#!/bin/bash

function usage {
  cat <<- EOF
  ./scrape.sh [options]

  Scrape facebook event pages.

  This script will always return an JSON array.

  OPTIONS:
    -e --event                        Facebook event id. Scrape a single Facebook
                                      event.
    -h --help -?                      print usage
    --events                          List of Facebook event ids. See examples for
                                      format.
    -p --page                         Facebook page id. Scrape all events of a
                                      specific facebook page.
    --pages                           List of Facebook page ids. See examples for
                                      format.
  NOTE:
  Events and pages needs to be public. Private events or pages are not yet
  supported.

  EXAMPLES:
EOF
}

event_ids="";
pages_ids="";

function scrape_event {
  local event_id;
  event_id="$1"
  if [ "" == "${event_ids}" ]; then
    event_ids="${event_id}"
  else
    event_ids="${event_ids},${event_id}"
  fi
}

function scrape_page {
  local page_id;
  page_id="$1"
  if [ "" == "${pages_ids}" ]; then
     pages_ids="${page_id}"
  else
    pages_ids="${pages_ids},${page_id}"
  fi
}

function parse_args {
  if [ "$1" = "" ]; then
    echo ""
  fi

  while [[ $# -gt 0 ]]; do
    key="$1"
    case $key in
      -e|--event|--events)
        shift
        scrape_event "$1"
        ;;
      -p|--page|--pages)
        shift
        scrape_page "$1"
        ;;
      *)
        usage
        exit 1
        ;;
    esac
    shift
  done
}

function install_node_dependencies {
  if ! [ -d node_modules ]; then
    yarn
  fi
}

function check_dependencies {
  local missing;
  missing=false;

  if [ ! $(command -v node) ]; then
    echo "Dependency missing. Please install node.js and make it available to the path as 'node'."
    missing=true
  fi

  if [ ! $(command -v yarn) ]; then
    echo "Dependency missing. Please install yarn and make it available to the path as 'yarn'."
    missing=true
  fi

  install_node_dependencies

  if [ "${missing}" != "false" ]; then
    exit 1;
  fi

  return 0;
}

function scrape {
  exec node scrape.js --event_ids="${event_ids}" --page_ids="${pages_ids}"
}

check_dependencies \
  && parse_args "$@" \
  && scrape