#!/bin/bash
# brief-nightly.sh - render the cross-repo briefing to a file, atomically.
#
# This is the ONLY writer in the briefing path, and it exists so that board.sh
# does not become one. board.sh is read-only by construction - it writes to no
# repo, no STATE.md and no mailbox - and a `--brief --out FILE` flag would have
# ended that for the sake of one redirect.
#
# Why not just `board.sh --brief > file` from launchd:
#
#   1. A plain redirect TRUNCATES the target before the renderer has produced
#      a byte. An unattended job that fails, or is read mid-run, then leaves
#      the operator an empty or half-written briefing - and the briefing is
#      read exactly when nobody is watching it being made. Rendering to a temp
#      file in the same directory and rename()-ing it into place means a reader
#      sees either the old briefing or the new one, never a partial one.
#   2. An EMPTY render is treated as a FAILED render and never replaces a good
#      briefing. Board prints nothing at all when its scan roots do not exist,
#      which is exactly what a mistyped path or a moved home directory looks
#      like - silent truncation to zero would destroy yesterday's briefing on
#      a bad launchd environment. A repo tree where nobody owes anything is a
#      different case entirely: that renders a valid, non-empty briefing saying
#      so, and is written normally.
#
# Zero model calls, by construction: it runs two shell scripts. That is the
# whole point - a nightly job on subscription auth draws from the same quota
# pool as interactive work, and every turn it would spend is a turn the
# operator does not get. Measured floor for one headless turn on
# claude-opus-5[1m]: ~0.25 USD-equivalent, which --max-budget-usd cannot
# prevent (it aborts AFTER turn one, never before it).
#
# ASCII only, bash 3.2 safe.
set -u

SELFDIR="$(cd "$(dirname "$0")" && pwd)"
BOARD="$SELFDIR/board.sh"
OUT="${CLAUDE_BRIEF_FILE:-$HOME/.claude/briefing.md}"

case "${1:-}" in
  -h|--help) grep '^#' "$0" | sed 's/^# \{0,1\}//'; exit 0 ;;
esac

OUTDIR="$(dirname "$OUT")"
mkdir -p "$OUTDIR" 2>/dev/null || {
  echo "brief-nightly: cannot create $OUTDIR" >&2; exit 1; }

# Same directory as the target: rename() is only atomic within one filesystem.
TMP="$OUT.tmp.$$"
trap '/bin/rm -f "$TMP" 2>/dev/null' EXIT

bash "$BOARD" --brief "$@" > "$TMP" 2>/dev/null
rc=$?

if [ "$rc" -ne 0 ]; then
  echo "brief-nightly: board.sh --brief exited $rc, keeping previous briefing" >&2
  exit 1
fi

if [ ! -s "$TMP" ]; then
  echo "brief-nightly: empty render, keeping previous briefing" >&2
  exit 1
fi

mv -f "$TMP" "$OUT" || {
  echo "brief-nightly: could not install $OUT" >&2; exit 1; }

exit 0