#!/usr/bin/env bash
# docker/vacuum-site-localdb.sh
#
# One-off maintenance: convert an EXISTING site LocalDb file to auto_vacuum=INCREMENTAL.
#
# Why this exists (deferred-work register row 104, arch-review 2026-08-19 P4-6): SQLite only
# honours `PRAGMA auto_vacuum` on a table-less database, and until Low-wave T4 the pragma ran
# AFTER LocalDb had created its bookkeeping tables — so every site file created before that
# fix is permanently auto_vacuum=NONE, and the event-log cap trim's `PRAGMA incremental_vacuum`
# is a silent no-op on it: freed `site_events` pages are reused but the file never shrinks.
# Fresh files are created correctly now (`SiteLocalDbSetup.EnsureAutoVacuumOnFreshFile`);
# this script is the recipe for the files that already exist.
#
# Changing auto_vacuum on a populated file requires a full VACUUM (a rewrite of the file),
# which is why it is NOT done automatically at boot: on a ~1 GB file it holds an exclusive
# lock for minutes. It must run with BOTH nodes of the pair STOPPED:
#   - stopped together, per the topology guide's "stop and start BOTH nodes together" rule
#     (the pair is a replication unit; a rolling restart is unsupported);
#   - VACUUM is CDC-invisible (it fires no triggers and changes no row content), the LWW
#     ledger keys by declared primary key (`(table_name, pk_json)`), and the oplog `seq`
#     watermark is an INTEGER PRIMARY KEY AUTOINCREMENT — all preserved by VACUUM. So the
#     pair's replication state is untouched; it simply resumes when the nodes restart.
#
# Usage:
#   bash docker/vacuum-site-localdb.sh <site>            # site = a | b | c  (one pair)
#   bash docker/vacuum-site-localdb.sh --all             # every site pair, one at a time
#   DRY_RUN=1 bash docker/vacuum-site-localdb.sh a       # report the current pragma only
#
# Destructive? No data is deleted; but the pair is OFFLINE for the duration (seconds on the
# rig, minutes on a 1 GB production file). Each file is integrity-checked before AND after.

set -euo pipefail

SCRIPT_DIR="$(cd "$(dirname "${BASH_SOURCE[0]}")" && pwd)"
COMPOSE="docker compose -f ${SCRIPT_DIR}/docker-compose.yml"
VOLUME_PREFIX="scadabridge-site"          # volumes: scadabridge-site-<x>-node-<a|b>-data
DB_FILE="site-localdb.db"                 # LocalDb:Path on the rig = /app/data/site-localdb.db
SQLITE_IMAGE="alpine:3.20"                # throwaway container; sqlite3 installed at run time
DRY_RUN="${DRY_RUN:-0}"

usage() { sed -n '2,30p' "${BASH_SOURCE[0]}"; exit 1; }
[[ $# -eq 1 ]] || usage

if [[ "$1" == "--all" ]]; then
  SITES=(a b c)
else
  [[ "$1" =~ ^[abc]$ ]] || usage
  SITES=("$1")
fi

# Runs a sqlite3 script against the DB inside a node's data volume and prints stdout.
sql_on_volume() {
  local volume="$1" script="$2"
  docker run --rm -v "${volume}:/data" "$SQLITE_IMAGE" sh -ec \
    "apk add --no-cache --quiet sqlite >/dev/null 2>&1; cd /data; sqlite3 '${DB_FILE}' \"${script}\""
}

vacuum_site() {
  local site="$1"
  local nodes=("site-${site}-a" "site-${site}-b")   # compose SERVICE names (containers carry a scadabridge- prefix)
  local volumes=("${VOLUME_PREFIX}-${site}-node-a-data" "${VOLUME_PREFIX}-${site}-node-b-data")

  echo "=== site-${site}"
  for v in "${volumes[@]}"; do
    if ! docker volume inspect "$v" >/dev/null 2>&1; then
      echo "  volume ${v} does not exist — skipping site-${site}"; return 0
    fi
  done

  if [[ "$DRY_RUN" == "1" ]]; then
    for v in "${volumes[@]}"; do
      echo "  ${v}: auto_vacuum=$(sql_on_volume "$v" 'PRAGMA auto_vacuum;')  (0=NONE 1=FULL 2=INCREMENTAL)"
    done
    return 0
  fi

  echo "  stopping BOTH nodes together: ${nodes[*]}"
  $COMPOSE stop "${nodes[@]}" >/dev/null

  for v in "${volumes[@]}"; do
    echo "  ${v}:"
    local before size_before size_after ic
    before="$(sql_on_volume "$v" 'PRAGMA auto_vacuum;')"
    size_before="$(docker run --rm -v "${v}:/data" "$SQLITE_IMAGE" stat -c %s "/data/${DB_FILE}")"
    ic="$(sql_on_volume "$v" 'PRAGMA integrity_check;')"
    if [[ "$ic" != "ok" ]]; then
      echo "    integrity_check BEFORE vacuum is not ok — aborting without touching the file:"; echo "$ic"
      $COMPOSE start "${nodes[@]}" >/dev/null; exit 2
    fi
    if [[ "$before" == "2" ]]; then
      echo "    already auto_vacuum=INCREMENTAL (${size_before} bytes) — nothing to do"
      continue
    fi
    # The pragma is recorded in the header by the VACUUM that follows it (SQLite docs:
    # "auto-vacuuming can only be changed by a VACUUM after setting the pragma").
    sql_on_volume "$v" 'PRAGMA auto_vacuum = INCREMENTAL; VACUUM;' >/dev/null
    ic="$(sql_on_volume "$v" 'PRAGMA integrity_check;')"
    size_after="$(docker run --rm -v "${v}:/data" "$SQLITE_IMAGE" stat -c %s "/data/${DB_FILE}")"
    echo "    auto_vacuum ${before} -> $(sql_on_volume "$v" 'PRAGMA auto_vacuum;'); size ${size_before} -> ${size_after} bytes; integrity_check=${ic}"
    [[ "$ic" == "ok" ]] || { echo "    integrity_check AFTER vacuum failed — pair left STOPPED for inspection"; exit 3; }
  done

  echo "  starting BOTH nodes together"
  $COMPOSE start "${nodes[@]}" >/dev/null
}

for s in "${SITES[@]}"; do vacuum_site "$s"; done
echo "done."