Class: QueryTracker

Inherits:
Object show all
Defined in:
app/volt/tasks/live_query/query_tracker.rb

Overview

The query tracker runs queries and then tracks the changes that take place.

Instance Attribute Summary collapse

Instance Method Summary collapse

Constructor Details

#initialize(live_query, data_store) ⇒ QueryTracker

Returns a new instance of QueryTracker.



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# File 'app/volt/tasks/live_query/query_tracker.rb', line 5

def initialize(live_query, data_store)
  @live_query = live_query
  @data_store = data_store

  # Stores the list of id's currently associated with this query
  @current_ids = []
  @results = []
  @results_hash = {}
end

Instance Attribute Details

#results ⇒ Object

Returns the value of attribute results.



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# File 'app/volt/tasks/live_query/query_tracker.rb', line 4

def results
  @results
end

Instance Method Details

#detect_added_and_moved(skip_channel) ⇒ Object

Loop through the new list, tracking in the old, notifies of any that have been added or moved.



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# File 'app/volt/tasks/live_query/query_tracker.rb', line 56

def detect_added_and_moved(skip_channel)
  previous_index = 0
  @current_ids.each_with_index do |id, index|
    if (cur_previous = @previous_ids[previous_index]) && cur_previous == id
      # Same in both previous and new
      previous_index += 1
      next
    end

    # We have an item that didn't match the current position's previous
    # TODO: make a hash so we don't have to do include?
    if @previous_ids.include?(id)
      # The location from the previous has changed, move to correct location.

      # Remove from previous_ids, since it will be moved and we will be past it.
      @previous_ids.delete(id)

      @live_query.notify_moved(id, index, skip_channel)
    else
      # TODO: Faster lookup
      data = @results_hash[id]
      @live_query.notify_added(index, data, skip_channel)
    end
  end
end

#detect_changed(skip_channel) ⇒ Object

Finds all items in the previous results that have new values, and alerts of changes.



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# File 'app/volt/tasks/live_query/query_tracker.rb', line 84

def detect_changed(skip_channel)
  not_added_or_removed = @previous_ids & @current_ids

  not_added_or_removed.each do |id|
    if @previous_results_hash[id] != (data = @results_hash[id])
      # Data hash changed
      @live_query.notify_changed(id, data, skip_channel)
    end
  end
end

#detect_removed(skip_channel) ⇒ Object 



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# File 'app/volt/tasks/live_query/query_tracker.rb', line 43

def detect_removed(skip_channel)
  # Removed models
  removed_ids = @previous_ids - @current_ids
  if removed_ids.size > 0
    @live_query.notify_removed(removed_ids, skip_channel)
  end

  # Update @previous_ids to relect the removed
  @previous_ids = @previous_ids & @current_ids
end

#process_changes(skip_channel) ⇒ Object

Looks at the changes in the last run and sends out notices all changes.



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# File 'app/volt/tasks/live_query/query_tracker.rb', line 33

def process_changes(skip_channel)
  if @previous_ids
    detect_removed(skip_channel)

    detect_added_and_moved(skip_channel)

    detect_changed(skip_channel)
  end
end

#run(skip_channel = nil) ⇒ Object

Runs the query, stores the results and updates the current_ids



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# File 'app/volt/tasks/live_query/query_tracker.rb', line 16

def run(skip_channel = nil)
  @previous_results = @results
  @previous_results_hash = @results_hash
  @previous_ids = @current_ids

  # Run the query again
  @results = @data_store.query(@live_query.collection, @live_query.query)

  # Update the current_ids
  @current_ids = @results.map { |r| r['_id'] }
  @results_hash = Hash[@results.map { |r| [r['_id'], r] }]

  process_changes(skip_channel)
end