require 'volt/models/persistors/store'
require 'volt/models/persistors/store_state'
require 'volt/models/persistors/query/query_listener_pool'
require 'volt/utils/timers'

module Volt
  module Persistors
    class ArrayStore < Store
      include StoreState


      @@query_pool = QueryListenerPool.new

      attr_reader :model, :root_dep

      def self.query_pool
        @@query_pool
      end

      def initialize(model, tasks = nil)
        # Keep a hash of all ids in this collection
        @ids = {}

        super

        # The listener event counter keeps track of how many things are listening
        # on this model and loads/unloads data when in use.
        @listener_event_counter = EventCounter.new(
          -> { load_data },
          -> { stop_listening }
        )

        # The root dependency tracks how many listeners are on the ArrayModel
        # @root_dep = Dependency.new(@listener_event_counter.method(:add), @listener_event_counter.method(:remove))
        @root_dep = Dependency.new(method(:listener_added), method(:listener_removed))

        @query = @model.options[:query]
      end

      def loaded(initial_state = nil)
        super

        # Setup up the query listener, and if it is already listening, then
        # go ahead and load that data in.  This allows us to use it immediately
        # if the data is loaded in another place.
        if query_listener.listening
          query_listener.add_store(self)
          @added_to_query = true
        end
      end

      def inspect
        "<#{self.class}:#{object_id} #{@model.path.inspect} #{@query.inspect}>"
      end

      # Called when an each binding is listening
      def event_added(event, first, first_for_event)
        # First event, we load the data.
        @listener_event_counter.add if first
      end

      # Called when an each binding stops listening
      def event_removed(event, last, last_for_event)
        # Remove listener where there are no more events on this model
        @listener_event_counter.remove if last
      end

      # Called by child models to track their listeners
      def listener_added
        @listener_event_counter.add
      end

      # Called by child models to track their listeners
      def listener_removed
        @listener_event_counter.remove
      end

      # Called when an event is removed and we no longer want to keep in
      # sync with the database.  The data is kept in memory and the model's
      # loaded_state is marked as "dirty" meaning it may not be in sync.
      def stop_listening
        Timers.client_set_timeout(5000) do
          Computation.run_without_tracking do
            if @listener_event_counter.count == 0
              if @added_to_query
                @query_listener.remove_store(self)
                @query_listener = nil

                @added_to_query = nil
              end

              @model.change_state_to(:loaded_state, :dirty)
            end
          end
        end

        Timers.flush_next_tick_timers! if Volt.server?
      end

      # Called the first time data is requested from this collection
      def load_data
        Computation.run_without_tracking do
          loaded_state = @model.loaded_state

          # Don't load data from any queried
          if loaded_state == :not_loaded || loaded_state == :dirty
            @model.change_state_to(:loaded_state, :loading)

            run_query
          end
        end
      end

      def run_query
        unless @added_to_query
          @model.clear

          @added_to_query = true
          query_listener.add_store(self)
        end
      end

      # Looks up the query listener for this ArrayStore
      # @query should be treated as immutable.
      def query_listener
        return @query_listener if @query_listener

        collection = @model.path.last
        query = @query

        # Scope to the parent
        if @model.path.size > 1
          parent = @model.parent

          parent.persistor.ensure_setup if parent.persistor

          if parent && (attrs = parent.attributes) && attrs[:id]
            query = query.dup

            query << [:find, { :"#{@model.path[-3].singularize}_id" => attrs[:id] }]
          end
        end

        query = Volt::DataStore.adaptor_client.normalize_query(query)

        @query_listener ||= @@query_pool.lookup(collection, query) do
          # Create if it does not exist
          QueryListener.new(@@query_pool, @tasks, collection, query)
        end

        # @@query_pool.print

        @query_listener
      end

      # Add query part adds a [method_name, *arguments] array to the query.
      # This will then be passed to the backend to run the query.
      #
      # @return [Cursor] a new cursor
      def add_query_part(*args)
        opts = @model.options
        query = opts[:query] ? opts[:query].deep_clone : []
        query << args

        # Make a new opts hash with changed query
        opts = opts.merge(query: query)
        Cursor.new([], opts)
      end

      # Call a method on the model once the model is loaded.  Return a promise
      # that will resolve the result of the method, or reject with any
      # Exceptions.
      def run_once_loaded(block)
        promise = Promise.new

        # call once the method is loaded.
        model_loaded = proc do
          begin
            result = yield
            promise.resolve(result)
          rescue Exception => error
            promise.reject(error)
          end
        end

        # Run the block after resolve if a block is passed in
        if block
          promise2 = promise.then do |val|
            block.call(val)
          end
        else
          promise2 = promise
        end

        if @model.loaded_state == :loaded
          model_loaded.call
        else
          proc do |comp|
            if @model.loaded_state == :loaded
              model_loaded.call

              comp.stop
            end
          end.watch!
        end

        promise2
      end

      # Returns a promise that is resolved/rejected when the query is complete.  Any
      # passed block will be passed to the promises then.  Then will be passed the model.
      def fetch(&block)
        Volt.logger.warn('Deprication warning: in 0.9.3.pre4, all query methods on store now return Promises, so you can juse use .all or .first instead of .first')
        promise = Promise.new

        # Run the block after resolve if a block is passed in
        promise = promise.then(&block) if block

        if @model.loaded_state == :loaded
          promise.resolve(@model)
        else
          proc do |comp|
            if @model.loaded_state == :loaded
              promise.resolve(@model)

              comp.stop
            end
          end.watch!
        end

        promise
      end

      # Alias then for now
      # TODO: Deprecate
      alias_method :then, :fetch

      # Called from backend when an item is added
      def add(index, data)
        $loading_models = true

        Model.no_validate do
          data_id = data['id'] || data[:id]

          # Don't add if the model is already in the ArrayModel (from the client already)
          unless @ids[data_id]
            @ids[data_id] = true
            # Find the existing model, or create one
            new_model = @@identity_map.find(data_id) do
              new_options = @model.options.merge(path: @model.path + [:[]], parent: @model)
              @model.new_model(data, new_options, :loaded)
            end

            @model.insert(index, new_model)
          end
        end

        $loading_models = false
      end

      # Called from the server when it removes an item.
      def remove(ids)
        $loading_models = true
        ids.each do |id|
          # TODO: optimize this delete so we don't need to loop
          @model.each_with_index do |model, index|
            if model.id == id
              @ids.delete(id)
              del = @model.delete_at(index)
              break
            end
          end
        end

        $loading_models = false
      end

      # Called when all models are removed
      def clear
        @ids = {}
      end

      def channel_name
        @model.path[-1]
      end

      # Called when the client adds an item.
      def added(model, index)
        if model.persistor
          # Tell the persistor it was added, return the promise
          promise = model.persistor.add_to_collection

          # Track the the model got added
          @ids[model.id] = true

          promise
        end
      end

      # Called when the client removes an item
      def removed(model)
        if model.persistor
          # Tell the persistor it was removed
          model.persistor.remove_from_collection

          @ids.delete(model.id)
        end

        if defined?($loading_models) && $loading_models
          return
        else
          StoreTasks.delete(channel_name, model.attributes[:id])
        end
      end
    end
  end
end