Output timezone select in Rails with some data attrs for JS

get_abbr.js

var d = new Date(); 
var tz_offset = d.getTimezoneOffset(); // seconds, not ms, because Javascript
var tz_select = $('#tz-select');
var abbr = tz_select.find("option[data-offset='" + tz_offset + "']").data('abbreviation');

time_is_validator.rb

# Usage 
# validates :event_time, time_is: { after_now: true }
# validates :last_event, time_is: { before_now: true }
# validates :event_time, time_is: { before: Time.zone.now - 5.days }
# validates :event_time, time_is: { after: Time.zone.now + 5.days }

class TimeIsValidator < ActiveModel::EachValidator

  # ignore time differences smaller than one second
  def compare(time_1, time_2)
    return -1 if time_1 - time_2 < -1
    return 1 if time_1 - time_2 > 1
    return 0
  end

  def validate_each(record, attribute, value)
    return unless value.present?

    raise ArgumentError.new("No options specified for time_is: on #{record.class.name}") unless options.is_a?(Hash)

    # use integers; otherwise Time tracks to the nanosecond, which can easily mess up tests
    now = Time.zone.now
    time_value = value

    if options[:before_now] && time_value - now >= 1
      record.errors[attribute] << "is not before now"
    end

    if options[:after_now] && time_value - now <= 1
      record.errors[attribute] << "is not afer now"
    end

    if options[:now_or_earlier] && time_value - now >= 1
      record.errors[attribute] << "is later than now"
    end

    if options[:now_or_later] && time_value - now <= -1
      record.errors[attribute] << "is earlier than now"
    end

    if options[:before]
      compare_to = options[:before]
      compare_to = record.send(compare_to) if compare_to.is_a?(Symbol)
      compare_to = compare_to.to_time
      if time_value - compare_to >= -1
        record.errors[attribute] << "is not before #{options[:before]}"
      end
    end

    if options[:at_or_before]
      compare_to = options[:at_or_before]
      compare_to = record.send(compare_to) if compare_to.is_a?(Symbol)
      compare_to = compare_to.to_time
      if time_value - compare_to <= 1
        record.errors[attribute] << "is not on or before #{options[:before]}"
      end
    end

    if options[:after]
      compare_to = options[:after]
      compare_to = record.send(compare_to) if compare_to.is_a?(Symbol)
      compare_to = compare_to.to_time
      if time_value - compare_to <= 1
        record.errors[attribute] << "is not after #{options[:before]}"
      end
    end

    if options[:at_or_after]
      compare_to = options[:at_or_after]
      compare_to = record.send(compare_to) if compare_to.is_a?(Symbol)
      compare_to = compare_to.to_time
      if time_value - compare_to >= -1
        record.errors[attribute] << "is not on or after #{options[:at_or_after]}"
      end
    end
  end
end

time_matchers.rb

# Usage
# expect(time_instance).to be_time(Time.zone.now)

# match times, but ignore differences smaller than one second.
# prevents race conditions in validation, expect() etc with times
# handy with TimeCop - https://github.com/travisjeffery/timecop

RSpec::Matchers.define :be_time do |expected|
  match do |actual|
    expected == actual || ((expected - actual) < 1 && (expected - actual) > -1)
  end

  failure_message do |actual|
    format = '%b %-d, %Y %H:%M:%S %N %z'
    "expected #{actual.strftime(format)} would be #{expected.strftime(format)}"
  end
end

tz_select_helper.rb

def time_zones_for_js(selected)
  prev_offsets = []
  html = ""
  time_zones = ActiveSupport::TimeZone.us_zones.reverse
  time_zones.each do |zone|
    next if prev_offsets.include?(zone.utc_offset)
    next unless zone.to_s =~ /Time/
    html << "<option value='#{zone.name}'
              data-abbreviation='#{zone.now.zone}'
              data-offset='#{zone.tzinfo.period_for_utc(Time.now).utc_total_offset}'
              {zone.name == selected ? 'selected=\'selected\'' : ''}>"
    html << "(GMT#{zone.formatted_offset}) #{zone.tzinfo.friendly_identifier}"
    html << "</option>"
    prev_offsets << zone.utc_offset
  end

  html << "<option disabled='disabled'>--------------</option>"
  ActiveSupport::TimeZone.all.each do |zone|
    next if prev_offsets.include?(zone.name)
    html << "<option value='#{zone.name}'
              data-abbreviation='#{zone.now.zone}'
              data-offset='#{zone.tzinfo.period_for_utc(Time.now).utc_total_offset}'
              #{zone.to_s == selected ? 'selected=\'selected\'' : ''}>"
    html << "(GMT#{zone.formatted_offset}) #{zone.tzinfo.friendly_identifier}"
    html << "</option>"
    prev_offsets << zone.utc_offset
  end
end

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