# A dynamic progress bar displayable in console.
#
# Example:
# ~~~nitish
# var max = 10
# var current = 0
# var pb = new TermProgress(max, current)
#
# pb.display
# for i in [current + 1 .. max] do
#	nanosleep(1, 0)
#	pb.update(i)
# end
#
# print "\ndone"
# ~~~
#
# Progress bar can accept metadata to display a small amount of data.
#
# Example with metadata:
# ~~~nitish
# var pb = new TermProgress(10, 0)
# for i in [0..10] do
#	pb.update(i, "Step {i}")
# end
# ~~~
class TermProgress

	# Max value of the progress bar (business value).
	var max_value: Int

	# Current value of the progress bar (business value).
	var current_value: Int

	# Number of columns used to display the progress bar.
	var max_columns = 70 is writable

	# Get the current percent value.
	fun current_percentage: Int do
		return current_value * 100 / max_value
	end

	# Display the progress bar.
	#
	# `metadata`  can be used to pass a small amount of data to display after
	# the progress bar.
	fun display(metadata: nullable String) do
		var percent = current_percentage
		var p = current_value * max_columns / max_value
		printn "\r{percent}% ["
		for i in [1..max_columns] do
			if i < p then
				printn "="
			else if i == p then
				printn ">"
			else
				printn " "
			end
		end
		printn "]"
		if metadata != null then printn " ({metadata})"
	end

	# Update and display the progress bar.
	#
	# See `display`.
	fun update(new_current: Int, metadata: nullable String) do
		current_value = new_current
		display(metadata)
	end
end