module Gtn::Metrics

# File _plugins/gtn/metrics.rb, line 31
def self.bin_width(values)
  # https://en.wikipedia.org/wiki/Freedman%E2%80%93Diaconis_rule
  2 * iqr(values) / (values.length**(1 / 3))
end

# File _plugins/gtn/metrics.rb, line 88
def self.collect_metrics(site)
  tutorials = site.pages.select { |x| x.data['layout'] == 'tutorial_hands_on' }
  # TODO: materials
  # materials = site.pages.select { |x| x.data['layout'] == 'tutorial_hands_on' }
  first_commit = Date.parse('2015-06-29')
  today = Date.today

  {
    'gtn_pages_total' => {
      value: segment_page_by_key(site.pages, 'layout'),
      help: 'Total number of Pages',
      type: 'counter'
    },
    'gtn_contributors_total' => {
      value: segment(site.data['contributors'].values.reject { |x| x['halloffame'] == 'no' }, 'orcid'),
      help: 'Total number of contributors',
      type: 'counter'
    },
    'gtn_organisations_total' => {
      value: segment(site.data['organisations'].values.reject { |x| x['halloffame'] == 'no' }, 'orcid'),
      help: 'Total number of organisations',
      type: 'counter'
    },
    'gtn_grants_total' => {
      value: segment(site.data['grants'].values.reject { |x| x['halloffame'] == 'no' }, 'orcid'),
      help: 'Total number of grants',
      type: 'counter'
    },
    'gtn_tutorials_total' => {
      value: tutorials.length,
      help: 'Total number of Hands-on Tutorials',
      type: 'counter'
    },
    'gtn_faqs_total' => {
      value: site.pages.select { |x| x.data['layout'] == 'faq' }.length,
      help: 'Total number of FAQs',
      type: 'counter'
    },
    'gtn_project_years_total' => {
      value: (today - first_commit).to_f / 365,
      help: 'Total years of project lifetime',
      type: 'counter'
    },
    'tutorial_update_age_days' => {
      type: 'histogram',
      help: 'How recently was every single Hands-on Tutorial touched within the GTN, ' \
            'grouped by days since last edited.',
      value: histogram_dates(
        tutorials
        .map do |page|
          Time.now - Gtn::ModificationTimes.obtain_time(page['path'].gsub(%r{^/}, ''))
        end
        .map { |seconds| seconds / 3600.0 / 24.0 }
      )
    },
    'tutorial_published_age_days' => {
      type: 'histogram',
      help: 'How recently was every single Hands-on Tutorial published within the GTN, ' \
            'grouped by days since first published.',
      value: histogram_dates(
        tutorials
        .map do |page|
          Time.now - Gtn::PublicationTimes.obtain_time(page['path'])
        end
        .map { |seconds| seconds / 3600.0 / 24.0 }
      )
    },
    'contributor_join_age_days' => {
      type: 'histogram',
      help: 'When did contributors join? Buckets of their ages by days since joined.',
      value: histogram_dates(
        site.data['contributors']
        .reject { |x| x['halloffame'] == 'no' }
        .map do |_, contributor|
          (Date.today - Date.parse("#{contributor['joined']}-01")).to_i
        end
      )
    },
  }
end

# File _plugins/gtn/metrics.rb, line 169
def self.generate_metrics(site)
  data = collect_metrics(site)
  data.map do |k, v|
    out = "# HELP #{k} #{v[:help]}\n# TYPE #{k} #{v[:type]}\n"

    if v[:value].is_a?(Array)
      v[:value].each do |val|
        attrs = val.except(:value).to_h
        out += "#{k}#{attrs.to_prometheus} #{val[:value]}\n"
      end
    else
      attrs = v.select { |k2, _v2| k2 != :value and k2 != :help and k2 != :type }.to_h
      out += "#{k}#{attrs.to_prometheus} #{v[:value]}\n"
    end

    out
  end.join("\n")
end

# File _plugins/gtn/metrics.rb, line 36
def self.histogram(values)
  values.map!(&:to_i)
  width = bin_width(values)
  bins = ((values.max - values.min) / width).ceil

  (0..bins).map do |bin_idx|
    left = values.min + (bin_idx * width)
    right = values.min + ((bin_idx + 1) * width)
    count = values.select { |x| left <= x and x < right }.length
    {
      :value => count,
      'le' => bin_idx == bins ? '+Inf' : right.to_s
    }
  end
end

# File _plugins/gtn/metrics.rb, line 52
def self.histogram_dates(values)
  day_bins = [1, 7, 28, 90, 365, 365 * 2, 365 * 3, 365 * 5, Float::INFINITY]
  last_bin = 0
  day_bins.map do |bin, _idx|
    count = values.select { |x| last_bin <= x and x < bin }.length
    last_bin = bin
    {
      :value => count,
      'le' => bin == day_bins[-1] ? '+Inf' : bin
    }
  end
end

# File _plugins/gtn/metrics.rb, line 21
def self.iqr(array)
  # https://stackoverflow.com/questions/8856716/calculate-interquartile-mean-from-ruby-array/8856863#8856863
  arr = array.sort
  length = arr.size
  quart = (length / 4.0).floor
  fraction = 1 - ((length / 4.0) - quart)
  new_arr = arr[quart..-(quart + 1)]
  ((fraction * (new_arr[0] + new_arr[-1])) + new_arr[1..-2].inject(:+)) / (length / 2.0)
end

# File _plugins/gtn/metrics.rb, line 65
def self.segment(values, attr)
  [
    {
      :value => values.select { |v| v.key? attr }.length,
      attr.to_s => true,
    },
    {
      :value => values.reject { |v| v.key? attr }.length,
      attr.to_s => false,
    }
  ]
end

# File _plugins/gtn/metrics.rb, line 78
def self.segment_page_by_key(values, key)
  possible_keys = values.map { |v| v.data[key].to_s }.sort.uniq
  possible_keys.map do |k|
    {
      :value => values.select { |v| v.data[key] == k }.length,
      key.to_s => k,
    }
  end
end