ministryofjustice/peoplefinder

class MembershipChangesPresenter < ChangesPresenter
  SENTENCE_EXCEPTIONS = %w[group_id role leader subscribed].freeze

  class ::Hash
    def to_membership_set
      MembershipChangeSet.new(deep_symbolize_keys)
    end
  end

  def format(raw_change_set)
    h = {}
    raw_change_set&.each do |membership_key, raw_changes|
      self.current_team = membership_key
      h[membership_key] = {}
      membership_template(h[membership_key], raw_changes)
    end
    h.deep_symbolize_keys
  end

  def each(&block)
    @changes.each do |membership|
      membership.each(&block)
    end
  end

  def each_pair
    @changes&.each_pair do |_membership, membership_changes|
      membership_changes.each_pair do |field, change|
        yield field, change[:message]
      end
    end
  end

private

  attr_reader :current_team

  def current_team=(membership_key)
    @current_team = Group.find(membership_key.to_s.sub("membership_", ""))
  end

  def membership_template(memo, raw_changes)
    set = raw_changes.to_membership_set
    if set.added? || set.removed?
      memo.merge! added_removed_template(set)
    else
      amended_changes(memo, raw_changes)
    end
  end

  def added_removed_template(set)
    key = set.added? ? :added : :removed
    template(key) do |h|
      h[key][:raw] = set.raw_changes
      h[key][:message] = set.sentence
    end
  end

  def amended_changes(memo, raw_changes)
    raw_changes.each do |field, raw_change|
      if bespoke_rule? field
        memo.merge! send("#{field}_change".to_sym, field, raw_change)
      else
        memo.merge! default(field, raw_change)
      end
    end
  end

  def bespoke_rule?(field)
    SENTENCE_EXCEPTIONS.include? field.to_s
  end

  def leader_change(field, raw_change)
    template(field) do |h|
      h[field][:raw] = raw_change
      h[field][:message] = leader_change_sentence(raw_change)
    end
  end

  def leader_change_sentence(leader_change)
    leader = Change.new(leader_change)
    if leader.addition?
      "Made you leader of the #{current_team} team"
    elsif leader.removal?
      "Removed you as leader of the #{current_team} team"
    end
  end

  def subscribed_change(field, raw_change)
    template(field) do |h|
      h[field][:raw] = raw_change
      h[field][:message] = subscribed_change_sentence(raw_change)
    end
  end

  def subscribed_change_sentence(subscribed_change)
    subscribed = Change.new(subscribed_change)
    subscribed_text(subscribed.addition?)
  end

  def subscribed_text(subscribed)
    "Changed your notification settings so you " \
      "#{subscribed ? 'do' : 'don\'t'}" \
      " get notifications if changes are made to the #{current_team} team"
  end

  def role_change(field, raw_change)
    template(field) do |h|
      h[field][:raw] = raw_change
      h[field][:message] = role_change_sentence(raw_change)
    end
  end

  def role_change_sentence(raw_change)
    change = Change.new(raw_change)
    if change.addition?
      "Added the role #{change.new_val} in the #{current_team} team"
    elsif change.removal?
      "Removed the role #{change.old_val} in the #{current_team} team"
    elsif change.modification?
      "Changed your role from #{change.old_val} to #{change.new_val} in the #{current_team} team"
    end
  end

  def group_id_change(field, raw_change)
    template(field) do |h|
      h[field][:raw] = raw_change
      h[field][:message] = team_change_sentence(raw_change)
    end
  end

  def team_change_sentence(raw_change)
    change = Change.new(raw_change)
    if change.addition?
      "Added you to #{team_name(change.new_val)} team"
    elsif change.removal?
      "Removed you from #{team_name(change.old_val)} team"
    elsif change.modification?
      "Changed your membership of #{team_name(change.old_val)} team to #{team_name(change.new_val)} team"
    end
  end

  def team_name(id)
    "the #{Group.find(id).name}"
  rescue ActiveRecord::RecordNotFound
    "a no longer existing"
  end
end