#!/bin/bash

# Live, consistent database backups.
#
# A file-level snapshot of a running database is "torn" — pages can be
# half-written when restic reads them, so the restored copy may not even
# mount. The fix is a *logical* dump taken while the service keeps running:
# mysqldump --single-transaction / pg_dump / sqlite3 .backup all produce a
# transactionally-consistent file with zero downtime. We snapshot that dump
# (and exclude the raw data dir, which is now redundant and unreliable), then
# replay it on restore.
#
# Apps declare their databases as compose labels so the metadata travels with
# the app (the compose is always copied to the install dir and always lives in
# the snapshot). One label per database:
#
#   labels:
#     libreportal.backup.db: "<kind>:<container>:<datadir>:<path>"
#
#   kind      mysql | mariadb | postgres | sqlite
#   container service container_name to `docker exec` into (server engines)
#   datadir   app-dir-relative folder holding raw DB files, excluded on live
#   path      app-dir-relative path to the sqlite file (sqlite only)
#
# Examples:
#   "mysql:nextcloud-db:db_data:"        MariaDB/MySQL in nextcloud-db, raw db_data/ excluded
#   "postgres:mastodon-db:postgres_data:" Postgres in mastodon-db
#   "sqlite:::data/gitea.db"             sqlite file at data/gitea.db
#
# An app with no database can still opt into live snapshots (its files are
# static enough to capture safely) with:
#   labels:
#     libreportal.backup.live: "true"

# Subdir (relative to the app dir) where consistent dumps are written. It sits
# at the app root so it is never inside an excluded datadir, and rides along in
# the snapshot.
backup_db_dump_subdir=".lp-backup/db"

# Emit one "kind:container:datadir:path" line per declared database, read from
# the *installed* compose so it reflects what is actually deployed.
backupDbDescriptors()
{
    local app="$1"
    local compose="$containers_dir$app/docker-compose.yml"
    [[ -f "$compose" ]] || return 0

    grep -E '^[[:space:]]*libreportal\.backup\.db[[:space:]]*:' "$compose" 2>/dev/null \
        | sed -E 's/^[[:space:]]*libreportal\.backup\.db[[:space:]]*:[[:space:]]*//' \
        | sed -E 's/[[:space:]]*#.*$//' \
        | sed -E 's/^["'\'']//; s/["'\'']$//' \
        | sed -E 's/[[:space:]]+$//'
}

backupDbHasDescriptors()
{
    local app="$1"
    if [[ -n "$(backupDbDescriptors "$app")" ]]; then return 0; fi
    return 1
}

# True when the app carries `libreportal.backup.live: "true"` — i.e. its data is
# safe to snapshot while running even though it has no database to dump.
backupAppIsLiveSafe()
{
    local app="$1"
    local compose="$containers_dir$app/docker-compose.yml"
    [[ -f "$compose" ]] || return 1
    if grep -qE '^[[:space:]]*libreportal\.backup\.live[[:space:]]*:[[:space:]]*["'\'']?true' "$compose" 2>/dev/null; then
        return 0
    fi
    return 1
}

# An app can be backed up live without downtime when we can make it consistent:
# it has a dumpable database, or it is explicitly blessed live-safe.
backupAppLiveCapable()
{
    local app="$1"
    if backupDbHasDescriptors "$app"; then return 0; fi
    if backupAppIsLiveSafe "$app"; then return 0; fi
    return 1
}

# Strategy options valid for one app, in .config "[a:b|c:d]" syntax. live is
# offered only where the app can actually do it, so the UI never shows a choice
# that would just fall back to stop.
backupAppStrategyOptions()
{
    local app="$1"
    local opts="auto:Automatic — recommended|stop-snapshot-start:Stop → snapshot → start|pause-snapshot-unpause:Pause → snapshot → unpause"
    if backupAppLiveCapable "$app"; then
        opts="$opts|live:Live — no downtime"
    fi
    echo "$opts"
    return 0
}

# Resolve the effective strategy for one app. Order of precedence:
#   1. per-app override  CFG_<APP>_BACKUP_STRATEGY  (advanced, defaults to auto)
#   2. global default    CFG_BACKUP_STRATEGY        (auto)
# An explicit stop/pause/live is honoured as-is; "auto" goes live only where the
# app is live-capable and otherwise uses the always-safe stop-snapshot-start.
backupResolveStrategy()
{
    local app="$1"
    local override_key="CFG_${app^^}_BACKUP_STRATEGY"
    local s="${!override_key}"
    if [[ -z "$s" || "$s" == "auto" ]]; then
        s="${CFG_BACKUP_STRATEGY:-auto}"
    fi

    case "$s" in
        live|pause-snapshot-unpause|stop-snapshot-start)
            echo "$s"; return 0 ;;
    esac
    if backupAppLiveCapable "$app"; then
        echo "live"
    else
        echo "stop-snapshot-start"
    fi
    return 0
}

# Deterministic dump filename for a descriptor — backup writes it, restore reads
# it, both deriving the same name from the descriptor with no side metadata.
_backupDbDumpName()
{
    local kind="$1" container="$2" path="$3"
    case "$kind" in
        sqlite) echo "sqlite-$(echo "$path" | tr '/' '_').sqlite.gz" ;;
        *)      echo "db-${container}.sql.gz" ;;
    esac
}

# Wait until a server database accepts connections (it has just been started
# fresh on restore, or is mid-load on a busy host).
_backupDbWaitReady()
{
    local kind="$1" container="$2" tries=30
    local i
    for ((i = 0; i < tries; i++)); do
        case "$kind" in
            postgres)
                docker exec "$container" sh -c 'pg_isready -U "${POSTGRES_USER:-postgres}" -q' >/dev/null 2>&1 && return 0 ;;
            *)
                docker exec "$container" sh -c 'mariadb-admin ping -uroot -p"${MARIADB_ROOT_PASSWORD:-$MYSQL_ROOT_PASSWORD}" 2>/dev/null || mysqladmin ping -uroot -p"${MARIADB_ROOT_PASSWORD:-$MYSQL_ROOT_PASSWORD}"' >/dev/null 2>&1 && return 0 ;;
        esac
        sleep 2
    done
    return 1
}

# Dump every declared database for an app to consistent files inside the app
# dir, while the containers keep running. Called on the live path only.
backupDbDump()
{
    local app="$1"
    local app_dir="$containers_dir$app"
    local dump_dir="$app_dir/$backup_db_dump_subdir"
    local desc kind container datadir path dump rc=0

    backupDbHasDescriptors "$app" || return 0

    sudo mkdir -p "$dump_dir"

    while IFS= read -r desc; do
        [[ -z "$desc" ]] && continue
        IFS=':' read -r kind container datadir path <<< "$desc"
        dump="$dump_dir/$(_backupDbDumpName "$kind" "$container" "$path")"

        case "$kind" in
            postgres)
                isNotice "Dumping postgres ($container) — live, consistent"
                if docker exec "$container" sh -c \
                    'export PGPASSWORD="${POSTGRES_PASSWORD:-}"; pg_dump --clean --if-exists -U "${POSTGRES_USER:-postgres}" -d "${POSTGRES_DB:-${POSTGRES_USER:-postgres}}"' \
                    2>/dev/null | gzip | sudo tee "$dump" >/dev/null; then
                    isSuccessful "postgres dump written ($container)"
                else
                    isError "postgres dump failed ($container)"; rc=1
                fi
                ;;
            mysql|mariadb)
                isNotice "Dumping $kind ($container) — live, consistent"
                if docker exec "$container" sh -c \
                    'RP="${MARIADB_ROOT_PASSWORD:-$MYSQL_ROOT_PASSWORD}"; DB="${MARIADB_DATABASE:-$MYSQL_DATABASE}"; (mariadb-dump -uroot -p"$RP" --single-transaction --routines --triggers --databases "$DB" 2>/dev/null || mysqldump -uroot -p"$RP" --single-transaction --routines --triggers --databases "$DB")' \
                    2>/dev/null | gzip | sudo tee "$dump" >/dev/null; then
                    isSuccessful "$kind dump written ($container)"
                else
                    isError "$kind dump failed ($container)"; rc=1
                fi
                ;;
            sqlite)
                isNotice "Dumping sqlite ($path) — live, consistent"
                local src="$app_dir/$path"
                if [[ ! -f "$src" ]]; then
                    # Declared but not found — could be a fresh app, or a wrong
                    # path. Treat as a dump failure so the caller falls back to
                    # the safe stop-snapshot-start rather than snapshotting a
                    # live sqlite file untorn.
                    isError "sqlite file $path not found — cannot dump"
                    rc=1
                    continue
                fi
                # .backup takes a consistent copy even while the app writes.
                local tmp="$dump_dir/.$(basename "$path").tmp"
                if sudo sqlite3 "$src" ".backup '$tmp'" 2>/dev/null && sudo gzip -c "$tmp" | sudo tee "$dump" >/dev/null; then
                    sudo rm -f "$tmp"
                    isSuccessful "sqlite dump written ($path)"
                else
                    sudo rm -f "$tmp"
                    isError "sqlite dump failed ($path)"; rc=1
                fi
                ;;
            *)
                isError "Unknown db kind '$kind' for $app — skipping"; rc=1 ;;
        esac
    done < <(backupDbDescriptors "$app")

    sudo chown -R "$docker_install_user":"$docker_install_user" "$dump_dir" 2>/dev/null
    return $rc
}

# Absolute paths to exclude from a live snapshot: the raw data dirs / sqlite
# files the dumps supersede. Echoed one per line for the engine adapters.
backupDbExcludePaths()
{
    local app="$1"
    local app_dir="$containers_dir$app"
    local desc kind container datadir path

    while IFS= read -r desc; do
        [[ -z "$desc" ]] && continue
        IFS=':' read -r kind container datadir path <<< "$desc"
        case "$kind" in
            sqlite)
                [[ -n "$path" ]] || continue
                echo "$app_dir/$path"
                echo "$app_dir/$path-wal"
                echo "$app_dir/$path-shm"
                ;;
            *)
                [[ -n "$datadir" ]] || continue
                echo "$app_dir/$datadir"
                ;;
        esac
    done < <(backupDbDescriptors "$app")
}

# Pre-start restore step. Runs after the snapshot is laid down but before the
# containers come up:
#   server  remove the (absent or stale) raw data dir so the engine first-run
#           init builds a clean, empty database for us to load into.
#   sqlite  put the consistent dump back at the real path so the app opens it.
restoreDbRehydratePreStart()
{
    local app="$1"
    local app_dir="$containers_dir$app"
    local dump_dir="$app_dir/$backup_db_dump_subdir"
    local desc kind container datadir path dump

    backupDbHasDescriptors "$app" || return 0

    while IFS= read -r desc; do
        [[ -z "$desc" ]] && continue
        IFS=':' read -r kind container datadir path <<< "$desc"
        dump="$dump_dir/$(_backupDbDumpName "$kind" "$container" "$path")"

        case "$kind" in
            sqlite)
                [[ -f "$dump" ]] || { isNotice "No sqlite dump for $path — leaving app to initialise"; continue; }
                sudo rm -f "$app_dir/$path" "$app_dir/$path-wal" "$app_dir/$path-shm"
                sudo mkdir -p "$(dirname "$app_dir/$path")"
                sudo gzip -dc "$dump" | sudo tee "$app_dir/$path" >/dev/null
                sudo chown -R "$docker_install_user":"$docker_install_user" "$(dirname "$app_dir/$path")"
                isSuccessful "sqlite $path rehydrated from dump"
                ;;
            *)
                [[ -f "$dump" ]] || { isNotice "No dump for $container — keeping restored data dir as-is"; continue; }
                [[ -n "$datadir" ]] && sudo rm -rf "${app_dir:?}/$datadir"
                isNotice "Cleared $datadir — $container will init fresh, then load the dump"
                ;;
        esac
    done < <(backupDbDescriptors "$app")
}

# Post-start restore step. Server engines load their dump into the freshly
# initialised database once it is accepting connections. sqlite is already in
# place from the pre-start step, so it is a no-op here.
restoreDbReplayPostStart()
{
    local app="$1"
    local app_dir="$containers_dir$app"
    local dump_dir="$app_dir/$backup_db_dump_subdir"
    local desc kind container datadir path dump

    backupDbHasDescriptors "$app" || return 0

    while IFS= read -r desc; do
        [[ -z "$desc" ]] && continue
        IFS=':' read -r kind container datadir path <<< "$desc"
        dump="$dump_dir/$(_backupDbDumpName "$kind" "$container" "$path")"
        [[ "$kind" == "sqlite" ]] && continue
        [[ -f "$dump" ]] || continue

        isNotice "Waiting for $container to accept connections"
        if ! _backupDbWaitReady "$kind" "$container"; then
            isError "$container never became ready — dump not loaded; data dir left for manual recovery"
            continue
        fi

        case "$kind" in
            postgres)
                if sudo gzip -dc "$dump" | docker exec -i "$container" sh -c \
                    'export PGPASSWORD="${POSTGRES_PASSWORD:-}"; psql -U "${POSTGRES_USER:-postgres}" -d "${POSTGRES_DB:-${POSTGRES_USER:-postgres}}"' >/dev/null 2>&1; then
                    isSuccessful "postgres dump loaded into $container"
                else
                    isError "Loading postgres dump into $container failed"
                fi
                ;;
            mysql|mariadb)
                if sudo gzip -dc "$dump" | docker exec -i "$container" sh -c \
                    'RP="${MARIADB_ROOT_PASSWORD:-$MYSQL_ROOT_PASSWORD}"; (mariadb -uroot -p"$RP" 2>/dev/null || mysql -uroot -p"$RP")' >/dev/null 2>&1; then
                    isSuccessful "$kind dump loaded into $container"
                else
                    isError "Loading $kind dump into $container failed"
                fi
                ;;
        esac
    done < <(backupDbDescriptors "$app")
}