chore(scripts): add random string generator utility

Author: mamchurovskyy

Makefile

@@ -72,6 +72,9 @@ clean: ## Remove build and coverage artifacts
 stress: docker-stack ## Run stress test script
 	./scripts/stress.sh
 
+gen-random: ## Generate random string of specified length (default: 32)
+	./scripts/gen-random-string.sh $(length)
+
 ##@ Docker
 docker-build: ## Build Docker image
 	$(DOCKER) build -t $(DOCKER_IMAGE):$(DOCKER_TAG) .

scripts/gen-random-string.sh

@@ -0,0 +1,104 @@
+#!/usr/bin/env bash
+set -euo pipefail
+
+# Generate a random string from lower/upper letters, digits, and symbol set.
+#
+# Usage:
+#   ./scripts/gen-random-string.sh
+#   ./scripts/gen-random-string.sh 48
+#   ./scripts/gen-random-string.sh 48 '!@#$%_-'
+#
+# Defaults:
+#   length  = 32
+#   symbols = !@#$%^&*()-_=+[]{}.,:;?
+
+DEFAULT_LENGTH=32
+DEFAULT_SYMBOLS='!@#$%^&*()-_=+[]{}.,:;?'
+
+LOWER='abcdefghijklmnopqrstuvwxyz'
+UPPER='ABCDEFGHIJKLMNOPQRSTUVWXYZ'
+DIGITS='0123456789'
+
+usage() {
+  cat <<USAGE
+Generate random string.
+
+Usage:
+  $(basename "$0") [length] [symbols]
+
+Arguments:
+  length   Positive integer. Default: ${DEFAULT_LENGTH}
+  symbols  Symbol set to include. Default: ${DEFAULT_SYMBOLS}
+
+Notes:
+  - For length >= 4, output guarantees at least one lowercase, uppercase,
+    digit, and symbol character.
+  - For length < 4, output is sampled from the full charset without guarantees.
+USAGE
+}
+
+if [[ "${1:-}" == "-h" || "${1:-}" == "--help" ]]; then
+  usage
+  exit 0
+fi
+
+length="${1:-$DEFAULT_LENGTH}"
+symbols="${2:-$DEFAULT_SYMBOLS}"
+
+if ! [[ "$length" =~ ^[0-9]+$ ]] || [[ "$length" -le 0 ]]; then
+  echo "length must be a positive integer" >&2
+  exit 2
+fi
+
+if [[ -z "$symbols" ]]; then
+  echo "symbols must be non-empty" >&2
+  exit 2
+fi
+
+full_charset="${LOWER}${UPPER}${DIGITS}${symbols}"
+
+rand_u32() {
+  od -An -N4 -tu4 /dev/urandom | tr -d ' \n'
+}
+
+rand_index() {
+  local n="$1"
+  local r
+  r="$(rand_u32)"
+  echo $(( r % n ))
+}
+
+pick_from() {
+  local set="$1"
+  local idx
+  idx="$(rand_index "${#set}")"
+  printf '%s' "${set:idx:1}"
+}
+
+shuffle_chars() {
+  local -n arr_ref=$1
+  local i j tmp
+  for (( i=${#arr_ref[@]}-1; i>0; i-- )); do
+    j="$(rand_index $((i+1)))"
+    tmp="${arr_ref[i]}"
+    arr_ref[i]="${arr_ref[j]}"
+    arr_ref[j]="$tmp"
+  done
+}
+
+out_chars=()
+
+if (( length >= 4 )); then
+  out_chars+=("$(pick_from "$LOWER")")
+  out_chars+=("$(pick_from "$UPPER")")
+  out_chars+=("$(pick_from "$DIGITS")")
+  out_chars+=("$(pick_from "$symbols")")
+fi
+
+while (( ${#out_chars[@]} < length )); do
+  out_chars+=("$(pick_from "$full_charset")")
+done
+
+shuffle_chars out_chars
+
+printf '%s\n' "${out_chars[*]}" | tr -d ' '