#!/usr/bin/env bash
set -euo pipefail

env_file="${1:-.env}"
defaults_file="${2:-.env.example}"

if [ ! -f "$env_file" ] || [ ! -f "$defaults_file" ]; then
  exit 0
fi

added=0
while IFS= read -r line || [ -n "$line" ]; do
  trimmed="${line#"${line%%[![:space:]]*}"}"
  if [ -z "$trimmed" ] || [[ "$trimmed" == \#* ]] || [[ "$trimmed" != *=* ]]; then
    continue
  fi
  key="${trimmed%%=*}"
  if ! grep -qE "^${key}=" "$env_file"; then
    if [ "$added" -eq 0 ]; then
      {
        echo
        echo "# Added from .env.example on $(date +%F)"
      } >> "$env_file"
    fi
    echo "$trimmed" >> "$env_file"
    added=$((added + 1))
  fi
done < "$defaults_file"

if [ "$added" -gt 0 ]; then
  echo "merged $added missing env defaults into $env_file"
fi