# IssuableFinder
#
# Used to filter Issues and MergeRequests collections by set of params
#
# Arguments:
#   klass - actual class like Issue or MergeRequest
#   current_user - which user use
#   params:
#     scope: 'created-by-me' or 'assigned-to-me' or 'all'
#     state: 'opened' or 'closed' or 'all'
#     group_id: integer
#     project_id: integer
#     milestone_title: string
#     assignee_id: integer
#     search: string
#     label_name: string
#     sort: string
#     non_archived: boolean
#     iids: integer[]
#
class IssuableFinder
  NONE = '0'.freeze

  attr_accessor :current_user, :params

  def initialize(current_user, params = {})
    @current_user = current_user
    @params = params
  end

  def execute
    items = init_collection
    items = by_scope(items)
    items = by_state(items)
    items = by_group(items)
    items = by_search(items)
    items = by_assignee(items)
    items = by_author(items)
    items = by_due_date(items)
    items = by_non_archived(items)
    items = by_iids(items)
    items = by_milestone(items)
    items = by_label(items)

    # Filtering by project HAS TO be the last because we use the project IDs yielded by the issuable query thus far
    items = by_project(items)
    sort(items)
  end

  def find(*params)
    execute.find(*params)
  end

  def find_by(*params)
    execute.find_by(*params)
  end

  # We often get counts for each state by running a query per state, and
  # counting those results. This is typically slower than running one query
  # (even if that query is slower than any of the individual state queries) and
  # grouping and counting within that query.
  #
  def count_by_state
    count_params = params.merge(state: nil, sort: nil)
    labels_count = label_names.any? ? label_names.count : 1
    finder = self.class.new(current_user, count_params)
    counts = Hash.new(0)

    # Searching by label includes a GROUP BY in the query, but ours will be last
    # because it is added last. Searching by multiple labels also includes a row
    # per issuable, so we have to count those in Ruby - which is bad, but still
    # better than performing multiple queries.
    #
    finder.execute.reorder(nil).group(:state).count.each do |key, value|
      counts[Array(key).last.to_sym] += value / labels_count
    end

    counts[:all] = counts.values.sum
    counts[:opened] += counts[:reopened]

    counts
  end

  def find_by!(*params)
    execute.find_by!(*params)
  end

  def group
    return @group if defined?(@group)

    @group =
      if params[:group_id].present?
        Group.find(params[:group_id])
      else
        nil
      end
  end

  def project?
    params[:project_id].present?
  end

  def project
    return @project if defined?(@project)

    project = Project.find(params[:project_id])
    project = nil unless Ability.allowed?(current_user, :"read_#{klass.to_ability_name}", project)

    @project = project
  end

  def projects(items = nil)
    return @projects = project if project?

    projects =
      if current_user && params[:authorized_only].presence && !current_user_related?
        current_user.authorized_projects
      elsif group
        GroupProjectsFinder.new(group: group, current_user: current_user).execute
      else
        ProjectsFinder.new(current_user: current_user, project_ids_relation: item_project_ids(items)).execute
      end

    @projects = projects.with_feature_available_for_user(klass, current_user).reorder(nil)
  end

  def search
    params[:search].presence
  end

  def milestones?
    params[:milestone_title].present?
  end

  def filter_by_no_milestone?
    milestones? && params[:milestone_title] == Milestone::None.title
  end

  def milestones
    return @milestones if defined?(@milestones)

    @milestones =
      if milestones?
        scope = Milestone.where(project_id: projects)

        scope.where(title: params[:milestone_title])
      else
        Milestone.none
      end
  end

  def labels?
    params[:label_name].present?
  end

  def filter_by_no_label?
    labels? && params[:label_name].include?(Label::None.title)
  end

  def labels
    return @labels if defined?(@labels)

    @labels =
      if labels? && !filter_by_no_label?
        LabelsFinder.new(current_user, project_ids: projects, title: label_names).execute(skip_authorization: true)
      else
        Label.none
      end
  end

  def assignee_id?
    params[:assignee_id].present? && params[:assignee_id] != NONE
  end

  def assignee_username?
    params[:assignee_username].present? && params[:assignee_username] != NONE
  end

  def no_assignee?
    # Assignee_id takes precedence over assignee_username
    params[:assignee_id] == NONE || params[:assignee_username] == NONE
  end

  def assignee
    return @assignee if defined?(@assignee)

    @assignee =
      if assignee_id?
        User.find_by(id: params[:assignee_id])
      elsif assignee_username?
        User.find_by(username: params[:assignee_username])
      else
        nil
      end
  end

  def author_id?
    params[:author_id].present? && params[:author_id] != NONE
  end

  def author_username?
    params[:author_username].present? && params[:author_username] != NONE
  end

  def no_author?
    # author_id takes precedence over author_username
    params[:author_id] == NONE || params[:author_username] == NONE
  end

  def author
    return @author if defined?(@author)

    @author =
      if author_id?
        User.find_by(id: params[:author_id])
      elsif author_username?
        User.find_by(username: params[:author_username])
      else
        nil
      end
  end

  private

  def init_collection
    klass.all
  end

  def by_scope(items)
    case params[:scope]
    when 'created-by-me', 'authored'
      items.where(author_id: current_user.id)
    when 'assigned-to-me'
      items.where(assignee_id: current_user.id)
    else
      items
    end
  end

  def by_state(items)
    case params[:state].to_s
    when 'closed'
      items.closed
    when 'merged'
      items.respond_to?(:merged) ? items.merged : items.closed
    when 'opened'
      items.opened
    else
      items
    end
  end

  def by_group(items)
    # Selection by group is already covered by `by_project` and `projects`
    items
  end

  def by_project(items)
    items =
      if project?
        items.of_projects(projects(items)).references_project
      elsif projects(items)
        items.merge(projects(items).reorder(nil)).join_project
      else
        items.none
      end

    items
  end

  def by_search(items)
    search ? items.full_search(search) : items
  end

  def by_iids(items)
    params[:iids].present? ? items.where(iid: params[:iids]) : items
  end

  def sort(items)
    # Ensure we always have an explicit sort order (instead of inheriting
    # multiple orders when combining ActiveRecord::Relation objects).
    params[:sort] ? items.sort(params[:sort], excluded_labels: label_names) : items.reorder(id: :desc)
  end

  def by_assignee(items)
    if assignee
      items = items.where(assignee_id: assignee.id)
    elsif no_assignee?
      items = items.where(assignee_id: nil)
    elsif assignee_id? || assignee_username? # assignee not found
      items = items.none
    end

    items
  end

  def by_author(items)
    if author
      items = items.where(author_id: author.id)
    elsif no_author?
      items = items.where(author_id: nil)
    elsif author_id? || author_username? # author not found
      items = items.none
    end

    items
  end

  def filter_by_upcoming_milestone?
    params[:milestone_title] == Milestone::Upcoming.name
  end

  def filter_by_started_milestone?
    params[:milestone_title] == Milestone::Started.name
  end

  def by_milestone(items)
    if milestones?
      if filter_by_no_milestone?
        items = items.left_joins_milestones.where(milestone_id: [-1, nil])
      elsif filter_by_upcoming_milestone?
        upcoming_ids = Milestone.upcoming_ids_by_projects(projects(items))
        items = items.left_joins_milestones.where(milestone_id: upcoming_ids)
      elsif filter_by_started_milestone?
        items = items.left_joins_milestones.where('milestones.start_date <= NOW()')
      else
        items = items.with_milestone(params[:milestone_title])
        items_projects = projects(items)

        if items_projects
          items = items.where(milestones: { project_id: items_projects })
        end
      end
    end

    items
  end

  def by_label(items)
    if labels?
      if filter_by_no_label?
        items = items.without_label
      else
        items = items.with_label(label_names, params[:sort])
        items_projects = projects(items)

        if items_projects
          label_ids = LabelsFinder.new(current_user, project_ids: items_projects).execute(skip_authorization: true).select(:id)
          items = items.where(labels: { id: label_ids })
        end
      end
    end

    items
  end

  def by_due_date(items)
    if due_date?
      if filter_by_no_due_date?
        items = items.without_due_date
      elsif filter_by_overdue?
        items = items.due_before(Date.today)
      elsif filter_by_due_this_week?
        items = items.due_between(Date.today.beginning_of_week, Date.today.end_of_week)
      elsif filter_by_due_this_month?
        items = items.due_between(Date.today.beginning_of_month, Date.today.end_of_month)
      end
    end

    items
  end

  def filter_by_no_due_date?
    due_date? && params[:due_date] == Issue::NoDueDate.name
  end

  def filter_by_overdue?
    due_date? && params[:due_date] == Issue::Overdue.name
  end

  def filter_by_due_this_week?
    due_date? && params[:due_date] == Issue::DueThisWeek.name
  end

  def filter_by_due_this_month?
    due_date? && params[:due_date] == Issue::DueThisMonth.name
  end

  def due_date?
    params[:due_date].present? && klass.column_names.include?('due_date')
  end

  def label_names
    if labels?
      params[:label_name].is_a?(String) ? params[:label_name].split(',') : params[:label_name]
    else
      []
    end
  end

  def by_non_archived(items)
    params[:non_archived].present? ? items.non_archived : items
  end

  def current_user_related?
    params[:scope] == 'created-by-me' || params[:scope] == 'authored' || params[:scope] == 'assigned-to-me'
  end
end