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module Mocha
# A state machine that is used to constrain the order of invocations.
# An invocation can be constrained to occur when a state {#is}, or {#is_not}, active.
class StateMachine
# Provides the ability to determine whether a {StateMachine} is in a specified state at some point in the future.
class StatePredicate
# @private
def initialize(state_machine, state, description, &active_check)
@state_machine = state_machine
@state = state
@description = description
@active_check = active_check
end
# @private
def active?
@active_check.call(@state_machine.current_state, @state)
end
# @private
def mocha_inspect
"#{@state_machine.name} #{@description} #{@state.mocha_inspect}"
end
end
# Provides a mechanism to change the state of a {StateMachine} at some point in the future.
class State < StatePredicate
# @private
def activate
@state_machine.current_state = @state
end
end
# @private
attr_reader :name
# @private
attr_accessor :current_state
# @private
def initialize(name)
@name = name
@current_state = nil
end
# Put the {StateMachine} into the state specified by +initial_state_name+.
#
# @param [String] initial_state_name name of initial state
# @return [StateMachine] state machine, thereby allowing invocations of other {StateMachine} methods to be chained.
def starts_as(initial_state_name)
become(initial_state_name)
self
end
# Put the {StateMachine} into the +next_state_name+.
#
# @param [String] next_state_name name of new state
def become(next_state_name)
@current_state = next_state_name
end
# Provides mechanisms to (a) determine whether the {StateMachine} is in a given state; or (b) to change the {StateMachine} into the given state.
#
# @param [String] state_name name of expected/desired state.
# @return [StatePredicate,State] (a) state predicate which, when queried, will indicate whether the {StateMachine} is in the given state; or (b) state which, when activated, will change the {StateMachine} into the given state.
#
# @overload def is(expected_state_name)
# Provides a mechanism to determine whether the {StateMachine} is in the state specified by +expected_state_name+ at some point in the future
# @param [String] expected_state_name name of expected state.
# @return [StatePredicate] state predicate which, when queried, will indicate whether the {StateMachine} is in the state specified by +expected_state_name+
#
# @overload def is(desired_state_name)
# Provides a mechanism to change the {StateMachine} into the state specified by +desired_state_name+ at some point in the future.
# @param [String] desired_state_name name of desired new state.
# @return [State] state which, when activated, will change the {StateMachine} into the state with the specified +desired_state_name+.
def is(state_name)
State.new(self, state_name, 'is') { |current, given| current == given }
end
# Provides a mechanism to determine whether the {StateMachine} is *not* in the state specified by +unexpected_state_name+ at some point in the future.
#
# @param [String] unexpected_state_name name of unexpected state.
# @return [StatePredicate] state predicate which, when queried, will indicate whether the {StateMachine} is *not* in the state specified by +unexpected_state_name+.
def is_not(unexpected_state_name) # rubocop:disable Naming/PredicateName
StatePredicate.new(self, unexpected_state_name, 'is not') { |current, given| current != given }
end
# @private
def mocha_inspect
%(#{@name} #{@current_state ? "is #{@current_state.mocha_inspect}" : 'has no current state'})
end
end
end
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