# This file is part of CPEE.
#
# CPEE 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 3 of the License, or (at your option) any later version.
#
# CPEE 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
# CPEE (file COPYING in the main directory).  If not, see
# <http://www.gnu.org/licenses/>.

require 'json'
require_relative 'fail'

module CPEE
  module Notifications

    def self::implementation(id,opts)
      Proc.new do
        if CPEE::Persistence::exists?(id,opts)
          on resource "notifications" do
            run CPEE::Notifications::Overview if get
            on resource "topics" do
              run CPEE::Notifications::Topics, opts if get
            end
            on resource "subscriptions" do
              run CPEE::Notifications::Subscriptions, id, opts if get
              run CPEE::Notifications::CreateSubscription, id, opts if post 'create_subscription'
              on resource do
                run CPEE::Notifications::Subscription, id, opts if get
                run CPEE::Notifications::UpdateSubscription, id, opts if put 'change_subscription'
                run CPEE::Notifications::DeleteSubscription, id, opts if delete
                on resource 'sse' do
                  run CPEE::Notifications::SSE, id, opts if sse
                end
              end
            end
          end
        else
          run CPEE::FAIL
        end
      end
    end

    class Overview < Riddl::Implementation #{{{
      def response
        Riddl::Parameter::Complex.new("overview","text/xml") do
          <<-END
            <overview xmlns='http://riddl.org/ns/common-patterns/notifications-producer/2.0'>
              <topics/>
              <subscriptions/>
            </overview>
          END
        end

      end
    end #}}}

    class Topics < Riddl::Implementation #{{{
      def response
        opts = @a[0]
        Riddl::Parameter::Complex.new("overview","text/xml") do
          File.read(opts[:topics])
        end
      end
    end #}}}

    class Subscriptions < Riddl::Implementation #{{{
      def response
        id = @a[0]
        opts = @a[1]
        Riddl::Parameter::Complex.new("subscriptions","text/xml") do
          ret = XML::Smart::string <<-END
            <subscriptions xmlns='http://riddl.org/ns/common-patterns/notifications-producer/2.0'/>
          END
          CPEE::Persistence::extract_handlers(id,opts).each do |de|
            ret.root.add('subscription').tap do |n|
              n.attributes['id'] = de[0]
              n.attributes['url'] = de[1] if de[1] && !de[1].empty?
            end
          end
          ret.to_s
        end
      end
    end #}}}

    class Subscription < Riddl::Implementation #{{{
      def response
        id = @a[0]
        opts = @a[1]
        key = @r[-1]
        if CPEE::Persistence::exists_handler?(id,opts,key)
          Riddl::Parameter::Complex.new("subscriptions","text/xml") do
            ret = XML::Smart::string <<-END
              <subscription xmlns='http://riddl.org/ns/common-patterns/notifications-producer/2.0'/>
            END
            url = CPEE::Persistence::extract_item(id,opts,File.join('handlers',key,'url'))
            ret.root.attributes['id'] = key
            ret.root.attributes['url'] = url if url && !url.empty?
            items = {}
            CPEE::Persistence::extract_handler(id,opts,key).each do |h|
              t, i, v = h.split('/')
              items[t] ||= []
              items[t] << [i,v]
            end
            items.each do |k,v|
              ret.root.add('topic').tap do |n|
                n.attributes['id'] = k
                v.each do |e|
                  n.add *e
                end
              end
            end
            ret.to_s
          end
        else
          @status = 404
       end
      end
    end #}}}

    class CreateSubscription < Riddl::Implementation #{{{
      def response
        id = @a[0]
        opts = @a[1]

        key = @p[0].name == 'id' ? @p.shift.value : Digest::MD5.hexdigest(Kernel::rand().to_s)
        url = @p[0].name == 'url' ? @p.shift.value : nil
        values = []
        while @p.length > 0
          topic = @p.shift.value
          base = @p.shift
          type = base.name
          values += base.value.split(',').map { |i| File.join(topic,type[0..-2],i) }
        end
        @header = CPEE::Persistence::set_handler(id,opts,key,url,values)

        Riddl::Parameter::Simple.new('key',key)
      end
    end #}}}

    class UpdateSubscription < Riddl::Implementation #{{{
      def response
        id = @a[0]
        opts = @a[1]
        key = @r.last

        if CPEE::Persistence::exists_handler?(id,opts,key)
          url = @p[0].name == 'url' ? @p.shift.value : nil
          values = []
          while @p.length > 0
            topic = @p.shift.value
            base = @p.shift
            type = base.name
            values += base.value.split(',').map { |i| File.join(topic,type[0..-2],i) }
          end
          @header = CPEE::Persistence::set_handler(id,opts,key,url,values,true)
        else
          @status = 404
        end
      end
    end #}}}

    class DeleteSubscription < Riddl::Implementation #{{{
      def self::set(id,opts,key)
        CPEE::Persistence::set_handler(id,opts,key,"",[],true)
      end

      def response
        id = @a[0]
        opts = @a[1]
        key = @r.last

        if CPEE::Persistence::exists_handler?(id,opts,key)
          DeleteSubscription::set(id,opts,key)
        else
          @status = 404
        end
        nil
      end
    end #}}}

    def self::sse_distributor(opts) #{{{
      conn = opts[:redis_dyn].call "Server SSE"
      conn.psubscribe('forward:*','event:state/change') do |on|
        on.pmessage do |pat, what, message|
          if pat == 'forward:*'
            id, key = what.match(/forward:([^\/]+)\/(.+)/).captures
            if sse = opts.dig(:sse_connections,id,key)
              sse.send message
            else
              DeleteSubscription::set(id,opts,key)
            end
          elsif pat == 'event:state/change'
            mess = JSON.parse(message[message.index(' ')+1..-1])
            state = mess.dig('content','state')
            if state == 'finished' || state == 'abandoned'
              opts.dig(:sse_connections,mess.dig('instance').to_s)&.each do |key,sse|
                EM.add_timer(10) do # just to be sure that all messages arrived. 10 seconds should be enough ... we think ... therefore we are (not sure)
                  sse.close
                end
              end
            end
          end
        end
      end
      conn.close
    end #}}}
    def self::sse_heartbeat(opts) #{{{
      opts.dig(:sse_connections).each do |id,keys|
        keys.each do |key,sse|
          sse.send_with_id('heartbeat', '42') unless sse&.closed?
        end
      end
    end #}}}
    class SSE < Riddl::SSEImplementation #{{{
      def onopen
        @opts = @a[1]
        @id = @a[0].to_s
        @key = @r[-2]
        if CPEE::Persistence::exists_handler?(@id,@opts,@key)
          @opts[:sse_connections][@id] ||= {}
          @opts[:sse_connections][@id][@key] = self
          true
        else
          false
        end
      end

      def onclose
        @opts.dig(:sse_connections,@id)&.delete(@key)
        @opts.dig(:sse_connections)&.delete(@id) if @opts.dig(:sse_connections,@id)&.length == 0
        DeleteSubscription::set(@id,@opts,@key)
      end
    end #}}}

  end
end