#-- copyright
# OpenProject is an open source project management software.
# Copyright (C) the OpenProject GmbH
#
# 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 COPYRIGHT and LICENSE files for more details.
#++

module API
  module Decorators
    module Sql
      module Hal
        extend ActiveSupport::Concern

        TO_BE_REMOVED = "_to_be_removed_".freeze

        included do
          extend ::API::V3::Utilities::PathHelper

          class_attribute :embed_map,
                          default: {}
          class_attribute :properties,
                          default: {}
          class_attribute :links,
                          default: {}
          class_attribute :embeddeds,
                          default: {}
        end

        class_methods do
          def properties_sql(select, walker_results)
            selected_properties(select)
              .map do |name, options|
              representation = if options[:representation]
                                 instance_exec(walker_results, &options[:representation])
                               else
                                 options[:column]
                               end

              if options[:render_if]
                render_if_condition(name,
                                    options[:render_if].call(walker_results),
                                    representation)
              else
                <<-SQL.squish
                 '#{name}', #{representation}
                SQL
              end
            end.join(", ")
          end

          def property(name,
                       column: name,
                       representation: nil,
                       render_if: nil,
                       join: nil)
            properties[name] = { column:, render_if:, representation:, join: }
          end

          def joins(select, scope)
            selected_joins(select).each do |name, column|
              options = column[:join]
              condition = <<~SQL.squish
                LEFT OUTER JOIN
                  #{options[:table]} #{options[:alias] || name.to_s.pluralize}
                ON #{options[:condition]}
              SQL
              scope = scope.joins(condition).select(options[:select])
            end

            scope
          end

          def link(name,
                   column: nil,
                   path: nil,
                   title: nil,
                   href: nil,
                   join: nil,
                   render_if: nil,
                   sql: nil,
                   **additional_properties)
            links[name] = { column:,
                            path:,
                            title:,
                            join:,
                            href:,
                            render_if:,
                            sql:,
                            additional_properties: }
          end

          def links_selects(select, walker_result)
            selected_links(select)
              .map do |name, link|
              if link[:sql]
                link_from_sql(name, link)
              else
                attributes = link_attributes(name, link, walker_result)

                if link[:render_if]
                  render_if_condition(name,
                                      link[:render_if].call(walker_result),
                                      "json_build_object(#{attributes.join(', ')})")
                else
                  link_with_default(name, attributes)
                end
              end
            end
              .join(", ")
          end

          def embedded(name,
                       representation: nil)
            embeddeds[name] = { representation: }
          end

          def embedded_selects(_selects, walker_results)
            # TODO: This does not yet support signaling
            embeddeds
              .map do |name, link|
              representation = if link[:representation]
                                 link[:representation].call(walker_results)
                               else
                                 link[:column]
                               end

              next unless representation

              <<-SQL.squish
               '#{name}', #{representation}
              SQL
            end
              .flatten
              .join(", ")
          end

          def select_sql(select, walker_result)
            <<~SELECT
              json_build_object(
                #{json_object_string(select, walker_result)}
              )::jsonb - '#{TO_BE_REMOVED}'
            SELECT
          end

          def ctes(_walker_result)
            {}
          end

          def to_sql(walker_result)
            ctes = walker_result.ctes.map do |key, sql|
              <<~SQL.squish
                #{key} AS (
                  #{sql}
                )
              SQL
            end

            ctes_sql = ctes.any? ? "WITH #{ctes.join(', ')}" : ""

            <<~SQL.squish
              #{ctes_sql}

              SELECT
                #{walker_result.selects} AS json
              FROM
                #{select_from(walker_result)}
            SQL
          end

          protected

          def json_object_string(select, walker_result)
            [properties_sql(select, walker_result),
             select_links(select, walker_result),
             select_embedded(select, walker_result)]
              .compact_blank
              .join(", ")
          end

          # All properties and links that the client can correctly signal to have selected.
          def valid_selects
            links.keys + properties.keys + [:*]
          end

          private

          def select_embedded(select, walker_result)
            namespaced_json_object("_embedded") do
              embedded_selects(select, walker_result)
            end
          end

          def select_links(select, walker_result)
            links_section = namespaced_json_object("_links") do
              links_selects(select, walker_result)
            end

            # If links come with a condition, they receive the key TO_BE_REMOVED if that condition fails
            # and we remove it here.
            "#{links_section}::jsonb - '#{TO_BE_REMOVED}'" if links_section
          end

          def select_from(walker_result)
            "(#{walker_result.projection_scope.to_sql}) element"
          end

          def selected_links(select)
            selected(select, links)
          end

          def selected_properties(select)
            selected(select, properties)
          end

          def selected_joins(select)
            selected_links(select)
            .merge(selected_properties(select))
            .select { |_, column| column[:join] }
          end

          def selected(select, list)
            selects = cleaned_selects(select)

            ensure_valid_selects(selects)

            if selects.include?(:*)
              list
            else
              list.slice(*selects)
            end
          end

          def cleaned_selects(select)
            select
              .symbolize_keys
              .select { |_, v| v.empty? }
              .keys
          end

          def ensure_valid_selects(requested)
            invalid = requested - valid_selects

            raise API::Errors::InvalidSignal.new(invalid, valid_selects, :select) if invalid.any?
          end

          def namespaced_json_object(namespace)
            json_object = yield

            return if json_object.blank?

            <<~SELECT
              '#{namespace}', json_build_object(
                #{json_object}
              )
            SELECT
          end

          def link_attributes(name, link, walker_result)
            title = link[:title] ? link[:title].call : "#{name}.name"

            attributes = ["'href'", link_href(link, name, walker_result)]

            if title
              attributes += ["'title'", title]
            end

            (link[:additional_properties] || {}).each do |key, value|
              attributes += ["'#{key}'", value]
            end

            attributes
          end

          def link_href(link, name, walker_result)
            path_name = link[:path] ? link[:path][:api] : name
            column = link[:column] ? link[:column].call : name

            link[:href] ? link[:href].call(walker_result) : "format('#{api_v3_paths.send(path_name, '%s')}', #{column})"
          end

          def link_from_sql(name, link)
            <<-SQL.squish
              '#{name}', #{link[:sql].call}
            SQL
          end

          def link_with_default(name, attributes)
            <<-SQL.squish
              '#{name}', '{ "href": null }'::jsonb || json_strip_nulls(json_build_object(#{attributes.join(', ')}))::jsonb
            SQL
          end

          def render_if_condition(name, condition, value)
            <<-SQL.squish
              CASE WHEN #{condition} THEN
                '#{name}'
              ELSE
                '#{TO_BE_REMOVED}'
              END,
              #{value}
            SQL
          end

          def sql_offset(walker_result)
            (walker_result.offset - 1) * walker_result.page_size
          end

          def sql_limit(walker_result)
            walker_result.page_size
          end

          def join_condition(name, options)
            <<~SQL.squish
              LEFT OUTER JOIN
                #{options[:table]} #{options[:alias] || name.to_s.pluralize}
              ON #{options[:condition]}
            SQL
          end
        end
      end
    end
  end
end