#!/usr/bin/env bash
# llm-gates.sh — the artifact gates every LLM endpoint runs before it starts.
#
# Why this file exists: the fleet law from the 2026-10-01 crash-loop is that
# a serve script and the deployer must refuse the SAME missing/truncated
# artifact, the SAME way. When the two gates were hand-written twins they
# drifted mid-cutover — green deploy, red unit, every time the payload moved.
# Both sides source this library, so the refusal is one text and one rule.
#
# Contract (public interface):
#   require_exec      PATH LABEL HINT
#   require_file      PATH LABEL HINT
#   require_bytes     PATH LABEL WANT_BYTES HINT
#   require_min_mib   PATH LABEL MIN_MIB HINT
#   require_dir_files DIR  LABEL HINT FILE...
#   require_image     REF  HINT
#
# Each returns 0 and prints nothing on success. On failure it prints two
# lines to stderr — the first naming the endpoint ($GATE_PREFIX) and the
# artifact, the second the remedy — and returns 1. It NEVER exits: the serve
# scripts run under `set -e` (so a refusal is terminal), while the deployer
# wants `|| return 1` so a failed gate reports a red deploy for that one
# service and the dispatcher's state marker stays pending.
# Lines are labelled by ARTIFACT CLASS, and the class is the whole label
# (the path rides in the same line): the class + path is what an operator
# acts on, so no wording order and no payload rename can make the two twins
# disagree. The deployer's old "halogen vision tower" and the serve script's
# "vision-tower" were one gate in two vocabularies that no grep could join.

# The size law is equality, not a floor, for `require_bytes`: a hub fetch
# that truncates is the fleet's standing hazard (curl exits 0 on 401/403 and
# writes the error body as the artifact), and the declared byte count is a
# contract in both directions — a bigger file is a DIFFERENT artifact.

# GATE_PREFIX names the endpoint in every refusal (e.g. frank-dragoon). The
# caller exports it; shellcheck cannot follow it across the source boundary,
# so the read site carries the directive.
# shellcheck disable=SC2034
: "${GATE_PREFIX:=gate}"

# Two bash laws make the `return 1` at every call site load-bearing:
#   * a function whose body ends inside an `if` returns the CONDITION's
#     status (true = 0), so a gate that ends on its own refusal prints the
#     refusal and reports SUCCESS;
#   * `set -e` is suspended for any command in a `… || …` chain, so a gate
#     that runs inside one must not be trusted to abort the caller.
# Every gate's refusal therefore carries an explicit `|| return 1`, and the
# caller consumes the status (`|| exit 1`, `|| return 1`).
_gate_fail() {
    printf '%s: %s\n' "$GATE_PREFIX" "$1" >&2
    printf '  hint: %s\n' "$2" >&2
    return 1
}

# require_file — PATH must be a regular file. A directory (an unpacked
# staging dir wearing the payload's name) and a symlink (a HuggingFace cache
# snapshot's entry, which dangles inside the container mount) both refuse.
require_file() {
    local path="$1" label="$2" hint="$3"
    if [[ -L "$path" || ! -f "$path" ]]; then
        _gate_fail "$label: missing at $path" "$hint" || return 1
    fi
    return 0
}

# require_exec — PATH must be an executable regular file. The native runtimes
# (llama.cpp's llama-server) are binaries the operator builds; a tree that
# compiled but lost its +x, or a directory wearing the binary's name, must
# refuse the same way a missing one does.
require_exec() {
    local path="$1" label="$2" hint="$3"
    if [[ -L "$path" || ! -x "$path" ]]; then
        _gate_fail "$label: missing at $path" "$hint" || return 1
    fi
    return 0
}

# require_bytes — PATH must exist AND be exactly WANT_BYTES bytes.
require_bytes() {
    local path="$1" label="$2" want="$3" hint="$4" got
    require_file "$path" "$label" "$hint" || return 1
    got="$(stat -c %s "$path")"
    if [[ "$got" != "$want" ]]; then
        _gate_fail "$label: is $got bytes, expected $want" "$hint" || return 1
    fi
    return 0
}

# require_min_mib — PATH must be at least MIN_MIB mebibytes. The floor form
# is for build products (a .rad container is a range of legal sizes; a
# truncated convert is not).
require_min_mib() {
    local path="$1" label="$2" min="$3" hint="$4" mib
    require_file "$path" "$label" "$hint" || return 1
    mib=$(( $(stat -c %s "$path") / 1048576 ))
    if (( mib < min )); then
        _gate_fail "$label: is $mib MiB, expected >= $min MiB" "$hint" || return 1
    fi
    return 0
}

# require_dir_files — DIR must be a directory and every named member a
# regular file (the flat-tokenizer law: snapshot symlinks dangle in the
# container mount even when the directory itself is real. A symlinked
# DIRECTORY is refused too: a HF cache snapshot can link the directory
# itself, and a link dangles inside the container mount.
require_dir_files() {
    local dir="$1" label="$2" hint="$3"
    shift 3
    local f
    if [[ -L "$dir" || ! -d "$dir" ]]; then
        _gate_fail "$label: missing at $dir" "$hint" || return 1
    fi
    for f in "$@"; do
        if [[ -L "$dir/$f" || ! -f "$dir/$f" ]]; then
            _gate_fail "$label: $dir/$f is missing or a symlink" "$hint" || return 1
        fi
    done
    return 0
}

# require_image — the image ref must be in podman storage. A name@sha256 ref
# exists only if THAT manifest was pulled, so the gate is the ref itself, in
# one command: no pipefail/grep race (the 2026-09-30 lesson).
require_image() {
    local ref="$1" hint="$2"
    if ! podman image exists "$ref"; then
        _gate_fail "image: $ref is not in podman storage" "$hint" || return 1
    fi
    return 0
}