# A Node in the static flow graph.
# A same `FlowContext` can be shared by more than one `ANode`.
class FlowContext
	# The reachable previous flow
	var previous = new Array[FlowContext]

	# Additional reachable flow that loop up to self.
	# Loops appears in `loop`, `while`, `for`, and with `continue`
	var loops = new Array[FlowContext]

	private var is_marked_unreachable: Bool = false

	# Is the flow dead?
	fun is_unreachable: Bool
	do
		# Are we explicitly marked unreachable?
		if self.is_marked_unreachable then return true

		# Are we the starting flow context?
		if is_start then return false

		# De we have a reachable previous?
		if previous.length == 0 then return true
		return false
	end

	# Flag to avoid repeated errors
	var is_already_unreachable: Bool = false

	# Mark that self is the starting flow context.
	# Such a context is reachable even if there is no previous flow
	var is_start: Bool = false

	# The node that introduce the flow (for debugging)
	var node: nullable ANode = null

	# Additional information for the flow (for debugging)
	var name: String = ""

	# The sub-flow to use if the associated expr is true
	var when_true: FlowContext = self

	# The sub-flow to use if the associated expr is true
	var when_false: FlowContext = self

	# Add a previous flow (iff it is reachable)
	private fun add_previous(flow: FlowContext)
	do
		if not flow.is_unreachable and not previous.has(flow) then
			previous.add(flow)
		end
	end

	# Add a previous loop flow (iff it is reachable)
	private fun add_loop(flow: FlowContext)
	do
		if not flow.is_unreachable and not previous.has(flow) then
			loops.add(flow)
		end
	end

end