url-alias.bash

#!/usr/bin/env bash

# All my gist code is licensed under the MIT license.

# Video demo: https://www.youtube.com/watch?v=2tRyBQqJdrc

# Note: In some browsers you need to type "g/" instead of just "g" so it gets
# recognized as a URL and not as a term for the default search engine.

# source of truth for URL aliases
# - used by url-alias-setup and url-alias
# - can be modified to add new aliases
declare -A __url_alias=(
  ["g"]="https://google.com"
  ["r"]="https://reddit.com"
  ["h"]="https://news.ycombinator.com"
)

# url-alias
# - print the current URL aliases
function url-alias () {
  local green="\033[32m"
  local cyan="\033[36m"
  local reset="\033[0m"

  echo "${green}URL aliases:${reset}"
  for alias in "${!__url_alias[@]}"; do
    echo "${cyan}${alias}${reset} -> ${__url_alias[${alias}]}"
  done

  echo "${green}To add new aliases, edit the ${cyan}__url_alias${green} array and run ${cyan}url-alias-setup${reset}"
}

# return either 'linux' or 'macos'
function get_platform () {
  case "$(uname -s)" in
    Darwin)
      echo "macos"
      ;;
    Linux)
      echo "linux"
      ;;
    *)
      echo "unsupported platform"
      exit 1
      ;;
  esac
}
platform=$(get_platform)

# url-alias-setup
# - sets up URL aliases
# - this is done by modifying the /etc/hosts file and the nginx configuration
# - if changes are made, nginx is (re)started
function url-alias-setup () {
  # nginx config (platform dependent) 
  if [[ "$platform" == "macos" ]]; then
    local nginx_config="/usr/local/etc/nginx/nginx.conf"
  else
    local nginx_config="/etc/nginx/nginx.conf"
  fi

  # create new nginx config and hosts file
  local new_hosts=""
  read -r -d '' new_nginx_config <<'EOF'
events {}
http {
EOF
  
  for alias in "${!__url_alias[@]}"; do
    local url="${__url_alias[$alias]}"

    new_hosts="${new_hosts}\n127.0.0.1 ${alias}"

    read -r -d '' server_blocks << EOF
    server {
        listen       80;
        server_name  ${alias};
        location / {
          rewrite ^ ${url} permanent;
        }
    }

EOF
    new_nginx_config="${new_nginx_config}\n    ${server_blocks}"
  done
  new_nginx_config="${new_nginx_config}\n}"
  
  # replace files
  # if file already exists, prompt user to overwrite
  echo "Saving new nginx config and hosts file..."
  if [[ -f "${nginx_config}" ]]; then
    echo "File ${nginx_config} already exists. Overwrite? (y/n)"
    read -r overwrite
    if [[ "${overwrite}" != "y" ]]; then
      echo "Aborting..."
      return 1
    fi
  fi
  echo -e "${new_nginx_config}" | sudo tee "${nginx_config}" > /dev/null
  if [[ -f "/etc/hosts" ]]; then
    echo "File /etc/hosts already exists. Overwrite? (y/n)"
    read -r overwrite
    if [[ "${overwrite}" != "y" ]]; then
      echo "Aborting..."
      return 1
    fi
  fi
  echo -e "${new_hosts}" | sudo tee /etc/hosts > /dev/null

  # start or restart nginx
  echo "Restarting nginx..."
  if [[ "$platform" == "macos" ]]; then
    nginx -s reload
  else
    sudo systemctl restart nginx
  fi
}