#!/bin/sh
# script/cibuild: run the CI build. The Dockerfile does not run
# script/check; it runs `make fmt-check` and `make lint` in its lint
# stage and `make test` in its builder stage. A successful build
# implies those three passed, provided they actually ran -- which is
# what the CHECK_EPOCH below is for.
# Generic: needs no adaptation. The Gitea workflow runs this on push.
set -eu

ROOT="$(cd "$(dirname "$0")/.." && pwd -P)"

main() {
    cd "$ROOT"
    # The Dockerfile's check layers are keyed on CHECK_EPOCH, so a
    # fresh value here is what forces them to re-run: without it an
    # unchanged tree replays them from cache, the checks never execute,
    # and the build still exits 0. The ARG sits immediately above the
    # check RUNs, so dependency and module layers still cache. The
    # Dockerfile also refuses to build at all when CHECK_EPOCH is empty,
    # so a missing value fails loudly here rather than passing quietly.
    #
    # The value must be unique per invocation, not per second. `date +%s`
    # is second-granular, so two concurrent invocations in the same
    # second get identical epochs and the later one can be served from
    # cache -- the original defect in miniature. `%N` alone does not fix
    # it: busybox silently drops %N, exits 0, and hands back second
    # granularity with no warning. `$$` is what makes this correct
    # regardless, since concurrent invocations have different pids.
    #
    # Assign the epoch on its own line rather than inline in the
    # argument. Under `set -eu` a command substitution that fails
    # inside an argument does NOT abort the script: CHECK_EPOCH would
    # become an empty string, an empty string is a constant, and a
    # constant CHECK_EPOCH is exactly the cached-check false green this
    # script exists to prevent -- so the guard would disarm itself and
    # still exit 0. As a bare assignment, `set -e` catches a failing
    # `date` and no build starts.
    epoch="$(date +%s%N)$$"
    docker build --build-arg CHECK_EPOCH="$epoch" .
}

main "$@"