#!/usr/bin/env bash
# Online SQLite backup using the .backup API.
# Safe to run while the bot is live — SQLite's backup API acquires only a short
# shared lock per page, never blocking the application for the full duration.
#
# Usage:
#   backup.sh --config /etc/mnemosyne/mnemosyne.conf [--keep-days N]
#
# Environment overrides:
#   MNEMOSYNE_BACKUP_DIR  — destination directory (default: /var/backups/mnemosyne)
#   MNEMOSYNE_DB_PATH     — database path (overrides config)

set -euo pipefail

# ── Defaults ─────────────────────────────────────────────────────────────────
CONFIG_FILE=""
KEEP_DAYS=30
BACKUP_DIR="${MNEMOSYNE_BACKUP_DIR:-/var/backups/mnemosyne}"

# ── Argument parsing ─────────────────────────────────────────────────────────
while [[ $# -gt 0 ]]; do
    case "$1" in
        --config)    CONFIG_FILE="$2"; shift 2 ;;
        --keep-days) KEEP_DAYS="$2";   shift 2 ;;
        *) echo "Unknown argument: $1" >&2; exit 1 ;;
    esac
done

# ── Resolve DB path ──────────────────────────────────────────────────────────
# Priority: env var > config file > error
if [[ -n "${MNEMOSYNE_DB_PATH:-}" ]]; then
    DB_PATH="$MNEMOSYNE_DB_PATH"
elif [[ -n "$CONFIG_FILE" ]]; then
    if [[ ! -f "$CONFIG_FILE" ]]; then
        echo "Config file not found: $CONFIG_FILE" >&2
        exit 1
    fi
    # Parse db.path from the INI config (section [db], key path)
    DB_PATH="$(awk -F'=' '/^\[db\]/{in_db=1; next} /^\[/{in_db=0} in_db && /^[[:space:]]*path[[:space:]]*=/{gsub(/[[:space:]#].*/, "", $2); print $2; exit}' "$CONFIG_FILE")"
    DB_PATH="${DB_PATH// /}"   # strip spaces
    if [[ -z "$DB_PATH" ]]; then
        echo "Could not read db.path from $CONFIG_FILE" >&2
        exit 1
    fi
else
    echo "Provide --config or set MNEMOSYNE_DB_PATH" >&2
    exit 1
fi

if [[ ! -f "$DB_PATH" ]]; then
    echo "Database not found: $DB_PATH" >&2
    exit 1
fi

# ── Ensure backup directory exists ───────────────────────────────────────────
mkdir -p "$BACKUP_DIR"

# ── Run backup ───────────────────────────────────────────────────────────────
TIMESTAMP="$(date +%Y%m%d-%H%M%S)"
BACKUP_FILE="$BACKUP_DIR/mnemosyne-${TIMESTAMP}.db"

# sqlite3 .backup uses the SQLite Online Backup API — consistent snapshot,
# safe under concurrent writes, no application downtime required.
sqlite3 "$DB_PATH" ".backup '$BACKUP_FILE'"

# Verify the backup is a valid SQLite database
if ! sqlite3 "$BACKUP_FILE" "PRAGMA integrity_check;" | grep -q "^ok$"; then
    echo "Backup integrity check failed: $BACKUP_FILE" >&2
    rm -f "$BACKUP_FILE"
    exit 1
fi

BYTES="$(wc -c < "$BACKUP_FILE")"
echo "Backup written: $BACKUP_FILE (${BYTES} bytes)"

# ── Prune old backups ─────────────────────────────────────────────────────────
if [[ "$KEEP_DAYS" -gt 0 ]]; then
    PRUNED="$(find "$BACKUP_DIR" -maxdepth 1 -name 'mnemosyne-*.db' \
                   -mtime "+${KEEP_DAYS}" -print -delete | wc -l)"
    [[ "$PRUNED" -gt 0 ]] && echo "Pruned $PRUNED backup(s) older than ${KEEP_DAYS} days"
fi