# urus-bench shell.nix
#
# Assumes you already have a working rust toolchain (cargo, rustc) and
# elixir/erlang in your environment. This shell adds:
#
#   - the load generators (wrk, wrk2)
#   - process introspection (pidstat, taskset)
#   - small conveniences (jq, sqlite CLI for poking at the WAL'd DBs)
#   - C toolchain bits so `rusqlite` (bundled SQLite) and `sqlx` compile
#
# Drop into the workspace root and run `nix-shell`. Then:
#   cargo build --release
#   ./runner.sh urus-mem s1
#
# For cowboy-server you'll use your existing rebar3/elixir setup; this
# shell deliberately doesn't pin a beam toolchain since you have one.

{ pkgs ? import <nixpkgs> {} }:

pkgs.mkShell {
  name = "urus-bench";

  # buildInputs vs nativeBuildInputs: for a developer shell the
  # distinction barely matters; either works. Keeping everything in
  # `packages` since that's the recommended modern form.
  packages = with pkgs; [
    # Load generators (the whole point of this shell).
    wrk     # closed-loop, used as the saturation probe
    wrk2    # constant-rate, latency-honest measurement

    # Runner deps.
    sysstat        # provides pidstat for CPU sampling
    util-linux     # provides taskset for CPU pinning
    jq             # pretty-prints result.json (runner falls back without it)
    curl           # the prepopulate step uses curl --config (-K)
    gawk           # explicit; busybox awk lacks some printf bits we use

    # SQLite tooling — handy for inspecting WAL'd DBs between runs.
    # rusqlite/sqlx bring their own embedded sqlite so this is *not* a
    # build dep, just a CLI for poking around.
    sqlite

    # C toolchain — rusqlite's `bundled` feature compiles sqlite from
    # source, and sqlx's macros also need a working cc. Without these
    # the rust build fails on a fresh nix shell.
    pkg-config
    gcc
  ];

  # Environment hints. Nothing strictly required, but these defaults
  # match what runner.sh already expects when invoked without env
  # overrides, so a fresh shell `just works` for `./runner.sh ...`.
  BEARER = "test-token-aaaaaaaaaaaaaaaaaaaa";

  shellHook = ''
    echo "urus-bench shell:"
    echo "  wrk       $(wrk --version 2>&1 | head -1 || echo missing)"
    echo "  wrk2      $(wrk2 --version 2>&1 | head -1 || echo missing)"
    echo "  pidstat   $(command -v pidstat || echo missing)"
    echo "  taskset   $(command -v taskset || echo missing)"
    echo "  cargo     $(command -v cargo   || echo 'NOT FOUND — expected on host')"
    echo
    echo "Build:  cargo build --release"
    echo "Run:    ./runner.sh urus-mem s1"
  '';
}