#-- encoding: UTF-8
#-- copyright
# OpenProject is a project management system.
# Copyright (C) 2012-2013 the OpenProject Foundation (OPF)
#
# This program is free software; you can redistribute it and/or
# modify it under the terms of the GNU General Public License version 3.
#
# OpenProject is a fork of ChiliProject, which is a fork of Redmine. The copyright follows:
# Copyright (C) 2006-2013 Jean-Philippe Lang
# Copyright (C) 2010-2013 the ChiliProject Team
#
# This program is free software; you can redistribute it and/or
# modify it under the terms of the GNU General Public License
# as published by the Free Software Foundation; either version 2
# of the License, or (at your option) any later version.
#
# This program is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
# GNU General Public License for more details.
#
# You should have received a copy of the GNU General Public License
# along with this program; if not, write to the Free Software
# Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301, USA.
#
# See doc/COPYRIGHT.rdoc for more details.
#++

class Query < ActiveRecord::Base

  @@user_filters = %w{assigned_to_id author_id watcher_id responsible_id}.freeze

  belongs_to :project
  belongs_to :user
  serialize :filters
  serialize :column_names
  serialize :sort_criteria, Array

  attr_protected :project_id #, :user_id

  validates_presence_of :name, :on => :save
  validates_length_of :name, :maximum => 255

  validate :validate_filters

  after_initialize :remember_project_scope

  @@operators = { "="   => :label_equals,
                  "!"   => :label_not_equals,
                  "o"   => :label_open_work_packages,
                  "c"   => :label_closed_work_packages,
                  "!*"  => :label_none,
                  "*"   => :label_all,
                  ">="  => :label_greater_or_equal,
                  "<="  => :label_less_or_equal,
                  "<t+" => :label_in_less_than,
                  ">t+" => :label_in_more_than,
                  "t+"  => :label_in,
                  "t"   => :label_today,
                  "w"   => :label_this_week,
                  ">t-" => :label_less_than_ago,
                  "<t-" => :label_more_than_ago,
                  "t-"  => :label_ago,
                  "~"   => :label_contains,
                  "!~"  => :label_not_contains }

  cattr_reader :operators

  @@operators_by_filter_type = { :list => [ "=", "!" ],
                                 :list_status => [ "o", "=", "!", "c", "*" ],
                                 :list_optional => [ "=", "!", "!*", "*" ],
                                 :list_subprojects => [ "*", "!*", "=" ],
                                 :date => [ "<t+", ">t+", "t+", "t", "w", ">t-", "<t-", "t-" ],
                                 :date_past => [ ">t-", "<t-", "t-", "t", "w" ],
                                 :string => [ "=", "~", "!", "!~" ],
                                 :text => [  "~", "!~" ],
                                 :integer => [ "=", ">=", "<=", "!*", "*" ] }

  cattr_reader :operators_by_filter_type

  @@available_columns = [
    QueryColumn.new(:project, :sortable => "#{Project.table_name}.name", :groupable => true),
    QueryColumn.new(:type, :sortable => "#{Type.table_name}.position", :groupable => true),
    QueryColumn.new(:parent, :sortable => ["#{WorkPackage.table_name}.root_id", "#{WorkPackage.table_name}.lft ASC"], :default_order => 'desc'),
    QueryColumn.new(:status, :sortable => "#{Status.table_name}.position", :groupable => true),
    QueryColumn.new(:priority, :sortable => "#{IssuePriority.table_name}.position", :default_order => 'desc', :groupable => true),
    QueryColumn.new(:subject, :sortable => "#{WorkPackage.table_name}.subject"),
    QueryColumn.new(:author),
    QueryColumn.new(:assigned_to, :sortable => ["#{User.table_name}.lastname", "#{User.table_name}.firstname", "#{User.table_name}.id"], :groupable => true),
    QueryColumn.new(:responsible, :sortable => ["#{User.table_name}.lastname", "#{User.table_name}.firstname", "#{User.table_name}.id"], :groupable => true),
    QueryColumn.new(:updated_at, :sortable => "#{WorkPackage.table_name}.updated_at", :default_order => 'desc'),
    QueryColumn.new(:category, :sortable => "#{Category.table_name}.name", :groupable => true),
    QueryColumn.new(:fixed_version, :sortable => ["#{Version.table_name}.effective_date", "#{Version.table_name}.name"], :default_order => 'desc', :groupable => true),
    # Put empty start_dates and due_dates in the far future rather than in the far past
    QueryColumn.new(:start_date, :sortable => ["CASE WHEN #{WorkPackage.table_name}.start_date IS NULL THEN 1 ELSE 0 END", "#{WorkPackage.table_name}.start_date"]),
    QueryColumn.new(:due_date, :sortable => ["CASE WHEN #{WorkPackage.table_name}.due_date IS NULL THEN 1 ELSE 0 END", "#{WorkPackage.table_name}.due_date"]),
    QueryColumn.new(:estimated_hours, :sortable => "#{WorkPackage.table_name}.estimated_hours"),
    QueryColumn.new(:done_ratio, :sortable => "#{WorkPackage.table_name}.done_ratio", :groupable => true),
    QueryColumn.new(:created_at, :sortable => "#{WorkPackage.table_name}.created_at", :default_order => 'desc'),
  ]
  cattr_reader :available_columns

  def initialize(attributes = nil, options = {})
    super
    self.filters ||= { 'status_id' => {:operator => "o", :values => [""]} }
  end

  # Store the fact that project is nil (used in #editable_by?)
  def remember_project_scope
    @is_for_all = project.nil?
  end

  def validate_filters
    return unless filters

    filters.each_key do |field|
      unless # filter requires one or more values
            (values_for(field) and values_for(field).first.present?) or
            # filter doesn't require any value
            ["o", "c", "!*", "*", "t", "w"].include? operator_for(field)
        errors.add :base, errors.full_message(WorkPackage.human_attribute_name(field),
                                              I18n.t('activerecord.errors.messages.invalid'))
      end
    end
  end

  def editable_by?(user)
    return false unless user
    # Admin can edit them all and regular users can edit their private queries
    return true if user.admin? || (!is_public && self.user_id == user.id)
    # Members can not edit public queries that are for all project (only admin is allowed to)
    is_public && !@is_for_all && user.allowed_to?(:manage_public_queries, project)
  end

  def available_filters
    return @available_filters if @available_filters

    types = project.nil? ? Type.find(:all, :order => 'position') : project.rolled_up_types

    @available_filters = { "status_id" => { :type => :list_status, :order => 1, :values => Status.find(:all, :order => 'position').collect{|s| [s.name, s.id.to_s] } },
                           "type_id" => { :type => :list, :order => 2, :values => types.collect{|s| [s.name, s.id.to_s] } },
                           "priority_id" => { :type => :list, :order => 3, :values => IssuePriority.all.collect{|s| [s.name, s.id.to_s] } },
                           "subject" => { :type => :text, :order => 8 },
                           "created_at" => { :type => :date_past, :order => 9 },
                           "updated_at" => { :type => :date_past, :order => 10 },
                           "start_date" => { :type => :date, :order => 11 },
                           "due_date" => { :type => :date, :order => 12 },
                           "estimated_hours" => { :type => :integer, :order => 13 },
                           "done_ratio" =>  { :type => :integer, :order => 14 }}

    principals = []
    if project
      principals += project.principals.sort
    else
      all_projects = Project.visible.all
      if all_projects.any?
        # members of visible projects
        principals += Principal.active.find(:all, :conditions => ["#{User.table_name}.id IN (SELECT DISTINCT user_id FROM members WHERE project_id IN (?))", all_projects.collect(&:id)]).sort

        # project filter
        project_values = []
        Project.project_tree(all_projects) do |p, level|
          prefix = (level > 0 ? ('--' * level + ' ') : '')
          project_values << ["#{prefix}#{p.name}", p.id.to_s]
        end
        @available_filters["project_id"] = { :type => :list, :order => 1, :values => project_values} unless project_values.empty?
      end
    end
    principals_by_class = principals.group_by(&:class)

    user_values = principals_by_class[User].present? ?
                    principals_by_class[User].collect{ |s| [s.name, s.id.to_s] }.sort :
                    []

    group_values = Setting.work_package_group_assignment? && principals_by_class[Group].present? ?
                      principals_by_class[Group].collect{ |s| [s.name, s.id.to_s] }.sort :
                      []

    assigned_to_values = (user_values + group_values).sort
    assigned_to_values = [["<< #{l(:label_me)} >>", "me"]] + assigned_to_values if User.current.logged?
    @available_filters["assigned_to_id"] = { :type => :list_optional, :order => 4, :values => assigned_to_values } unless assigned_to_values.empty?

    author_values = []
    author_values << ["<< #{l(:label_me)} >>", "me"] if User.current.logged?
    author_values += user_values
    @available_filters["author_id"] = { :type => :list, :order => 5, :values => author_values } unless author_values.empty?


    group_values = Group.all.collect {|g| [g.name, g.id.to_s] }
    @available_filters["member_of_group"] = { :type => :list_optional, :order => 6, :values => group_values, :name => I18n.t('query_fields.member_of_group') } unless group_values.empty?

    role_values = Role.givable.collect {|r| [r.name, r.id.to_s] }
    @available_filters["assigned_to_role"] = { :type => :list_optional, :order => 7, :values => role_values, :name => I18n.t('query_fields.assigned_to_role') } unless role_values.empty?

    @available_filters["responsible_id"] = { :type => :list_optional, :order => 4, :values => assigned_to_values } unless assigned_to_values.empty?

    if User.current.logged?
      # populate the watcher list with the same user list as other user filters if the user has the :view_work_package_watchers permission in at least one project
      # TODO: this could be differentiated more, e.g. all users could watch issues in public projects, but won't necessarily be shown here
      watcher_values = [["<< #{l(:label_me)} >>", "me"]]
      user_values.each { |v| watcher_values << v } if User.current.allowed_to_globally?(:view_work_packages_watchers, {})
      @available_filters["watcher_id"] = { :type => :list, :order => 15, :values => watcher_values }
    end

    if project
      # project specific filters
      categories = project.categories.all
      unless categories.empty?
        @available_filters["category_id"] = { :type => :list_optional, :order => 6, :values => categories.collect{|s| [s.name, s.id.to_s] } }
      end
      versions = project.shared_versions.all
      unless versions.empty?
        @available_filters["fixed_version_id"] = { :type => :list_optional, :order => 7, :values => versions.sort.collect{|s| ["#{s.project.name} - #{s.name}", s.id.to_s] } }
      end
      unless project.leaf?
        subprojects = project.descendants.visible.all
        unless subprojects.empty?
          @available_filters["subproject_id"] = { :type => :list_subprojects, :order => 13, :values => subprojects.collect{|s| [s.name, s.id.to_s] }, :name => I18n.t('query_fields.subproject_id') }
        end
      end
      add_custom_fields_filters(project.all_work_package_custom_fields)
    else
      # global filters for cross project issue list
      system_shared_versions = Version.visible.find_all_by_sharing('system')
      unless system_shared_versions.empty?
        @available_filters["fixed_version_id"] = { :type => :list_optional, :order => 7, :values => system_shared_versions.sort.collect{|s| ["#{s.project.name} - #{s.name}", s.id.to_s] } }
      end
      add_custom_fields_filters(WorkPackageCustomField.find(:all, :conditions => {:is_filter => true, :is_for_all => true}))
    end
    @available_filters
  end

  def add_filter(field, operator, values)
    # values must be an array
    return unless values and values.is_a? Array # and !values.first.empty?
    # check if field is defined as an available filter
    if available_filters.has_key? field
      filter_options = available_filters[field]
      # check if operator is allowed for that filter
      #if @@operators_by_filter_type[filter_options[:type]].include? operator
      #  allowed_values = values & ([""] + (filter_options[:values] || []).collect {|val| val[1]})
      #  filters[field] = {:operator => operator, :values => allowed_values } if (allowed_values.first and !allowed_values.first.empty?) or ["o", "c", "!*", "*", "t"].include? operator
      #end
      filters[field] = {:operator => operator, :values => values }
    end
  end

  def add_short_filter(field, expression)
    return unless expression
    parms = expression.scan(/\A(o|c|!\*|!|\*)?(.*)\z/).first
    add_filter field, (parms[0] || "="), [parms[1] || ""]
  end

  # Add multiple filters using +add_filter+
  def add_filters(fields, operators, values)
    if fields.is_a?(Array) && operators.is_a?(Hash) && values.is_a?(Hash)
      fields.each do |field|
        add_filter(field, operators[field], values[field])
      end
    end
  end

  def has_filter?(field)
    filters and filters[field]
  end

  def operator_for(field)
    has_filter?(field) ? filters[field][:operator] : nil
  end

  def values_for(field)
    has_filter?(field) ? filters[field][:values] : nil
  end

  def label_for(field)
    label = available_filters[field][:name] if available_filters.has_key?(field)
    label ||= field.gsub(/\_id\z/, "")
  end

  def available_columns
    return @available_columns if @available_columns
    @available_columns = ::Query.available_columns
    @available_columns += (project ?
                            project.all_work_package_custom_fields :
                            WorkPackageCustomField.find(:all)
                           ).collect {|cf| ::QueryCustomFieldColumn.new(cf) }
    if WorkPackage.done_ratio_disabled?
      @available_columns.select! {|column| column.name != :done_ratio }.length
    end
    @available_columns
  end

  def self.available_columns=(v)
    self.available_columns = (v)
  end

  def self.add_available_column(column)
    self.available_columns << (column) if column.is_a?(QueryColumn)
  end

  # Returns an array of columns that can be used to group the results
  def groupable_columns
    available_columns.select {|c| c.groupable}
  end

  # Returns a Hash of columns and the key for sorting
  def sortable_columns
    {'id' => "#{WorkPackage.table_name}.id"}.merge(available_columns.inject({}) {|h, column|
                                               h[column.name.to_s] = column.sortable
                                               h
                                             })
  end

  def columns
    if has_default_columns?
      available_columns.select do |c|
        # Adds the project column by default for cross-project lists
        Setting.work_package_list_default_columns.include?(c.name.to_s) || (c.name == :project && project.nil?)
      end
    else
      # preserve the column_names order
      column_names.collect {|name| available_columns.find {|col| col.name == name}}.compact
    end
  end

  def column_names=(names)
    if names
      names = names.inject([]) { |out, e| out += e.to_s.split(',') }
      names = names.select {|n| n.is_a?(Symbol) || !n.blank? }
      names = names.collect {|n| n.is_a?(Symbol) ? n : n.to_sym }
      # Set column_names to nil if default columns
      if names.map(&:to_s) == Setting.work_package_list_default_columns
        names = nil
      end
    end
    write_attribute(:column_names, names)
  end

  def has_column?(column)
    column_names && column_names.include?(column.name)
  end

  def has_default_columns?
    column_names.nil? || column_names.empty?
  end

  def sort_criteria=(arg)
    c = []
    if arg.is_a?(Hash)
      arg = arg.keys.sort.collect {|k| arg[k]}
    end
    c = arg.select {|k,o| !k.to_s.blank?}.slice(0,3).collect {|k,o| [k.to_s, o == 'desc' ? o : 'asc']}
    write_attribute(:sort_criteria, c)
  end

  def sort_criteria
    read_attribute(:sort_criteria) || []
  end

  def sort_criteria_key(arg)
    sort_criteria && sort_criteria[arg] && sort_criteria[arg].first
  end

  def sort_criteria_order(arg)
    sort_criteria && sort_criteria[arg] && sort_criteria[arg].last
  end

  # Returns the SQL sort order that should be prepended for grouping
  def group_by_sort_order
    if grouped? && (column = group_by_column)
      column.sortable.is_a?(Array) ?
        column.sortable.collect {|s| "#{s} #{column.default_order}"}.join(',') :
        "#{column.sortable} #{column.default_order}"
    end
  end

  # Returns true if the query is a grouped query
  def grouped?
    !group_by_column.nil?
  end

  def display_sums?
    display_sums && any_summable_columns?
  end

  def any_summable_columns?
    Setting.work_package_list_summable_columns.any?
  end

  def group_by_column
    groupable_columns.detect {|c| c.groupable && c.name.to_s == group_by}
  end

  def group_by_statement
    group_by_column.try(:groupable)
  end

  def project_statement
    project_clauses = []
    if project && !project.descendants.active.empty?
      ids = [project.id]
      if has_filter?("subproject_id")
        case operator_for("subproject_id")
        when '='
          # include the selected subprojects
          ids += values_for("subproject_id").each(&:to_i)
        when '!*'
          # main project only
        else
          # all subprojects
          ids += project.descendants.collect(&:id)
        end
      elsif Setting.display_subprojects_work_packages?
        ids += project.descendants.collect(&:id)
      end
      project_clauses << "#{Project.table_name}.id IN (%s)" % ids.join(',')
    elsif project
      project_clauses << "#{Project.table_name}.id = %d" % project.id
    end
    project_clauses <<  WorkPackage.visible_condition(User.current)
    project_clauses.join(' AND ')
  end

  def statement
    # filters clauses
    filters_clauses = []
    filters.each_key do |field|
      next if field == "subproject_id"
      v = values_for(field).clone
      next unless v and !v.empty?
      operator = operator_for(field)

      # "me" value subsitution
      if @@user_filters.include? field
        if v.delete("me")
          if User.current.logged?
            v.push(User.current.id.to_s)
            v += User.current.group_ids.map(&:to_s) if field == 'assigned_to_id'
          else
            v.push("0")
          end
        end
      end

      sql = ''
      if field =~ /\Acf_(\d+)\z/
        # custom field
        db_table = CustomValue.table_name
        db_field = 'value'
        is_custom_filter = true
        sql << "#{WorkPackage.table_name}.id IN (SELECT #{WorkPackage.table_name}.id FROM #{WorkPackage.table_name} LEFT OUTER JOIN #{db_table} ON #{db_table}.customized_type='WorkPackage' AND #{db_table}.customized_id=#{WorkPackage.table_name}.id AND #{db_table}.custom_field_id=#{$1} WHERE "
        sql << sql_for_field(field, operator, v, db_table, db_field, true) + ')'
      elsif field == 'watcher_id'
        db_table = Watcher.table_name
        db_field = 'user_id'
        if User.current.admin?
          # Admins can always see all watchers
          sql << "#{WorkPackage.table_name}.id #{operator == '=' ? 'IN' : 'NOT IN'} (SELECT #{db_table}.watchable_id FROM #{db_table} WHERE #{db_table}.watchable_type='WorkPackage' AND #{sql_for_field field, '=', v, db_table, db_field})"
        else
          sql_parts = []
          if User.current.logged? && user_id = v.delete(User.current.id.to_s)
            # a user can always see his own watched issues
            sql_parts << "#{WorkPackage.table_name}.id #{operator == '=' ? 'IN' : 'NOT IN'} (SELECT #{db_table}.watchable_id FROM #{db_table} WHERE #{db_table}.watchable_type='WorkPackage' AND #{sql_for_field field, '=', [user_id], db_table, db_field})"
          end
          # filter watchers only in projects the user has the permission to view watchers in
          project_ids = User.current.projects_by_role.collect {|r,p| p if r.permissions.include? :view_work_package_watchers}.flatten.compact.collect(&:id).uniq
          sql_parts << "#{WorkPackage.table_name}.id #{operator == '=' ? 'IN' : 'NOT IN'} (SELECT #{db_table}.watchable_id FROM #{db_table} WHERE #{db_table}.watchable_type='WorkPackage' AND #{sql_for_field field, '=', v, db_table, db_field})"\
                       " AND #{Project.table_name}.id IN (#{project_ids.join(',')})" unless project_ids.empty?
          sql << "(#{sql_parts.join(' OR ')})"
        end
      elsif field == "member_of_group" # named field
        if operator == '*' # Any group
          groups = Group.all
          operator = '=' # Override the operator since we want to find by assigned_to
        elsif operator == "!*"
          groups = Group.all
          operator = '!' # Override the operator since we want to find by assigned_to
        else
          groups = Group.find_all_by_id(v)
        end
        groups ||= []

        members_of_groups = groups.inject([]) {|user_ids, group|
          if group && group.user_ids.present?
            user_ids << group.user_ids
          end
          user_ids.flatten.uniq.compact
        }.sort.collect(&:to_s)

        sql << '(' + sql_for_field("assigned_to_id", operator, members_of_groups, WorkPackage.table_name, "assigned_to_id", false) + ')'

      elsif field == "assigned_to_role" # named field
        if operator == "*" # Any Role
          roles = Role.givable
          operator = '=' # Override the operator since we want to find by assigned_to
        elsif operator == "!*" # No role
          roles = Role.givable
          operator = '!' # Override the operator since we want to find by assigned_to
        else
          roles = Role.givable.find_all_by_id(v)
        end
        roles ||= []

        members_of_roles = roles.inject([]) {|user_ids, role|
          if role && role.members
            user_ids << role.members.collect(&:user_id)
          end
          user_ids.flatten.uniq.compact
        }.sort.collect(&:to_s)

        sql << '(' + sql_for_field("assigned_to_id", operator, members_of_roles, WorkPackage.table_name, "assigned_to_id", false) + ')'
      else
        # regular field
        db_table = WorkPackage.table_name
        db_field = field
        sql << '(' + sql_for_field(field, operator, v, db_table, db_field) + ')'
      end
      filters_clauses << sql

    end if filters and valid?

    (filters_clauses << project_statement).join(' AND ')
  end

  # Returns the result set
  # Valid options are :order, :include, :conditions
  def results(options={})
    Results.new(self, options)
  end

  # Returns the journals
  # Valid options are :order, :offset, :limit
  def work_package_journals(options={})
    query = Journal.includes(:user)
                   .where(journable_type: WorkPackage.to_s)
                   .joins("INNER JOIN work_packages ON work_packages.id = journals.journable_id")
                   .joins("INNER JOIN projects ON work_packages.project_id = projects.id")
                   .joins("INNER JOIN users AS authors ON work_packages.author_id = authors.id")
                   .joins("INNER JOIN types ON work_packages.type_id = types.id")
                   .joins("INNER JOIN statuses ON work_packages.status_id = statuses.id")
                   .where(statement)
                   .order(options[:order])
                   .limit(options[:limit])
                   .offset(options[:offset])

    query.find :all
  rescue ::ActiveRecord::StatementInvalid => e
    raise ::Query::StatementInvalid.new(e.message)
  end

  private

  # Helper method to generate the WHERE sql for a +field+, +operator+ and a +value+
  def sql_for_field(field, operator, value, db_table, db_field, is_custom_filter=false)
    sql = ''
    case operator
    when "="
      if value.present? then
        if (value.include?("-1")) then
          sql = "#{db_table}.#{db_field} IS NULL OR "
        end

        sql += "#{db_table}.#{db_field} IN (" + value.collect{|val| "'#{connection.quote_string(val)}'"}.join(",") + ")"
      else
        # empty set of allowed values produces no result
        sql = "0=1"
      end
    when "!"
      if value.present?
        sql = "(#{db_table}.#{db_field} IS NULL OR #{db_table}.#{db_field} NOT IN (" + value.collect{|val| "'#{connection.quote_string(val)}'"}.join(",") + "))"
      else
        # empty set of forbidden values allows all results
        sql = "1=1"
      end
    when "!*"
      sql = "#{db_table}.#{db_field} IS NULL"
      sql << " OR #{db_table}.#{db_field} = ''" if is_custom_filter
    when "*"
      sql = "#{db_table}.#{db_field} IS NOT NULL"
      sql << " AND #{db_table}.#{db_field} <> ''" if is_custom_filter
    when ">="
      if is_custom_filter
        sql = "#{db_table}.#{db_field} != '' AND CAST(#{db_table}.#{db_field} AS decimal(60,4)) >= #{value.first.to_f}"
      else
        sql = "#{db_table}.#{db_field} >= #{value.first.to_f}"
      end
    when "<="
      if is_custom_filter
        sql = "#{db_table}.#{db_field} != '' AND CAST(#{db_table}.#{db_field} AS decimal(60,4)) <= #{value.first.to_f}"
      else
        sql = "#{db_table}.#{db_field} <= #{value.first.to_f}"
      end
    when "o"
      sql = "#{Status.table_name}.is_closed=#{connection.quoted_false}" if field == "status_id"
    when "c"
      sql = "#{Status.table_name}.is_closed=#{connection.quoted_true}" if field == "status_id"
    when ">t-"
      sql = date_range_clause(db_table, db_field, - value.first.to_i, 0)
    when "<t-"
      sql = date_range_clause(db_table, db_field, nil, - value.first.to_i)
    when "t-"
      sql = date_range_clause(db_table, db_field, - value.first.to_i, - value.first.to_i)
    when ">t+"
      sql = date_range_clause(db_table, db_field, value.first.to_i, nil)
    when "<t+"
      sql = date_range_clause(db_table, db_field, 0, value.first.to_i)
    when "t+"
      sql = date_range_clause(db_table, db_field, value.first.to_i, value.first.to_i)
    when "t"
      sql = date_range_clause(db_table, db_field, 0, 0)
    when "w"
      from = l(:general_first_day_of_week) == '7' ?
      # week starts on sunday
      ((Date.today.cwday == 7) ? Time.now.at_beginning_of_day : Time.now.at_beginning_of_week - 1.day) :
        # week starts on monday (Rails default)
        Time.now.at_beginning_of_week
      sql = "#{db_table}.#{db_field} BETWEEN '%s' AND '%s'" % [connection.quoted_date(from), connection.quoted_date(from + 7.days)]
    when "~"
      sql = "LOWER(#{db_table}.#{db_field}) LIKE '%#{connection.quote_string(value.first.to_s.downcase)}%'"
    when "!~"
      sql = "LOWER(#{db_table}.#{db_field}) NOT LIKE '%#{connection.quote_string(value.first.to_s.downcase)}%'"
    end

    return sql
  end

  def add_custom_fields_filters(custom_fields)
    available_filters # compute default available_filters
    return available_filters if available_filters.any? { |key, _| key.starts_with? 'cf_' }

    custom_fields.select(&:is_filter?).each do |field|
      case field.field_format
      when "int", "float"
        options = { :type => :integer, :order => 20 }
      when "text"
        options = { :type => :text, :order => 20 }
      when "list"
        options = { :type => :list_optional, :values => field.possible_values, :order => 20}
      when "date"
        options = { :type => :date, :order => 20 }
      when "bool"
        options = { :type => :list, :values => [[l(:general_text_yes), "1"], [l(:general_text_no), "0"]], :order => 20 }
      when "user", "version"
        next unless project
        options = { :type => :list_optional, :values => field.possible_values_options(project), :order => 20}
      else
        options = { :type => :string, :order => 20 }
      end
      @available_filters["cf_#{field.id}"] = options.merge({ :name => field.name })
    end
  end

  # Returns a SQL clause for a date or datetime field.
  def date_range_clause(table, field, from, to)
    s = []
    if from
      s << ("#{table}.#{field} > '%s'" % [connection.quoted_date((Date.yesterday + from).to_time.end_of_day)])
    end
    if to
      s << ("#{table}.#{field} <= '%s'" % [connection.quoted_date((Date.today + to).to_time.end_of_day)])
    end
    s.join(' AND ')
  end
end