#!/bin/bash
# plex_db_sync.sh — Mirror Plex DB from primary → secondary when secondary Plex service is NOT running.
# - Safe to run from cron or on a schedule.
# - Assumes official plexinc images & standard appdata layout.
# - Set DRY_RUN=1 for a preview (no changes).

set -u  # (no -e so we can control exit paths and log errors ourselves)

# --- Config ------------------------------------------------------------------
SRC="/mnt/user/appdata/Plex-Media-Server/Library/Application Support/Plex Media Server/Plug-in Support/Databases"
DEST="/mnt/user/appdata/Plex-Media-Server-Secondary/Library/Application Support/Plex Media Server/Plug-in Support/Databases"
CONTAINER="Plex-Media-Server-Secondary"

# Process name pattern to detect inside container
PLEX_PROCESS_PATTERN="${PLEX_PROCESS_PATTERN:-Plex Media Server}"

LOG_FILE="/var/log/plex_db_sync.log"
LOCK_FILE="/var/tmp/plex_db_sync.lock"

# Optional: DRY_RUN=1 rsyncs with -n (no changes).
DRY_RUN="${DRY_RUN:-0}"

# --- Helpers -----------------------------------------------------------------
ts()   { date "+%Y-%m-%d %H:%M:%S %Z"; }
log()  { echo "$(ts): $*" | tee -a "$LOG_FILE"; }
die()  { log "ERROR: $*"; exit 1; }

have() { command -v "$1" >/dev/null 2>&1; }

container_running() {
  docker inspect -f '{{.State.Running}}' "$1" 2>/dev/null | tr -d '[:space:]' || echo "false"
}

# Returns "true" if the Plex process appears to be running inside the container.
plex_proc_running_in_container() {
  local c="$1"
  local pat="${2:-$PLEX_PROCESS_PATTERN}"

  # If the container itself is not running, report "false" (service not running).
  if [ "$(container_running "$c")" != "true" ]; then
    echo "false"
    return
  fi

  # Prefer pgrep if available in the container; fall back to ps|grep.
  if docker exec "$c" sh -c 'command -v pgrep >/dev/null 2>&1'; then
    if docker exec "$c" sh -lc "pgrep -f \"${pat}\" >/dev/null 2>&1"; then
      echo "true"
    else
      echo "false"
    fi
  else
    if docker exec "$c" sh -lc "ps aux 2>/dev/null | grep -F \"${pat}\" | grep -v grep >/dev/null"; then
      echo "true"
    else
      echo "false"
    fi
  fi
}

DISABLE_FILE="/var/tmp/plex_backup_in_progress"
if [ -f "$DISABLE_FILE" ]; then
  log "Backup flag found ($DISABLE_FILE). Skipping database sync."
  exit 0
fi

# Prefer flock (fd 9), else mkdir lock
take_lock() {
  if have flock; then
    exec 9>"$LOCK_FILE" || die "Unable to open lock file: $LOCK_FILE"
    flock -n 9 || { log "Another sync is running (flock). Skipping."; exit 0; }
    # flock auto-releases when fd 9 closes on exit
  else
    if ! mkdir "$LOCK_FILE" 2>/dev/null; then
      log "Another sync is running (mkdir lock). Skipping."
      exit 0
    fi
    trap 'rmdir "$LOCK_FILE" 2>/dev/null || true' EXIT
  fi
}

nice_wrap() {
  # Use ionice/nice if available; otherwise run command as-is
  if have ionice; then
    ionice -c2 -n7 nice -n 10 "$@"
  else
    nice -n 10 "$@"
  fi
}

# --- Start -------------------------------------------------------------------
take_lock

have docker || die "docker not found in PATH."
have rsync  || die "rsync not found in PATH."

# Ensure paths exist
[ -d "$SRC" ]  || die "Source path missing: $SRC"
if [ ! -d "$DEST" ]; then
  log "Destination path missing: $DEST (creating...)"
  mkdir -p "$DEST" || die "Could not create $DEST"
fi

# Decide based on *internal* Plex process state
CONTAINER_STATE="$(container_running "$CONTAINER")"
PLEX_INSIDE_RUNNING="$(plex_proc_running_in_container "$CONTAINER" "$PLEX_PROCESS_PATTERN")"

if [ "$CONTAINER_STATE" = "true" ] && [ "$PLEX_INSIDE_RUNNING" = "true" ]; then
  log "Plex service in $CONTAINER appears ACTIVE (matched: \"$PLEX_PROCESS_PATTERN\"). Skipping DB sync."
  exit 0
fi

if [ "$CONTAINER_STATE" = "true" ] && [ "$PLEX_INSIDE_RUNNING" = "false" ]; then
  log "Container $CONTAINER is RUNNING, but Plex service is STOPPED. Proceeding with database sync…"
elif [ "$CONTAINER_STATE" != "true" ]; then
  log "Container $CONTAINER is STOPPED. Proceeding with database sync…"
fi

# --- rsync build -------------------------------------------------------------
RSYNC_ARGS=(
  -aH --delete
  --itemize-changes
  --info=stats2,flist2,del2
  --human-readable
  --inplace
  --exclude=".DS_Store"
  --exclude="lost+found"
)

# Dry-run?
if [ "$DRY_RUN" = "1" ]; then
  RSYNC_ARGS+=( -n )
  log "DRY_RUN=1 enabled: no changes will be made."
fi

# --- Execute -----------------------------------------------------------------
SRC_DIR="$SRC/"
DEST_DIR="$DEST/"

if OUTPUT="$(nice_wrap rsync "${RSYNC_ARGS[@]}" -- "$SRC_DIR" "$DEST_DIR" 2>&1)"; then
  CHANGES="$(printf '%s\n' "$OUTPUT" | awk '/^[-dchslp\.][^ ]/ {print}' | wc -l | tr -d ' ')"
  if [ "$DRY_RUN" = "1" ]; then
    log "DRY-RUN completed. Would change items: $CHANGES"
  else
    log "Sync completed successfully. Changed items: $CHANGES"
  fi
  printf '%s\n' "$OUTPUT" | awk '/Number of files:|Number of regular files:|Number of created files:|Number of deleted files:|Total transferred file size:|Literal data:|Matched data:|File list size:|Total bytes sent:|Total bytes received:/' >> "$LOG_FILE"
  exit 0
else
  RC=$?
  log "ERROR: rsync failed with exit code $RC"
  printf '%s\n' "$OUTPUT" | tail -n 50 >> "$LOG_FILE"
  exit "$RC"
fi