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require 'couchrest'
require 'fileutils'
module Tapicero
class CouchChanges
attr_accessor :db
def initialize(db, seq_filename)
@db = db
@seq_filename = seq_filename
read_seq(seq_filename)
end
def created(hash = {}, &block)
if block_given?
@created = block
else
@created && @created.call(hash)
end
end
def deleted(hash = {}, &block)
if block_given?
@deleted = block
else
@deleted && @deleted.call(hash)
end
end
def listen
Tapicero.logger.info "listening..."
Tapicero.logger.debug "Starting at sequence #{since}"
db.changes :feed => :continuous, :since => since, :heartbeat => 1000 do |hash|
callbacks(hash)
store_seq(hash["seq"])
end
end
protected
def since
@since ||= 0 # fetch_last_seq
end
def callbacks(hash)
#changed callback
return unless changes = hash["changes"]
return deleted(hash) if hash["deleted"]
created(hash) if changes[0]["rev"].start_with?('1-')
#updated callback
end
def read_seq(seq_filename)
Tapicero.logger.debug "Looking up sequence here: #{seq_filename}"
FileUtils.touch(seq_filename)
unless File.writable?(seq_filename)
raise StandardError.new("Can't access sequence file")
end
@since = File.read(seq_filename).to_i
Tapicero.logger.debug "Found sequence: #{@since}"
rescue Errno::ENOENT => e
Tapicero.logger.warn "No sequence file found. Starting from scratch"
end
def store_seq(seq)
File.write(@seq_filename, seq)
end
#
# UNUSED: this is useful for only following new sequences.
#
def fetch_last_seq
hash = db.changes :limit => 1, :descending => true
Tapicero.logger.info "starting at seq: " + hash["last_seq"]
return hash["last_seq"]
end
end
end
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