Support host UID/GID for Docker runtime

docker-entrypoint.sh

@@ -8,6 +8,42 @@ is_true() {
     esac
 }
 
+is_integer() {
+    case "${1:-}" in
+        '' | *[!0-9]*) return 1 ;;
+        *) return 0 ;;
+    esac
+}
+
+run_as_requested_user() {
+    uid="${USER_UID:-}"
+    gid="${USER_GID:-}"
+
+    if [ -z "$uid" ] && [ -z "$gid" ]; then
+        return 1
+    fi
+
+    if [ -z "$uid" ] || [ -z "$gid" ]; then
+        echo "Both USER_UID and USER_GID must be set together." >&2
+        exit 1
+    fi
+
+    if ! is_integer "$uid" || ! is_integer "$gid"; then
+        echo "USER_UID and USER_GID must be numeric." >&2
+        exit 1
+    fi
+
+    mkdir -p /app/.ani-cli-web/home
+    chown "$uid:$gid" /downloads /app/.ani-cli-web /app/.ani-cli-web/home
+
+    cd /app
+    exec setpriv \
+        --reuid "$uid" \
+        --regid "$gid" \
+        --clear-groups \
+        env HOME=/app/.ani-cli-web/home ./ani-cli-web "$@"
+}
+
 mkdir -p /downloads /app/.ani-cli-web
 
 if is_true "${UPDATE_ON_START:-false}"; then
@@ -15,5 +51,7 @@ if is_true "${UPDATE_ON_START:-false}"; then
     sudo ani-cli --update
 fi
 
+run_as_requested_user "$@" || true
+
 cd /app
 exec ./ani-cli-web "$@"