#!/bin/sh
# Praxis v0.4 — Nightly Postgres backup (D-055, G-008).
#
# Host-side cron script (decoupled from praxis service uptime —
# RESEARCH-v0.4 §1.5). Runs pg_dump inside the postgres container and
# writes a compressed custom-format dump to the pgbackups volume.
#
# The %u date format = day-of-week 1..7 (Monday=1, Sunday=7) → rolling
# 7-file retention with zero cleanup logic (D-055). Re-running overwrites
# the same day-of-week file.
#
# Cron entry (host, 03:30 CT nightly):
#   30 3 * * * /opt/praxis/scripts/backup-pg.sh
#
# Restore drill (G-008 — run at least once in staging to prove the backup
# is valid; NEVER restore into a live DB without stopping praxis first):
#   docker compose stop praxis
#   docker compose exec postgres pg_restore -U praxis -d praxis \
#     --clean --if-exists /backups/praxis-3.dump
#   # verify: \d operators; SELECT count(*) FROM operators; (etc. for all 5 tables)
#   docker compose start praxis
#
# POSIX-sh compatible (no bashisms). Exit 0 on success, 1 on failure.
# Args: none. Env: COMPOSE_PROJECT_DIR (default: current dir).

set -eu

PROJECT_DIR="${COMPOSE_PROJECT_DIR:-$(pwd)}"
cd "$PROJECT_DIR"

DOW="$(date +%u)"
DUMP_FILE="/backups/praxis-${DOW}.dump"

echo "backup-pg: dumping praxis DB → ${DUMP_FILE} (day-of-week ${DOW})"

# -Fc = custom compressed format (works with pg_restore --clean --if-exists).
# -T stops the container from streaming while dumping? No — pg_dump is
# consistent within a transaction; the praxis service can stay up.
docker compose exec -T postgres pg_dump -U praxis -Fc praxis -f "$DUMP_FILE"

# Verify the dump is non-empty (sanity — a 0-byte dump means failure).
SIZE=$(docker compose exec -T postgres stat -c '%s' "$DUMP_FILE" 2>/dev/null || echo 0)
if [ "$SIZE" -le 0 ]; then
    echo "backup-pg: ERROR — dump file is empty (${DUMP_FILE})" >&2
    exit 1
fi

echo "backup-pg: OK — ${DUMP_FILE} is ${SIZE} bytes"
echo "backup-pg: restore drill (G-008): docker compose exec postgres pg_restore -U praxis -d praxis --clean --if-exists ${DUMP_FILE}"
exit 0