """Mirror cargo's sparse index path convention for a crate name."""
    if len(name) <= 2:
        return pathlib.Path(str(len(name))) / name
    if len(name) == 3:
        return pathlib.Path("3") / name[0] / name
    return pathlib.Path(name[0:2]) / name[2:4] / name


def write_index(out_dir: pathlib.Path, crate: bytes) -> None:
    entry = {
        "name": CRATE,
        "vers": VERSION,
        "deps": [],
        "cksum": hashlib.sha256(crate).hexdigest(),
        "features": {},
        "yanked": False,
    }
    path = out_dir / index_path(CRATE)
    path.parent.mkdir(parents=True, exist_ok=True)
    path.write_text(json.dumps(entry) + "\n", encoding="utf-8")


def write_config_json(out_dir: pathlib.Path) -> None:
    # Cargo requires a fully-qualified "dl" download template, so this bakes
    # in a placeholder that nginx's sub_filter rewrites to the real
    # https://<host used by the client>/ at request time (see
    # cargo-repo.nginx.conf) - the host and port this fixture is actually
    # reached on aren't known at image-build time.
    config = {
        "dl": "__BASE_URL__/api/v1/crates/{crate}/{version}/download",
        "api": "__BASE_URL__",
    }
    (out_dir / "config.json").write_text(json.dumps(config), encoding="utf-8")


def main() -> None:
    OUT_DIR.mkdir(parents=True, exist_ok=True)
    crate = build_crate()
    download_path = OUT_DIR / "api/v1/crates" / CRATE / VERSION / "download"
    download_path.parent.mkdir(parents=True, exist_ok=True)
    download_path.write_bytes(crate)
    write_index(OUT_DIR, crate)
    write_config_json(OUT_DIR)


if __name__ == "__main__":
    main()