Class: Analysand::ViewStreaming::Builder

Inherits:
Object
  • Object
show all
Defined in:
lib/analysand/view_streaming/builder.rb

Overview

Private: A wrapper around JSON::Stream::Parser that extracts data from a CouchDB view document.

Defined Under Namespace

Classes: ObjectNode

Constant Summary collapse

CALLBACK_METHODS =

JSON::Stream::Parser callback methods.

%w(
  start_object end_object start_array end_array key value
)
KNOWN_KEYS =

If we find a key in the toplevel view object that isn’t one of these, we raise UnexpectedViewKey.

%w(
  total_rows offset rows
)

Instance Attribute Summary collapse

Instance Method Summary collapse

Constructor Details

#initialize ⇒ Builder

Returns a new instance of Builder.



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# File 'lib/analysand/view_streaming/builder.rb', line 27

def initialize
  @in_rows = false
  @parser = JSON::Stream::Parser.new
  @stack = []
  @staged_rows = []

  CALLBACK_METHODS.each { |name| @parser.send(name, &method(name)) }
end

Instance Attribute Details

#offset ⇒ Object (readonly)

Returns the value of attribute offset.



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# File 'lib/analysand/view_streaming/builder.rb', line 9

def offset
  @offset
end

#staged_rows ⇒ Object (readonly)

Rows constructed by the JSON parser that are ready for StreamingViewResponse#each.



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# File 'lib/analysand/view_streaming/builder.rb', line 14

def staged_rows
  @staged_rows
end

#total_rows ⇒ Object (readonly)

Returns the value of attribute total_rows.



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# File 'lib/analysand/view_streaming/builder.rb', line 10

def total_rows
  @total_rows
end

Instance Method Details

#<<(data) ⇒ Object 



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# File 'lib/analysand/view_streaming/builder.rb', line 36

def <<(data)
  @parser << data
end

#check_toplevel_key_validity(k) ⇒ Object 



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# File 'lib/analysand/view_streaming/builder.rb', line 115

def check_toplevel_key_validity(k)
  if !KNOWN_KEYS.include?(k)
    raise UnexpectedViewKey, "Unexpected key #{k} in top-level view object"
  end
end

#end_array ⇒ Object 



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# File 'lib/analysand/view_streaming/builder.rb', line 81

def end_array
  if @in_rows
    obj = @stack.pop

    # If there's nothing on the row stack, it means that we've hit the
    # end of the rows array.
    if @stack.empty?
      @in_rows = false
    else
      @stack.last << obj
    end
  end
end

#end_object ⇒ Object 



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# File 'lib/analysand/view_streaming/builder.rb', line 48

def end_object
  if @in_rows
    # If the stack's empty and we've come to the end of an object, assume
    # we've exited the rows key.  Trailing keys are handled by
    # check_toplevel_key_validity.
    if @stack.empty?
      @in_rows = false
    else
      obj = @stack.pop.to_object

      # If obj was the only thing on the stack and we're processing rows,
      # then we've completed an object and need to stage it for the
      # object stream.
      if @stack.empty?
        staged_rows << obj
      else
        @stack.last << obj
      end
    end
  end
end

#key(k) ⇒ Object 



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# File 'lib/analysand/view_streaming/builder.rb', line 95

def key(k)
  if !@in_rows
    check_toplevel_key_validity(k)
    @stack.push k
  else
    @stack.last << k
  end
end

#start_array ⇒ Object 



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# File 'lib/analysand/view_streaming/builder.rb', line 70

def start_array
  # If we're not in the rows array but "rows" was the last key we've
  # seen, then we're entering the rows array.  Otherwise, we're building
  # an array in a row.
  if !@in_rows && @stack.pop == 'rows'
    @in_rows = true
  elsif @in_rows
    @stack.push []
  end
end

#start_object ⇒ Object 



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# File 'lib/analysand/view_streaming/builder.rb', line 40

def start_object
  # We don't need to do anything for the toplevel view object, so just
  # focus on the objects in rows.
  if @in_rows
    @stack.push ObjectNode.new
  end
end

#value(v) ⇒ Object 



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# File 'lib/analysand/view_streaming/builder.rb', line 104

def value(v)
  if !@in_rows
    case @stack.pop
    when 'total_rows'; @total_rows = v
    when 'offset'; @offset = v
    end
  else
    @stack.last << v
  end
end