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require "active_support/core_ext/array/wrap"
require "active_support/core_ext/array/extract_options"
module ActiveSupport
# This class is responsible to track files and invoke the given block
# whenever one of these files are changed. For example, this class
# is used by Rails to reload the I18n framework whenever they are
# changed upon a new request.
#
# i18n_reloader = ActiveSupport::FileUpdateChecker.new(paths) do
# I18n.reload!
# end
#
# ActionDispatch::Reloader.to_prepare do
# i18n_reloader.execute_if_updated
# end
#
class FileUpdateChecker
attr_reader :paths, :last_update_at
# It accepts two parameters on initialization. The first is
# the *paths* and the second is *calculate*, a boolean.
#
# paths must be an array of file paths but can contain a hash as
# last argument. The hash must have directories as keys and the
# value is an array of extensions to be watched under that directory.
#
# If *calculate* is true, the latest updated at will calculated
# on initialization, therefore, the first call to execute_if_updated
# will only evaluate the block if something really changed.
#
# This method must also receive a block that will be the block called
# once a file changes.
#
# This particular implementation checks for added files and updated files,
# but not removed files. Directories lookup are compiled to a glob for
# performance.
def initialize(paths, calculate=false, &block)
@paths = paths
@glob = compile_glob(@paths.extract_options!)
@block = block
@updated_at = nil
@last_update_at = calculate ? updated_at : nil
end
# Check if any of the entries were updated. If so, the updated_at
# value is cached until flush! is called.
def updated?
current_updated_at = updated_at
if @last_update_at != current_updated_at
@updated_at = updated_at
true
else
false
end
end
# Flush the cache so updated? is calculated again
def flush!
@updated_at = nil
end
# Execute the block given if updated. This call
# always flush the cache.
def execute_if_updated
if updated?
@last_update_at = updated_at
@block.call
true
else
false
end
ensure
flush!
end
private
def updated_at #:nodoc:
@updated_at || begin
all = []
all.concat @paths
all.concat Dir[@glob] if @glob
all.map { |path| File.mtime(path) }.max
end
end
def compile_glob(hash) #:nodoc:
return if hash.empty?
globs = []
hash.each do |key, value|
globs << "#{key}/**/*#{compile_ext(value)}"
end
"{#{globs.join(",")}}"
end
def compile_ext(array) #:nodoc:
array = Array.wrap(array)
return if array.empty?
".{#{array.join(",")}}"
end
end
end
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