#!/bin/bash
# postgres-fuse-wrap: recreate FUSE-volatile dirs then exec postgres as mem0.
# Run by supervisord as root on every (re)start so dirs exist even after the
# ~80s crash-recovery fsync window during which FUSE drops empty dirs.
set -e

PGDATA=/data/pgdata

# Dirs that must exist AND be completely empty (Postgres repopulates them).
for dir in pg_replslot pg_twophase pg_dynshmem pg_notify \
           pg_snapshots pg_logical/snapshots pg_logical/mappings; do
  mkdir -p "$PGDATA/$dir"
  find "$PGDATA/$dir" -mindepth 1 -delete 2>/dev/null || true
done

# Dirs that must exist; contents are written by Postgres — only recreate if missing.
for dir in pg_subtrans pg_xact pg_multixact/members pg_multixact/offsets; do
  mkdir -p "$PGDATA/$dir"
done

# Dirs that tolerate marker files (Postgres ignores unknown files here)
for dir in pg_commit_ts pg_serial pg_stat pg_stat_tmp; do
  mkdir -p "$PGDATA/$dir"
  find "$PGDATA/$dir" -mindepth 1 -name '.git' -type d -exec rm -rf {} + 2>/dev/null || true
done

# pg_tblspc must be a symlink to tmpfs — FUSE drops real empty dirs
mkdir -p /tmp/pg_tblspc
rm -rf "$PGDATA/pg_tblspc"
ln -sfn /tmp/pg_tblspc "$PGDATA/pg_tblspc"

# Fix ownership: this wrapper runs as root but postgres runs as mem0.
# Only chown the dirs we just created — no recursive chown over FUSE (kills mount).
chown mem0:mem0 \
  "$PGDATA/pg_subtrans" \
  "$PGDATA/pg_xact" \
  "$PGDATA/pg_multixact" \
  "$PGDATA/pg_multixact/members" \
  "$PGDATA/pg_multixact/offsets" \
  "$PGDATA/pg_snapshots" \
  "$PGDATA/pg_logical" \
  "$PGDATA/pg_logical/snapshots" \
  "$PGDATA/pg_logical/mappings" \
  "$PGDATA/pg_commit_ts" \
  "$PGDATA/pg_serial" \
  "$PGDATA/pg_stat" \
  "$PGDATA/pg_stat_tmp" \
  "$PGDATA/pg_replslot" \
  "$PGDATA/pg_twophase" \
  "$PGDATA/pg_dynshmem" \
  "$PGDATA/pg_notify" \
  2>/dev/null || true
chown -h mem0:mem0 "$PGDATA/pg_tblspc"

# Background loop: FUSE can drop empty dirs at any time during runtime, not
# just at startup. Re-assert critical dirs every 5s while postgres is alive.
fuse_keepalive() {
  while true; do
    sleep 5
    for dir in pg_replslot pg_twophase pg_dynshmem pg_notify \
               pg_snapshots pg_logical/snapshots pg_logical/mappings; do
      if [ ! -d "$PGDATA/$dir" ]; then
        mkdir -p "$PGDATA/$dir" 2>/dev/null && \
          chown mem0:mem0 "$PGDATA/$dir" 2>/dev/null || true
      fi
    done
    if [ ! -L "$PGDATA/pg_tblspc" ]; then
      rm -rf "$PGDATA/pg_tblspc"
      ln -sfn /tmp/pg_tblspc "$PGDATA/pg_tblspc" 2>/dev/null
      chown -h mem0:mem0 "$PGDATA/pg_tblspc" 2>/dev/null || true
    fi
  done
}
fuse_keepalive &
KEEPALIVE_PID=$!

# Drop to mem0 and exec postgres.
# Note: exec replaces this shell, so trap cleanup of keepalive on exit.
trap "kill $KEEPALIVE_PID 2>/dev/null" EXIT
exec gosu mem0 /usr/lib/postgresql/15/bin/postgres \
  -D "$PGDATA" \
  -c config_file="$PGDATA/postgresql.conf"